WO2008025098A1 - Procédé de traitement et appareil - Google Patents

Procédé de traitement et appareil Download PDF

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Publication number
WO2008025098A1
WO2008025098A1 PCT/AU2007/001281 AU2007001281W WO2008025098A1 WO 2008025098 A1 WO2008025098 A1 WO 2008025098A1 AU 2007001281 W AU2007001281 W AU 2007001281W WO 2008025098 A1 WO2008025098 A1 WO 2008025098A1
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WO
WIPO (PCT)
Prior art keywords
vessel
waste
aqueous organic
organic waste
lower section
Prior art date
Application number
PCT/AU2007/001281
Other languages
English (en)
Inventor
Tito Pica
David Halliday
Original Assignee
Active Research Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2006904803A external-priority patent/AU2006904803A0/en
Application filed by Active Research Pty Ltd filed Critical Active Research Pty Ltd
Priority to AU2007291890A priority Critical patent/AU2007291890A1/en
Publication of WO2008025098A1 publication Critical patent/WO2008025098A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/02—Biological treatment
    • C02F11/04—Anaerobic treatment; Production of methane by such processes
    • 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
    • C02F3/28—Anaerobic digestion processes
    • C02F3/2806—Anaerobic processes using solid supports for microorganisms
    • 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
    • C02F3/28—Anaerobic digestion processes
    • C02F3/286—Anaerobic digestion processes including two or more steps
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M21/00—Bioreactors or fermenters specially adapted for specific uses
    • C12M21/04—Bioreactors or fermenters specially adapted for specific uses for producing gas, e.g. biogas
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M23/00—Constructional details, e.g. recesses, hinges
    • C12M23/34—Internal compartments or partitions
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M25/00—Means for supporting, enclosing or fixing the microorganisms, e.g. immunocoatings
    • C12M25/02—Membranes; Filters
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M41/00—Means for regulation, monitoring, measurement or control, e.g. flow regulation
    • C12M41/12—Means for regulation, monitoring, measurement or control, e.g. flow regulation of temperature
    • C12M41/18—Heat exchange systems, e.g. heat jackets or outer envelopes
    • C12M41/24—Heat exchange systems, e.g. heat jackets or outer envelopes inside the vessel
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel

Definitions

  • the present invention relates to waste treatment processing, in particular, processing of waste such as, for example, aqueous based organic waste, winery effluent, sewage or industrial grease trap waste.
  • wastewater In addition to sewage waste, large quantities of wastewater are generated by industries such as breweries, sugar mills, distilleries, food-processing industries, tanneries, paper and pulp industries and livestock industries.
  • industries such as breweries, sugar mills, distilleries, food-processing industries, tanneries, paper and pulp industries and livestock industries.
  • the nature of the wastewater depends on its source and also its treatment process. Depending on its source, the wastewater may contain not only organic and inorganic matter, but also bacteria, viruses, oil, grease, nutrients such as nitrogen and phosphorous, heavy metals and organochlorines.
  • the discharge of industrial waste water is subject to what is known as a "Trade
  • Waste Agreement with the local water authority in which industrial waste must be treated so that it meets certain quality standards before discharge or reuse.
  • the most common way of treating trade waste is physio/chemical where the pH is adjusted and a polymer is added to flocculate the solids in the waste. Such treatment produces masses of residual waste known as sludge.
  • the treated water may be recycled, used for irrigation or released into the sewer.
  • Disposal of sludge to land is widely practised, but is coming under increasing pressure as (a) suitable sites become scarce (b) the higher costs associated with landfilling and (c) the introduction of tighter controls on the discharge of hazardous substances into the environment. As such, the volume of sludge has to be reduced.
  • sludge treatment is digestion in lagoons which may occur under anaerobic or aerobic conditions.
  • Anaerobic lagoons are more widely used since anaerobic bacteria decompose more organic matter per unit lagoon volume than aerobic bacteria.
  • the anaerobic process is not dependent on the maintenance of dissolved oxygen, the lagoons can be much deeper thereby reducing the amount of required surface area and the need for agitation of the lagoon to introduce oxygen is eliminated which can otherwise be quite expensive to operate.
  • a drawback with anaerobic lagoons is that they can produce an offensive odour if not properly managed.
  • Another drawback with both aerobic and anaerobic lagoons is the lengthy treatment turnaround time which is, on average, about 15 to 20 days.
  • the present invention provides a method of treating aqueous organic waste to form a treated product, the method comprising introducing the aqueous waste into a vessel having an upper section and a lower section wherein microbes capable of converting the aqueous organic waste into a treated product reside in the upper and lower sections of the vessel; and maintaining the aqueous waste within the vessel in a fluidised and suspended state by the introduction of a fluidising medium into the lower section of the vessel.
  • the fluidising medium is fluid recycled from the vessel, however any type of fluid such as, for example, fresh aqueous organic waste may be used.
  • the treated product substantially comprises a mixture of methane gas and water.
  • the methane gas is collected from the upper section of the vessel and used as a fuel source to heat the vessel contents.
  • the lower section of the vessel houses acidogenic microbes which convert organics in the aqueous organic waste primarily into a mixture of organic acids and the upper section houses methanogenic microbes which convert the mixture of organic acids primarily into methane.
  • the introduction of the fluidising medium into the lower section of the vessel is achieved through intermittent injection.
  • fluidising medium is injected into the vessel lower section no more than about 5 times per 24 hours with each injection lasting about 1 to 2 minutes. It will be appreciated, however, that aqueous organic waste with higher BOD loadings will produce more sludge and therefore the duration and the number of times the fluidisation medium is injected into the vessel will depend on the BOD of the aqueous organic waste.
  • the aqueous organic waste will have a tendency to settle forming a sludge blanket at the bottom of the vessel.
  • any pH adjustment of the aqueous organic waste through the use of, for example, magnesium hydroxide tends to promote the settling of the heavier components within the waste.
  • Such settling of the sludge may lead to the formation of sludge blanket which may cause mixing and temperature problems within the vessel thereby adversely affecting the microbial population and lowering the conversion efficiency of aqueous organic waste into treated product.
  • the fluidisation of the sludge allows temperature control to be more readily achieved throughout the reactor.
  • the present invention provides a method of treating aqueous waste containing organic material to form a treated product, the method comprising: anaerobically digesting at least a portion of the organic material into, primarily, a mixture of organic acids with acidogenic bacteria and converting the organic acids primarily into methane with methanogenic bacteria, wherein the overall conversion of the organic material into methane is capable of being achieved in about, or less than about, 24 hours.
  • the anaerobic digestion is performed at about 38 0 C and at a pH of about 7.3.
  • the methane is collected and used as fuel source to heat the vessel contents and to maintain the anaerobic digestion at about 38 0 C.
  • Treatment of the aqueous organic waste according to the method of the first and second aspects of the invention may be preceded by a separation step comprising a screening step and/or clarification.
  • a screening step preferably removes solids greater than about 20 mm in size and clarification allows the settling of particulate matter.
  • Treatment of the aqueous organic waste according to the method of the first and second aspects of the invention may also be followed by one or more disinfection steps.
  • the treatment is followed by an ozonation step.
  • the treatment step and/or the ozonation step may also be followed by a filtration step.
  • the filtration step comprises zeolite filtration.
  • aqueous organic waste having a Biological Oxygen Demand (BOD) of about 2,000 to 80,000 ppm may be treated.
  • BOD Biological Oxygen Demand
  • aqueous organic waste having a BOD of about 6,000 to about 10,000 ppm, preferably about 8,000 ppm is continuously introduced into the lower section of the vessel and caused to move from the lower section of the vessel to the upper section of the vessel such that it is substantially converted into the treated product in about 24 hours - that is, the retention time of the vessel is preferably about 24 hours. It will be appreciated, however, that the retention time of the vessel will be dependent on the BOD of the aqueous organic waste with longer retention times being required for aqueous organic waste having higher BOD loadings.
  • the vessel contents are maintained at a temperature of 36 0 C - 38°C. Most preferably, the vessel contents are maintained at a temperature of about 38 0 C.
  • the vessel contents are maintained at a pH of about 7.0 to about 7.5 Most preferably, the vessel contents are maintained at a pH of about 7.3.
  • the present invention provides an apparatus for treating aqueous organic waste to form a treated product, the apparatus comprising a vessel having an upper section and a lower section and at least one waste circulation system that retains the aqueous organic waste in a suspended state.
  • the present invention provides an apparatus for treating aqueous organic waste to form a treated product, the apparatus comprising a vessel and one or more heating means, the vessel comprising: a lower section housing acidogenic microbes which convert organics in the aqueous organic waste primarily into a mixture of organic acids; and an upper section housing methanogenic microbes which convert the mixture of organic acids primarily into methane; and at least one waste circulation system that retains the aqueous organic waste in a suspended state as it moves from the lower section to the upper section of the vessel.
  • the vessel is operated in continuous mode and the residence time of the aqueous organic waste in the vessel is about 24 hours or less.
  • the present invention provides an apparatus for treating aqueous organic waste to form a treated product, the apparatus comprising: a receiving tank in which the aqueous organic waste is introduced wherein any particulate material is allowed to settle; an anaerobic digester comprising a vessel in which a mixture of acidogens and methanogens reside, wherein the acidogens convert at least a portion of any organic material in the aqueous organic waste into, primarily, volatile fatty acids and wherein the methanogens convert at least a portion of the volatile fatty acids into, primarily, methane; at least one waste circulating system, and optionally, an ozone tower and/or a filter unit.
  • the vessel according to the third aspect of the invention may be of any shape, although, preferably, the vessel has a base that is of an inverted conical configuration extending from a cylindrical vessel body. It will be appreciated that the inverted conical shape of the vessel base assists in the collection and/or disposal of any solid matter which settles in the trough of the inverted cone.
  • the vessel according to any aspects directed to the apparatus of the invention further comprises a platform on which a microbial population may grow.
  • the platform advantageously allows the passage of fluids like gas and water therethrough, however substantially prevents the passage of microbes such as, for example, bacteria, yeast or fungi.
  • the platform is of a mesh configuration and may be made from any material, for example, polypropylene.
  • the platform is an extruded polypropylene mesh.
  • the platform is desirably positioned within the vessel in a manner that serves to substantially separate the mixing of the contents in the upper section with those in the lower section, thereby avoiding the mixing of the acidogenic and methanogenic microbial populations.
  • the platform also advantageous serves to prevent washout of the microbial population from the vessel during bulk fluid flow of the vessel contents from the bottom to the top of the vessel.
  • the apparatus preferably comprises one or more waste circulating systems located in the lower section of the vessel through which a fluidising medium is introduced into the vessel.
  • the one or more waste circulating systems are located and arranged to allow the fluidising medium to be introduced into the vessel in a direction that is substantially at right angles to the bulk flow of waste as it moves from the lower section to the top section of the vessel.
  • the waste circulation system comprises three pipes arranged in a pronged and planar configuration. It will be appreciated however that other configurations are possible such as a single, dual or multi-pipe configuration.
  • the one or more waste circulating systems comprise three pipes arranged in a pronged configuration which are orientated so that the flow direction of the fluidising medium ejected from the pipes is substantially at right angles to the bulk flow of the waste as it moves from the lower section to the top section of the vessel.
  • the fluidising medium is at least a portion of the treated product recirculated from the vessel contents, however, it will be understood that any liquid capable of achieving fluidisation of vessel contents is suitable.
  • the apparatus comprises at least one waste circulating system comprising a nozzle positioned substantially at the base of the vessel through which a fluid is fed and ejected in the upward direction under pressure by means of a pump, for example, a circulating pump.
  • the fluid fed through the nozzle may be any fluid, for example, water or recycled matter from the vessel, ie digestate.
  • the apparatus according to the second or third aspects of the invention may further include a waste circulating system fitted within the vessel base.
  • the vessel base is of an inverted conical configuration thereby assisting in the collection of matter.
  • the waste circulating system preferably comprises an elongate conduit positioned centrally within the vessel base having a first end positioned at or near the trough region of said inverted cone and a second end positioned at about 20% of the vessel height wherein the conduit is provided with a internal co-axially mounted screw-like device. .
  • the screw-like device serves as an Archimedes screw so that solid matter that settles at the base of the vessel is swept up by the screw-like device within the conduit and is moved (or lifted) in the upward direction.
  • the point at which the solid matter exits the conduit comprises an overhanging lip that extends in the downward direction toward the base or trough of the vessel and is outwardly extended to about 20% of the vessel width.
  • the apparatus alternatively or additionally includes a heating means in the form of a heating coil located in the lower section of the vessel and a waste circulating system.
  • the waste circulating system comprises three pipes arranged in pronged configuration wherein the centre pipe of the three pipes is angled so that fluidising medium is ejected directly onto the heating coil. In this way, the sludge is prevented from forming a blanket around the heating coil and the vessel contents are maintained in a mixed and suspended state thereby achieving uniform heating throughout the vessel.
  • the apparatus may have one or more sweeper arms attached to a centrally located rotatable longitudinal member extending from between the top and the bottom of a vessel.
  • the one or more sweeper arms may be attached to the longitudinal member proximate to and above the vessel liquid surface. At this location, the one or more sweeper arms desirably break up any surface scum that may accumulate at the liquid surface as the longitudinal member is rotated. Alternatively or additionally to the above, one or more sweeper arms may be attached to the longitudinal member proximate to and under the platform on which microbes grow. At this location, the one or more sweeper arms desirably break up or disengage gas bubbles which may occur at the platform surface as the longitudinal member is rotated. This is desirable as gas bubbles tend to cause particulate matter to accumulate under the platform which is sometimes referred to as "raft".
  • one or more sweeper arms may be attached to the longitudinal member proximate to the base of the vessel.
  • the one or more sweeper arms desirably move settled matter, for example, heavy inorganic material, that accumulates at the base of the vessel. This allows for easier collection and eventual removal of such matter from the vessel.
  • the one or more sweeper arms may comprise brushes (or a broom), chains or the like extending therefrom. These desirably assist in disengaging or breaking up any settled or accumulated matter or floating scum.
  • the present invention provides a method of treating aqueous organic waste to form a treated product, the method comprising treating the aqueous organic waste in an apparatus according to any one of the third, fourth or fifth aspects of the invention.
  • the present invention provides the use of an apparatus according to any one of the third, fourth or fifth aspects of the invention to treat aqueous waste and to form a treated product.
  • the present invention provides a product produced in accordance with the method of the first or second aspects of the invention.
  • FIG. 1 is a schematic diagram of the apparatus in accordance with an embodiment of the invention.
  • Figure 2 is a photograph of the waste circulating system in accordance with an embodiment of the invention.
  • Figure 3 is a photograph of the waste circulating system shown from a different perspective.
  • Figure 4 is a photograph of the fluidising pump connected to the waste circulating system used to pump and inject the fluidising medium into the vessel via the waste circulating system.
  • Figure 5 depicts a flowchart of the process in accordance with an embodiment of the invention.
  • FIG. 6 is a schematic diagram of the apparatus in accordance with an embodiment of the invention.
  • Figure 7 is a schematic diagram of a base plate in accordance with an embodiment of the invention.
  • Figure 8 is a schematic diagram of the apparatus in accordance with an embodiment of the invention.
  • Figure 9 is a diagram showing the waste circulating system of figures 2 and 3 in plan view.
  • the treatment technology of the present invention is based on managed anaerobic digestion of aqueous organic waste.
  • Various anaerobic acidogenic and methanogenic bacteria convert the organic load into methane, water, CO 2 and a small amount of residual sludge.
  • the process is preferably contained in an above ground reactor vessel which incorporates a gas/liquid/solid disengagement zone dominated by a microbial population held in the reactor.
  • the acidogenic and methanogenic bacteria are capable of converting aqueous organic waste into, primarily methane, which may be recycled and used as a fuel source, or transported off site for alternative use.
  • One of the more common reasons that leads low rates of conversion and long retention times in anaerobic digesters is improper mixing of the digester contents.
  • a treated product of a high quality standard ie clean water with a BOD 10 mg/1
  • This clean water may be used, for example, for irrigation of vegetable crops.
  • Aqueous organic waste may be pre-treated prior to entry into the receiving tank. This may be achieved by the use of a bar screen (eg 20 mm bar screen) to capture any solid objects which may exist in the waste stream.
  • the aqueous organic waste (or pretreated aqueous organic waste) is transferred to the receiving tank by a transfer pump, eg a positive displacement pump.
  • a transfer pump eg a positive displacement pump.
  • Persons skilled in the art will understand that other methods of feeding the waste into the receiving tank are possible, such as, for example, gravity feed.
  • the receiving tank preferably comprises a cone base that allows for ready collection and draw-off of the settled solid matter.
  • the draw-off of the settled matter is preferably achieved through vacuum, however persons skilled in the art will understand that other methods of collection are possible.
  • the tank may also be fitted with an override switch which cuts power to the transfer pump in the event the tank is in danger of overfilling.
  • the receiving tank may be fabricated from any suitable material known to persons skilled in the art such as, for example, reinforced vinyl ester fibreglass.
  • the receiving tank may also be equipped with a level indicator so that the level of the tank may be deduced externally of the tank by visual means.
  • the receiving tank primarily serves as an initial separation device and also acts as a buffer to minimise process variances and surges. As such, a more uniform aqueous organic waste composition is fed to the digester.
  • any air discharged from the receiving tank is passed through a filtration system (discussed below) to minimise odour emissions.
  • the waste is preferably transferred under substantially isolated (sealed) conditions, eg from a truck, to minimise the emission of unpleasant odours.
  • Treatment of the aqueous organic waste is preferably achieved in a vessel comprising an upper section and a lower section wherein a microbial population is retained within the upper and lower sections of the vessel.
  • the vessel may be of any configuration, for example, circular or rectangular.
  • aqueous organic waste is introduced into the lower section of the vessel and caused to flow in the upward direction towards the upper section of the vessel.
  • the aqueous organic waste travels from the lower to the upper section of the vessel, it comes into intimate contact with the microbial population retained in the reactor and is converted by anaerobic digestion into a mixture of products such as organic acids, methane, water and carbon dioxide.
  • the microbial population is preferably a mixture of acidogens and methanogens.
  • the acidogens are preferably retained within the lower section of the vessel and convert the aqueous organic waste into a mixture of organic acids.
  • the methanogens are preferably retained within the upper section of the vessel and convert the mixture of organic acids primarily into methane.
  • a platform made from, for example, polypropylene extruded mesh may be suspended within the vessel which serves as a support on which the bacteria are able to adhere and grow. The platform also serves in minimising or preventing the microbial population from being carried upward with the bulk flow of the aqueous organic waste at the waste moves from the lower section of the vessel to the upper section of the vessel.
  • the treatment process in accordance with the invention focuses on managed anaerobic digestion in which the anaerobic bacteria convert the organic load into water and methane gas and small amount of residual sludge.
  • the methane gas produced may be utilised elsewhere in the process, transported offsite or subsequently converted to a mixture of water and carbon dioxide.
  • the methane generated through the anaerobic digestion process may be captured and used as fuel source on-site or may be transported off-site.
  • the digester has a domed top, fixed or floating, in which any methane that is generated is collected and drawn from the digester.
  • the methane drawn from the digester may dried and burnt immediately, or alternatively, may be burnt in an internal combustion engine which in turn drives an alternating current generator which can supply electrical power on-site.
  • the methane gas may be collected and used to fuel a burner which in turn heats water used to heat the digester by way of a closed loop water-filled coil.
  • the heating of the digester may also be supplemented with LPG, or LPG may also be used as the primary fuel source during start-up of the process and before any methane is generated.
  • volume of methane produced is dependent on the nature and volume of the waste being treated. For example, the higher the BOD load the greater the amount of organic material to be consumed. The ultimate amount of gas produced is directly proportional to the BOD load.
  • rate of methane gas production will vary according to digester temperature, movement, pH and the microbial population in the vessel.
  • Effluent from the digester is preferably subjected to disinfection to produce a high quality effluent.
  • disinfection is achieved through ozonation.
  • ozone is a strong oxidiser and is therefore able to reduce odour emissions arising from components such as hydrogen sulphide and ammonia present in waste streams such as sewage sludge
  • the ozone is generated onsite and passed through an ozonation tower through which effluent from the digester is also passed and contacted with the ozone.
  • Ozone is produced when an oxygen molecule(O 2 ) is dissociated by an energy source into oxygen atoms and subsequently collide with another oxygen atom to form an unstable gas, ozone (O 3 ).
  • Ozone may be generated by, for example, imposing UV irradiation or a high voltage alternating current (6 to 20 kV) across a dielectric discharge gap that contains an oxygen-bearing gas.
  • ozone is a highly unstable gas and rapidly decomposes to elemental oxygen, it is preferably generated onsite.
  • the treated water may be subject to a zeolite filtration step.
  • Zeolite filtration is desirable to trap any residual particulate matter.
  • Zeolite filtration is also desirable to collect heavy metals such as, for example, zinc, copper or lead that may be present in the treated product.
  • any air expelled from the process is passed through a filtration system to remove odour components, for example, hydrogen sulphide and ammonia.
  • the expelled air is passed through an activated carbon filter (eg Riga-Sorb).
  • an activated carbon filter eg Riga-Sorb
  • any waste material is preferably unloaded into the receiving tank through a direct connection piping system from, for example, a truck to the receiving tank. This not only minimises odour emission, but also minimises the risk of any spill of waste material.
  • Treated water may be tested and stored in tanks for reuse onsite, transported for reuse offsite or released into the sewer.
  • the vessel or digester 1 is shown according to an embodiment of the invention.
  • the digester 1 has a height of 4.5 metres, a diameter of
  • the digester 1 comprises an off-centre cone 2 in the base angled towards a 100mm ball valve 3 through which drainage of the vessel contents may be achieved.
  • This cone configuration assists in the collection and removal of dead bacterial cells and any residual sludge.
  • a connection point (by way of a 100 mm Kamlock) is built into the base of the cone to allow for any drainage that may be required.
  • the digester 1 is sealed and all flow streams in and out of the digester 1 are contained within pipe work that are sealed and connected to other components (eg a truck loaded with waste) or a vessel (eg the receiving tank or ozonator) so as so as to minimise contamination of, or the release of offensive odours into, the external environment.
  • other components eg a truck loaded with waste
  • a vessel eg the receiving tank or ozonator
  • aqueous organic waste (distillery waste having a BOD of about 8,000 ppm) is pumped from a receiving tank (as shown in figure 5) to the digester 1 using a 3ph 2.5 KW positive displacement pump fitted with a variable speed gearbox at a rate of 1 kL/h through 40 mm piping.
  • Flow measurement is achieved with a Magflow meter and the waste is fed into the digester 1 at inlet port 4.
  • the aqueous organic waste moves from the lower section 5 of the digester 1 to the upper section 7 of the digester 1.
  • Acidogenic bacteria residing in the lower section 5 convert the organic matter in the waste to organic acid (eg acetic acid) which is subsequently converted to methane gas and water by methanogenic bacteria residing in the upper section 7 of the digester 1.
  • a 1.5m layer of extruded polypropylene mesh 9 (BioBlok) which serves as a growing platform for the bacteria.
  • the polypropylene mesh 9 also serves to slow down or minimise wash-out of the bacteria as the waste flows from the lower section 5 to the upper section 7 of the digester 1.
  • the top of the digester 1 is of a domed configuration 11 which provides strength and also allows for the collection and draw-off of methane gas that is produced during anaerobic digestion of the waste.
  • Heat transfer to the vessel contents is achieved by way of a stainless steel heat coil 13 situated in the lower section 5 of the digester 1 through which circulating hot water (75 0 C) is continuously passed.
  • the heat coil 13 (2 loops) is approximately 12 metres long and 50 mm in diameter.
  • Temperature control is achieved with a reactor temperature device (RTD) 15 situated in the top of the digester 1 in which a temperature probe 17 is inserted.
  • the RTD 15 switches a circulating hot water pump (not shown) on and off as required.
  • the vessel contents are maintained at about 37-38 0 C.
  • Temperature control is further aided by providing external insulation to the vessel (side and bottom) using insulation rubber (19 mm in thickness) (not shown).
  • About 200 mm from the top of the digester 1 is an overflow port 19 where the treated product (water) flows to the ozonator by gravity.
  • the concave (domed) top 11 comprises a collection point (25 mm) 21 where the generated methane gas is collected and piped away. Adjacent to the collection point 21 is a temperature controller, a temperature probe and relay (not shown). The domed top 11 also comprises a sealable insertion point for a pH probe (not shown).
  • a small positive displacement pump (0.5 kW) 23 to circulate a portion of the vessel contents through piping (25 mm) 25 from either the middle or the top of the digester 1.
  • a pH probe 27 which controls a magnesium hydroxide dosing pump (20 mm peristaltic pump, not shown). In this way, the pH of the recirculated feed into the digester 1 may be controlled and maintained at a desired setpoint (ie 7.3).
  • a temperature sensor is also included with the pH probe (not shown).
  • the digester 1 further comprises a waste circulation system 29 as will now be described in detail with reference to figures 2 to 4.
  • the waste circulation system 29 comprises a pronged piping arrangement which allows a fluidising medium (eg recirculated waste) to be injected into the digester 1. This assists in maintaining the sludge within the vessel contents in a fluidised and suspended state which not only promotes contact with the bacterial population thereby increasing conversion efficiency, but also allows greater mixing of the vessel contents thereby achieving better temperature control throughout the digester 1.
  • the waste circulating system comprises a pronged piping arrangement having three pipes (eductors) 31, 33 and 35 arranged in a planar fashion through which fluidising medium is injected.
  • the centre pipe (eductor) 35 has a bent section which is angled towards the heating coil 13 (shown in figure 1). In this way, the settling of the sludge over the heating coil 13 is prevented thereby preventing the formation of a sludge blanket. This allows greater temperature control to be achieved throughout the digester 1.
  • the fluidising medium is pumped through waste circulating system by means of a fluidising pump (Ebara DWO 200 stainless steel open impeller) 37 as shown in Figure 4. Fluidising medium is intermittently pumped through pipes 31, 33 and 35 at a frequency of about 3 to 5 times per 24 hours each time for a period of 3 to 5 minutes.
  • the pipes 31, 33 and 35 preferably include eductor nozzles (not shown) at each of their ends which increases the volume of medium circulated without having to increase the pump speed or capacity. In this way, sufficient fluidisation is achieved so as to maintain the sludge in a suspended state, but high flows and shear rates are avoided to ensure that the microbial population within the digester is not disturbed.
  • the fluidising pump 37 is located in the lower section 5 of the digester 1 and draws liquid from the digester 1 which serves as the fluidising medium as it is injected into the waste circulating system 29 and through eductors 31, 33 and 35.
  • aqueous organic waste (wine distillery waste having a BOD of 8,000 ppm) is continuously pumped from a receiving tank 41 into the bottom of the digester 1 through a 40 mm pipe 39 fitted with a backflow preventer (not shown). Any air dispelled from the receiving tank 31 is passed through an activated carbon filter 43 prior to discharge into the environment.
  • the wine distillery waste is continuously fed into the digester 1 at a feed rate so as to achieve a retention time of about 24 hours. In this time, the organic matter in the wine distillery waste is substantially converted to methane gas (which is collected and drawn off via piping 20) and water.
  • the treated water product overflows and travels, by gravity, to the next stage of the process which is ozonation in an ozonation tower 45.
  • the collection point 19 is situated approximately 300 mm below the water line of the digester 1.
  • a goose neck arrangement (as can be seen in piping 18 on figures 1 and 5) is used to maximise the vessel 1 capacity.
  • a vacuum breaking device (not shown) is also mounted atop the gooseneck of piping 18.
  • a 40 mm pipe (not shown) having a rectangular cross-section (1.3 m x 1.5 m) is suspended horizontally across the digester 1.
  • This pipe of rectangular cross-section comprises a series of holes (10 mm in diameter) along its uppermost section through which water is able to flow and overflow to the ozonator, yet any particulate matter is prevented from entering.
  • ozone is produced in the ozonation tower 45 by pumping water through a 5 mm venturi (not shown) from the bottom of the ozonation tower 45 through an ozone generator 47.
  • the venturi draws air across two UV producing lamps (not shown), each one meter in length and contained in individual stainless tubes.
  • the tubes are jacketed to provide for water cooling of the lamps.
  • Liquid organic waste is introduced into the vessel or digester 101 through port 103 into an anaerobic environment.
  • the vessel is essentially divided into three sections, upper, middle and lower, wherein the middle section comprises a polypropylene platform 109 (Bioblok) on which the microbial population is able to grow.
  • Acidogenic bacteria reside in the lower section 105 and convert the organic matter in the waste to organic acid (eg acetic acid) which is subsequently converted to methane gas and water by methanogenic bacteria residing in the upper section 107 of the digester 101.
  • the digester 101 further comprises a central drive shaft 108 which extends from the top of the digester 101, through the Bioblok platform 109 to a point near the digester base 116 but clear of a base plate 220 (as shown in, and described further with reference to, figure 7) bolted onto the digester base 116.
  • Attached to the drive shaft 108 is a gas sweeper 110, a platform sweeper 112, and a floor sweeper 114 as shown in figure 6. All three sweepers slowly revolve as the drive shaft 108 is rotated (at approximately 5 revolutions per minute).
  • the gas sweeper 110 is situated approximately 150 mm above the digester 101 water line (WL) and is comprised of two arms attached to the drive shaft 108 protruding to a point just clear of the digester internal wall 102.
  • the gas sweeper 110 further comprises stainless steel chains 118 which hang to a point not more than 20 mm below the digester 101 water line (WL). As the gas sweeper arms 110 rotate, the stainless steel chains 118 disrupt the formation of surface scum and release any entrained gas. The disrupted solids sink to the bottom of the digester 101 and are removed through a drain 236 (as shown in figure 7) of the base plate 220 (see figure 7) bolted onto the digester base 116.
  • the platform sweeper 112 (sometimes also referred to as a "raft" sweeper) is situated approximately 150 mm beneath the under-surface of the Bioblok platform 109.
  • the platfo ⁇ n sweeper 112 comprises two opposite arms attached to the drive shaft 108 that protrude to a point just clear of the digester internal wall 102. Attached to the upper side of the platform sweeper arms 112 is a polypropylene "broom" 117 which gently sweeps the underside of the Bioblok platform 109 as the platform sweeper 112 rotates. The effect is to disengage gas bubbles which adhere to particulate matter thereby breaking-up a potentially disruptive raft. The allows the release of trapped gases which then move though the digester 101.
  • the floor sweeper 114 located near the digester base 116 comprises two arms attached to the drive shaft 108.
  • the floor sweeper arms 114 protrude from the drive shaft 108 to a point just clear of the digester internal wall 102.
  • the arms (one on either side of the drive shaft 108) are upward facing at an angle approximately equivalent to the angle of the conical digester base 116.
  • Attached to the underside of the floor sweeper arms 114 is a polypropylene "broom" 122 which gently sweeps across the digester floor 119 to move heavy inorganic material to the centre of the tank and eventual removal through drain 240 (as shown in, and described with reference to, figure 7).
  • Base plate 220 comprises a mixing device 225 having a nozzle 232 fed by circulating pump 234. Under pressure, the nozzle 232 acts in a venturi-like manner by a factor of 4 and creates an inverted conical plume when the material is discharged.
  • the conical plume will consist of newly introduced material together with existing digester contents.
  • the plume will cause a continuous flow of material over the heat exchanger (not shown) thereby preventing (or at least minimising) the accumulation of material on and around the heat exchanger. This helps maintain a uniform temperature throughout the digester and also achieves efficient temperature control.
  • Base plate 220 also is collected and discharged from the digester 101.
  • FIG 8. Another embodiment of the invention is shown in figure 8.
  • material to be treated is introduced into digester 301 through port 303 and travels through a longitudinal member in the form of a hollow stainless steel drive shaft 308 and exits the drive shaft 308 at points 340 and 341 into the lower section of digester 301.
  • Digester 301 is much like digester 101 previously described with reference to figure 6.
  • the digester 301 in this embodiment comprises an Archimedes screw 330 which serves to lift and resuspend any mixed settled solids at the digester base or trough 316.
  • the screw 330 is formed by the introduction of grooves to the drive shaft 308.
  • the screw 330 may be encased in a lined fixed conduit 329 to prevent backflow, and rises from the digester base 316 to approximately 20% of the digester height.
  • material is lifted from the bottom of the digester 301 and rises to a point where it overflows the fixed lined conduit 329.
  • An overhanging lip 331 is located on the top edge of the fixed conduit 329 which faces downwards and outwards to about 20% of the width of the digester 301.
  • digester 301 may also have a base plate 220 as shown in, and described with reference to, figure 7, bolted to its base 316, with a screw 330 to achieve mixing and suspension of the digester contents instead of a mixing device 225.

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Abstract

La présente invention concerne un procédé de traitement de déchets organiques aqueux pour former un produit traité, ledit procédé consistant à introduire le déchet aqueux dans une cuve comprenant une partie supérieure et une partie inférieure, des microbes capables de transformer le déchet organique aqueux en un produit traité étant disposés dans les parties supérieure et inférieure de la cuve ; et à maintenir le déchet aqueux dans la cuve à l'état fluidisé et suspendu par l'introduction d'un milieu de fluidisation dans la partie inférieure de la cuve. La présente invention concerne également un appareil destiné à traiter un déchet organique aqueux comprenant une cuve et un ou plusieurs systèmes de circulation des déchets situés dans ladite cuve.
PCT/AU2007/001281 2006-09-01 2007-08-31 Procédé de traitement et appareil WO2008025098A1 (fr)

Priority Applications (1)

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AU2007291890A AU2007291890A1 (en) 2006-09-01 2007-08-31 A treatment process and apparatus

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AU2006904803 2006-09-01

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2336292A1 (fr) * 2009-12-18 2011-06-22 HF Biotec Berlin GmbH Dispositif et procédé de fermentation de matériaux peu visqueux
EP2460771A1 (fr) * 2010-12-06 2012-06-06 National University of Ireland, Galway Réacteur anaérobique pour traitement psychrophile et/ou mésophile des eaux usées
WO2012158013A1 (fr) * 2011-05-13 2012-11-22 Ronser Bio-Tech Sdn Bhd Traitement anaérobie des eaux usées organiques
US8329455B2 (en) 2011-07-08 2012-12-11 Aikan North America, Inc. Systems and methods for digestion of solid waste
CN103920697A (zh) * 2014-05-04 2014-07-16 千智伟 一种食品废弃物资源化利用处理设备及处理方法
CN104556611A (zh) * 2014-11-27 2015-04-29 中山大学 一种污泥厌氧反应器

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4349355A (en) * 1981-07-29 1982-09-14 Lingappa Banadakoppa T Methane generator
US4505819A (en) * 1980-08-18 1985-03-19 Unisearch Limited Method for the anaerobic degradation of organic material
US4568464A (en) * 1979-11-19 1986-02-04 Celanese Corporation Anaerobic filter
US4613434A (en) * 1983-01-18 1986-09-23 Oy Tampella Ab Device for treatment of wastewater by means of anaerobic fermentation
US6926830B2 (en) * 2002-06-28 2005-08-09 Kingsford Environmental (H.K.) Ltd. Combined activated sludge-biofilm sequencing batch reactor and process

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4568464A (en) * 1979-11-19 1986-02-04 Celanese Corporation Anaerobic filter
US4505819A (en) * 1980-08-18 1985-03-19 Unisearch Limited Method for the anaerobic degradation of organic material
US4349355A (en) * 1981-07-29 1982-09-14 Lingappa Banadakoppa T Methane generator
US4613434A (en) * 1983-01-18 1986-09-23 Oy Tampella Ab Device for treatment of wastewater by means of anaerobic fermentation
US6926830B2 (en) * 2002-06-28 2005-08-09 Kingsford Environmental (H.K.) Ltd. Combined activated sludge-biofilm sequencing batch reactor and process

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2336292A1 (fr) * 2009-12-18 2011-06-22 HF Biotec Berlin GmbH Dispositif et procédé de fermentation de matériaux peu visqueux
EP2460771A1 (fr) * 2010-12-06 2012-06-06 National University of Ireland, Galway Réacteur anaérobique pour traitement psychrophile et/ou mésophile des eaux usées
EP2649017B1 (fr) * 2010-12-06 2018-11-21 National University of Ireland Galway Réacteur anaérobie de traitement des eaux usées
WO2012158013A1 (fr) * 2011-05-13 2012-11-22 Ronser Bio-Tech Sdn Bhd Traitement anaérobie des eaux usées organiques
US8329455B2 (en) 2011-07-08 2012-12-11 Aikan North America, Inc. Systems and methods for digestion of solid waste
US8492134B2 (en) 2011-07-08 2013-07-23 Aikan North America, Inc. Systems and methods for digestion of solid waste
US9328323B2 (en) 2011-07-08 2016-05-03 Aikan North America, Inc. Systems and methods for digestion of solid waste
CN103920697A (zh) * 2014-05-04 2014-07-16 千智伟 一种食品废弃物资源化利用处理设备及处理方法
CN103920697B (zh) * 2014-05-04 2016-01-20 千智伟 一种食品废弃物资源化利用处理设备及处理方法
CN104556611A (zh) * 2014-11-27 2015-04-29 中山大学 一种污泥厌氧反应器

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