WO2005100264A2 - Method and apparatus providing improved throughput and operating life of submerged membranes - Google Patents
Method and apparatus providing improved throughput and operating life of submerged membranes Download PDFInfo
- Publication number
- WO2005100264A2 WO2005100264A2 PCT/US2005/010976 US2005010976W WO2005100264A2 WO 2005100264 A2 WO2005100264 A2 WO 2005100264A2 US 2005010976 W US2005010976 W US 2005010976W WO 2005100264 A2 WO2005100264 A2 WO 2005100264A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- fluid
- membrane
- gas
- specific gravity
- zone
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/14—Ultrafiltration; Microfiltration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/14—Ultrafiltration; Microfiltration
- B01D61/18—Apparatus therefor
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/12—Activated sludge processes
- C02F3/1236—Particular type of activated sludge installations
- C02F3/1268—Membrane bioreactor systems
- C02F3/1273—Submerged membrane bioreactors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2313/00—Details relating to membrane modules or apparatus
- B01D2313/24—Specific pressurizing or depressurizing means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2315/00—Details relating to the membrane module operation
- B01D2315/06—Submerged-type; Immersion type
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/28—Degradation or stability over time
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Definitions
- the present invention relates to methods and devices for processing, refining, and/or treating liquid compositions. More specifically, the invention relates to membrane separation methods and devices employing a selective, semi-permeable, microporous, or other partitioning membrane for processing, refining, and/or treating liquid compositions, for example membrane waste-water purification processes and apparatus.
- a number of wastewater treatment processes comprise "biological" systems utilizing microorganisms contained in an activated biomass, or sludge for the removal of COD, phosphorous and/or nitrogen from wastewater. These treatment processes typically incorporate multiple treatment phases or “zones", namely: (1) a preliminary treatment area; (2) a primary treatment area; and (3) a secondary treatment area.
- Preliminary treatment is primarily concerned with the removal of solid inorganics from untreated wastewater.
- this preliminary treatment encompasses a two-stage treatment process in which the debris is removed by screens and/or settling. Organic matter is carried out in the fluid stream for subsequent treatment.
- Primary treatment entails a physical process wherein a portion of the organics, including suspended solids such as feces, food particles, etc.
- Secondary treatment typically encompasses a biological treatment process where microorganisms are utilized to remove remaining organics, nitrogen and phosphorous from the wastewater fluid stream. Microorganism growth and metabolic activity are exploited and controlled through the use of controlled growth conditions.
- biological treatment processes typically utilize a basin or other reservoir in which the wastewater is mixed with a suspension of biomass/sludge. Subsequent growth and metabolism of the microorganisms, and the resultant treatment of the wastewater, is carried out under aerobic and/or anaerobic/anoxic conditions. In most large scale municipal or industrial treatment systems, the various components of the treatment process are performed in discrete basins or reactors.
- Biomass containing the active microorganisms may be recycled from one process step to another.
- the conditioning of such biomass to enhance growth of particularized subgroups of microorganisms possessing a proclivity for performing a specific type of metabolic process, e.g. phosphate removal, nitrogen removal has been the subject matter of numerous patents, including: U.S. Pat. No. 4,056,465; U.S. Pat. No.
- No 5,503,748 discloses a long vertical shaft aerator applied to the SBR technology.
- the SBR process employs a number of discrete steps, typically comprising sequential fill, reaction, settlement and decantation of wastewater with biomass in an enclosed reactor.
- wastewater is transferred into a reactor containing biomass, and combined to form a mixed liquor.
- the microorganisms of the biomass utilize and metabolize and/or take up the nitrogen, phosphorous and/or organic sources in the wastewater. These latter reactions may be performed under anaerobic conditions, anoxic conditions, aerobic conditions, or a combination thereof to manipulate organism growth, population dynamics and contaminant processing.
- the length of this stage will be dependent on the waste's characteristic, concentration of the biomass, and other factors.
- the biomass in the mixed liquor is allowed to settle out.
- a sludge blanket settles on the bottom of the reactor leaving a treated effluent supernatant.
- the treated and clarified wastewater i.e. effluent
- the reactor vessel is then refilled and the treatment process cycle reinitiated.
- the sequencing batch reactor's process is based on discrete operation in time, whereas other wastewater treatment processes are based on distinct operations in space, e.g., by performance of different reactions in separate vessels.
- a number of additional wastewater treatment designs feature an air-lift reactor, which is a mechanically simple, combined gas-liquid flow device characterized by fluid circulation in a defined cyclic pattern through a set of specifically designed channels. Fluid motion is due to the mean density difference in an upflow (riser) and downflow (downcomer) sections of the reactor.
- the air-lift reactor is ordinarily comprised of distinct zones with different flow patterns.
- the riser is typically the zone where the gas is injected creating a fluid density difference, resulting in upward flow of both liquid and gas phases.
- a gas-liquid separator section which is typically a region of horizontal fluid flow and flow reversal where gas bubbles disengage from the liquid phase.
- the downcomer is the zone where the gas-liquid dispersion or degassed liquid ordinarily recirculates to the riser.
- the downcomer zone exhibits either single-phase, two- phase cocurrent, or two-phase mixed cocurrent-countercurrent downward flow, depending on whether the liquid velocity is greater than the free-rise velocity of the bubbles.
- the base section at the lower end of the vessel communicates the exit of the downcomer to the entrance of the riser.
- the air-lift reactor has predominantly been used for microorganism fermentation processes such as the ICI single cell protein production. Nonetheless, a number of systems are known which utilize air-lift reactors for wastewater treatment. Among these examples is the Betz reactor (Gasner, Biotech. Bioeng.
- U.S. Pat. No. 4,279,754, 5,645,726, and 5,650,070 issued to Pollock each disclose a modified vertical shaft bioreactor system for the treatment of biodegradable wastewater and/or sludge.
- these vertical shaft bioreactor systems comprise a bioreactor, a solid/liquid separator and intervening apparatus in communication with the bioreactor and separator.
- the bioreactor comprises a circulatory system which includes two or more vertical, side-by-side or coaxial chambers, a downflow chamber (downcomer) and an upflow chamber (riser).
- these chambers are connected at their upper ends through a surface basin and communicate at their lower ends via a common "mix zone" adjacent the lower end of the downcomer.
- these reactors feature a "plug flow zone" located below the mix zone and communicating therewith.
- the term "plug flow” has referred to a net downward migration of solid particles from the mix zone toward an effluent outlet located at the lower end of the reactor.
- the net downward migration has been reported by Guild et al. (Proceedings WEF conf, Atlanta Ga., Oct 2001), to include local back mixing only, but over extended periods of operation (e.g., about 16 hours), inter-zonal mixing occurs.
- the waste-containing liquor (“mixed liquor”) is driven through the circulating system (i.e., between the downflow and upflow chambers, the surface basin and the mix zone) by injection of an oxygen-containing gas, usually air, near the bottom of the reactor (e.g., at the mix zone and plug flow zone).
- an oxygen-containing gas usually air
- a portion of the circulating flow is directed to the plug flow zone and is removed at the lower end thereof as effluent.
- the air is typically injected 5-10 feet above the bottom of the reactor and, optionally, immediately below the lower end of the downcomer.
- the deepest air injection point divides the plug flow zone into a quasi plug flow zone with localized back mixing above the deepest point of air injection, and a strict plug flow zone with reportedly no mixing below the deepest point of air injection.
- the surface basin is ordinarily fitted with a horizontal baffle at the top of the upflow chamber to force the mixed liquor to traverse a major part of the basin and release spent gas before re- entering the downflow chamber for further treatment.
- U.S. Pat. No. 5,650,070 discloses a process where influent waste water is introduced at depth into the riser chamber through an upwardly directed outlet arm of an influent conduit. A zone of turbulence is created at the lower end of the downflow chamber by the turn-around velocity head as the circulating flow reverses from downward to upward flow. This mix zone is not well defined but typically is between 15-25 feet deep.
- a portion of the mixed liquor in the mix zone flows downwardly into the top of the plug flow zone in response to an equal amount of treated effluent being removed from the lower end of the plug flow zone into an effluent line, as discussed above.
- the flow of influent liquor to and effluent liquor from the bioreactor are controlled in response to changes in level of liquid in the connecting upper basin.
- nitrogen removal is accomplished by converting ammonia contained in a mixed liquor stream to nitrites and nitrates, in the presence of oxygen, which is known as an aerobic nitrifying stage.
- Ammonia conversion to nitrite is carried out by microbes known as Nitrosomonas, while the conversion of nitrite to nitrate is accomplished by Nitrobacters.
- Nitrate conversion to nitrogen gas occurs in an anoxic denitrifying stage that takes place in a suspended growth environment devoid of dissolved oxygen. Nitrogen, carbon dioxide and water is produced, with the gas being vented from the system.
- Nitrification rates can be optimized by regulating interdependent waste stream parameters such as temperature, dissolved oxygen levels (D.O.), pH, solids retention time (SRT), ammonia concentration and BOD/TKN ratio (Total Kjeldahl Nitrogen, or TKN, is organic nitrogen plus the nitrogen from ammonia and ammonium). Higher temperatures and higher dissolved oxygen levels tend to promote increased nitrification rates, as does pH levels in 7.0 to 8.0 range. Sludge retention times of from 3.5 to 5, and preferably 5-8, days dramatically increase nitrification efficiency, after which time efficiencies tend to remain constant.
- interdependent waste stream parameters such as temperature, dissolved oxygen levels (D.O.), pH, solids retention time (SRT), ammonia concentration and BOD/TKN ratio (Total Kjeldahl Nitrogen, or TKN, is organic nitrogen plus the nitrogen from ammonia and ammonium).
- Sludge retention times of from 3.5 to 5, and preferably 5-8, days dramatically increase nitrification efficiency,
- Refractory treatment and polishing stages may be added to the process, downstream of the final clarification stage.
- the majority of organic compounds 80%-90%) are easily biodegraded.
- the remaining fraction biodegrade more slowly and are termed "refractory" compounds.
- Prior art biological nutrient removal designs incorporate a single sludge and a single clarifier, for example, U.S. Pat. No. 3,964,998 to Barnard, but in that case the overall oxidation rate of the system has to be reduced to satisfy the slowest compound to oxidize.
- Biological nutrient removal (BNR) systems can take various process configurations.
- One such embodiment is the five stage Modified BardenphoTM process, which is based upon U.S. Pat. No. 3,964,998 to Barnard. It provides anaerobic, anoxic and aerobic stages for removal of phosphorous, nitrogen and organic carbon. More than 24 BardenphoTM treatment plants are operational, with most using the five stage process as opposed to the previously designed four stage process. Most of these facilities require supplemental chemical addition to meet effluent phosphorous limits of less than 1.0 mg/L. Plants using this process employ various aeration methods, tank configurations, pumping equipment and sludge handling methods. WEF Manual of Practice No. 8, "Design of Municipal Wastewater Treatment Plants", Vol. 2, 1991.
- Pollock U.S. Pat. No. 5,651 ,892, issued July 29, 1997, incorporated herein by reference discloses an innovative process utilizing a vertical bioreactor linked to a flooded filter via a flotation separator. According to this design, improved reaction rates are achieved by separating the biomass into a high rate aerobic organic carbon removal step, followed by an aerobic nitrification step using a separate nitrifying biomass. These steps are then followed by a high rate denitrification step in an anoxic environment created by feeding influent and return mixed liquor or effluent into that zone to provide a source of organic carbon and consume the oxygen.
- Membrane separation which employs a selective, semi-permeable, or partitioning membrane is a rapidly evolving aspect of industrial separation technology for processing, refining, and or treating liquid compositions, for example as employed in modern membrane waste-water purification processes and apparatus.
- a first liquid composition for example an influent liquid waste water stream or flow
- one or more constituents of the first liquid composition typically pass through the membrane, often as a result of a driving force or forces, for form a second liquid composition, for example an effluent flow stream at a second surface of the membrane, whereby one or more separated or partitioned components of the first liquid composition are excluded or left behind (i.e., they are partitioned or retained at the first membrane surface to remain in solution, suspension, or contact, with the first liquid composition.
- Membrane separation technologies that can be employed within the methods and devices of the invention for processing, refining or treating liquid compositions include microfiltration, ultraf ⁇ ltration, nanofiltration, reverse osmosis, electrodialysis, electrodeionization, pervaporation, membrane extraction, membrane distillation, membrane stripping, membrane aeration, and other membrane-based processes.
- driving forces may be used principally, or in combination with other driving forces disclosed herein, to effectuate or enhance membrane function, depending on the type of the membrane separation employed.
- Pressure-driven membrane filtration also known as membrane filtration, includes microfiltration, ultraf ⁇ ltration, nanofiltration and reverse osmosis, and uses pressure as a driving force, whereas electrical driving force is used in electrodialysis and electrodeionization.
- membrane separation processes or systems have not been considered cost effective for water treatment due to the adverse impacts that membrane scaling, membrane fouling, membrane degradation and the like impose on the efficiency of removing solutes from aqueous water streams. More recently, however, advancements in technology have made membrane separation a more commercially viable technology for treating aqueous compositions suitable for use in industrial and residential water treatment processes.
- small treatment plants such as those using improved long vertical shaft bio-reactors that provide tertiary treatment, could be strategically placed throughout the urban areas and could be privately owned and operated without municipal involvement. In low demand periods, they could discharge directly into the surface water drains, thereby substantially reducing loads on municipal plants.
- the improved long vertical shaft bio-reactors accomplish BNR treatment in a single integrated bioreactor that uses sequential zones, each dedicated to a specific part of the total treatment. Therefore each zone may be optimized individually.
- Technological advances in membrane separation, processing, and treatment technologies have been occurring at a rapid pace. The flux rate of membranes (flow rate per sq. feet of membrane surface) has been increasing while the cost per sq. feet has steadily decreased.
- the cleaning frequency depends on the type of membranes and their operating environment, and is typically as frequent as every few months.
- the existing reactors typically are not operational during membrane cleaning, causing a temporary and reoccurring loss of wastewater treatment capacity. Further, cleaning often involves use of expensive, specialized chemicals requiring compliance with environmental regulations in use and disposal.
- the invention provides methods and apparatus having improved through-put and operating life of submerged membranes used in biological treatment of waste waters, and increased time between cleaning and maintenance of the membranes. More specifically, the invention relates to membrane separation methods and devices employing a selective, semi-permeable, microporous, or other partitioning membrane for processing, refining, and/or treating liquid compositions, for example membrane waste-water purification processes and apparatus. Other aspects of the invention improve diffusion of a gas in a liquid by creating a substantially uniform pressure differential between opposite sides of a membrane. [44] Within one aspect of the invention a submerged membrane assembly and associated methods and apparatus are provided .
- the submerged assembly typically includes a membrane having at least a first surface and a second surface, which most often comprise opposing faces of a planar membrane.
- the opposing surfaces of the membrane are square or rectangular, and the membrane has a vertical axis (e.g., a vertical defined by one side of a square-configured membrane or an elongated side of a rectangular membrane).
- the membrane is permeable between the first and second surfaces by molecules of less than a predetermined size.
- the submerged membrane assembly includes a first fluid compartment that contains a first fluid having a first specific gravity in fluid communication with the first membrane surface.
- the assembly also includes a second fluid compartment that contains a second fluid having a second specific gravity in fluid communication with the second membrane surface.
- the membrane assembly typically includes means for imposing a differential hydraulic head between the first fluid contained in the first compartment and the second fluid contained in the second compartment, and means for changing the second specific gravity.
- the differential hydraulic head imposing means may include the first fluid compartment, wherein the first fluid compartment defines a first column height, and the second fluid compartment, wherein the second fluid compartment defines a second column height.
- the second column height may be selected relative to the first column height to produce a selected pressure differential across the membrane along the vertical axis of the membrane at the first specific gravity and a changed second specific gravity (i.e., the second specific gravity altered from an initial second specific gravity value to the changed second specific gravity value by operation of said means for changing the second specific gravity).
- the first column height and the second column height may each be established solely by gravity and construction and design of the first and second fluid compartments (typically by having an outflow or overflow port or opening in the second fluid compartment that is lower in correspondence to the membrane vertical axis than a fluid column height in the first fluid compartment).
- the differential hydraulic head imposing means may alternatively include a means for applying a pressure differential between the first and second fluid compartments. For example, a negative pressure generating means or vacuum may be applied to the second compartment or fluid to generate a reduced pressure in the second fluid compared to fluid pressure of the first fluid in the first compartment. Alternatively, a positive pressure generating means or pressurizing device may be applied to the first compartment or fluid to generate an elevated pressure in the first fluid compared to fluid pressure of the second fluid in the second compartment.
- the second specific gravity changing means may include a means for directly or indirectly introducing gas into the second fluid in the second compartment.
- gas can be directly dissolved in the second fluid or directly introduced into the second fluid in the form of bubbles, thereby reducing the second specific gravity to the desired, changed second specific gravity value.
- the first fluid contains a dissolved gas, and gas is introduced from the first fluid to the second fluid by passing through the membrane from the first side to the second side, either in solution or in the form of microbubbles or larger gas bubbles.
- dissolved gas (e.g., air or oxygen) in the first fluid passes between the first and second surfaces of the membrane and, at or near the second surface, nucleates to form gas bubbles that are incorporated in the second fluid.
- the gas introducing means thus involves transfer of dissolved gas from the first fluid into the second fluid, the gas can nucleate at or near the second membrane surface, which may include nucleation between the first and second membrane surfaces, at the second membrane surface, within the second fluid compartment, and/or dissolution of the gas within the second fluid.
- the gas introducing means can alternately achieve dissolved gas introduction from the first to the second fluid without dissolution of the gas and formation of bubbles, which can alternatively take place after the gas introduction or not at all.
- the dissolved gas of the first fluid may nucleate in response to a mechanical action imparted by passing through the membrane, in response to a pressure differential across the membrane, or in the second fluid in response to a difference in dissolved gas levels between the first fluid and the second fluid.
- the means for changing the second specific gravity may include a gas introduction port coupled to the second fluid compartment for introduction of gas into the second fluid. Gas can be introduced into the second fluid via this gas introduction port in the form of pressurized gas or in other forms, for example by introducing a gas-saturated fluid that mixes with the second fluid.
- the submerged membrane assembly includes a membrane having a first surface, a second surface, and a vertical axis, and which is permeable between the surfaces by molecules of less than a predetermined size.
- the assembly further includes a first fluid compartment in fluid communication with the first membrane surface that contains a first fluid having a first specific gravity at a first column height, a second fluid compartment in fluid communication with the second membrane surface that contains a second fluid having a second specific gravity at a second column height, and means for changing the second specific gravity.
- the second column height selected relative to the first column height to produce a selected pressure differential across the membrane along the vertical axis at the first specific gravity and the changed second specific gravity.
- the second specific gravity changing means may include a gas added to the second fluid, and the gas may be added by direct or indirect introduction of gas into the second fluid (typically in bubble form, but optionally in an initially dissolved form).
- the second specific gravity changing means includes a gas added to the second fluid by a dissolved gas of the first fluid permeating through the membrane and nucleating proximate to, or within, the second fluid.
- the gas may nucleate at or near at least a portion of the second surface of the membrane and optionally impart a desired scouring action on the membrane by nucleation (either between the first and second membrane surfaces in the event nucleation occurs within the membrane, or more typically at or near the second membrane surface) and/or by the mechanical effects of bubbles rising in the second fluid.
- the membrane assembly may optionally include a gas inlet port coupled to the second fluid compartment for direct introduction of gas (e.g., dissolved in a fluid, or in pressurized gas form) into the second fluid.
- gas e.g., dissolved in a fluid, or in pressurized gas form
- the assembly may further include a fluid collector that collects fluid from the second compartment, for example through an overflow port at or near the second fluid column height.
- the first fluid compartment may be a head tank or a saddle tank of a vertical bioreactor or other wastewater treatment apparatus.
- the membrane assembly of the invention typically includes a semi-permeable membrane that excludes particle exchange between the first and second surfaces (permeation) by particles of a size greater than a selected size indicated for the processed (effluent) water.
- the selected membrane pore size will be less than or equal to about 2 microns, more typically less than or equal to 0.5 microns, and often less than or equal to 0.1 micron.
- the membrane may include any of a variety of commercially available membranes for use in wastewater treatment applications, for example a flat plate membrane, or a hollow fiber membrane.
- the submerged membrane assembly includes a membrane having a first surface, a second surface, and a vertical axis, and is permeable between the first and second surfaces by molecules of less than a predetermined size.
- the assembly includes a first fluid compartment in fluid communication with the first membrane surface which contains a first fluid having a first specific gravity at a first column height.
- the assembly also includes a second fluid compartment in fluid communication with the second membrane surface which contains a second fluid having a second specific gravity at a second column height.
- the second fluid contains, or is altered to contain, a gas in an amount sufficient to adjust the second specific gravity to more closely approximate the first specific gravity.
- the gas contained in the second fluid is in the form of gas bubbles.
- a fluid collector is fluidly connected to the second compartment at the second fluid column height to collect fluid from the second compartment.
- the second column height is selected relative to the first column height to produce a selected pressure differential across the membrane along the vertical axis.
- the first fluid compartment further may include a first fluid outflow at the first column height.
- the first fluid may include dissolved gas.
- the gas in the second fluid may include bubbles formed by a dissolved gas of the first fluid that has permeated the membrane and nucleated (within or proximate to the second fluid, for example by nucleating at or near the second membrane surface). A gas bubble rising in the second fluid may impart a cleaning action on the second membrane surface.
- the second fluid compartment may include a gas inlet port to introduce gas directly into the second fluid (as an alternate, or complementary gas introduction means to gas that permeates between the first and second membrane surfaces from the first fluid.
- the first column height and the second column height may be established without a mechanical device, e.g., solely as determined by gravity, or by application of negative pressure to the second fluid or positive pressure to the first fluid.
- membrane run time can be extended by adding CO2 to the first and/or second fluids, which is also desirable for pH adjustment of the water.
- Industrial filters for example filters to remove sediment and precipitated protein from chilled beer, this will also be advantageous for recarbonation prior to bottling.
- Inert gas filtration such as gasoline purification using nitrogen gas, is also amenable to optimization using the methods and devices of the invention.
- a gas recovery system is provided downstream of the membrane, and a repressurization system may also be employed.
- Nitrous oxide may also be employed as an added gas (e.g., as a gas introduced into the second fluid) to yield desired fuels/additives.
- inert gases such as nitrogen, argon, helium, carbon dioxide
- active gasses such as methane
- Some gasses are sensitive to pH changes. For instance, bicarbonate of soda dissolves in water without pressure but a shift in pH will release CO2 in the same fashion that pressure changes do.
- Other fluid processing technologies to which the methods and devices of the invention can be applied include, for example, desalinization plants, biotechnical and biomedical separation procedures (e.g., dialysis of blood and other body fluids), and environmental decontamination processes (e.g., oil and other petroleum contaminant removal from marine and fresh water sites).
- methods for treating fluids by membrane separation employ a selective, semi-permeable, microporous, or other partitioning membrane for processing, refining, and/or treating liquid compositions, for example membrane waste-water purification processes and apparatus.
- These methods include containing a first fluid having a first specific gravity, containing a second fluid having a second specific gravity, separating the first fluid from the second fluid with a permeable membrane having a first surface in fluid communication with the first fluid, a second surface in fluid communication with the second fluid, the membrane further having a vertical axis and being permeable between the surfaces by molecules of less than a predetermined size.
- the method further includes imposing a differential hydraulic head (e.g., passively by gravity and differential chamber overflow levels, or actively by application of positive or negative pressure as described herein) between the first fluid and the second fluid, adjusting the second specific gravity (typically by introduction of gas), and collecting the second fluid.
- Imposing the differential hydraulic head may further include containing the first fluid at a first column height, and containing the second fluid at a second column height, wherein the second column height is selected relative to the first column height to produce a selected pressure differential across the membrane along the membrane vertical axis at the first specific gravity and the adjusted second specific gravity.
- Another aspect of the invention provides a method of treating a fluid by membrane separation employing a selective, semi -permeable, microporous, or other partitioning membrane for processing, refining, and/or treating liquid compositions, for example membrane waste-water purification processes and apparatus.
- the method includes containing a first fluid having a first specific gravity at a first column height, and containing second fluid having a second specific gravity at a second column height.
- the method includes separating the first fluid from the second fluid with a permeable membrane having a first surface in fluid communication with the first fluid, and a second surface in fluid communication with the second fluid.
- the membrane has a vertical axis and is permeable between the surfaces by molecules of less than a predetermined size.
- the method further includes adjusting the second specific gravity to more closely approximate the first specific gravity in value.
- Alternate normalization of specific gravities between the first and second fluids can be achieved in other ways, for example by introduction of non-gaseous solutes into the first fluid.
- the second specific gravity is adjusted to within approximately +/- 5 percent of the first specific gravity (i.e., to a value that is 95% of the value of the first specific gravity).
- the second specific gravity is adjusted to within approximately +/- 2.5 percent of the first specific gravity.
- the method also includes production of a selected pressure differential across the membrane along its vertical axis at the adjusted second specific gravity, for example by providing or selecting a second column height that differs from the first column height.
- the method further includes collecting the second fluid, for example by overflowing or off-draining the second fluid as a processed effluent.
- Another aspect of the invention provides an improved vertical shaft bioreactor and associated methods for treatment of wastewater.
- the vertical bioreactor and associated methods are as described herein, above.
- the bioreactor receives an influent of wastewater containing biodegradable matter for treatment and produces an effluent flow which is directed to a submerged membrane assembly of the invention.
- the improvement in the bioreactor includes a membrane-adapted head tank that functions as a normal vertical shaft bioreactor head tank but is modified to receive and contain the effluent flow and removably receive the submerged membrane.
- the submerged membrane includes a permeable membrane having a first surface, a second surface, and a vertical axis, and which is permeable between the surfaces by molecules of less than a predetermined size.
- the first membrane surface is in fluid communication with the effluent flow in the head tank
- the second membrane surface is in fluid communication with a second fluid having a second specific gravity and contained in a second fluid compartment.
- the improvement includes a means for imposing a differential hydraulic head between the effluent flow contained in the tank and the second fluid contained in the second fluid compartment, and a means for adjusting the second specific gravity.
- the improvement also includes a fluid collector that collects the second fluid.
- the invention provides an improved bioreactor for treatment of wastewater, the bioreactor receiving an influent of wastewater containing biodegradable matter for treatment and producing effluent flow having a first specific gravity.
- the improvement includes a tank that receives and contains the effluent flow at a first column height, and that removably mounts a submerged membrane assembly, and a fluid collector that collects the second fluid.
- the submerged membrane assembly includes a permeable membrane having a first surface, a second surface, and a vertical axis, and which is permeable between the surfaces by molecules of less than a predetermined size.
- the first membrane surface is in fluid communication with the effluent flow.
- a second fluid compartment (separated by the membrane from the head tank) contains a second fluid having a second specific gravity at a second column height, and the second membrane surface is in fluid communication with the second fluid.
- the improvement further includes a means for adjusting the second specific gravity.
- the second column height is selected relative to the first column height to produce a selected pressure differential across the membrane along the vertical axis at the changed second specific gravity. A portion of the contained effluent flow may be exposed to a normal atmospheric pressure.
- the invention provides a submerged membrane gas diffusion apparatus.
- the apparatus includes a membrane having a first surface and a second surface, and a vertical axis, and which is permeable between the surfaces by molecules of less than a predetermined size.
- the apparatus includes a first containment member, typically a tubular containment member, having a bubble capture aperture, a first membrane mounting portion in fluid communication with the first surface of the membrane, and a first chamber in fluid communication with the first membrane mounting portion and the bubble capture aperture, the chamber including a rising gas bubble capture portion proximate to the bubble capture aperture and having a first vertical length.
- the apparatus further includes a second containment member, typically a tubular containment member, having a gas release aperture, a second membrane mounting portion in fluid communication with the first surface of the membrane, and a second chamber in fluid communication with the second membrane mounting portion and the gas release aperture, the chamber including a gas reservoir portion proximate to the gas release aperture and having a second vertical length that is less than the first vertical length.
- a second containment member typically a tubular containment member, having a gas release aperture, a second membrane mounting portion in fluid communication with the first surface of the membrane, and a second chamber in fluid communication with the second membrane mounting portion and the gas release aperture, the chamber including a gas reservoir portion proximate to the gas release aperture and having a second vertical length that is less than the first vertical length.
- the first and second containment members can be constructed and dimensioned according to a variety of designs to function in the manner disclosed herein below, whereas the tubular design described herein is provided for exemplary purposes only.
- the assembly includes a membrane having a first surface and a second surface, and a vertical axis, and which is permeable between the surfaces by molecules of less than a predetermined size.
- the assembly includes an aeration compartment that contains a first fluid and rising bubbles of a gas, a static fluid compartment that contains a second fluid, and a fluid treatment compartment that contains a fluid to be treated in fluid communication with the second membrane surface.
- the assembly also includes a first tubular member having a bubble capture aperture located in the aeration compartment, a first membrane mounting portion in fluid communication with the first surface of the membrane, and a first chamber in fluid communication with the first membrane mounting portion and the bubble capture aperture, the chamber including a rising gas bubble capture portion proximate to the bubble capture aperture and having a first vertical length.
- the assembly further includes a second tubular member having a gas release aperture located in the static fluid compartment, a second membrane mounting portion in fluid communication with the first surface of the membrane; and a second chamber in fluid communication with the second membrane mounting portion and the gas release aperture, the chamber including a gas reservoir portion proximate to the gas release aperture and having a second vertical length that is less than the first vertical length.
- a further aspect of the invention provides a method for diffusing a gas into a target fluid.
- the method includes permeably separating the target fluid from the gas with a membrane, the membrane having a first surface in contact with the gas, a second surface in contact with the target fluid, and which is permeable between the surfaces by molecules of less than a predetermined size.
- the method also includes capturing the gas by receiving a first fluid that includes rising bubbles of the gas into a bubble capture aperture of a first chamber, the first chamber including a rising gas bubble capture portion proximate to the bubble capture aperture and having a first vertical length.
- the method further comprises imposing a hydraulic head on the gas in the first chamber using a buoyancy of the gas in the first fluid to displace the first fluid from the bubble capture portion.
- Imposition of the hydraulic head forces the gas to flow between the gas bubble capture portion of the first chamber and a first membrane mounting portion of the first chamber, which is in fluid communication with the first surface of the membrane.
- the method further includes permeation of at least a portion of the gas through the membrane and into the target liquid in response to imposition of the hydraulic head.
- the gas flows between a second membrane mounting portion, which is in fluid communication with the first surface of the membrane, and a second chamber.
- the second chamber has a gas reservoir portion proximate to a gas release aperture and a second vertical length that is less than the first vertical length. The method automatically releases the gas through the gas release aperture when the hydraulic head displaces a second fluid from the gas reservoir portion.
- Figure 1 is a diagrammatic vertical section through one embodiment of a bioreactor according to the invention for use in waste water treatment.
- Figure 2 is a diagrammatic vertical section through one embodiment of a bioreactor according to the invention for use in waste water treatment. This embodiment features a conventional sedimentation clarifier followed by an aerated polishing biofrlter followed by an ultra violet light disinfection chamber and back wash tank.
- Figure 3 is a diagrammatic vertical section through one embodiment of a bioreactor according to the invention for use in waste water treatment. This embodiment features an integrated circular sedimentation clarifier surrounding the circular zone 2 head tank which surrounds the circular zone 1 head tank. All three tanks being concentric with the vertical reactor. A provision is made to return settled activated sludge by gravity to either zone 1 or zone 2.
- FIG 4 is a diagrammatic vertical section through one embodiment of a bioreactor according to the invention for use in waste water treatment.
- This embodiment features moving bed media circulating in zone 2 or alternately fixed media suspended in the head tank of zone 2.
- Figure 5 is a diagrammatic vertical section through one embodiment of a bioreactor according to the invention for use in waste water treatment.
- This embodiment features a pressurized head tank, an off-gas collector means, said off-gas driving an air lift influent pump required to overcome said head tank pressure, a membrane filtration cartridge operating under pressure to separate biomass from liquid and a clean water ultraviolet (UV) disinfecting chamber also serving as back wash storage for membrane backwashing.
- UV water ultraviolet
- Figure 6 is a diagrammatic vertical section through one embodiment of a bioreactor according to the invention for use in waste water treatment. This embodiment features an integrated clarifier followed by an aerated polishing biofrlter followed by an ultra violet light disinfection chamber and filter back wash tank.
- Figure 7 is a diagrammatic vertical section through one embodiment of a bioreactor according to the invention for use in treatment of biosolids. This embodiment features an inter zonal self batching air lock at the bottom of the bioreactor. In this case, zone 2 head tank is concentric and internal to zone 1 head tank.
- Figure 8 is an isometric vertical section through one embodiment of the bioreactor according to the invention for use in waste water treatment. This section shows typical arrangement of various channels and the position of the aeration distribution header, zone 1 head tank, zone 2 head tank and an integral sedimentation clarifier.
- Figure 9 is an isometric vertical section of a portion of reactor internal channels and downcomer flanged and bolted. This figure shows a downcomer expansion tool which is used during insertion of the assembly into the reactor casing.
- Figure 10 is a diagrammatic end view of the reactor internal section showing the downcomer and radial baffles.
- the element in the center represents the expansion tool in its relaxed position.
- the downcomer is also in its relaxed position.
- the removable expansion tool which is operated by actuation means from the ground level, is inserted in its relaxed position during fabrication.
- Figure 11 is a diagrammatic end view of the reactor internal section showing the downcomer forced out of round by the expansion tool.
- the radial baffles connected to the downcomer are shown relaxed from the casing wall, allowing easy insertion.
- Figure 12 provides a graphical representation of the EPA time and temperature requirements for class A bio-solids.
- Figure 13 provides an exemplary block flow diagram of the present invention adapted to produce recycle quality water, Class A bio-solids, and clean odorless off-gas.
- Preliminary treatment A Fine screens
- B Solids hopper-Screenings and washed grit C Hyrdaclone degritter Waste water BNR treatment as described herein
- D Deoxygenation unit (channel 32+40 )
- E Denitrification (head tank 16 )
- Anoxic/anaerobic unit (channel 12 )
- Aerobic unit zone 1 channel 80 )
- H Nitrification zone 2 head tank, 110 and 82
- I Sedimentation clarifier 120
- J Waste activated sludge float thickener K
- K Alum or ferric chloride feeder
- M Flocculating tank
- N Cloth disk filter 0 Chlorination
- Ultraviolet disinfection Q
- Backwash pump Thermophilic
- Figures 14-1 through 14-7 illustrate a presence of nucleated dissolved air or applied dispersed air on the clean water (or permeate) side of a permeable membrane, creation of an equalized pressure differential along a vertical axis of a submerged permeable membrane assembly, and scouring the clean water side of the membrane with rising bubbles, according to an embodiment of the invention.
- Figure 15 is a top perspective view of a bioreactor head tank, and a membrane bioreactor head having plurality of saddle tanks mounting membrane bioreactor assemblies, according to an embodiment of the invention.
- Figure 16A is a top view of the saddle tank of the membrane bioreactor head of Figure 15 illustrating a top membrane bioreactor assembly that includes a plurality of flat plate permeable membranes, according to an embodiment of the invention
- Figure 16B is a cross-sectional side view of the bioreactor head tank of Figure 15, and of the saddle tank having a stack of four membrane bioreactor assemblies positioned vertically above each other, according to an embodiment of the invention.
- Figure 17 illustrates a folded saddle tank system that includes a first folded saddle tank and a second folded saddle tank that collectively carry the membrane assemblies, according to an embodiment of the invention.
- Figure 18 illustrate results of a series of membrane throughput tests conducted on bench test apparatus of under varying condition and levels of diffused gas in water, according to an embodiment of the invention.
- Figure 19 illustrates results of a series of temperature vs. viscosity tests conducted on the bench test apparatus.
- Figure 20 illustrates a cross-sectional view of a gas diffusion apparatus that maintains equal pressure differentials across a plurality membranes in a gas-liquid system, according to an embodiment of the invention.
- Figure 21 illustrates several aspects of the gas diffusion apparatus of Figure 20, according to an embodiment of the invention.
- the instant invention provides a long vertical shaft bioreactor 10 for wastewater treatment.
- the bioreactor of the invention shares a number of structural and functional characteristics with previously described vertical shaft bioreactor systems (see, e.g., U.S. Pat. Nos. 4,279,754, 5,645,726, and 5,650,070 issued to Pollock, each incorporated herein by reference), but departs in several important and novel aspects therefrom.
- the vertical shaft bioreactor 10 of the invention features a wastewater circulation system which includes two or more substantially vertical channels, including at least one downflow channel, or downcomer channel 12, fluidly interconnected in a circuitous, open or closed, path with at least one upflow channel, or riser channel 14.
- the downcomer and riser channels are typically interconnected at their upper ends via a surface basin or head tank 16, which may be open or closed, and at a lower junction corresponding to a mix zone 18 situated below a lower port or aperture 20 of the downcomer.
- the downcomer 12 and riser 14 channels are typically defined by separate conduits, for example by separate, cylindrical-walled pipes. Alternatively, they may be defined as interconnected compartments or channels sharing one or more walls, for example as parallel channels separated by partitioning structures (e.g., radial partitions or septa) within an elongate, compartmentalized reactor vessel or frame.
- the downcomer and riser channels are preferably oriented substantially parallel to one another, for example in a side-by-side or coaxial relative configuration.
- the downcomer 12 and riser 14 channels are defined as separate conduits over at least a portion of their lengths.
- the downcomer channel is defined by a separate, cylindrical-walled downcomer conduit (e.g., a steel pipe) 22 nested coaxially within a larger diameter, cylindrical walled riser conduit 24 (which will often correspond to an outer wall or casing of the entire bioreactor assembly).
- a separate, cylindrical-walled downcomer conduit e.g., a steel pipe
- cylindrical walled riser conduit 24 which will often correspond to an outer wall or casing of the entire bioreactor assembly.
- the wastewater treatment bioreactor 10 of the invention is constructed to service a small residential community of about 5,000 population.
- two parallel bioreactors are installed in accordance with EPA redundancy requirements, in vertical in-ground shafts bored using conventional drilling technology.
- the bioreactor of the invention can be constructed, configured with secondary features, or adjusted to provide the secondary and/or tertiary levels of treatment, listed below. a) Secondary treatment (BOD and TSS removal) only. b) Secondary treatment with nitrification of ammonia (conversion of ammonia to nitrate). c) Secondary treatment with nitrification and denitrification (removal of ammonia and nitrate).
- the secondary treatment of a) above may be completely aerobic both in the zone 1 head tank 16 and downcomer channel 12 of zone 1, and in the zone 2 upflow channel(s) 82 and head tank 15. This configuration requires a shaft of about 30 inches diameter and 250 feet deep, a zone 1 head tank of about 6 feet diameter x 10 feet deep and a concentric zone 2 head tank of about 12 feet diameter x 10 feet deep.
- the concentric clarifier is about 28 feet diameter x 10 feet deep and is fitted with a rake mechanism to assist in sludge removal.
- this reactor will treat residential sewage from at least a 2,500 member human population and produce ⁇ 30 mg/L TBOD and ⁇ 30 mg/L TSS.
- the secondary treatment process of b) is also completely aerobic and of the same general dimensions as a) except the zone 2 head tank is about 16 feet in diameter. A larger portion of the air originating at the bottom of zone 1 is diverted into zone 2 using a diverter mechanism 84.
- the treatment system of c) above is designed for anoxic conditions in the head tank and downcomer of zone 1. In certain embodiments, this reactor will treat residential sewage from at least a 2,500 member human population and produce ⁇ 1 mg/L ammonia-N, ⁇ 15 mg/L TBOD, and ⁇ 15 mg/L TSS.
- Only a small fraction of air from the lower portion of zone 1 is diverted into the zone 1 upflow channel(s) 40.
- zone 1 In addition to raw influent feed in the upper end of zone 1, recycled nitrified effluent or return activated sludge from the clarifier or, alternatively from zone 2 head tank, is added to the raw influent to create the anoxic conditions.
- zone 1 head tank In this treatment process the reactor is enlarged to approximately 36 inches in diameter, zone 1 head tank is increased to about 8 feet diameter, zone 2 head tank is increased to about 16 feet in diameter.
- the concentric clarifier has an outside diameter of about 30' and is fitted with a rake mechanism.
- this process will treat residential sewage from a human population of 2,500 or greater to ⁇ 5 mg/L TKN, ⁇ 10 mg/L TBOD, and ⁇ 10 mg/L TSS.
- the treatment system of d) above is the same general dimension of c).
- alum of ferric chloride may be added into zone 2 for chemical precipitation of phosphorus. It is usually uneconomic to use only a biological phosphorus removal process alone to achieve a high degree of phosphorus removal (e.g., 2-3 mg/L residual) on small plants, since a pre-fermentation step to produce volatile fatty acids (VFA) may be required.
- Typical characteristics of effluent from this plant are: TBOD ⁇ 10 mg/L; TSS ⁇ 10 mg/L; TN ⁇ 5 mg/L; PO4 ⁇ 1 mg/L.
- zone 1 surrounds zone 2, or may be adjacent to zone 2 throughout the major portion of the reactor length and zone 2 head tank 15' surrounds the zone 1 head tank 16'.
- Zone 1 and zone 2 are hydraulically connected at the bottom of zone 2 through a self batching air lock device which precludes zone 1 contents from entering zone 2 while processing each batch.
- the thermophilic aerobic digester volume of configuration e) is about one half the volume of the wastewater treatment reactor producing the biomass. Because sludge storage provision is more economic to build than redundancy in reactors, only one digester is required for two treatment reactors. Accordingly the small town of about 5000 people requires 2 treatment reactors and 1 sludge digester all of the same size.
- the superior channels can be effective between 150 and 50 feet deep, preferably 80-88 feet which is the standard length of two joints of double random length pipe.
- air compressors are readily available in 100, 125 and 150 psi models corresponds to shaft depth of 200, 250 and 300 feet.
- airlift bioreactors have been built between 60 feet and 500 feet depths, a more common range is 150 to 350 feet depth and a range of 200 feet to 300 feet is now most common.
- Conventional water well rigs can drill holes up to about 48 inches and deep foundation equipment for pilings can drill up to about ten feet in diameter.
- Augers (where geology permits) can drill up to about 20-feet diameter but are limited to about 200-feet depth.
- Mined shafts can be up to 30 feet diameter and of virtually any depth.
- Small municipal plant reactors (5000 population) will typically be placed with conventional water well rigs and preferably be about 24 to 48 inches in diameter.
- Larger communities (10,000-50,000 population) may require shafts of 5 to 10 feet diameter x 200 feet depth placed by deep foundation piling machines and augers, whereas very large industrial plants (e.g. pulp mills) may require shafts placed by mining techniques.
- the long vertical shaft bioreactor 10 of the invention receives influent, typically wastewater or sludge, through an influent conduit 30 which introduces the influent into an influent channel 32.
- the influent flows downward to the bottom of the influent channel, where it exits through a shielded influent port 34 and combines with upflow in a zone 1 upflow channel 40 delineated at its lower end by the influent port.
- the influent port is upturned or otherwise shielded to prevent admission of bubbles from below the zone 1 upflow channel from entering the influent channel.
- the influent channel 32 can optionally accept recycle flow of liquor from the head tank 16 portion of zone 1 of the bioreactor 10.
- This flow is regulated by a zone 1 recycle flow regulator 50, for example a manual or motor-actuated baffle, valve or other flow-regulating apparatus.
- the influent flow through the zone 1 recycle regulator 50 is ordinarily throttled via an influent flow throttling control mechanism.
- This can include, for example, a system control unit 51 (e.g., a system control microprocessor) operatively linked to a valve or baffle actuator 52 and an optional flow sensor 53 or 53' for determining influent and/or zone 1 recycle flow or alternatively dissolved oxygen DO probe 49 to monitor oxygen levels.
- Control of influent flow through the regulator functions in part to adjust the air lift in zone 1 upflow channel 40 and facilitate gravity influent flow.
- the combined flow in the zone 1 upflow channel contains some anoxic air bubbles (see below) and is therefore lighter than the fluid in influent channel 32, and rises.
- anoxic air bubbles is meant bubbles predominately containing gasses other than useable oxygen.
- Flow in the zone 1 upflow channel 40 traverses a horizontal degas plate 54 and descends substantially free of entrained bubbles in the downcomer channel 12 under gravity and enters the main riser channel 14 in the vicinity of the mix zone 18, where it is intensively aerated.
- the compressed air or other oxygen-containing gas or liquid serving as the oxygenation source for the bioreactor 10 is typically delivered through one or more dedicated oxygenating lines, typically compressed air lines 62.
- a dedicated compressed air line is connected to a compressed air supply at the surface and runs downward parallel to the riser channel (e.g., nested within the riser conduit 24) extending to an oxygenation port, typically an air delivery port 64, that opens in fluid connection with the riser channel 14.
- the air delivery port 64 is generally positioned beneath the air distribution header 60 to release the compressed air for dispersal by the header, as described above.
- compressed air (or other oxygen-containing gas or liquid) is optionally, or additionally, delivered within the bioreactor by a dual-service aeration/solids extraction line 66.
- Functioning of this line can be controlled, e.g., by a system control unit 51 as described above, to optionally deliver compressed air or other oxygen-containing gas or liquid and, in a second operation mode, serve as a waste solids extraction line 66 to purge waste solids from a sump 67 portion of the reactor located at the bottom of the riser channel.
- the waste solids extraction line extends from the surface (e.g., from a surface-located, waste-solids extraction/flotation reservoir) to a aeration/waste solids extraction port 68 opening in fluid connection with the sump. Solid particles that settle into the sump will accumulate over a period of hours of operation. For the majority of the bioreactor' s operation time, the aeration/solids extraction line is continuously purged by flow of compressed air, and therefore the sump 67 is substantially mixed and aerated and forms a functional part of the mix zone 18. Periodically, the aeration/extraction line can be depressurized, whereby settled solids within the sump will rush to the top of the reactor to be purged therefrom.
- the improved vertical shaft bioreactor 10 features two simultaneously-operating aeration lines or ports to enhance the formation of small, dispersed bubbles to generate upflow currents and supply process air within the bioreactor.
- the use of two aeration lines is exemplified by the dedicated compressed air line 62 and dual-function aeration/solids extraction line 66, which each operate at least for a majority of the bioreactor process time in a compressed air delivery mode.
- the two lines in concert provide a cooperative, multiple source compressed air injection mechanism of the invention, which serves to enhance the turbulence and small bubble- forming capacity within the mixing zone 18 of the reactor, which is in turn expanded by the cooperation of multiple compressed aeration lines or ports.
- a first aeration line opening exemplified by the air delivery port 64 of dedicated air line 62, is positioned below the air distribution header 60 and above a second aeration line opening, exemplified by aeration/extraction port 68 of the dual-function aeration solids extraction line.
- Compressed air released from this lower aeration port stimulates fluid mixing and bubble formation near the bottom of the riser channel 14 to set up a first circulation path or vector.
- the resultant circulating fluid-bubble mixture impinges upwardly and/or transversely against mixed fluid and bubbles generated by the introduction of compressed air from the first, upper air line 62. This results in increased shear forces and the production of smaller air bubbles in an enlarged mixing zone, compared to the results achieved by operation of a single aeration line (see, Figure 1).
- certain embodiments of the invention incorporate a modified (typically stepped, chambered, or baffled) header, or a multi-component header complex, to augment the enhanced mixing/bubble forming mechanism provided by multiple, interactive aeration sources.
- a second, cooperating shear header 70 is mounted within the riser chamber 14 below the main bubble distribution header 60 and works in conjunction with two, vertically tiered aeration sources generally as described above.
- the shear header can be any flow diverting or channeling device that enhances an upward and/or transverse or radial flow component within the mixing zone generated by a second, lower-positioned aeration source (exemplified by the aeration/solids extraction port 68).
- the shear header comprises an internally stepped draught tube ( Figure 1) attached by vertical struts to the underside of the distribution header. Compressed air fed into the aeration/solids extraction line 66 causes an air lift effect in the stepped draught tube, thus establishing a separate circulation pattern or vector in the lower portion of the mix zone as shown in Figure 1.
- This upward and/or transverse or radial circulating flow impinges against mixed fluid and bubbles generated by the introduction of compressed air from the first, upper air line 62 near the perimeter of the distribution header, which interaction is regulated in part by air delivered though the aeration/solids extraction port, while the balance of process air is delivered though the dedicated air delivery port 64.
- the novel interactive flow mechanism and cooperative header design of the invention generates substantially smaller bubbles, typically about one quarter to one half inch, often less than one quarter inch, down to as small as one-fifth to one-eighth inch or less in diameter.
- bubbles about 2mm are the optimum diameter for mixing and oxygen transfer.
- bubbles of this size do not form naturally at an orifice without some mechanism for shearing the bubble.
- the bubble size is determined when the buoyancy force equals the attraction forces at the orifice and bubble size is not necessarily a function of orifice size. Since bubbles of this size range have a rise rate of about 0.8-1.0 feet/sec. in water, a downward circulation velocity of greater than 1 feet/sec. in the vicinity of the serrated skirt 60 will cause the bubble to be sheared from the orifice.
- the circulation velocity is regulated by the amount of air injected in line 68 and can be adjusted independently of the air being applied at orifice 64. Samples extracted periodically in line 66 can be measured for dissolved oxygen. The circulation velocity between aerator elements 60 and 70 can be adjusted to maximize the oxygen transfer. This novel design provides enhanced mixing and bubble distribution without unacceptable risk of clogging.
- Yet additional embodiments of the invention are distinguished by virtue of their novel features for channeling, circulating, and segregating fluid, air and/or biomass within the reactor 10. These features are in turn variable, combinable in alternative reactor configurations, and/or adjustable within additional aspects of the invention — allowing use or modification of the reactor for different wastewater treatment applications and results.
- the bioreactor of the invention features a first treatment or processing "zone" designated zone 1, wherein the majority (e.g., greater than 80%, up to 90-95% or greater) of the primary reaction between waste, dissolved oxygen, nutrients and biomass (including an active microbial population), takes place.
- this zone is defined to include an upper circulating zone of the bioreactor comprising the surface basin or head tank 16, a primary reaction chamber 80 comprising a central volume of the riser channel 14, the downcomer channel 12, and the mix zone 18.
- the majority of the contents of the mix zone 18 represent a fluid-bubble mixture that is less dense than the fluid in the downcomer channel 12 and therefore circulates upwardly from the mix zone into the primary reaction chamber 80.
- Undissolved gas mostly nitrogen, expands to help provide the gas lift necessary to drive circulation of the liquor in the upper part of the reactor 10 in the patterns as shown by the arrows throughout the Figures.
- the products of this primary reaction are carbon dioxide and additional biomass which, in combination with unreacted solid material present in the influent wastewater, forms a sludge (or biosolids).
- upflow of fluid in the primary reactor channel 80 is segregated into multiple, smaller upflow channels in an upper section of the bioreactor 10.
- upflow from the primary reactor channel is diverted into at least two discrete superior upflow channels, as exemplified by the zone 1 upflow channel 40 and a zone 2 (typically operated as a polishing zone) upflow channel 82 depicted in Figure 1.
- zone 1 upflow channel 40 and a zone 2 (typically operated as a polishing zone) upflow channel 82 depicted in Figure 1.
- flow diversion from the primary reactor channel into multiple, superior channels is achieved by employing a fixed or adjustable diversion plate 84 or comparable flow diverting device that is anchored near the top of the primary reactor channel.
- the diversion plate 84 is configured and dimensioned to segregate the primary reactor channel 80 upflow into multiple superior channels.
- the diverter plate is configured and dimensioned to intercept and divert a larger fraction of total upflow volume of the fluid-bubble mixture from the primary reactor channel into a selected "aerobic" upflow channel, depending on the desired mode of operation of the bioreactor 10, as further explained below.
- the diverter plate features a vertical baffle 86 that facilitates segregation and channeling of the fluid-bubble mixture flowing upward in the primary reactor channel toward an upwardly angled, laterally or radially extending flow diverting extension 88 of the diverter plate that diverts a larger fraction of the total upflow volume of fluid and bubbles from the primary reactor channel into one or the other of the first zone upflow channel 40, or second zone upflow channel 82. Accordingly, a smaller fraction of the total upflow volume of fluid and bubbles is allowed to pass into the remaining superior upflow channel 40, thereby limiting as a primary process determinant the flow of aerated fluid into this remaining channel so as to contribute to generation of anoxic conditions in this channel, if desired.
- the diverter plate 84 can be positioned, shaped, dimensioned and/or adjusted to channel upflow of the fluid-bubble mixture from the primary reactor channel 80 into one or more superior channels to achieve higher aerobic environmental conditions in the selected channel(s), while limiting the upflow (particularly of high oxygen-containing fluid) into one or more superior channels selected for lower aerobic, even anoxic, environmental conditions.
- adjustable baffles 86 and 84 the following steady state functionality of adjustable baffles 86 and 84 is described. In Figure 1, 10 bubbles are depicted as rising uniformly at the top of zone 1 immediately below baffle 86.
- the baffle is adjusted so that 3 bubbles are segregated into area 39 and 7 are segregated into area 81.
- the oxygen demand and supply in the superior channels and head tanks can be calculated.
- the average BOD in the area 39 and 81 is about 10 mg/L and the average ammonia -N concentration to be removed is 15 mg/L (after ammonia used in cell synthesis) and the denitrified recycle flow is 1.75Q.
- baffle 86 can be adjusted to accommodate a wide range of load and flow criteria.
- the improved long vertical shaft bioreactor functions for multi-purpose waste treatment by providing aerobic digestion of BOD as well as single mixed liquor processing BNR treatment.
- the flow diverter 84 is constructed and configured as shown (compare alternate diverter configuration setting shown by phantom line 90) to divert a majority fraction of total upflow volume of the fluid-bubble mixture from the primary reactor channel into the zone 2 upflow channel 82, while limiting the upflow volume of fluid and bubbles from the primary reactor channel 80 into the zone 1 upflow channel 40.
- Volume ratio in influent channel 32 and flow down and into the zone 1 upflow channel (which intercepts only a small fraction of the bubbles from the primary reactor channel) can be finely controlled.
- zone 1 upflow channel compared to the lift and circulation in the zone 2 upflow channel in this diverter configuration.
- the residence time of the fluid mixture in the zone 1 upflow channel is therefore increased, and the oxygen transfer capability in zone 1 upflow channel 40 is reduced due to the reduced bubble upflow.
- the bubbles in the zone 1 upflow channel are mostly nitrogen, because the oxygen is largely consumed in the lower and middle part of zone 1 (particularly including the mix zone 18 and the primary reactor channel 80 below the diverter).
- the superior channel referred to as the zone 1 upflow channel 40 can be selected to provide an anoxic environment, achieved in part by the low relative influx of oxygen and the high oxygen demand of the raw influent stream.
- This anoxic zone continues throughout the circulation path between the zone 1 upflow channel and the downcomer channel 12, as approximately indicated by the arrows in Figure 2.
- a final step of BNR processing denitrification of nitrate initially contained in the mixture of fluid in the zone 1 upflow channel, occurs.
- the relative lower liquid upflow fraction thus segregated includes the majority of bubbles originating at the lower end of zone 1 (e.g., bubbles generated by the dedicated air line 62 and optional multi- purpose aeration/waste solid extraction line 66, functioning in concert with the bubble distribution header 60 and optional shearing enhancer mechanism exemplified by the shear header 70).
- This active, fluid-bubble mixture segregated into zone 2 by operation of the diverter 84 enters the zone 2 upflow channel, then mixes with vigorous re-circulating flow entering zone 2 through a zone 2 recirculation channel 110 (which recycles liquor from the zone 2 head tank 15).
- This recirculation flow is optionally regulated by a zone 2 recirculation flow regulator 112, for example a manual or motor-actuated baffle, valve or other flow-regulating apparatus.
- This recycle flow regulator is also optionally controlled by the system control unit 51 (e.g., system control microprocessor) operatively linked to a valve or baffle actuator 52 and optional flow sensor 53 for determining zone 2 recycle flow).
- nitrification of mixed liquor can be efficiently conducted and controlled within zone 2 of the bioreactor, in accordance with the above-described construction and operation details.
- Some of the mixed liquor from zone 2 may be discharged to a detached 120 or integrated 120' solids-liquid separator (clarifier) (see, e.g., Figures 2-4, and 6).
- Some of the mixed liquor from zone 2 may be returned to the influent channel 32, where it undergoes denitrification, as described above, and the cycle repeats.
- some clarified effluent may be returned to channel 32 during low flow periods, thereby removing more nitrogen compounds overall.
- influent, return clarified effluent e.g., recycled from a separate clarifier 120 or integrated clarifier 120'
- return activated sludge are combined in a preselected ratio to facilitate operation of the bioreactor 10.
- zone 1 activated sludge return channel 122 and a zone 2 activated sludge return channel 124 which receive activated sludge (e.g., via a sludge extractor line 126 connected to the clarifier) and direct the sludge into the zone 1 influent channel 32 or zone 2 recycle channel 110, respectively (see, e.g., Figures 2-4, and 8).
- flow regulators 50 operatively interconnected with valve or baffle actuators 52 and/or flow sensors, all of which are operatively integrated and controlled by one or more system control unit(s) 52.
- the selected mix ratio per volume of influent of typical municipal waste may be as high as 3 volumes of clarified effluent and 1 volume of return activated sludge to as low as 1 volume of clarified effluent and 1 volume of return activated sludge.
- Approximately 85% of total nitrogen will be converted to N 2 with 1.75 volumes of either clarified effluent or mixed liquor per volume of influent (see, e.g., Naohiro Taniguchi et al. report on air lift recirculation for nitrification and denitrification , R&D Division, Japan sewage works agency 1987, inco ⁇ orated herein by reference.) It should be noted, however, that some industrial wastes may require 100 or more recycled volumes per volume of influent.
- the system can readily inco ⁇ orate, or be coupled with, additional system features or components to enhance BNR process functions. Because the BOD is low in zone 2, growth of BOD-removing organisms is generally minimized, which allows nitrifying bacteria to dominate the biomass. In addition to this advantage, a substantial improvement in the rate of conversion of ammonium to nitrite and nitrate can also be realized by increasing the concentration of nitrifying bacteria.
- the BNR processes of the bioreactor can be substantially improved by including suspended media 130 that encapsulate or provide substrate for nitrifying bacteria within the recycling circulation path of zone 2 (see, also, T Lessel et al" réelle mit getauchten Festbettreaktorn fur die Nitrifkation" 38.settinggang, Heft 12/1991, Seite 1652 bis 1665, inco ⁇ orated herein by reference), which modification is facilitated by the novel relative positioning and interzonal separation between zone 1 and zone 2.
- the moving bed media can be prevented from escaping in the effluent, for example by simple screens.
- fixed media 132 can be secured within in the head tank to increase the biomass of microorganisms adapted for BNR processing.
- These modifications yield a superior BNR performance.
- the combination of a zone 2 regime that minimizes BOD-removing bacteria along with the increased attached growth biomass of nitrifying bacteria e.g. 15-20 g/L equivalent nitrifiers
- a single sludge extended aeration process typically contains 15-20% of nitrifying bacteria (by weight or population percentage of sludge mass).
- the biomass of nitrifiers can be expanded up to greater than 30%, often up to 60-70%, as much as 75-85% or more of nitrifiers in the system population.
- This relates to the relative exhaustion of BOD in this process stage and zone of the system, as well as to the effective use of fixed or circulating attachment media within zone 2.
- the bioreactor according to the invention for use in waste water treatment may inco ⁇ orate a conventional, stand-alone sedimentation clarifier 120.
- the bioreactor is further optionally fluidly connected with an aerated polishing biofilter 133 and/or an ultra violet light disinfection chamber 134 and/or back wash tank.
- line 136 returns backwash to the influent.
- Figures 3 and 8 illustrate an additional embodiment of the bioreactor 10 according to the invention — featuring an integrated circular sedimentation clarifier 120' surrounding a circular zone 2 head tank 15 which in turn surrounds a circular zone 1 head tank 16 (all three tanks being concentric in this vertical reactor). In these embodiments, settled activated sludge is returned by gravity to either zone 1 or zone 2.
- Alternate embodiments of the bioreactor 10 illustrated in Figure 4 feature moving bed media 130 circulating in zone 2 and, additionally or alternatively, fixed media 132 suspended in the head tank 15 of zone 2.
- FIG. 5 Another embodiment, as illustrated in Figure 5, inco ⁇ orates a pressurized head tank 135, and an optional off-gas collector 136 (see, e.g., U.S.Pat. No. 4,272,379 to Pollock, inco ⁇ orated herein by reference), for example with off-gas driving an air lift influent pump 137 required to overcome the head tank pressure, as well as an optional membrane filtration cartridge 138 (see, e.g., George Heiner et al 'Membrane Bioreactors" Pollution Engineering Dec 1999, inco ⁇ orated herein by reference) operating under pressure to separate biomass from liquid and a clean water, ultraviolet (UV) disinfecting chamber 139 also serving as back wash storage for membrane backwashing.
- an optional off-gas collector 136 see, e.g., U.S.Pat. No. 4,272,379 to Pollock, inco ⁇ orated herein by reference
- an optional membrane filtration cartridge 138 see, e.g., George Heiner et al
- Still other embodiments feature an integrated clarifier 120' fluidly connected to an aerated polishing biofilter 133 and an ultra violet light disinfection chamber 134 and filter back wash tank.
- the optimum biological air supply rate required for bio-oxidation process creates excessive "voidage" at the top of the reactor, comparable in the present case to the superior upflow channels exemplified by the zone 1 upflow channel 40 and zone 2 upflow channel 82. Excessive voidage produces undesirable slugging (water hammer), which can cause reactor damage attributed to vibration. The occurrence of slugging air voidage also signifies poor oxygen transfer characteristics within the circulating fluids.
- the invention addresses these problems in a number of ways, including by providing novel means for regulating circulation velocities and modulating gas content in selected parts or channels of the reactor.
- increasing velocity only reduces the operating efficiency of the reactor. Increased flow decreases bubble contact time and slows oxygen transfer, thus more aeration is required to optimize the process. Similarly, reducing aeration reduces reactor capacity.
- One proposed method for resolving air voidage and related problems is presented in U.S. Patent Application Serial No. 09/570,162, filed May 11 , 2000 (inco ⁇ orated herein by reference) describing the "VerTreat II" bioreactor.
- flow velocity is beneficially reduced by inco ⁇ oration of an orifice plate in the lower section of the riser channel.
- this solution does not substantially resolve the problem of slugging, and the orifice plate creates additional problems including risk of fouling and flow aberrations particularly in small municipal plants.
- the bioreactor 10 of the present invention resolves these problems in part by inco ⁇ orating a novel relative configuration of zone 1 and zone 2.
- the present invention can control flow and gas content in each zone, independently.
- Conventional prior art "Deep Shaft” reactors start slugging at a upflow velocity of about 2 feet per second.
- the above-noted VerTreat ⁇ reactors with orifice plates can operate down to about one and a quarter feet per second.
- this value can be dampened to as little as one quarter to one half feet per second in the lower part of the riser channel. At lower riser velocities, some heavier solid particles will settle into the sump 67. These solids are conveniently extracted, along with su ⁇ lus biomass (e.g., circulating within the shear header 70 and surrounding mix zone 18) when desired, by purging of the dual-pu ⁇ ose aeration/solids extraction line 66.
- su ⁇ lus biomass e.g., circulating within the shear header 70 and surrounding mix zone 18
- the invention provides substantially more efficient new features and methods for slowing velocity over prior art methods, which includes the ability to dilute the air lift stream in one or more superior upflow channel(s) of the reactor with bubble free fluid, as described above.
- the advantage of these features and methods over the VerTreat II technology includes the elimination of potential plugging of the orifice plate in the lower and inaccessible section of the riser channel, which is particularly problematic in smaller diameter reactors.
- the volume of gas in a defined volume of liquid changes with the pressure (gas laws).
- the invention provides novel features and method for controlling voidage and ameliorating the adverse effects of slugging. Briefly, these features and methods reduce the quantity of bubbles per unit of fluid in one or more selected channels or chambers of the reactor 10, either by adding more fluid or reducing the gas.
- liquid flow in one or more superior upflow channels of the reactor is increased by recycling liquor from an upper segment (e.g., 60-90') of the reactor, through a degas step, and back down to a lower, recycling influx point near the bottom of the upper segment (e.g., 60-90 feet below the surface). It is generally considered that total gas flow (air flow) is determined by biological optimization requirements, however this total gas flow can also be proportioned into selected, superior upflow channels in the upper part of the reactor using novel flow control mechanisms described herein.
- zone 1 and zone 2 of the reactor comprise approximately equal fluid volume, but in the case of BNR removal zone 2 is expanded in volume for nitrification by increasing the diameter of the zone 2 head tank 15.
- the voidage in the zone 2 recycle channel can be readily controlled under a wide range of operating conditions by designing for sufficient, adjustable recycle flow of degassed liquor from the zone 2 head tank 15 as regulated by the zone 2 recycle regulator 112.
- the bubble volume in the zone 1 upflow channel 40 can therefore be diluted by degassed liquor to the extent limited by the acceptable range of minimum and maximum values for influent flow, which is somewhat limited.
- a regulated amount of liquor may be diverted through the zone 1 recycle port by adjustment of the zone 1 recycle flow regulator 50 (effectuated by operation of the system control unit 51). Controlling flow from the head tank in this coordinated manner is necessary to maintain gravity feed of the effluent.
- the instant invention therefore provides a number of separate and optionally cooperative mechanisms and methods to alleviate the problems of slugging at low bioreactor 10 flow velocities.
- this problem is alleviated by providing a choice of adjustable diverter or baffle devices, exemplified by the fixed or adjustable diverter mechanism 84.
- the configuration (including size, shape, location and orientation) of this exemplary diverter plate can be fixed at the time of construction and installation of the reactor.
- these and other flow diverter parameters can be selectably altered, for example by employing a manual or motorized diverter plate adjustment mechanism optionally integrated for functional control (e.g., to control positional and orientation parameters) by the system controller 51.
- Operation of the flow diverter serves to direct a greater or lesser fraction of air bubbles entrained in the upflow from the primary reactor channel 80 into one or more selected superior channels, for example to divert a greater fraction of the fluid-bubble mixture toward the zone 2 upflow channel 82, allowing a lesser to pass upward into the zone 1 upflow channel 40.
- zone 2 upflow channel 82 Once the desired fraction of bubbles have been thus diverted into the zone 2 upflow channel 82, the voidage in this channel can be easily corrected by changing the amount of zone 2 recycle flow through adjustment of the zone 2 recycle flow regulator 112.
- the circulatory loop (following arrows between zone 2 upflow channel 82, across zone 2 degas plate 150, through zone 2 recycle regulator 112, down zone 2 recycle channel 110, and through zone 2 shielded recirculation port 152), together with a surface basin or zone 2 head tank 15 at the top, comprise zone 2 and represent the polishing process and optional nitrification features of the bioreactor which are driven by waste gas from zone 1.
- zone 2 circulation characteristics are ideal for the application of fixed media 132 ( Figure 4) and, alternatively or cooperatively, membrane separation components ( Figure 5).
- Moving bed media 130 ( Figure 4) can also be used, since zone 2 circulates completely separately from zone 1, to enhance nitrification within alternative process modes of the reactor.
- zone 1 is a closed loop, namely zone 1 upflow channel 40, zone 1 head tank 16, downcomer 12 and primary reactor channel 80
- the number of recycles in this loop and the liquid velocity depends directly on the volume of air bubbles diverted by diverter plate 84 into zone 1 upflow channel 40.
- the number of internal recycles is approximately the BOD in mg/L divided by the O 2 potential in the reactor, divided by the oxygen transfer efficiency.
- oxygen is injected at about 7.3 atmospheres of pressure. Solubility of O 2 in water at 1 atmosphere and 20° C is about 8 mg/L.
- zone 2 any flow from zone 1 that enters zone 2 must leave as effluent from zone 2. Since the lower portion of zone 2 comprising upflow channel 82 and adjacent downflow channel 110 typically has no internal recycle connection with zone 1, any air diverted from zone 1 into zone 2 will simply cause circulation in the superior channel(s) of zone 2 with no change in the circulation rate of zone 1 (change in air rate in zone 1 does, however, affect the circulation rate in zone 2, but not vice versa).
- influent flow into zone 1 upflow into zone 2 and effluent from zone 2 within the reactor 10 are equal in quantity, i.e., influent flow entering the reactor in zone 1 exits through zone 2.
- the internal recycle flow is about ten to twelve times the influent flow, or effluent flow.
- the present process which features novel air lift controls as described above, can reduce this flow by about a 2-3 fold reduction, often a 5-6 fold or even greater reduction.
- the selected bubble fraction only (not typically the same as the liquid flow fraction) in the primary reactor channel can be segregated among any desired number of channels (typically 2, 4 or 6, depending on reactor size and pu ⁇ ose) in any ratio selected to achieve optimum operation of zone 1 and zone 2 (note that each superior channel shown in Figure 8 has a companion channel opposite it, which is a typical layout for larger reactors using two or more clarifiers. Smaller reactors have only 4 channels and a center downcomer, as illustrated in Figure 7).
- typical flow values in the zone 1 upflow channel 40 may be selected to be 6-8 times (alternatively, 2-3 times with BNR) the flow entering zone 2 at the top of zone 1 at the level of the diverter plate 84 (immediately below the zone 2 upflow channel 82), but only require 20-30% the amount of air to produce a non slugging air lift effect.
- the flow into the zone 2 upflow channel may be selected to be about one sixth the flow in the zone 1 upflow channel, but conversely receive about 75-85% of the air.
- Air flow settings into the zone 2 upflow channel can thus be set over a broad range of flow settings, for example 10-15%, 20-30%, 30-50%, 50-75%, 75-90% or greater.
- zone 2 upflow channel After diluting the zone 2 upflow, for example using 8 to 10 times the recycle flow from the zone 2 head tank 15 via the zone 2 recycle regulator 112, the air lift effect in the zone 2 upflow channel can be readily controlled. This control depends on the novel mechanisms and methods set forth above for segregating flow in an aerated and flowing vertical column, providing for selectable channeling of flow in different proportions into two or more other superior vertical columns, while the air bubbles may be split in a completely different ratio among these vertical columns.
- One set of criteria for Class A bio-solids requires a minimum volatile solids reduction, as well as a Time-Temperature relationship, for example a 38% volatile Solids reduction and a 60°C temperature for 5 hours qualifies as a Class A product.
- the bioreactor 10 is designed to function alternatively as a waste sludge digester and to meet the minimum volatile solids reduction and Time-Temperature relationship criteria for Class A biosolids production.
- the reactor is specially designed and operated with a unique flow and zonal separation regime that provides for production of Class A biosolids in as little as 5-6 days, often in 3-4 days or less, using thermophilic bacteria operating at 58-65°C but typically 58°-62°C and often 60°C.
- the 38% volatile solids reduction is a measure of stability of the biomass or vector attraction reduction (VAR), while the elevated temperatures pasteurize the product to control E-coli and virtually eliminate salmonellae. Consuming 38% of the volatile matter minimizes odor potential and provides enough food energy for Thermophilic bacteria to raise the temperature of the reactor to over 60°C, without applying exogenous heat.
- VAR vector attraction reduction
- a second area of concern for previous vertical bioreactors directed to high quality biosolids production is that there is insufficient liquid to liquid separation between zones 1 and 2.
- Published data of tracer studies in VerTad reactors show that the zone 2 (polishing zone) behaves as a plug flow reactor, with a critical feature of localized back-mixing. Over a period of about 8 hours, zone 2 begins to mix with zone 1 and the whole system (zone 1 and zone 2) is mixed in 16-20 hrs.
- the improved bioreactor/digester 10' of the present invention is configured in a distinct manner with zone 1 surrounding zone 2 ( Figure 7), such that for any given volume of reactor the surface to volume ratio is smaller than in previously described reactors directed to quality biosolids production, whereby the heat lost to the surrounding geology is much less.
- the improved bioreactor/digester provides enhanced liquid to liquid separation at a transfer point between zone 1 and zone 2.
- the transfer point is delineated by an air lock mechanism 172 (e.g., a diaphragm-less air operated valve) typically including an air lock baffle 170 as depicted in Figure 7.
- the baffle extends upward into an air pocket formed by the introduction of clean, pressurized air from a dedicated air line 62 with air delivery port 64 or aeration/solids extraction line with corresponding port 68 located near sump 67.
- Zone 1 is aerated through port 69.
- waste biomass is fed continuously or intermittently into the reactor/digester 10', e.g., into the zone 1 head tank 16'.
- the reactor/digester 10' e.g., into the zone 1 head tank 16'.
- a pressure differential develops across the center baffle 170 in the air lock.
- the zone 1 liquid level in the air lock exceeds the baffle height and fluid transfers from zone 1 to zone 2.
- Line 64 air supply is placed slightly below the liquid level of zone 2 within the airlock, whereby at the first onset of flow between zone 1 and zone 2, the bubbles are swept away into zone 2 and the air lock collapses. Flow stops when the head tank levels are again equal and the airlock re-establishes itself.
- a batch can also be initiated by draining the zone 2 head tank 15'.
- Figure 7 shows zone 2 head tank being drained and the air lock approaching batch transfer. The size of the batch is the change in head tank level multiplied by the surface area of the tank. Therefore the baffle 170 need only penetrate into the air lock 172 by a foot or two because 1-2 feet of liquid level change in the head tank would typically represent a full batch.
- zone 1 and zone 2 being hydraulically separated by a diaphragm-less air valve (air lock 172), the lower portion of each zone functions as a pseudo plug flow zone while the top portion of each zone is circulated in the superior channels and is well mixed.
- zone 1 and 2 is further divided into two additional smaller zones to double guard against reinocculation of the finished product with the raw influent.
- baffle 86 extends to about 70-90 % of the reactor depth and baffle 84 completely seals off the bottom of zone 2 from zone 1.
- zone 2 may be further sealed with second outer wall 197 in close proximity to the outer casing 196 as shown in Figure 10 and Figure 11.
- the air locks 170 are shown penetrating the septa wall between zonel and zone 2 at a location above baffle 84, but below ports 34 and 152.
- Zone 1 has an aerated volume below zone 2 of at least one batch volume and preferably two.
- the reactor/digester 10' of Figure 7 is thus very similar in its operation to the waste water treatment reactor illustrated in Figure 1, but differs in four principal aspects: 1.
- the zone 1 surrounds zone 2; 2.
- Zone 2 extends downward about 70-90% of the depth of the reactor within zone 1; 3.
- Each zone has its own aeration means; 4.
- Each of zone one and zone two is further divided into an upper circulating zone and a lower pseudo plug flow zone.
- sludge Once sludge enters the reactor/digester 10' it has a mean residence time of approximately 2 to 3 days in zone 1, and 2 to 3 days in zone 2.
- the EPA criteria for the production of class A bio-solids dictates the time between batches, which varies with temperature—as an example the minimum residence time for a batch at 60° C is 5 hours, or about 4.8 batches per day. Therefore, zone 1 and zone 2 theoretically contain between 9.6 and 14.4 batches each. In practice, however, each batch would be about 8 hours, and therefore zone 1 and zone 2 would contain between 6 to 9 batches each.
- the overall residence time is determined by the biodegradabihty of the sludge.
- the process must achieve a minimum of 38% volatile solids reduction which typically takes 3.5-5 days.
- the batching time is determined by the temperature (see, e.g., Figure 12).
- the preferred operating temperatures of 58°C-62°C require approximately 8-4 hours.
- the air line 62 can be operated to maintain the air pressure in the air lock 172 of the reactor/digester 10' to control batching. Stopping the air flow in line 62 will also trigger a batch discharge after the appropriate processing time has elapsed. A batch can also be triggered by lowering the liquid level in the zone 2 head tank 15'.
- the head tank level in zone 1 is automatically lowered an equal amount by the action of the automatic batching valve located between the bottoms of zone 1 and 2, and the cycle repeats.
- the automatic batching valve located between the bottoms of zone 1 and 2, and the cycle repeats.
- thermophilic aerobic digested sludge from a vertical shaft reactor having certain features in common with the reactor of the present invention was fed to a mesophilic anaerobic digester, the retention time in the anaerobic digester was reduced, the overall volatile solids reduction was better, the dewaterability was better and required less polymer.
- the thermophilic aerobic digester is operated with a about a 2 day retention time and can generate enough heat to comply with Class A biosolids.
- Struvite magnesium ammonium phosphate
- Struvite is readily formed in anerobic digesters of plants using biological phosphorus removal but not in plants using chemical phosphorus removal. Controlling the reactor temperature to below 60°C may allow ammonium bicarbonate crystals to form which would easily float separate with the sludge.
- thermophilic aerobic digested sludge that was taken from a deep vertical thermophilic aerobic digester similar to the present invention. It is known that thermophilically digested sludge will dewater better than anaerobically digested biosolids however at much higher polymer dose. Previous studies investigated the cause of the high polymer requirement and found that monovalent ions such as sodium, potassium, and particularly ammonium ions can interfere with the charge-bridging mechanisms in the floe. In conventional thermophilic aerobic digesters the nitrification of ammonia is inhibited over 42°C and therefore the ammonia produced is in largely in solution, as evidenced by typically high pH.
- the carbon dioxide produced is substantially stripped out by the large air flows required in these digestors and less carbon dioxide remains in solution to form ammonium bicarbonate. Since the air bubble contact is in the order of seconds, and the rate of solution of ammonia is much faster than that of carbon dioxide, the environment does not favor the formation of ammonium bicarbonate.
- concentration of biopolymer (proteins and polysaccharides) in thermophilically areobic digestion could be minimized by limiting the residence time of the thermophilic digestion.
- the present invention has 1/3 tol/2 the residence times of conventional thermophilic aerobic digesters.
- the presence of biopolymer and monovalent ions, particularly ammonia, in solution correlates well to an increase of polymer consumption.
- ammonium bicarbonate would significantly reduce ammonium ions.
- Lowering the pH with acid to about 5.0 causes the biosolids to float to about 10- 12% concentration.
- Digestion below 60°C controls the reactor pH to 7.8-8.0 while digestion over 60°C results in an operating pH of 8.6-8.8, reflecting the effect of more free ammonia due to the decomposition of the ammonia bicarbonate.
- Flotation separating is better below 60°C than above 60°C, in all categories, where the less acid used yields a thicker float blanket and better nutrient fractionation.
- These biosolids can be further centrifuged to 30- 35% solids concentration using a low polymer dose of about 15 pounds polymer per ton dry weight biomass. The acidification process may cause some cell lysis, which will also help dewater the sludge. [155] These results are substantially better than conventional thermophilic aerobic digestion processes which require 30-50 pounds polymer per ton dry weight biosolids and centrifuge to only 20-25% solids. Acidifying the conventional thermophilic aerobic digester product does not float separate the solids, presumably due to the lack of ammonium bicarbonate.
- the float solids were 1.5 times more concentrated compared to the digested sludge solids; the total nitrogen in the float was 1.7 times as concentrated; the ammonia in the float was 1.2 times as concentrated; the organic nitrogen was 2.1 times as concentrated; and the total phosphorus was 1.3 times as concentrated.
- the nutrient concentration factor, including ammonia ranged from 1.2 to 2.1 when the solids concentration factor was 1.5.
- twin bioreactors (to satisfy EPA redundancy requirements) will often be placed in cased and grouted steel shafts approximately 36 inches in diameter and 250 feet deep.
- the exemplary scope and reactor design described here for illustration pu ⁇ oses is suited for a community of about 5000 people requiring a tertiary treatment plant with biological nutrient removal would proceed as follows. Also described here for illustration pu ⁇ oses is a novel, modular bioreactor assembly design, while it will be understood that the use of a modular assembly method is not necessary to practice the invention.
- the inner head tank for this exemplary installation is about 8 feet in diameter and approximately 12 feet high.
- the shop fabricated reactor internals include 6 flanged tube bundles each about 40-feet long.
- the bottom 40-feet length (first length) is made up of the aeration distributor 60, the shear header 70, the airlines 62 and 66, attached to a short length of downcomer 12.
- the second, third and fourth tube bundles include 40 feet, modular sections 190 typically including a central downcomer conduit 22 with airlines 62 and 66 attached (see, e.g., Figures 9-11). These sections are joined, e.g., bolted, together sequentially at modular section joints 192 to the preceding section as the sections are sequentially lowered into the shaft.
- the top two sections, 5 and 6, comprise the downcomer air lines and superior channels formed as a unit by using the central downcomer 22 and radial channel partitions 194.
- the radial partitions will assume a light press fit in the reactor shell (e.g., against an inner wall 196 of the riser conduit 24.
- the superior channel- forming radial partitions 194 are relaxed from the inner wall 196 of the reactor during insertion by expanding the diameter of the central (e.g., downcomer 22) conduit in a direction generally pe ⁇ endicular to the radial partition (see, e.g., Figure 11).
- Figure 9 depicts a novel conduit expansion device 198, which is provided, for example, in the form of a spreader sized and dimensioned for insertion within the downcomer conduit.
- the spreader typically has paired, opposed and reciprocating spreader parts 200, 202, which can be manually, reciprocatingly repositioned between relaxed and expanded configurations (e.g., by remotely turning a threaded expansion driver 204 that engages each of the reciprocating spreader parts and causes them to spread in the direction of the outwardly directed arrows in Figure 9, or to cooperatively relax in the opposite direction).
- Figure 10 provides a diagrammatic end view of the reactor internal section showing the downcomer and radial baffles.
- FIG. 11 provides a diagrammatic end view of the reactor internal section showing the downcomer forced out of round by the expansion tool in its expanded configuration, wherein the radial baffles 194 connected to the downcomer are forcibly retracted away from the inner casing wall 196 to allow insertion of the reactor section 190 therein.
- a sealed zone 2 can be provided by adding a second outer wall 197 on half the assembly. Because this second wall is applied to only half the circumference, it does not prevent the spreaders from deforming the center tube thus relaxing the wall pressure of the septa partitions during installation.
- zone 1 head tank 16 is bolted to the top of the last section.
- the zone 2 head tank 15 is field-erected from pre-fabricated sections.
- the modular reactor tube bundles can be delivered to a site for installation by a single truck, and the head tanks by a second truck.
- the clarifier 120 shell can be cast in place using concrete or made from prefabricated steel sections.
- the clarifier is fitted with a conventional skimmer mechanism. Finally the compressors and other ancillary equipment are connected. Because of the small footprint these small plants can easily be housed in a building.
- Figure 13 provides an exemplary block- flow diagram which can be used to identify the various flow patterns and further understand the inter-relationship of unit processes.
- Figure 13 is divided into four areas, as delineated by the broken lines.
- the bottom left area is a conventional preliminary treatment area where the waste water is passed through a fine screen in unit A and is degritted in a hydroclone separator C.
- the screenings and grit are deposited in a hopper B and sent to landfill.
- the upper left area of figure 13 is the wastewater treatment and BNR part of the bio-reactor of the invention and represents certain exemplary components thereof.
- Unit D represents a deoxygenation step or pre-denitrification step and references channel 40 channel 32 and recycle 50 of Figure 1.
- the unit D is agitated by the anoxic waste gas originating in lower zone 1 (channel 80 of Figure 1.
- the line 301 schematically represents the waste gas transfer from lower zone 1 (channel 80) to upper zone 1 (channel 40) but in this aspect of the invention the lower zone 1 is immediately below upper zone 1 and no transfer line is needed.
- Unit D receives raw influent (channel 30) from unit C, recycle from head tank E and nitrified recycle from zone 2 (unit H).
- Unit D represents the head tank 16. This unit receives anoxic gas (309) from unit D which serves to mix the contents of head tank 16. Unit E also accepts raw waste water containing about 25mg/L of ammonia and 1.75 volumes of nitrated recycle containing no ammonia or appreciable BOD.
- the denitrification process liberates, e.g., about 2.6 mg oxygen/mg of nitrate denitrified and some of the alkalinity is recovered. These quantities are exemplary and beneficial to the process. Denitrification is quite a fast reaction and is accomplished by the microbes naturally occurring in the waste water.
- Unit F receives, e.g., about 2.75 volumes of denitrified wastewater containing approximately 9 mg/L ammonia and 72 mg/L BOD. Since there is no molecular oxygen or bound oxygen, the biomass will become anaerobic and start using some of the proteins in the raw sewage to make amino acids. The poly P microbes in the system will give up their phosphorus and load up on VFA's. There is some evidence that VFA's can be produced in anaerobic sewer lines where anaerobic slime is allowed to accumulate on the pipe wall. A rope like open weave tube (131) may be hung from the head tank down inside the clean bore channel 12.
- Unit G represents the lower portion of zone 1. This area is highly aerated and is designed to reaerate the anaerobic mixed liquor as quickly as possible. Since the mixed liquor that enters the lower portion of zone 1 is rich in BOD, ammonia and sufficient VFA's, the oxygen demand in the lower portion of zone 1 will be the maximum for any part of the reactor.
- the BOD removal step requires ammonia of cell synthesis which is 5% of the BOD or about 4 mg/L.
- Experience with vertical bio-reactors has shown that some of the ammonia is actually nitrified in the lower zone 1.
- Unit H represents head tank 15 and operates under very low loading rates.
- the feed rate into zone 2 head tank is 2.75Q containing 3mg/L ammonia and 10 mg/LBOD.
- Zone 2 receives its air supply from zone 1 (shown schematically as line 302). Because of the low BOD the biomass production will be low and the biomass produced by nitrification is 1/5 - 1/3 that of BOD reduction. Because of the slow growth of nitrifying bacteria, they cannot be permitted to be washed out of zone 2 in the 1.75 recycle flow to zone 1. Fortunately these bacteria are attachment microbes and will grow on any fixed or moving bed media.
- moving bed media can advantageously be used, because the lower end of zone 2 is designed not to allow any back-flow into zonel, and simple screening will prevent the media from escaping at the top.
- Fixed media may also be employed but fixed media tends to plug up occasionally and requires cleaning or changing. Moving bed media tends to be self-cleaning but does wear out over time.
- Unit I is a conventional sedimentation clarifier which separates the biosolids from the effluent and returns these biosolids (activated sludge, RAS) to unit D or E. In a BNR plant the RAS should never become anoxic because the nitrate in the effluent and RAS will denitrify causing the sludge to start floating in the clarifier.
- the upper right of Figure 13 is the final chemical treatment of tertiary water to meet recycle quality standards. By current law, chemical flocculation, filtration and residual chlorine must be used.
- Unit M is a flocculating tank with mechanical mixer.
- Unit N is a rotating cloth disk filter.
- Unit P is a ultra violet disinfection channel and combined back wash tank.
- Unit O is a chlorination step where just enough chlorine is added to maintain a residual in the pipe line.
- Unit Q is a back wash pump which can be used to backwash the cloth filter or the membranes if required.
- the lower right of Figure 13 is the thermophilic aerobic digestion section of the plant.
- Unit R represents the first aerobic stage (zone 1) of the two step process.
- Unit S represents the second stage of the digestion or zone 2. These two zones are connected through an air lock valve.
- Unit W represents the acid flotation thickening step.
- Unit T is an acid feeder.
- Unit V represents the dewatering step, in this case a centrifuge, with a
- Denitrified liquor from head tank 16 descends in channel 12 under anoxic or optionally anaerobic conditions completing the denitrification process or optionally creating VFA's.
- downflow in channel 12 enters the bottom of zone 1 in the vicinity of the aeration distributor in an area of vigorous mixing.
- Channel 80 which is the major portion of zone 1 is highly aerobic, removes the BOD, rapidly oxidizes the VFA's consuming phosphorus and in some cases nitrifies a portion of the ammonia.
- rising liquor in channel 80 splits into the deoxygenation area and a portion passes upward into zone 2.
- Zone 2 substantially degrades the remainder of the BOD and converts the remainder of the ammonia to nitrate.
- waste gas from channel 80 circulates via deoxygenation channels 32 and 40 and also provides the oxygen for bio-oxidation of BOD and ammonia in zone 2.
- nitrified liquor can be returned to the denitrification step where the nitrate -N is converted to nitrogen gas while a second portion goes to a clarification step where the biomass is separated from the effluent.
- the biomass is returned to the denitrification step and the clarified effluent is discharged.
- anoxic gas is used for mixing anoxic liquor.
- Unit D deoxygenates not only the various liquid streams, but the gas stream passing through the unit. This deoxygenated gas can be used subsequently to mix the contents of the denitrification unit E. This eliminates the need for mechanical mixers saving energy, maintenance and capital.
- Unit F is a long vertical channel which may converted to an anaerobic chamber for the pu ⁇ ose of creating VFA's.
- the pu ⁇ ose of the fixed media is to accumulate attached growth anaerobic bacteria (acid formers).
- the amount of fixed media and anaerobic biomass can be adjusted from the surface by rolling up a portion of the rope or fabric tube. The amount of media can be monitored on line by measuring the weight of the rope.
- wasting sludge through an air line 66 or 69 provides instant spontaneous flotation upon depressurization.
- Float solids are suitable for digestion without any further thickening.
- Membrane Separation System [181] This description next addresses membrane separation systems, methods and devices employing a selective, semi-permeable, microporous, or other partitioning membrane for processing, refining, and/or treating liquid compositions, for example membrane waste-water purification processes and apparatus. These systems, methods, and devices provide improved throughput and/or improved operating life of submerged membranes, particularly membrane bioreactors providing biological treatment of wastewater s.
- the effluent from the biological treatment membrane reactor can be further treated by using ultrafiltration, nanofiltration , or reverse osmosis (RO).
- RO reverse osmosis
- This quality of water is suitable for aquifer recharging etc.
- a second consideration is that recycle quality water not only requires the removal of biological oxygen demand (BOD) and total suspended solids (TSS), but also requires the removal of the nutrients, nitrogen and phosphorus, (N & P) to low levels that will not support aquatic growth. This requires the use of a good biological nutrient removal (BNR) process.
- Typical existing membrane bioreactor processes operate on a single sludge back- mixed bioreactor, which is less efficient and more expensive to build and operate than the improved long vertical shaft bio-reactors.
- twin 0.25 MGD 0.5 MGD total
- conventional membrane biological reactors is estimated to cost about 1.2 million dollars, (reactor and membranes only), occupy about 8000 sq. feet, draw about 75 HP, and require 1000 standard cubic feet per minute (scfrn) of air.
- twin improved long vertical shaft 0.25 MGD reactors would cost about 1.0 million dollars including the price of the membranes estimated at $400,000.
- the improved long vertical shaft bio-reactors would occupy about 1000 sq. feet and draw about 30 HP.
- the improved long vertical shaft bio-reactors operate in a plug flow configuration with internal recycle streams.
- Plug flow reactors are known to produce a better quality effluent than back-mixed reactors. This is because in a plug flow reactor the effluent is at the lowest possible concentration achievable with that biomass.
- the effluent constituents are at the same concentration as the contents of the reactor. Indeed, in some cases in a back-mixed reactor, a portion of the influent may short circuit directly to the effluent.
- a membrane separator was adapted to an existing long vertical shaft aeration reactor.
- a principal hydraulic characteristic of vertical aerators is that the reactor circulates a mixture of biosolids, liquid, dissolved gasses and dispersed gas (bubbles), in a very long vertical pathway.
- the pressure at the lower end of this pathway can be up to 150 psi.
- These supersaturated gasses represent a significant resource of stored energy. For example, in a 0.25 MGD improved long vertical shaft bio-reactor, the surface area in contact with the moving fluid in the reactor changes from about 4000 sq.
- a vertical bioreactor that had run 22 years was recently dismantled.
- the head tank was made of steel plate, sand blasted and coated with 6-mil (.006") epoxy.
- the remainder of the reactor was bare steel.
- the epoxy coated surfaces were exceptionally clean and even the bolts in the epoxy coated head tank could be easily undone.
- the dissolved gas content at that point would be about 25-35 Mg/L and the colloidal gas content would be about 40-50 ml/L (50-65 Mg/L).
- whiskers were found on the membrane only on one side, and only in the proximity, of the air line. It is likely that the abrupt change in flow causes the dissolved gas to nucleate and to erode /wear the polymeric surface. Cavitation may be occurring because the whiskers are protruding outward and appears to have been lifted from the surface. The remainder of the membrane was unaffected by the high levels of dissolved gas and had no evidence of surface deterioration when examined under the microscope.
- the amount of dissolved gas is su ⁇ rising.
- the solubility of air in water is about 21 mg/L at one atmosphere of pressure.
- a 500 ft. deep vertical shaft reactor could theoretically dissolve 287 mg/L of air.
- the total dissolved air may be calculated quite accurately in the liquid in a vertical reactor by using a dissolved oxygen probe. Under no load conditions, i.e., no BOD load, the total dissolved air is about 2.61 times the dissolved oxygen reading. Under load, the oxygen readings are reduced but the oxygen consumption can be calculated from the BOD values.
- the vertical bioreactor was operating under a typical diurnal organic load patterns. Note that when the riser air is maintained at substantially a constant value (55-65 scfrn) the dissolved oxygen values increase by a factor of nearly two when only 43 scfrn of down-comer air is applied.
- the down-comer air is mainly responsible for dissolved gas while the riser air is mainly responsible for dispersed.
- the dissolved oxygen level in the permeate (even though reduced 50-60% by the BOD reaction) reaches supersaturated values (nitrogen gas and carbon dioxide gas would therefore be even higher) proving that supersaturated gasses in the liquid easily pass easily through the membrane.
- some of the dissolved gas, perhaps half, is also precipitating on the outside of the membrane.
- the invention provides for the employment of supersaturated dissolved gasses in fluid processing methods and devices to clean surfaces that the subject fluids contact.
- Various observations that validate these results include: a) Polymeric surfaces submerged in liquid flowing at wide range of velocities from about 0.1 to 4.0 feet / sec. do not experience a build up of biomass in the presence about 20-30 Mg/L of dissolved gas and /or about 30-50 Mg/L or colloidal gasses in the liquid.
- Biomass build up is experienced in the absence of dissolved gasses even at relatively high liquid velocities of 3-4 feet / sec.
- Biomass build up can occur on metallic (steel) surfaces at flow velocities up to about 4 feet/sec. This biomass contains phospholipids that protect the metal by bio- passivation.
- Flow velocities over about 10-feet/sec and in the presence of large amounts of air (over about 100 mg/L) prevent the build up of biomass and the build up of the corrosion inhibiting phospholipids.
- Non-permeable polymeric membranes can delaminate if the pores do not go right through the wall.
- the high airflow rates suggested by membrane manufacturers are not necessary for efficient operation of submerged membranes in a presence of supersaturated dissolved gases.
- Kubota a leading membrane manufacturer, states in its literature on membranes used for solid-liquid separation of mixed liquor that a thin film biomass is allowed to form on the surface of the membrane to increase its effectiveness in removing small particles. At a flux rate of about 0.5 gal/hr/sq. feet the time between cleaning membranes is about 6 months. A minimum air rate of about 40 scfrn / 1000 sq.
- Zenon membranes operate at a nearly double the flux rate of the Kubota membranes, but provision is made for pulse reverse flow cleaning. In one mode of operation a ten-second pulse is applied for every ten minutes of operation. Zenon also use a mechanically-applied vacuum to draw on the membrane. Overall, the Zenon technology requires a lower air rate to stimulate and clean the membrane than the Kubota membrane. The airflow rates suggested by these two leading membrane manufacturers is 8 to 10 times higher than the airflow rate typically available in improved long vertical shaft bioreactors. Both Kubota and Zenon have designed their membranes to operate in relatively shallow basins.
- the improved long vertical shaft bio-reactor is configured on a vertical axis, and allows membranes to be stacked 2-5 units high and still maintain enough driving head in the reactor to circulate the system.
- the driving head that causes air/liquid circulation through the membranes amounts to a few inches at best.
- the driving head might be 10-12 feet.
- a redistribution header is located between each deck of membranes thus allowing the same air to be used 4-5 times.
- a first trial design of a 0.25 MGD improved long vertical shaft bio-reactors plant inco ⁇ orating membrane bioreactor technology indicates it would supply about half the air and about 1/3 liquid flow velocities recommended by the membrane manufacturers.
- the dissolved air fraction in the liquid flow is a far more important factor in keeping the membranes clean than either the air rate or the liquid rate.
- Over-design is to be avoided because it is possible to clean the membranes too well and destroy the required thin bio- film.
- the scouring action can be adjusted by using fewer decks of membranes or less air. Conversely, one can always add air and more decks if more velocity and/or scouring are needed.
- a Y branch to allow the mixed liquor to transfer from the riser to the downcomer via a head tank.
- the head tank is approximately 25 feet long, 6 feet wide and 4.5 feet deep.
- the configuration of this reactor is ideal for tests since it allows the ratio of dissolved to dispersed air to be selectively changed. Applying more downcomer air results in more dissolved air while applying more riser air results in more dispersed (bubbles) air. As shown later, the ratio of dissolved to dispersed air makes up to a nine-fold difference in membrane flow rates at the same hydraulic head.
- test bioreactor was fitted with a sample port in the head tank located close to the outlet of the membrane. Dissolved gas concentrations across the membrane were measured with a dissolved oxygen meter (DO meter) and reactor circulation velocities across the membrane are calculated from the time to circulate tracers such as soap. Permeate flow out of the membrane was measured in a calibrated flask, and the hydraulic head is maintained by an overflow to the flotation tanks. In this test case, the head over the membrane was maintained at 1 foot. A drop leg was provided to cause a siphon effect of one meter, a typical operating value for this type of membrane.
- DO meter dissolved oxygen meter
- the membrane support frame can hold a lower membrane submerged between, about 6-9 feet, and an upper membrane submerged between about 1-4 feet.
- the overflow heights are the same for both membrane locations.
- Table 3 is a plot of data points of Table 2.
- the data of Table 2 do not reflect the importance of the dissolved air fraction. However, the effect of varying the air rates was noted and the information provided in Tables 2 and 3.
- point 1 has 108 scfrn in the riser (mostly dispersed) and no downcomer air (i.e. no dissolved air).
- point 1 the highest air rate and the highest circulation rate yields the lowest flow rate out of the membrane.
- the dissolved air fraction in the wastewater has a dominant effect on the throughput of the membrane.
- Other factors will also influence the performance of the membrane. Among these factors are the concentration of biomass, the sludge age, the biological health of the sludge, the amount of exo-cellular polymer present, the condition of the membrane, etc. These factors are expected to have a minor impact on overall results since most of the results are from one-day's operation during which sludge conditions are not predicted to change much during the subject period.
- One important cause of increased membrane through-put within the present invention relates to gas dynamics of vertical bioreactors.
- deep shaft reactor systems provide significant advantages over other bioreactors and fluid treatment apparatus by providing a high dissolved air fraction.
- they involve distinct biochemical and physicochemical processes, for example oxidation of organic carbon, and dissolution of oxygen and other gases that result in supersaturated levels of desired gases, e.g., carbon dioxide.
- rheology describes a complex, non-linear relationship between fluid deformation and stress occurring in fluid flow patterns. The increased throughput phenomena is believed related to a change in rheology on a membrane surface. Because of high amounts of dissolved gas in the fluid, the rheology of both the biomass (solids containing fluid and gas) and the fluid media change on contact with the membrane, perhaps making the membrane more permeable. [214] The test membrane was fitted with clear vinyl tubing, which allowed visual observation of the permeate stream. The permeate stream contained a significant amount of bubbles, perhaps 1/16 to 1/8 inch in diameter. It is estimated that as much as 10-15 % of the permeate flow is made up of discrete bubbles.
- the dissolved gas passes through the membrane unimpeded and then nucleates at or near the membrane surface, which may include nucleation between the surfaces, at the membrane surface, or within a fluid proximate to the membrane surface, and causes an air-lift effect proximate to the membrane surface. It is reasonably expected that discrete bubbles will not pass at high levels through a semi-permeable membrane. Unless there is dissolved air present in the water passing through the membrane, (or alternatively air bubbled into the clean water side of the membrane) no air-lift can be expected on the permeate side of the test membrane.
- FIGS 14-1 through 14-7 illustrate several aspects of a submerged permeable membrane assembly 400 for membrane separation according to the invention.
- the membrane assembly is a "U-shaped" assembly, while it will be appreciated that various alternative designs and configurations of the assembly can be constructed and operated according to the disclosure herein.
- the exemplary membrane assembly includes a "U-shaped" container 405 that is 6 feet tall and has a first fluid compartment 420 and a second fluid compartment 430. Also in this exemplary embodiment, the compartments are separated by a separator member 414 and a membrane 410 that is 3 feet high and installed at the bottom of the "U" where the two fluid compartments connect.
- the membrane 410 has a first surface 411, a second surface 412, and a vertical axis 402.
- the first fluid compartment 420 is configured to contain a first fluid 424 in fluid communication with the first surface 411 of the membrane 410.
- the second fluid compartment 430 is configured to contain a second fluid 434 in fluid communication with the second surface 412 of the membrane 410.
- the first fluid 424 has a first specific gravity, or density
- the second fluid 434 has a second specific gravity.
- the membrane 410 schematically represented in Figures 14-1 through 4-7 may be any membrane structure, including plate and frame, tubular, hollow fiber, and spiral wound.
- the membrane may be any selective, semi-permeable, microporous, or other partitioning membrane for processing, refining, and/or treating liquid compositions, for example membrane waste-water purification processes and apparatus.
- the membrane may be made from any material, and may include one or more selected from cellulose acetate, polyvinyl chloride, polysulfones, polycarbonates, and polyacrylonitriles.
- the membrane 410 is generally permeable by molecules of less than a predetermined size, and includes pores 415 between the surfaces 411 and 412 having a pore size permitting movement of molecules smaller than a removal size between the first and second surfaces 411, 412 and rejecting movement of larger molecules.
- the particle removal size for semi-permeable membranes used in membrane bioreactor applications typically range between 10.0 and 0.05 microns.
- a particle removal size may be selected in conjunction with other parameters relevant to a particular use of the membrane, in a certain embodiment a semi- permeable membrane having a particle removal size in a range of between approximately 0.05 to 0.1 microns generally produced good results filtering wastewater. This range removes most viruses, most long-chain molecules (macromolecules), and all bacteria. In another embodiment, a membrane that substantially removes particles larger than 0.1 microns is generally expected to produce satisfactory results filtering wastewater. [218] Figures 14-1 through 14-7 also illustrate the fluids 420 and 430 being contained at various vertical column heights in the assembly 400.
- the exemplary, "U-shaped" assembly has a maximum column height of six feet, and the Figures include other illustrative dimensions of the vertical column height from zero to six feet along the vertical axis 402, with zero feet starting at the maximum height of the assembly 400, and six feet at the maximum depth of the membrane 410.
- the first fluid compartment 420 contains the first fluid 424 at a first column height 422 of six feet.
- the second fluid compartment 430 contains the second fluid 434 at a second column height 432 of six feet.
- the vertical axis 402 of the membrane 410 is typically aligned with a corresponding first chamber vertical axis 423 and a second chamber vertical axis 433.
- the first chamber vertical axis 423 and second chamber vertical axis are approximately parallel and correspond to an effective vertical gravitational axis that is roughly coincident with a direction of bubble rise in the first and/or second chambers.
- the direction of bubble rise is vertical within the first and second chambers.
- the membrane vertical axis is roughly parallel to the first chamber vertical axis 423 and second chamber vertical axis.
- the membrane may not be oriented vertically, for example it may be positioned with the first and second surfaces tilted relative to the direction of gas bubble rise and vertical axes of the first and second chambers.
- the membrane vertical axis 402 is not parallel to the first and second membrane surfaces, and instead corresponds to the direction of bubble rise in the first and/or second chambers.
- the first fluid compartment 420 contains the first fluid 424 for filtration, such as dirty water, wastewater, or sewage to be filtered
- the second fluid compartment 430 contains the second fluid 434 as filtrate, such as clean water, recyclable water, or permeate.
- the submerged membrane assembly 400 is illustrated with the first fluid 424 illustrated as dirty water, and the second fluid 434 illustrated as clean water. Both fluids (420, 430) have a specific gravity of one. In Figure 14-1, neither the second fluid 434 in the second fluid compartment 430 nor the first fluid 424 in first fluid compartment 420 have any air or bubbles present.
- gas in the form of air bubbles 426 is present in the first fluid 424 contained in the first fluid compartment 420.
- the air bubbles 426 may be added to scour and clean the first membrane surface 411.
- the amount of air bubbles 426 present in the first fluid 424 (dirty water) to adequately scour the first surface 411 of the membrane 410 reduces the specific gravity of the first fluid 424 from 1.0 to about 0.9. Again, it can be calculated that the pressures at the top of the assembly 400 is 0 psig.
- the pressure on the second membrane surface 412 (the clean water side) at the top of the membrane 410, i.e., at the three-foot elevation on the column height, is 1.298 psig
- the pressure on the first membrane surface 411 (the dirty water side) is 1.168 psig
- the pressure on the second membrane surface 412 (the clean water side) at the bottom of the membrane 410, i.e., at the six-foot elevation on the column height is 2.597 psig
- on the pressure on the first membrane surface 411 (the dirty water side) is 2.337 psig.
- the second fluid 434 (clean water) will try to flow through the membrane 410 into first fluid 424 (dirty-water) of the membrane 410 because of the reverse pressure differential.
- the pressure differential across the top of the membrane 410 is 0.13 psig while the pressure differential across the bottom of the membrane is 0.26 psig. Not only will water try to flow in the wrong direction, but more water will flow across the membrane at the bottom than at the top.
- Figure 14-3 shows that, if the second column height 432, or liquid level, on the second fluid 434 contained in the second fluid compartment 430 (clean water) is reduced by 0.62 feet with respect to the first column height 422, then the pressure on both the second membrane surface 412 (clean water side) and on the first membrane surface 411 (dirty water side) at the bottom, i.e., six-foot elevation of the column height, will be equal at 2.337 psig. Note however that the pressure on the second membrane surface 412 (the clean water side) at the top of the membrane 410, i.e., at the three-foot elevation on the column height, is 1.03 psig, while the pressure on the first membrane surface 411 (the dirty water side) is 1.168 psig.
- the second fluid column height 432 may be varied with respect to the first fluid column height 422 by any suitable method, device, or means, including providing an outlet or overflow for the second fluid 434 at a selected elevation, applying a vacuum to the second fluid 434, and/or applying a pressure to the first fluid 424.
- Figure 14-4 illustrates a pressure differential across the membrane 410 resulting from a change in the specific gravity of the second fluid 434 of the membrane assembly 400 of Figure 14-3, according to an embodiment of the invention.
- a gas in the form of air bubbles 426, is present in the first fluid 424 (dirty water) contained in the first fluid compartment 420 and forms aerated water.
- Sufficient air bubbles 436 may be added to the second fluid 434 (clean-water) contained in the second fluid compartment 430 to change or adjust the specific gravity of the second fluid to more closely approximate the first specific gravity of the first fluid 424 contained in the first compartment 420. This reduces the second specific gravity of the second fluid 434 to the first specific gravity of the first fluid 424.
- the pressures with respect the membrane 410 at various depths along a column height can be calculated.
- the pressures will be 90% of the pressures in Figure 14-1 because, in this case, the aerated water (434) specific gravity is 90% of unaerated water specific gravity.
- the pressure differential across the membrane 410 at all elevations is zero.
- the presence of rising bubbles of the air 436 proximate to the second surface 412 (clean water or permeate side) of the permeable membrane imparts a scouring action on the second surface of the membrane 412, according to an embodiment of the invention.
- Figure 14-5 illustrates a submerged membrane assembly 401 having a selected differential hydraulic head 452 imposed between the first fluid 424 contained in the first fluid compartment 420 and the second fluid 434 contained in the second fluid compartment 430, according to an embodiment of the invention.
- Alternative embodiments for imposing the differential hydraulic head are described below. If the specific gravity of the second fluid 434 is adjusted to more closely approximate the specific gravity of the first fluid 424, and a selected differential hydraulic head 452 is imposed between the first fluid 424 and the second fluid 434, a selected pressure differential across the membrane 410 results along the vertical axis of the membrane 410.
- the second specific gravity is adjusted to equal the first specific gravity, and a 2.0-foot differential head 452 is additionally imposed between the first fluid 424 and the second fluid 434.
- the pressures at the top and bottom of the membrane 410 can be calculated.
- the pressure differential across the membrane 410 is uniform (0.779 psig) along its vertical axis, from top to bottom. Now, each pore on the membrane 410 sees approximately the same driving pressure, and each pore will transmit about the same amount of water.
- the membrane assembly 401 typically produces more flow than the membrane assemblies having unequal pressure differentials of Figure 14-3 and Figure 14-6 for example.
- the selected pressure differential across the membrane is expected to vary only a minor degree along the vertical axis of the membrane.
- variation of the pressure differential along the vertical axis is expected to be generally uniform, i.e., not vary more than +/- 30%) per vertical linear foot, when the second specific gravity is adjusted to within approximately +/- 5 percent of the first specific gravity.
- the differential hydraulic head 452 is imposed by selecting the second fluid column height 432 with respect to the fist fluid column height 422 to produce a selected pressure differential across the membrane 410 along the vertical axis at the first specific gravity and the adjusted or changed second specific gravity.
- Figure 14-5 illustrates a selected second column height 432 of 4.0 feet and a first column height 422 of 6.0 feet producing a selected differential hydraulic head 452 of 2.0 feet.
- the second fluid column height 432 may be varied with respect to the first fluid column height 422 by any suitable method, device, or means, including providing an outlet or overflow for the second fluid 434 at a selected elevation, applying a vacuum to the second fluid 434, and/or applying a pressure to the first fluid 424.
- the column heights 422 and 432 may be established by providing fluid outlets or overflows from the fist fluid compartment 420 at 6.0 feet and from second fluid compartment 430 at 4.0 feet.
- the differential hydraulic head 452 can be imposed by enclosing the first fluid compartment 420 and applying a pressure, such as by compressed air generated by a mechanical compressor, thus increasing the first column height 422 without physically increasing the vertical dimension of the first fluid compartment.
- the differential hydraulic head 452 can imposed by applying a vacuum, such as generated by a mechanical vacuum pump, to the second fluid compartment 430, thus decreasing the second column height 432 without physically decreasing the vertical dimension of the second fluid compartment.
- a vacuum such as generated by a mechanical vacuum pump
- Additional features of the embodiment illustrated in Figure 14-5 include flowing the first fluid 424 past the first surface 411 of the membrane 410 while maintaining the first column height 422. This embodiment also allows the second fluid 434 to be collected from the second fluid compartment 430 as filtered, clear, or clean water while still maintaining the selected second column height 432 to impose the differential hydraulic head 452.
- Figure 14-6 illustrates a comparison of how existing Zenon and Kubota membranes typically react with the 2.0-foot differential hydraulic head 452 imposed as illustrated in Figure 14-5.
- the existing apparatus and methods for operating these membranes do not change or adjust the specific gravity of the second fluid 434 to closely approximate the specific gravity of the first fluid 424.
- Simply imposing the differential hydraulic head 452 across the membrane 410 does not achieve a generally uniform pressure differential across the membrane along the vertical axis. It only results in a pressure differential that is considerably higher at the top of the membrane than at the bottom. In other words, the pressure differential varies along the vertical axis of the membrane.
- an aspect of the invention includes changing and/or adjusting the second specific gravity to more closely approximate the first specific gravity in value.
- the second specific gravity is adjusted to within approximately +/- 5 percent of the first specific gravity.
- the second specific gravity is adjusted to within approximately +/- 2.5 percent of the first specific gravity.
- Figures 14-5 and 14-7 illustrate alternative embodiments of the invention for including bubbles 436 in the second fluid 434 to change the second specific gravity, and optionally to impart a scouring action to the second surface 412 of the membrane 410.
- the bubbles 436 are sourced from supersaturated dissolved gases present in the first fluid 424.
- long shaft vertical reactors receive at their head tank substantial concentrations of fluid having supersaturated dissolved gases. If the fluid 424 is such a fluid having a substantial concentration of supersaturated dissolved gases, a portion of the supersaturated dissolved gas will nucleate on the first surface 411 of the membrane 410.
- This nucleated gas will impart a scouring action on the first surface 411 as the nucleated bubbles rise in the fluid 424.
- Another portion of the supersaturated dissolved gases of the fluid 424 permeate the membrane 410 by passing from the first surface 411 through the pores of the membrane and emerging on or proximate to the second surface 412 and in the second fluid 434.
- a portion of this passed-through supersaturated dissolved gas will nucleate and form gas bubbles 436, thus adding diffused gas to the second fluid 434.
- the mechanism by which the supersaturated dissolved gas nucleates in the second fluid 434 is not fully understood. The nucleation may be caused in whole or in part by a mechanical action of the dissolved gas passing through the membrane 410.
- the nucleation may be caused in whole or in part by the pressure differential between the first fluid 424 in the first compartment 420 and the second fluid 434 in the second fluid compartment 430 imposed by the differential hydraulic head 452.
- the nucleation may be caused by a difference in dissolved gas levels between the first fluid 424 and the second fluid 434.
- the nucleation may be on the second surface 412, within the second fluid 434, within the second fluid 434 proximate to the second surface 412, or within the membrane 410.
- the gas bubbles 436 nucleate on or proximate to the second surface 412, and impart a scouring and/or cleaning action on the second surface as they rise in the second fluid 434.
- FIG 14-7 illustrates a submerged membrane assembly 402 with differential hydraulic head 452 and gas inlet 438, in accordance with an embodiment of the invention.
- the assembly is substantially similar to the membrane assembly 401 of Figure 14-5, with an added optional inlet 438 coupled to the second fluid compartment 430.
- the optional inlet 438 includes configuration for adding air or gas into the second fluid compartment 430, and forming bubbles 436 in the second fluid 434.
- the air may be added by providing air or a gas to the inlet 438, and diffusing the air or gas within the second fluid compartment 430.
- a diffusing device may be included with the inlet 438 to assist bubble formation within the second fluid compartment.
- the air or gas may be first diffused in another liquid, which is then flowed through the inlet 438 into the second fluid compartment 430 and added to the second liquid 434 in sufficient quantities to adjust the second specific gravity to closely approximate the first specific gravity, and optimally, equalize the first and second specific gravities.
- the bubbles 436 of air or gas may be proved by other sources, such as a chemical reaction, an ultrasonic device, and a microwave device.
- the Zenon and Kubota submerged membrane processes of Figure 14-6 can be improved by adding air or gas to the second fluid compartment 430 (clean water side) of the membrane 410 using the submerged membrane assembly 402 with the gas inlet 438 as illustrated in Figure 14-7. While adding a gas directly to the second fluid compartment 430 of the Zenon and Kubota processes comprises an improvement to those processes, it is not expected to produce a similar degree of scouring of the second membrane surface 412 in the clean water side to that produced by bubble nucleation on the second surface resulting from a supersaturated mixed liquor media as is present in long vertical shaft bioreactors.
- Figures 15 and 16 illustrate an improved long vertical shaft bio-reactor 500 for treatment of waste waters having a membrane bioreactor head 503 that includes plurality of submerged membrane bioreactor assemblies 510, according to an embodiment of the invention.
- the long vertical shaft bioreactor may be any type of long vertical shaft bioreactor that has substantial concentrations of supersaturated dissolved gas at the head tank 502 level, such as the bioreactors of Figure 5 or Figure 8.
- Figure 15 is a top perspective view of a bioreactor head tank 502, and a membrane bioreactor head 503 having plurality of saddle tanks 506A-D mounting the membrane bioreactor assemblies 510.
- Figure 16A is a top view of saddle tank 506A of the membrane bioreactor head 503, illustrating the top membrane bioreactor assembly 510D that includes a plurality of flat plate semi -permeable membranes 511.
- Figure 16B is a cross-sectional side view of the bioreactor head tank 502, and of the saddle tank 506 A having a stack of four membrane bioreactor assemblies 510A-D positioned vertically above each other.
- FIGs 15 and 16 illustrates an embodiment of a membrane bioreactor head 503, having four stacks or columns of membrane bioreactor assemblies 510 arranged circumferentially around the outside of and in fluid communication with the head tank 502.
- each saddle tank 506 includes four tiers of submerged membrane assemblies 510A-D positioned vertically above each other.
- Each assembly 510 is approximately 4 feet high, for a total membrane bioreactor head 503 column height 424 of approximately 16 feet. If a membrane fails, it may be replaced by shutting down only one of the saddle tanks 506, thus allowing the reactor and the other seven saddle tanks to continue operation.
- Each membrane bioreactor assembly 510 includes a plurality of flat plate semi- permeable membranes 511 coupled by a membrane output line 512 to an exterior manifold 514.
- the exterior manifold 514 is coupled by a collection line 516 to a collection trough 538.
- the plate membranes 511 are typically include a frame that supports two rectangular semi-permeable membranes having their second surfaces 412 facing each other and defining in cooperation with the fame an interior second fluid compartment 430 between.
- the first surfaces 411 of the semi-permeable membrane are exposed to a fluid surrounding the exterior of the membrane assembly 510.
- the collection line 516 maybe made of any tubular member suitable for carrying permeate or fluid outputted by the plate membranes 511.
- the collection line 516 may be transparent or clear, allowing a user to visually inspect the bubble 436 content and clarity of the output from each individual plate membrane 511.
- the collection lines 510A-C flow permeate upward into the collection trough 538 as illustrated in Figure 16B.
- the collection line 510D is formed into a siphon that flows permeate from the membrane 511 downward, discharging into the trough 538.
- the first column height 422 is defined between the lowest point of the lowest membrane 511 and the level of the outflow 528 from the saddle tank 506.
- the second column height 432 is defined between the lowest point of the lowest membrane 511 and the level of the trough 538.
- each membrane assembly 510 includes 75 flat plate membranes.
- the head tank 502 diameter in this embodiment is approximately 9 feet, and with the saddle tanks 506 makes the reactor about 13 feet in diameter.
- the first fluid 424 as inflow 526 of effluent from the long vertical shaft bioreactor flows into the bottom of the saddle tank 506A from a long vertical shaft bioreactor (not shown).
- the first fluid 424 has a first specific gravity, and includes bubbles 426 and supersaturated dissolved air.
- the first fluid 424 rises through the saddle tank 506A past the column of submerged membrane bioreactor assemblies 510A-D, and becomes outflow 528 as it overflows the saddle tank at a 12 foot elevation.
- the outflow 528 returns to the long vertical shaft bioreactor for further processing or removal from the reactor.
- the individual flat plate membranes 511 filter the first fluid 424 as described in conjunction with Figures 14-1 through 14-7, and primarily as described in conjunction Figure 14-5.
- the first fluid 424 has a first column height 422 of 16 feet between the bottom of the bottom flat plate membranes 511 and the out flow 528.
- the second fluid 434 has a second vertical column height 434 of 12 feet established by the collection trough 538 and the collection lines 516 leading into it.
- a differential hydraulic head 452 is imposed between the first fluid 424, the effluent, and the second fluid 434, the permeate or filtered water.
- each membrane 511 is the same as it is at the bottom, and the pressure differential across the top tier of membranes 510D (which is under a siphon head) is exactly the same as the pressure differential across each of the other three tiers of membranes 510A-C.
- the pressure differential of 1.168 psig is equivalent to about 33 inches of water.
- FIG. 17 illustrates a folded saddle tank system 550 that includes a first folded saddle tank 556A and a second folded saddle tank 556B that collectively carry the membrane assemblies 510A-C, according to an embodiment of the invention.
- a folded saddle tank such as the folded saddle tank 556 can be used advantageously.
- the membrane assemblies 510A-B are contained in a first saddle tank 556A
- the membrane assemblies 510C-D are contained in a second saddle tank 556B.
- the second saddle tank 556A includes an inlet 568 for fluid coupling the inflow 526 of effluent from a bioreactor (not shown).
- a fluid coupling member 558 couples the out flow 558 of the first saddle tank 556A into the second saddle tank 556B.
- the second saddle tank 556B is open to the atmosphere, but the first saddle tank 556A is not.
- the second column height 432 exists in two segments across the folded saddle tank system 550, a fist portion 432A across the first saddle tank 556A, and a second portion 432B across the second saddle tank 556B.
- the first column height 422 is not shown in Figure 17, but its effective dimension is from the out flow level 558 of the second saddle tank 556B at atmospheric pressure to the lowest point of a membrane plate of submerged bioreactor assembly 510A of the first saddle tank 556A.
- the system 550 includes two collection troughs 538A and 538B receiving permeate or clean water (532) from the submerged membrane bioreactor assemblies 510A-D of the first and second saddle tanks 556A and 556B respectively.
- the folded saddle tank system 550 functions substantially similarly to the system 500 of Figures 15 and 16.
- Inflow 526 enters the first saddle tank 556A through inlet 568, and flows upward past the submerged membrane bioreactor assemblies 510A and 510B.
- the liquid overflow and pressurized off-gas 559 are piped through the fluid coupling member 558 into the bottom of the second saddle tank 556B, and flows upward past the submerged membrane bioreactor assemblies 510C and 510D.
- the hydraulic calculations are the same as for the four tier high arrangement. As before each membrane sees the same pressure differential top to bottom and from tier to tier.
- FIG. 17 illustrates several pressure gages [P] 571 and valves 570 introduced for clarity and understanding. The pressure, in psig, at each gage location is shown next to the gage.
- the discharge line from membrane 5 IOC is under a hydraulic head of 1.75 psi (4 feet) and the discharge line from membrane 510D is under a siphon (vacuum) of 1.75 psi.
- a siphon line vacuum
- air bubbles are permitted in a siphon line provided the lines are sized properly to maintain adequate discharge flow velocities, generally of greater than 2 ft./sec.
- a bench test apparatus was constructed according to the teachings herein and was used to conduct a series of bench tests of membrane throughput under varying membrane conditions and levels of diffused gas in water.
- Figure 18 illustrates results of a series of tests conducted on the bench test apparatus.
- FIG. 18 shows the performance of a section of the Kubota membrane that had been previously used in a reactor for more than two months. A series of eight permeability tests were done over a period of a week on the Kubota membrane using the bench test apparatus.
- the test apparatus membrane section was approximately 1/130 of the area of both sides of a full size (1/2 m x 1 m) Kubota membrane.
- the test apparatus was configured like an aeration shaft with an outer casing of 3.488" ID with a downcomer of 1" inside diameter.
- the liquid circulation was driven with a large aquarium air pump with two injection ports near the bottom of the downcomer.
- the membrane was located in a machined recess at the bottom of the 3.5 " diameter tube and a removable bottom cover supports the membrane from movement in the downward direction.
- the bottom cover plate included a series of machined grooves dimensioned similarly to the grooves in the Kubota membrane.
- a piece of coarse felt blotter membrane, taken from the field trial membrane unit, is installed between the membrane and the permeate collection system.
- Membrane discharge tubes were installed both vertically upward and downward from lower surface of the membrane. Additionally, the lower tube can be used as a siphon or drain to remove permeate from the lower side of the membrane.
- the test apparatus used a porous felt layer under the membrane and a channeled permeate collection system similar to the Kubota design.
- the area of the test membrane is 9.5 sq. in. or 1/130 of the area of both sides of the field test Kubota membrane.
- the membrane used in the field was (' ⁇ meter x 1 meter) and had a rated surface area of 8.6 sq.ft. or 1238 sq.in.
- Run 1 was on tap water and used the dirty membrane. The water was airlift circulated. Run 2 was done in the same way but using fresh soda water as the liquid. Air-lift circulation was not used in run 2 because it caused too much foam.
- a second step was to clean the membrane according to field observations. Soda water was air circulated across the face of the membrane ovemight. This simulated the bubble nucleation concept seen in the field.
- a third step was to establish permeate base line flows on clean membranes. Run 3 used the stale soda water that had been aerated overnight. Run 4 used tap water.
- a fourth step was to determine the effect of gas content (function of soda water " out of the bottle” age) on permeate flow compared to tap water.
- Run 5 was on 1 hour-old soda water.
- Run 6 was on tap water.
- Run7 was on 12 hr old soda water.
- a fifth step was to approximate the gas content of the liquor in a typical bioreactor. Run 8 was on 50% tap water and 50% soda water. The soda water / tap water mixture was changed frequently to keep the age of the soda water to less than 30 minutes out "of the bottle.” In the field the CO2 in a long shaft vertical reactor is replenished every 6-10 minutes, so run 8 is conservative.
- Zenon membrane produces about 50 % more flow per sq. ft. than the Kubota membrane but the Zenon membrane uses a vacuum on the permeate discharge line. It may be that Zenon membranes are influenced by the drop in partial pressure across the membrane thus causing a nucleating gas effect. From a differential density across the membrane perspective, a 40" tall Kubota membrane should perform better than a 60" tall Zenon membrane. 4) To quantify the effect of the membrane cleaning process of step 3, tap water was re-run on the alleged cleaned membrane. This time the permeate flow increased from
- Run 6 on tap water produced slightly less permeate flow (5% ) than fresh soda water in Run 5.
- the permeate flow (1950 micro liters per min.) was 23% less than the 1-6 hr old soda permeate rate of (2400 micro liters per min.).
- the permeate flow rate for 12 hr old soda (1950 micro liters per min.) was su ⁇ risingly (16%) lower than for the tap water run 6 (2275micro liters per min.). It would appear that when the filters are clean the rheological properties of the stale soda water_and the tap water behave similarly.
- the data indicates that the difference in permeate flow of the two soda water runs, is related to the age of the soda which in turn is a function of the amount of dissolved gas present.
- the tap water permeate flow exceeded the stale soda water run indicating that there is really no difference in the rheology of the two fluids when processed on a clean membrane.
- the influence on flow due to the pressure differential variation from top to bottom of the vertically oriented membrane is in addition to the increase of flow due to the degassing phenomenon, cited above, occurring at the face of the membrane. Combined, these two effects could potentially double membrane throughput. Based in part on the above, it is contemplated that the increase in flow of permeate through the membrane is due to one or more factors selected from a change in partial pressure of the gas effect, a nucleating gas effect, or a release of stored energy effect.
- Figure 19 illustrates results of a series of temperature, viscosity, and flow tests conducted on the bench test apparatus. Several trials were performed on a test apparatus to see what difference temperature would make on membrane permeate flow. Viscosity and temperature are inversely related, and throughput fluid flow was expected to be strongly related to temperature. Figure 19 quantifies these factors based on several trials on the test apparatus and confirms these expected relationships. An important point is that viscosity varies about 10% between 15 and 25°C. However, between 15 and 25°C, the fluid flow varies almost 50%, or 550 micro liters /min. As illustrated in Figure 19, the membranes are sensitive to temp and viscosity changes in the 15-25 degree range.
- aspects of the invention may be used to improve membrane throughput and/or membrane self-cleaning in saltwater desalination, separation in a chemical process, or in any other situation where membranes are used to separate solute particles, suspended materials and other contaminants from a fluid or solvent.
- the invention therefore includes treating an influent that includes removal of a targeted fluid from the influent with increased membrane throughput.
- the method typically involves a flowing influent stream that includes a fluid that includes a dissolved gas, and a flowing permeate stream that consists essentially of the fluid and the gas.
- the two streams are separated with a permeable membrane having a first surface in fluid communication with the influent stream, and a second surface in fluid communication with the permeate stream.
- the membrane is permeable between the surfaces by molecules of less than a predetermined size, the permeability size being selected to allow the targeted fluid to pass and reject unwanted components of the influent stream.
- the gas may be dissolved in the fluid by any manner or means, for example by injection and as a result of a chemical process occurring within the influent.
- the amount of the dissolved gas in the fluid of the influent stream is an amount that increases the permeate stream flow over the permeate stream flow when the fluid of the influent stream does not include the dissolved gas. This amount may vary depending on the nature of the fluid, the gas, and operating parameters of a system performing the membrane separation.
- the amount of dissolved gas in the fluid of the influent stream may be at least the saturation level of the gas, or may be a supersaturation level of the gas.
- the dissolved gas may include air, or a component of air such as carbon dioxide.
- the targeted fluid may be water, blood, or any other fluid.
- Another aspect of the invention includes treating an influent that includes imparting a self-cleaning action on membrane surfaces.
- the method includes a flowing influent stream that includes a fluid that includes a dissolved gas, and a flowing permeate stream that consists essentially of the fluid and the gas.
- the two streams are separated with a permeable membrane having a first surface in fluid communication with the influent, and a second surface in fluid communication with the permeate.
- the membrane is permeable between the surfaces by molecules of less than a predetermined size, the permeability size being selected to allow the targeted fluid to pass and reject unwanted components of the influent stream.
- the fluid of the influent stream includes the dissolved gas in an amount that permeates the membrane and nucleates proximate to the second surface.
- the fluid of the influent stream may include the dissolved gas in an amount that imparts a scouring action on the first surface.
- the fluid of the influent stream may include the dissolved gas in an amount that nucleates on the second surface and imparts a scouring action on the second surface.
- the nucleation of the gas proximate to membrane surface imparts a scouring action on the surface that helps clean the surface. This increases operating life of the membranes by increasing time between scheduled membrane cleaning cycles that remove the membrane from service.
- Previous Figures 14 through 17 describe aspects of the invention creating a selected pressure differential across membranes along a vertical axis in a liquid- liquid system.
- an embodiment of the present apparatus can be used for creating a selected pressure differential along a vertical axis of membranes in a gas-liquid or a gas-gas system.
- Membrane Diffuser A common conventional technology uses low-pressure horizontally orientated membrane diffusers, typically flat plate membranes placed horizontally on a floor of an aeration tank. The floor area, even if completely covered with membranes, has a relatively small area compared to the tank volume to be aerated. In such horizontal applications, a liquid being aerated is contained above the membrane. This liquid subjects the entire membrane surface to a hydrostatic pressure. A disadvantage of this horizontal membrane design is that bubbles generated are quite large when they leave the surface of the membrane.
- FIG. 20 schematically illustrates a submerged membrane gas diffusion apparatus
- FIG. 21 is a partial cross-sectional front view of the gas diffusion apparatus 600 of Figure 20 and illustrates several aspects of the apparatus, according to an embodiment of the invention.
- the membrane gas diffusion apparatus 600 includes three separate compartments, a fluid treatment compartment 601, a bubbling fluid compartment 602, and a static fluid compartment 603.
- the compartments (601, 602, 603) are preferably located proximate to each other for convenience.
- the membrane gas diffusion apparatus 600 also includes at least one membrane bundle that diffuses a gas into a liquid. In the exemplary embodiment illustrated in Figure 20, three hollow tube membrane bundles 610A-C are positioned at different elevations in the fluid treatment compartment 601 of the gas diffusion apparatus 600. This embodiment of the invention can alternately employ one or more membranes.
- the membranes can be of any type suitable for membrane gas diffusion, such as plate and frame, tubular, hollow fiber, and spiral wound membranes. Further, the membranes can be made from any suitable material, such as cellulose acetate, polyvinyl chloride, polysulfones, polycarbonates, and polyacrylonitriles.
- Elements of the submerged membrane gas diffusion apparatus 600 include a membrane bundle 610, a membrane-mounting member 612, a fluid treatment compartment
- Membrane bundles 610B and 610C are substantially similar to membrane bundle 610A.
- each membrane bundle is about 6 inches in diameter and about 30 inches long, and typically includes a plurality of hollow tubular membranes.
- the hollow tubular membranes have a typical inside diameter of about one inch.
- Figure 21 illustrates the membrane bundle as including three hollow tubular membranes 610A-1, 610A-2, and 610A-3. However, there may be any number of tubular membranes in each tier of membrane bundles 610.
- the membrane bundles 610A-610C are oriented such that the fluid to be treated 634, such as a mixed liquor, flows among tubular membrane bundles of each of the several tiers during aeration.
- Each tubular membrane has a first surface, a second surface, and is permeable between the surfaces by molecules of less than a predetermined size, such as described in conjunction with Figures 14-1 through 14-7.
- Each membrane-mounting member 612 which is a tubular member with a right hand 612R and a left hand 612L portion in a preferred embodiment, mounts or carries a respective end of the membrane bundle 610 at a membrane-mounting portion.
- Each membrane-mounting member 612 includes a chamber 614 that provides the fluid communication FC between the bubbling fluid compartment 602, the first surface 411 of each membrane of the membrane bundle 410 mounted to the mounting member, and the static water compartment 603.
- the chamber 614L of left-hand portion 612L of the membrane mounting member 612 includes a substantially vertically orientated bubble capture chamber 617 and a bubble capture aperture 619, which are illustrated in Figure 21 as part of a rising gas bubble capture member 615.
- the member 615 is coupled with the mounting member 612L to form an assembly.
- the chamber 614R of the right-had portion 612R of the membrane mounting member 612 includes a substantially vertically orientated gas reservoir chamber 618 and gas release aperture 611, which are illustrated in Figure 21 as part of a release member 616.
- the member 616 is coupled with the mounting member 612R to form an assembly.
- the chambers 617 and 618 each have a vertical length, the vertical length 654 of the chamber 617 being greater than the vertical length 656 of chamber 618.
- a fluid to be diffused 620 is described as air 620.
- the fluid 620 to be diffused may be any type of gas, or may be a liquid. Diffusion will be described herein as aeration, but the invention is not so limited.
- a liquid 634 to be treated into which the diffusion occurs will be described as wastewater or water.
- the fluid 634 to be treated may be any type of liquid or gas.
- the fluid treatment compartment 601 includes a configuration that contains the wastewater 634, such as a reactor basin tank that contains high concentrations of suspended solids or mixed liquor for aeration in conjunction with treatment.
- the bubbling fluid compartment 602 includes a configuration that contains a first fluid 632 and the rising bubbles 626 of the air 620.
- the first fluid 632 will be described as clean water 632, but may be any fluid having a specific gravity greater than the air 620.
- the compartment 602 optionally includes a source for the bubbles 626, which may include a gas inlet port 622 that receives the air 620 to be formed into air bubbles 626 in the water 632.
- the port may receive the air 620 from an external source that, upon entry into the bubbling fluid compartment 602 and the clean water 632, forms the bubbles 626.
- the port 622 may receive the clean water 632 including the bubbles 626 into the compartment 602.
- the gas inlet 622 may include any apparatus that forms the air bubbles 626 in the water 632.
- the static fluid compartment 603 includes a configuration that contains a static fluid 636, described as clean water 636, but which may be any fluid, but may be any fluid having a specific gravity greater than the air 620.
- the compartment 603 includes a configuration allowing a user to visually observe whether any bubbles of the gas 620 are being discharged from the gas release aperture 611 of the gas release member 616, or are otherwise present.
- Figure 20 illustrates the assembly 600 arranged with the bubbling fluid compartment 602 and the static water compartment 603 each abutting the fluid treatment compartment 601.
- the compartments may be defined in a single tank or structure.
- the compartments maybe separate tank structures, one of more of which abuts another.
- the compartments 602 and 603 can also abut each other.
- one compartment may be a distance from another compartment.
- Figure 19 also illustrates a "zero" elevation at a lowest point in the apparatus 600, with the elevation increasing in an upward or vertical direction.
- the three tiers of hollow tube membrane bundles 610A-C are mounted in a fluid treatment compartment 601 at elevations 4.0, 6.5, and 9.0 feet respectively.
- any suitable number of the membrane bundles 610 may be used, the membrane bundles may have any separation, and can be only inches apart.
- the rising bubble capture portion of the first chamber 614L shown as capture member 615 and bubble capture aperture 619, are located in the bubbling fluid compartment 602.
- the gas reservoir portion of the second chamber 614R shown as release member 616 and gas release aperture 611, are located in the static water compartment 603.
- the rising bubble capture members 615 are illustrated with a 2.5 foot-long vertical length measured from the bubble capture aperture 619 to the lowest elevation of the respective membrane bundles 610 to which they are coupled.
- Gas release members 616 are illustrated with a 2.0 foot- long vertical length measured from the gas release aperture 611 to the lowest elevation of the respective membrane bundles 610 to which they are coupled.
- the rising bubble-capture members 615 and the gas release member 616 may be any length.
- the gas release members 616 are shorter that the rising bubble-capture members 615. A length differential of 0.5 feet is expected to provide satisfactory results. If there is a significant difference in the specific gravity of the aerated clean water 632 and the static clean water 636, the length differential between the gas release member 616 and the bubble-capture member 616 is adjusted to provide the automatic gas release functionality described below.
- the bubbling fluid compartment 602 is filed with aerated clean water 632, and the static water compartment 603 is filled with static clean water 636.
- the fluid treatment compartment 601 is filled with the wastewater 634 to be aerated to a level sufficient to submerge the membranes 610A-C.
- the wastewater 634 optimally is flowed through the compartment 601 from a low elevation to a high elevation proximate to the second surfaces of the membranes in a manner that facilitates aeration, and then flowed from the compartment.
- Figure 20 illustrates an initial static water level of 12 feet in the assembly 600, which then increases to 12.6 feet in the compartments 601 and 602 as the water 632 and wastewater 634 are aerated.
- the air 620 is pumped at a relatively low pressure into the bubbling fluid compartment 602 through port 622, and the air bubbles 626 are formed in the clean water contained in the compartment to form the aerated water 632. Only a small amount air pressure is required to pump the air 620 through the port 622 and into the compartment 602, saving energy compared to existing systems requiring an increased pressure to force air bubbles from diffusion membranes.
- the bubbles 626 are formed in a diameter sufficient to cause the bubbles to rise in the aerated water 632.
- the bubbles 626 rise in the aerated water 632, and a portion of the bubbles rise through the capture member bubble capture aperture 619 and are captured in the rising bubble capture member chamber 617.
- the rising bubbles 626 coalesce and ultimately release the air 620 above an aerated water 632/air 620 interface 658 within the capture member chamber 617.
- the capture member chamber 617 is in fluid communication with membrane-mounting member portion of the chamber 614, which is in turn in fluid communication with the first surface of the membranes of the membrane bundle 610, the released air 620 flows or is communicated with the first surface of the membranes along the fluid communication path FC.
- the vertical position of the aerated water 632/air 620 interface 658 within the capture member chamber 617 with respect to a lowest elevation of the membranes of the membrane assembly defines a gas column 652 having a vertical length, which can also be described as a hydraulic head or differential hydraulic head.
- the gas column 652 imposes a hydraulic head on the air 620, which is a function of the buoyancy of the air 620 in the aerated water 632. That imposed hydraulic head is transmitted to the portion of the air 620 in fluid communication with the first surface of the membrane of the tube membrane bundle 610.
- Figure 20 illustrates the gas column length 652 as one foot of the water 632, establishing hydraulic head equal to one- foot of water.
- the one- foot hydraulic head applies a pressure to the molecules of the air 620 in fluid communication FC with the first surface 411 of the membranes of the membrane bundles 610, forcing some of the air molecules through pores of the membranes to form aeration air bubbles 628 in the water 634.
- the gas column 652 vertical length and resulting differential hydraulic head are established by the amount of the bubbles 626 in the bubbling fluid compartment 602 that enter the bubble capture aperture 619.
- Increasing the number of air bubbles 626 formed in the aerated water 632 increases the number of air bubbles rising into the bubble capture aperture 619, thus increasing the flow of air into the membrane-mounting member chamber 614. This increased air flow will exceed that which can permeate the membranes 610 at the existing imposed hydraulic head.
- the air 620 will accumulate in the chambers 614, 617, and 618, and the vertical elevation of the aerated water 632/air 620 interface 658 will decrease.
- This increases the gas column length 652, and increases the imposed hydraulic head on the released air 620, thus increasing the air flow through the membranes until an equilibrium is reached in response to the amount of bubbles 626 in the bubbling fluid compartment 602.
- the internal air pressure of the membrane bundles 610 self adjusts to the air flow provided by the bubbles 626. The higher the air flow provided by the bubbles 626, the lower the water 632 level in the rising bubble capture member 615, and the greater the differential hydraulic head 652.
- the membrane bundle 610 is connected to clean water compartments 602 and 603, no internal fouling of the membranes should occur.
- the membrane surfaces of the membranes of the tubular membrane bundle 510 have differing vertical elevations.
- a top hollow tube membrane of the bundle is at elevation 9.0 feet and a bottom hollow tube is at 8.5 feet, initially, the top membrane in the tube membrane 610C bundle will see a little greater pressure differential than the bottom membrane because it is at a lesser depth, and will therefore produce a little more air bubbles 628 until its maximum flow rate is achieved, thus increasing the internal pressure on the air 620 and causing the bottom membrane to approach maximum transfer as well.
- the hydraulic head across the membrane surfaces of the top bundle tubes of the membrane bundle 610C is the pressure of the water 634 outside the second membrane surface 412 minus the pressure of the air 620 inside at the first membrane surface 411.
- the hydraulic head is 0.62 psig.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP05740138A EP1789162A4 (en) | 2004-04-06 | 2005-03-31 | Method and apparatus providing improved throughput and operating life of submerged membranes |
JP2007507377A JP2007532297A (en) | 2004-04-06 | 2005-03-31 | Method and apparatus for improving immersion membrane throughput and operating life |
CA002560193A CA2560193A1 (en) | 2004-04-06 | 2005-03-31 | Method and apparatus providing improved throughput and operating life of submerged membranes |
AU2005233102A AU2005233102A1 (en) | 2004-04-06 | 2005-03-31 | Method and apparatus providing improved throughput and operating life of submerged membranes |
US11/679,789 US20080017558A1 (en) | 2005-03-31 | 2007-02-27 | Methods and Devices for Improved Aeration From Vertically-Orientated Submerged Membranes |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/895,432 | 2004-04-06 | ||
US10/895,432 US20050218074A1 (en) | 2004-04-06 | 2004-04-06 | Method and apparatus providing improved throughput and operating life of submerged membranes |
US57238704P | 2004-05-18 | 2004-05-18 | |
US60/572,387 | 2004-05-18 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/679,789 Continuation-In-Part US20080017558A1 (en) | 2005-03-31 | 2007-02-27 | Methods and Devices for Improved Aeration From Vertically-Orientated Submerged Membranes |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2005100264A2 true WO2005100264A2 (en) | 2005-10-27 |
WO2005100264A3 WO2005100264A3 (en) | 2006-11-30 |
Family
ID=35150536
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2005/010976 WO2005100264A2 (en) | 2004-04-06 | 2005-03-31 | Method and apparatus providing improved throughput and operating life of submerged membranes |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1789162A4 (en) |
JP (1) | JP2007532297A (en) |
AU (1) | AU2005233102A1 (en) |
CA (1) | CA2560193A1 (en) |
WO (1) | WO2005100264A2 (en) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007053890A1 (en) * | 2005-11-08 | 2007-05-18 | Siemens Water Technologies Corp. | Combination membrane/biolytic filtration |
AU2006312995B2 (en) * | 2005-11-08 | 2011-09-08 | Evoqua Water Technologies Llc | Combination membrane/biolytic filtration |
CN101508512B (en) * | 2009-03-16 | 2012-12-19 | 俞敏厚 | Core-three-circulation combined water treatment process |
CN103517746A (en) * | 2010-09-27 | 2014-01-15 | 世界水务工程股份有限公司 | Floated solids separation |
US8910799B2 (en) | 2011-08-01 | 2014-12-16 | Enveera, Inc. | Integrated membrane system for distributed water treatment |
US10550022B2 (en) | 2016-01-18 | 2020-02-04 | DOOSAN Heavy Industries Construction Co., LTD | Sewage/wastewater treatment system using granular activated sludge and membrane bio-reactor and sewage/wastewater treatment method using the same |
CN113735385A (en) * | 2021-09-24 | 2021-12-03 | 浙江省海洋水产研究所 | Breeding wastewater treatment device and treatment method thereof |
TWI757891B (en) * | 2019-09-27 | 2022-03-11 | 日商洛奇科技股份有限公司 | Decompression filter device |
US11851356B2 (en) | 2020-01-06 | 2023-12-26 | The Research Foundation For The State University Of New York | Bioreactor system and method for nitrification and denitrification |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2580622B1 (en) * | 1985-04-23 | 1991-04-19 | Degremont | DEVICE FOR INTRODUCING A GAS INTO A LIQUID |
US4961854A (en) * | 1988-06-30 | 1990-10-09 | Envirex Inc. | Activated sludge wastewater treatment process |
NL9302260A (en) * | 1993-12-24 | 1995-07-17 | Stork Friesland Bv | Membrane bioreactor with gas-lift system. |
US5451317A (en) * | 1994-09-08 | 1995-09-19 | Kubota Corporation | Solid-liquid separator |
CA2271170C (en) * | 1999-05-05 | 2006-07-11 | Craig L. Glassford | A gas/liquid mixing apparatus and method |
AU2002307836B2 (en) * | 2001-02-23 | 2007-11-08 | V.A.I. Ltd. | Methods and apparatus for biological treatment of waste waters |
-
2005
- 2005-03-31 AU AU2005233102A patent/AU2005233102A1/en not_active Abandoned
- 2005-03-31 WO PCT/US2005/010976 patent/WO2005100264A2/en active Application Filing
- 2005-03-31 CA CA002560193A patent/CA2560193A1/en not_active Abandoned
- 2005-03-31 EP EP05740138A patent/EP1789162A4/en not_active Withdrawn
- 2005-03-31 JP JP2007507377A patent/JP2007532297A/en active Pending
Non-Patent Citations (1)
Title |
---|
See references of EP1789162A4 * |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007053890A1 (en) * | 2005-11-08 | 2007-05-18 | Siemens Water Technologies Corp. | Combination membrane/biolytic filtration |
US7708887B2 (en) | 2005-11-08 | 2010-05-04 | Siemens Water Technologies Corp. | Combination membrane/biolytic filtration |
AU2006312995B2 (en) * | 2005-11-08 | 2011-09-08 | Evoqua Water Technologies Llc | Combination membrane/biolytic filtration |
CN101508512B (en) * | 2009-03-16 | 2012-12-19 | 俞敏厚 | Core-three-circulation combined water treatment process |
CN103517746A (en) * | 2010-09-27 | 2014-01-15 | 世界水务工程股份有限公司 | Floated solids separation |
US8910799B2 (en) | 2011-08-01 | 2014-12-16 | Enveera, Inc. | Integrated membrane system for distributed water treatment |
US10550022B2 (en) | 2016-01-18 | 2020-02-04 | DOOSAN Heavy Industries Construction Co., LTD | Sewage/wastewater treatment system using granular activated sludge and membrane bio-reactor and sewage/wastewater treatment method using the same |
US10961141B2 (en) | 2016-01-18 | 2021-03-30 | DOOSAN Heavy Industries Construction Co., LTD | Sewage/wastewater treatment system using granular activated sludge and membrane bio-reactor and sewage/wastewater treatment method using the same |
TWI757891B (en) * | 2019-09-27 | 2022-03-11 | 日商洛奇科技股份有限公司 | Decompression filter device |
US11851356B2 (en) | 2020-01-06 | 2023-12-26 | The Research Foundation For The State University Of New York | Bioreactor system and method for nitrification and denitrification |
CN113735385A (en) * | 2021-09-24 | 2021-12-03 | 浙江省海洋水产研究所 | Breeding wastewater treatment device and treatment method thereof |
Also Published As
Publication number | Publication date |
---|---|
EP1789162A2 (en) | 2007-05-30 |
JP2007532297A (en) | 2007-11-15 |
WO2005100264A3 (en) | 2006-11-30 |
AU2005233102A1 (en) | 2005-10-27 |
EP1789162A4 (en) | 2007-08-15 |
CA2560193A1 (en) | 2005-10-27 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20050218074A1 (en) | Method and apparatus providing improved throughput and operating life of submerged membranes | |
US20080017558A1 (en) | Methods and Devices for Improved Aeration From Vertically-Orientated Submerged Membranes | |
AU2002307836B2 (en) | Methods and apparatus for biological treatment of waste waters | |
Visvanathan et al. | Membrane separation bioreactors for wastewater treatment | |
Bohdziewicz et al. | Landfill leachate treatment by means of anaerobic membrane bioreactor | |
AU2002307836A1 (en) | Methods and apparatus for biological treatment of waste waters | |
WO2005100264A2 (en) | Method and apparatus providing improved throughput and operating life of submerged membranes | |
Rodríguez-Hernández et al. | Comparison between a fixed bed hybrid membrane bioreactor and a conventional membrane bioreactor for municipal wastewater treatment: a pilot-scale study | |
Engelhardt et al. | Integration of membrane filtration into the activated sludge process in municipal wastewater treatment | |
RU2181344C2 (en) | Plant for and method of biological purification of impurities and sewage water | |
Cote et al. | Wastewater treatment using membranes: the North American experience | |
US20120012524A1 (en) | Membrane bioreactor process | |
CN105384249B (en) | A kind of sewage water treatment method and device for having both advanced nitrogen dephosphorization and muddy water Gravity Separation | |
CN101734794B (en) | Lateral flow type membrane bioreactor device and sewage treatment method using same | |
Rodríguez-Hernández et al. | Evaluation of a hybrid vertical membrane bioreactor (HVMBR) for wastewater treatment | |
US7041219B2 (en) | Method and apparatus for enhancing wastewater treatment in lagoons | |
CN205528260U (en) | Sewage treatment system | |
Kim et al. | Membrane fouling control through the change of the depth of a membrane module in a submerged membrane bioreactor for advanced wastewater treatment | |
Ng et al. | Effects of solid retention time on the performance of submerged anoxic/oxic membrane bioreactor | |
CN201305510Y (en) | Lateral flow type membrane bioreactor device | |
Hussain et al. | Membrane bio reactors (MBR) in waste water treatment: a review of the recent patents | |
Castelo‐Grande et al. | Design and application of a membrane bioreactor unit to upgrade and enhance the required performance of an installed wastewater treatment plant | |
Du Toit et al. | The Performance and Kinetics of Biological Nitrogen and Phosphorus Removal with Ultra-Filtration Membranes for Solid-Liquid Separation | |
Capodaglio et al. | Application of membrane and membrane-like technologies for state-of-the-art wastewater treatment | |
Hagstrom et al. | A Modified Design and Operational Approach for Membrane Bioreactors |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A2 Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BW BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE EG ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NA NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SM SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW |
|
AL | Designated countries for regional patents |
Kind code of ref document: A2 Designated state(s): BW GH GM KE LS MW MZ NA SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LT LU MC NL PL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
WWE | Wipo information: entry into national phase |
Ref document number: 2560193 Country of ref document: CA |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2007507377 Country of ref document: JP |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
WWW | Wipo information: withdrawn in national office |
Ref document number: DE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 6204/DELNP/2006 Country of ref document: IN Ref document number: 2005233102 Country of ref document: AU |
|
WWE | Wipo information: entry into national phase |
Ref document number: 550731 Country of ref document: NZ |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2005740138 Country of ref document: EP |
|
ENP | Entry into the national phase |
Ref document number: 2005233102 Country of ref document: AU Date of ref document: 20050331 Kind code of ref document: A |
|
WWP | Wipo information: published in national office |
Ref document number: 2005233102 Country of ref document: AU |
|
WWE | Wipo information: entry into national phase |
Ref document number: 200580018454.0 Country of ref document: CN |
|
WWE | Wipo information: entry into national phase |
Ref document number: 11679789 Country of ref document: US |
|
WWP | Wipo information: published in national office |
Ref document number: 2005740138 Country of ref document: EP |
|
WWP | Wipo information: published in national office |
Ref document number: 11679789 Country of ref document: US |