FR2723934A1 - METHOD AND DEVICE FOR TREATING A FLUID, IN PARTICULAR WASTEWATER, BY FILTRATION - Google Patents

Abstract

The present invention relates to a process for the treatment of waste water containing particulate matter and free oil. According to the invention, free oil is removed from the waste water, the waste water is passed through a first filtration medium having an effective nominal pore size of about 200 mum or less, the waste water is subjected to a dynamic filtration using a second filtration medium having an effective nominal pore size of about 5 µm or less and the waste water is contacted with an adsorbent bed to form a stream of purified water. The invention applies in particular to the treatment of marine wastewater.

Description

The present invention relates to a method of treatment

  of a fluid. More particularly, the present invention relates to an improved method for the treatment of waste water, in particular greywater, for recovering purified water and reducing effluents as well as an apparatus for carrying out this treatment.

waste water.

  Wastewater treatment to reduce effluent and recycle usable water is of utmost importance in the overall effort to reduce pollution and conserve water. One particular area is the treatment of wastewater on board ships and vessels, eg marine greywater. Greywater is defined as combined effluent wastewater from kitchens, laundry kitchens, dishwashers, laundry, shower, sink and wash basin (including deep basins in work areas such as engine rooms and medical waters ) on board the boats. Contaminants are typically large food particles (such as food slices), animal fats, vegetable oils, soaps, detergents, body oils, human hair, metal particles , kitchen and machine rooms, solvents and small clothes (such as socks) that may have gone through the laundry system. Greywater is usually differentiated from both black water that is a saline-based collection of body wastes and paper materials from the spaces at the bow of the boat and local waters that are a water-based accumulation. salt water from all other waste waters of the vessel and

  may contain chemical solvents and the like.

  Although the rate of production is highly variable as well as the concentration and type of contaminants, greywater is produced at an average rate of about -75 liters per man per day on board. So, for example,

2 2723934

  the production of greywater can be of the order of about 1,000 1 / day for a naval frigate with a crew of 200 men to 450,000 1 / day for an aircraft carrier with a crew of 6,000 men. The average flows of greywater aboard such boats can be between about 10 1 / min and about 315 1 / min, with flow rates of

  peak ranging from about 32 l / min to about 950 l / min.

  Conventional coalescing means and centrifugal separators are not suitable for treating and purifying greywater because, for example, the viscosities and surface tensions of soaps and water are too close to allow satisfactory separation. Many boats unload gray water directly, without treatment, into navigable waters, including lakes and waters near the coast. Some boats are equipped with concentration, holding and transfer tanks to store greywater until they can be pumped to a sanitary system at the port. These vessels use the concentration, holding and transfer tanks in an attempt to avoid evacuation of greywater in lakes and waters near the coast but usually evacuate greywater on the high seas or when the tanks are filled up. at their full capacity in other navigable waters. In the larger and larger areas where greywater disposal is prohibited, expensive and cumbersome means are used such as unloading greywater stored on boats.

  tanks or simply ignore the prohibitions.

  There remains, therefore, a need for an efficient and economical way to reduce wastewater effluent, especially greywater discharged from boats. The object of the present invention is to provide such a processing means. Another purpose is to concentrate the contaminants in the wastewater to make them easier to store and reject, while allowing the evacuation of the purified water recovered from the waste water. The present invention also aims to

3 2723934

  provide a means of treating wastewater, especially gray water, to recycle water

  usable and thus conserve water.

  The present invention provides a method and apparatus for the treatment of wastewater. The present method and the present apparatus are particularly suitable for the treatment of wastewater containing particulate matter and free oil, in particular

the gray waters of the sea.

  The present method for the treatment of waste water containing particulate matter and free oil consists of removing the free oil from the waste water, passing the wastewater through a first filtration medium having an effective pore size calibration. about 200 μm or less, to subject the wastewater to dynamic filtration using a second filtration medium having effective pore size of about 5 μm or less, and to contact the wastewater with an adsorbent bed for form a stream of water

purified.

  The apparatus according to the present invention for treating wastewater containing particulate matter and free oil comprises: (a) means for removing free oil from waste water, (b) means for passing water after removal of the free oil to a first filtration medium, (c) a first filtration medium having an effective pore size of about 200 μm or less, (d) a means for passing the wastewater after passing through the first filtration medium to a dynamic filtration apparatus, (e) a dynamic filtration assembly comprising a second filtration medium having an effective pore size of about 1 mm or less, (f) a to pass the wastewater, after passing through the second medium of

  filtration, to an adsorbent bed, and (f) an adsorbent bed.

4 2723934

  The present invention is based on the discovery that wastewater can be treated to concentrate contaminants in wastewater and form a stream of purified water by pretreatment of wastewater to remove large particles and free oil, subjecting waste water at dynamic filtration using a filter media having effective pore size of about 5 μm or less and then contacting the wastewater with a suitable adsorbent bed to remove any remaining contaminants. The stream of purified water can then be better treated, recycled and / or evacuated as appropriate while the concentrated streams can be further treated or maintained for proper discharge. While the present invention is particularly well adapted to the treatment of greywater, particularly marine greywater, the present method and apparatus according to the invention can be used to treat other types of wastewater. Other suitable uses of the present invention include the treatment of wastewater from food processing facilities such as breweries, bakeries, dairies, sweet potato starch processing facilities, and water treatment plants. poultry, laundries, textile factories, pharmaceutical factories and the like. The present invention is described herein in the context of marine greywater treatment, although it can be understood that it is within the competence of any person to apply this present invention.

invention to other contexts.

  Characteristics of waste water and purified water. The present invention, applied to the treatment of marine greywater, has the function of reducing the quantity and / or the concentrations of various contaminants to levels below the standards established for receiving water, ie, natural waters in which can be

2723934

  evacuated greywater by a boat. The typical characteristics of gray water and receiving water are

data below.

  Characteristic Water Receiving Greens Total Solids (TS) (mg / l) 259-11700 30-11600 Total Suspended Solids 101-4695 (TSS) (mg / l) Biochemical Oxygen Demand 137-2616 (BOD) ( mg / l) Chemical oxygen demand 304-7839 0-90 (COD) (mg / l) Oils & fats (O & G) (mg / l) 5-1210 0-15 Fecal coliforms (FC) 0-104 14 (# / 100 ml) pH 5.7-11.2 6.5-8.5 Residual chlorine (RC) (mg / l) 0-10 0.0002 Dissolved oxygen (DO) (mg / l) 0 2 5 Solids totals (TS) are the sum of total suspended solids (TSS) and total dissolved solids. Total solids form the residue that will remain after evaporation. Biochemical Oxygen Demand (BOD) is the amount of dissolved oxygen required during the stabilization of decomposable organic matter by aerobic biochemical action in water. Chemical Oxygen Demand (COD) is a measure of the amount of the components

oxidizable agents present in the water.

  Thus, the present invention is particularly well suited to wastewater treatment comprising at least about 150 mg / l of total solids, at least about 1 mg / l of total solids in suspension, at least about 1 mg / l of BOD, at least about 200 mg / l of DOC, and / or at least about 15 mg / l of oils and fats. Such wastewater may also contain faecal coliforms, e.g., at a concentration of up to 106, 108, or more, faecal coliforms / 100 ml. Waste water

6 2723934

  may also contain residual chlorine, e.g., at a concentration of up to about 20 mg / l or more and may contain less than about 5 mg / l of dissolved oxygen, or even substantially no dissolved oxygen. The pH of such wastewater can generally be of any value (depending on the stability of the equipment that is used), although the present invention works best with pH

about 5-12.

  The treatment of the waste water according to the present invention implies, on the one hand, the successive separation of

  smaller particles of the wastewater stream.

  While such a separation process may be effective in removing suspended particles from wastewater, it will usually be desirable to pretreat

  wastewater to remove free and post-oil

  treat the effluent to remove other contaminants. The preferred embodiment of the present invention comprises

these pre- and post-treatments.

  The present invention preferably treats the wastewater so that the stream of purified water contains less than about 150 mg / l, preferably less than about mg / l total solids, less than about 100 mg / l, preferably less than about 30 mg / l of total solids in suspension, less than about 100 mg / l, preferably less than about 30 mg / l BOD, less than about 100 mg / l, preferably less than about 90 mg / l of DOC, and less than about mg / l of oils and fats. The stream of purified water also preferably has less than about 14 faecal coliforms / 100 ml, less than about 0.0002 mg / l residual chlorine, and at least about 5 mg / l dissolved oxygen. The pH of the purified water stream is preferably about 6-9, more preferably about 6.5-8.5. More preferably, the purified water stream is suitable for disposal in restricted receiving waters under US conditions, ie, the stream of purified water contains less than about 1 mg / l of total suspended solids, less than about 1 mg / l BOD, less than about 14 faecal coliforms / 100 ml,

7 2723934

  less than about 0.0002 mg / l of residual chlorine, and at least

  about 5 mg / l of dissolved oxygen with a pH of about 6.5

  8.5. Pretreatment The pretreatment of the wastewater before subjecting the waste water to dynamic filtration preferably consists of removing the free oil from the wastewater and then passing the wastewater through a first filtration medium. The free oil may be removed from the wastewater by any suitable means, preferably by contacting the waste water with a material such as cotton, preferably in the form of sponge-towels, which absorbs the free oil. The first filtration medium preferably has effective pore size of about 200 μm or less and more preferably about 160 nm or less. The removal of free oil and relatively larger particulate matter, wastewater, before dynamic filtration of the wastewater is designed to ensure the proper operation of the subsequent dynamic filtration process and to prevent fouling premature filtration medium

  used in the dynamic filtration apparatus.

  In order to facilitate the efficient treatment of the waste water, the waste water is preferably passed through a sieve before passing through the first filtration medium (and preferably also before the free oil is removed, although this is not the case. not as important). Any suitable sieve can be so used, eg, a duplex sieve and the sieve is designed to remove larger particulates (such as hair, laundry items and the like) and, as such, it will typically be a perforated plate or preferably a mesh. A suitable mesh screen may be of any suitable configuration, but will preferably have about 4-20 threads per linear cm in each direction, with any suitable wire diameter, eg, about 50-500 mm. Preferably, such a screen in mesh will have about 8-16 threads per

8 2723934

  linear cm, and more preferably about 12 wires per linear cm in each direction, with any suitable wire diameter, e.g., about 50-500 μm and preferably about 125-250 μm. The sieve desirably removes larger particles than at least about 1000 Mm, more preferably

  large than at least about 600 μm in diameter.

  The sieve is preferably sized to reduce the frequency of clogging while removing as much particulate matter as possible, particularly particulate matter that would interrupt the satisfactory operation of the first filtration medium. To enable continuous operation, a duplex sieve is preferably used such that, while a sieve is clogged, it is taken offline and the flow is switched to the second sieve. The off-line screen is then backwashed by any appropriate means, eg, with relatively small volume of the wastewater that has passed through it, or purified water or pulsed air means, to clean it for use. ulterior. Any effluent can be passed to an appropriate reservoir of the concentrate for subsequent discharge. Backwashing can be done automatically to avoid the need for intervention

of the operator in this process.

  The waste water is also preferably passed into a holding tank before passing through the first filtration medium (and also, preferably before passing through the sieve, if it is used before removal of the free oil. although, again, this is not so important). The holding tank is preferably designed to allow high density materials entrained in the waste water to settle to the bottom of the holding tank, thereby

  to separate them from the waste water.

  For example, the holding tank may contain baffles and / or the outlet of the holding tank may be placed a short distance, e.g., a few centimeters, above the bottom of the holding tank to allow

9 2723934

  high density materials, entrained in the waters

  waste, to be deposited at the bottom of the holding tank.

  From this point of view, the bottom of the holding tank may have a removable access cover to facilitate periodic occasional removal of high density contaminants. The sieve and / or the means for effecting the removal of any free oil may be contained in the holding tank, and this is preferable. In particular, the holding tank preferably contains sloped surfaces so that the wastewater must alternately flow up and down, which sloping surfaces not only help to remove the high-density materials. wastewater but also help to separate any

  free oil, and waste water.

  In addition to facilitating the disposal of high-density wastewater materials, the holding tank provides some balance for incoming wastewater. The volume and concentration of contaminant in wastewater may vary during the day in particular end-uses, such as onboard vessels, and therefore subsequent treatment will produce a more consistent result while average flow changes and concentrations will be made or balanced by the holding tank. This balancing can have a particular effect on possible excursions of BOD, pH, and other output parameters. Moreover, in many end uses, particularly on boats, the holding tank is desirably sized to collect and contain a volume equivalent to the peak flow for a reasonable period of time, eg about one hour to several hours to ensure that the treatment system will not be submerged during periods of excessive wastewater production (although the volume of the holding tank may be smaller or larger

2723934

  according to the specific production of waste water as well as

  the capacity of the treatment system).

  At any point in the pretreatment process, desirably prior to the passage of the wastewater through the first filtration medium and preferably after passing through a suitable holding tank to remove the high density material, the wastewater may be subjected to any appropriate action that reduces the size of the particulate matter in the wastewater, eg contact with rotating blades, to facilitate the removal of such particulate matter without unduly affecting subsequent filter media. The means by which the size of the particles is reduced can also be the means by which the wastewater is removed from the holding tank to be passed downstream to further processing, e.g., to the sieve and the first filter medium. Thus, for example, the outlet of the holding tank can be connected by a suitable fluid path to a maceration pump. The maceration pump will draw the wastewater out of the holding tank, reduce the solids to smaller particles and provide the pressure to force the wastewater through the remainder of the treatment system. The maceration pump can be placed outside the holding tank or in the holding tank. If a maceration pump is used, it is preferably provided with an integral inlet screen, which is placed in the holding tank, allowing debris collected on the screen to be backwashed, according to the need, towards the bottom

  holding tank for subsequent disposal.

  The inlet screen is preferably sized to reduce the frequency of cleaning while eliminating all particulates of sufficient size that

  otherwise would submerge the maceration pump.

  During the pretreatment process, suitable chemicals for the treatment may be provided to the wastewater, although this is generally not necessary. Such chemicals may be added to the wastewater by any appropriate means, e.g., by chemical feed systems. Such chemical feed systems will preferably include a piston pump and an electronic controller such that downstream sensors are capable of sending signals to the electronic controller to automatically regulate the rate of chemical feed. Chemical feed pumps can be directly connected to appropriate storage containers or canisters containing the chemicals to be added to the wastewater by any means.

  appropriate means, e.g., by suction hoses.

  In particular, acid can be added to the wastewater to neutralize it and a coagulant can be added to the wastewater to improve efficiency.

  separation of the dynamic filtration assembly.

Dynamic filtration.

  After pre-treatment of the wastewater, they are subjected to dynamic filtration using a second filtration medium having effective pore size of about 5 μm or less. The dynamic filtration process is intended to remove substantially all particulate matter remaining in the wastewater, preferably without the need for further filtration,

e.g., ultrafiltration.

  At this level of filtration in an efficient and practical greywater treatment system on board a ship, it has been found that effective filtration can not be

  accomplished only by the use of dynamic filtration.

  More particularly, the actual pore sizes of the filter media are so small and the effective areas of the filter media are so limited as the clogging of the pores of the filter media and the formation of bread layers near the surface of the media forming Filters Appear as Problems

12 2723934

  with the use of filter elements of the type

ordinary barrier.

  For greywater treatment, single-pass barrier filtration is not as satisfactory as dynamic filtration for a wide variety of reasons. Some of these reasons are that contaminant volumes and concentrations are generally too high for effective use of single-pass filters, that an effective back-flush system will be too large and that pre-coating (which is necessary to keep the compressible or sticky contaminants away from the filter medium) requires the introduction of additional chemicals that may need to be removed with

concentrated waste.

  Dynamic filtration is an extension of the cross-flow filtration concept. The operating principle is to maintain a filter medium without clogging or fouling by pushing back particulate matter from the filter element and interrupting the formation of the bread layers near the filter medium. These results are achieved by displacing the fluid that is filtered sufficiently rapidly relative to the filtration medium to produce high shear rates as well as high shedding forces on the particles, such as the use of rotating, oscillating, back and forth or vibratory. Shear at the fluid interface / filter medium is almost independent of any flow velocity of the cross-flow fluid in contrast to tangential or cross-flow filtration techniques (which suffer from other problems such as premature clogging of the filter due to of

  the adsorption of the compound and significant falls in

  uniform pressure associated with high velocities tangential to the length of the filter, possibly causing a flow back through the medium of

  filtration and reducing filtration).

13 2723934

  Dynamic filtration offers a number of performance advantages in the context of the present invention. Very high shear rates can be produced in the dynamic filtration assembly to produce better lift to repel small particles and / or allow high permeate flow rates. Increases in permeate flux rate have been observed to be nearly linear with increasing shear rate in some systems. This means that the required filter area can be dramatically reduced compared to any other filtration means. Since shear can be delivered uniformly throughout the system, uniformly high rates of flow can be obtained and maintained throughout the system so that progressive fouling is eliminated and extended filtration times can be achieved. Moreover, high concentrations of agglomerated particulate matter can be obtained for the removal of the treated fluid,

  using dynamic filtration.

  A dynamic filtration assembly has the ability to treat a wide variety of contaminants, to obtain a remarkably high concentration of retained solids, to be able to operate continuously over long periods of time without the need for filtration aids and / or against -rushing and get a uniformly high performance of the filter to minimize the total size of the system. The dynamic filtration assembly may be of any suitable configuration and will typically include a housing that contains a filter unit comprising one or more filter media and means for effecting relative movement between the filtration medium and the wastewater. The filtration media of the filter unit as well as the means for effecting the relative movement between the fluid being filtered and the filtering medium can be in one of a wide variety of suitable configurations. A wide variety of suitable motor means can be used to effect this relative movement,

14 2723934

  as, for example, means of rotation, oscillation,

back and forth or vibratory.

  The dynamic filtration assembly may be any suitable device. Suitable cylindrical dynamic filtration systems are described in US Patents 3,797,662, 4,066,554, 4,093,552, 4,427,552, 4,900,440 and 4,956,102. Suitable rotary disk dynamic filtration systems are described in US Pat. U.S. Patents 3,997,447 and 5,037,562, and in the patent application

  U.S. No. 07/812 123. Oscillating assemblies, with and without

  Comes or vibratory for dynamic filtration, which are suitable, are generally described in US Patents 4,872,988, 4,952,317, and 5014,564. Other dynamic filtration devices are described by Murkes, "Fundamentals of Crossflow Filtration," Separation and Purification Methods, 19 (1), 1-29 (1990) In addition, many dynamic filtration assemblies are commercially available, for example, suitable assemblies for dynamic filtration include Pall's BDF-LAB, the CROT filter. ASEA Brown Bovery rotary and New Logic V-SEP While the desired removal of particulate matter can be achieved by any suitable dynamic filtration assembly, it has been found that the use of vibratory dynamic filtration, as generally represented by the New Logic V-SEP, was particularly well adapted in the

context of the present invention.

  Desirably, the dynamic filtration creates shear forces of at least about 20,000 s -1, preferably at least about 100,000 s -1. The best filtration rates will be obtained at high shear rates and since the shear degradation of the concentrate is not a problem in the treatment of waste water, maximum shear is preferred in

practical limits of the equipment.

  Any suitable filtration medium may be used in the dynamic filtration assembly. In general, filter media having dimensions

2723934

  effective nominal pore size to minimize or avoid the need for post-treatment of wastewater. Thus, while the filtration medium has effective nominal pores of about 5 μm or less, the filtration medium preferably has effective nominal pores.

  about 1 μm or less and more preferably about 0.5 μm or less.

  The dynamic filtration medium is quite preferably a molecular weight cutoff of about 200 daltons or less, and, most desirably, it is a dynamic filtration medium that is a reverse osmosis membrane capable of a salt rejection of at least 97% (which is considered to be equivalent to a membrane having a molecular weight cut of approximately 50 daltons). The reverse osmosis membrane capable of at least 97% salt rejection is the finest-pore membrane that is of practical use in the context of the present invention. After the waste water has passed through the dynamic filtration assembly, the waste water need not necessarily be subjected to further filtration by passage through a filtration medium, but on the contrary it can simply be subjected to a bed

  adsorbent (and possibly other post-treatment

  filtration such as ozonation and UV exposure) to

  remove all remaining contaminants.

  The dynamic filtration assembly is connected, by a suitable fluid path, to a suitable reservoir of the concentrate. Concentrated contaminants from the dynamic filtration assembly are preferably periodically removed to the concentrate reservoir. Any suitable means can be used to control the assembly

  dynamic filtration, as an appropriate means to counteract

  reaction. It is preferable that the control by

  Reaction is used in conjunction with the motor mechanism of the dynamic filtration assembly to detect increased torque conditions associated with increased viscosity of concentrated contaminants and actuate control valves to automatically remove contaminants

16 2723934

  concentrated in the concentrate tank. In wastewater treatment, the dynamic filtration assembly will remove much of the particulate load. In particular, the dynamic filtration assembly will remove the vast majority of total suspended solids and reduce the portion of BOD and DOC that is associated with particulate matter. The dynamic filtration assembly also preferably removes undesirable molecules and agglomerates, for example, those having molecular weights of at least about 500 daltons (up to about 30,000 daltons or more), and most preferably those having molecular weights of at least about 200 daltons and more preferably those having molecular weights of at least about daltons. In wastewater treatment, the dynamic filtration assembly preferably removes a large number of small organic compounds, particularly those bound in soap micelles, which has the effect of reducing BOD and lowering the pH. in that a high pH is due to the soap solutions. The dynamic filtration assembly also preferably has the effect of virtually eliminating suspended solids and

faecal coliforms.

  While the concentrate of the dynamic filtration assembly eventually passes through a suitable fluid path to a suitable reservoir of the concentrate, this can be accomplished after recycling the concentrate for further concentration. Since the dynamic filtration process is enhanced by the higher fluid velocities that tend to reduce the fouling rate of the filter media, it is preferred that the dynamic filtration assembly employ a recirculation pump to take the suction of the filter media. the outlet end of the dynamic filtration assembly and discharge it into the inlet end of the dynamic filtration assembly. Recirculation rates between one and ten times the exit rate are preferred with higher rates of recirculation being most preferred in the treatment of fluids.

17 2723934

  contaminated. Two or more dynamic filtration assemblies can be assembled into a multiplex system to enable switching to a clean dynamic filtration assembly

  when the other is dirty.

  Post-treatment The filtrate of the dynamic filtration assembly can be essentially sterilized water, depending on the precise nature and quantity of the contaminants in the wastewater as well as the nominal pore size.

  particular in the dynamic filtration assembly.

  The dynamic filtration assembly can remove bacteria, yeasts, fungi and the like from waste water and, if it does not remove them, reduces the endotoxins of the wastewater. While the filtrate of the dynamic filtration assembly does not necessarily have to be further processed, the filtrate is further processed to reduce and preferentially remove all residual microorganisms, viruses and organic and inorganic compounds. Thus, after the waste water has been subjected to dynamic filtration, the waste water is brought into contact with a suitable adsorbent bed to eliminate all these possible contaminants remaining in the waste water, in particular organic and inorganic contaminants such as chlorine ions. and metals (especially arsenic that is used on board as a poison for rats and that can pass into the greywater marine), as well as some microbial contaminants, which may have crossed the middle

dynamic filtration.

  The adsorbent bed may be any suitable adsorbent material and will typically comprise one or more components selected from the group consisting of carbon sorbent, activated alumina, silica hydrogel, zeolite, and metal components that generate metal cations. The carbonaceous sorbent may be based on charcoal, fruit shells such as coconut husks, wood-based coatings, activated petroleum-based coals,

18 2723934

  synthetic coals and mixtures thereof. The carbonaceous sorbent is preferably activated carbon. The metal components that produce metal cations are preferably selected from the group consisting of copper, zinc, brass, manganese, silver, and mixtures thereof, and more preferably

they are brass particles.

  Since the precise nature of the wastewater may be unknown and may vary from day to day, the adsorbent bed is preferably a mixed adsorbent bed containing a wide variety of adsorbents capable of treating a wide variety of potential contaminants. Such a preferred mixed adsorbent bed may contain, for example, about 40-80% by weight of the carbonaceous sorbent, about 5-20% by weight of the activated alumina, about 5-20% by weight of silica hydrogel, about 5-20% by weight of zeolite, and about 0-10% by weight of

  metal components that generate metal cations.

  The adsorbent bed is quite preferably composed of activated charcoal, activated alumina, silica hydrogel, zeolite, and brass particles. Preferred adsorbent beds are described for example in the patent

  U.S. 5,178,768 and U.S. Patent Application No. 08/118,998.

  When the adsorbent bed is loaded with contaminants and its ability to remove other contaminants is adversely affected, the adsorbent bed can be replaced or preferably regenerated and reused. The adsorbent bed can be regenerated using any suitable means, e.g., with water at about 93 ° C, according to the method described in the patent

U.S. 5,281,344.

  While the filtrate of the dynamic filtration assembly preferably passes through a suitable fluid path directly to the adsorbent bed, the filtrate from the dynamic filtration assembly can pass through an appropriate fluid path to a system. ozonisation before contact of the waste water with the adsorbent bed. The ozonization system produces ozone to polish filtered wastewater by the fact that ozone is able to sterilize waste water and oxidize

19 2723934

  numerous organic compounds as well as killing micro-

  organisms and viruses that may have escaped from the upstream filters. Such sanitary action can typically be performed with an ozone concentration of at least about 0.5 mg / l, preferably at least about 1 mg / l, in water. Ozone does not produce any harmful side effects and disappears quickly from the treated water. Ozone can be

provided by any appropriate means.

  The ozonization system preferably comprises a pressure swing adsorption air dryer, an ozone generator, an ozone contactor, and most preferably a UV lamp and another ozone contactor. The ozone generator may be any suitable device, e.g., a conventional device that produces

  ozone by accelerating electrons between two electrodes.

  The power of the ozone generator is either dry filtered air or oxygen. An oxygen supply produces more ozone and a higher concentration. The concentrations are typically between 1 and 8% by weight, 2% by weight being typical of an air supply,

  and 3% by weight being typical of an oxygen supply.

  In the case of the air supply, compressed air is dried by a double bed pressure swing adsorption air dryer. With the appropriate filters, this unit provides air of the required quality by treating air, preferably, compressed air which passes through an appropriate inlet to the pressure swing adsorption air dryer. In the case of a supply of oxygen, the oxygen in the compressed air is concentrated by a purge sweep adsorber. Such a system is similar to that for the pressure swing adsorption air dryer

  with the exception of the adsorbent and the details of the cycle.

  The use of an oxygen supply system requires much more air and a larger adsorption system and, therefore, the air supply system is preferred. The pressure swing adsorption air dryer is used to purify and dry the air at a low point of

2723934

  dew, e.g. about -57 ° C dew point, so that the ozone generator receives filtered, very dry air to function well and produce high concentrations of ozone

over long periods of time.

  Ozone contactor allows contact time for reaction of organic residue in waste water

  filtered with ozone produced by the ozone generator.

  Ozone is generated in the gas phase and must be dissolved in the filtered wastewater. Many transfer or contact methods are available to accomplish the dissolution of ozone in wastewater. For example, ozone can be bubbled through a column

  waste water with or without packing materials.

  Ozone can also be injected into a pipe carrying the wastewater. The transfer of ozone to wastewater is enhanced by the use of a

mixer in line without movement.

  The waste water treatment system preferably also includes a second ozone contactor with a UV light source. Ultraviolet light, particularly at 254 nm, will produce hydroxyl radicals in ozonated water, which radicals will work with ozone to oxidize most of the organic compounds. The second ozone contactor with UV light source ensures that any necessary or desirable oxidation by ozone

  in the waste water will be complete.

  Residual ozone can be allowed to naturally decompose to oxygen because its half-life is about 20 minutes in water at about 21 C. The decomposition of ozone can be accelerated by heating it. Another method, which has other benefits as described above, is the use of irradiation of UV light. An adsorbent bed can also be used to remove ozone, particularly because the surface of the adsorbent bed can form a site for the decomposition of ozone. Thus, since the wastewater is contacted by ozone, this contact preferably occurs before the

21 2723934

  contact of the waste water with the adsorbent bed. An ozone analyzer can be used to analyze treated wastewater or vent gases to verify the complete removal of ozone from the water. The treated wastewater then moves from the treatment system to

  through an appropriate outlet into a stream of purified water.

  A concentrate reservoir can be designed to contain the concentrate produced throughout the treatment process for rejection at a later point and more convenient over time. For example, for marine greywater produced on board ships, the concentrate can be pumped when the vessel is alongside and shore facilities are available or barge or offshore facilities are available.

restricted waters.

  The treated wastewater may be further treated, recycled and / or disposed of as appropriate. The treatment system is preferably designed to purify greywater to the point that it can be

  evacuate to otherwise restricted receiving waters.

  The effectiveness of the treatment system is such that it can have a footprint of about 6 m long x 3 m wide x 3 m high while being able to treat up to about 19 liters of greywater minute aboard the boat,

with minimal maintenance.

  Apparatus Any suitable apparatus may be used to implement the present method according to the invention. In general, such apparatus for the treatment of wastewater containing particulate matter and free oil will comprise (a) means for removing free oil from waste water, (b) means for passing waste water, after removing the free oil, to a first filtration medium, (c) a first filtration medium having an effective nominal pore size of about 200 μm or less, (d) a means for passing the wastewater , after passing through the filtration medium, to a dynamic filtration apparatus, (e) a

22 2723934

  dynamic filtration assembly comprising a second filtration medium having a nominal effective pore size of about 5 μm or less, (f) means for passing the wastewater, after passing through the second filtration means, to a bed adsorbent, and (g)

adsorbent bed.

  The apparatus will preferably further include a screen for passing waste water through the first filtration media. Such a screen will preferably be a mesh as described above in the context of the present invention. The first filtration medium preferably has an effective nominal pore size of about 160 μm or less, and the means for free oil removal preferably comprises means for contacting the wastewater with the a material that absorbs

  free oil, such as cotton (e.g., towels-sponges).

  As has been explained in more detail with reference to the present method of the invention, the dynamic filtration assembly is preferably capable of creating shear forces of at least about 20,000 s-1, and preferably shear forces of at least about 000 s-1. The dynamic filtration assembly is

  preferably a vibratory dynamic filtration assembly.

  The second filtration medium preferably has a molecular weight cutoff of about 200 daltons or less and better is a reverse osmosis membrane capable of at least 97% of

salt rejection.

  As also explained above in addition to the details with reference to the present method of the invention, the adsorbent bed can contain any suitable adsorbent materials designed to remove contaminants that could eventually pass through the dynamic filtration. The adsorbent bed is preferably composed of a carbonaceous sorbent (especially activated charcoal), activated alumina, silica hydrogel, zeolite, and metal components which produce cations.

23 2723934

  metallic (like copper, zinc, brass, manganese, silver,

  and mixtures thereof, in particular brass particles).

  The apparatus may further include an ozone contactor for contacting the wastewater with ozone prior to contact with the adsorbent bed (which may be used to remove residual ozone and / or facilitate its decomposition as well. to eliminate all the reaction products of ozone). The apparatus may further include an ultraviolet light irradiation source for irradiating ozonated waste water with ultraviolet light, preferably prior to water contact.

waste with the adsorbent bed.

  In most applications, as described above for the method of the present invention, the apparatus will further include a holding tank which allows the deposition of high density material entrained in the wastewater at the bottom. of the holding tank, before passing the waste water through the sieve. The apparatus may also include a means for reducing the size of the particles in the wastewater before the passage of

  wastewater through the first filtration means.

  The apparatus will typically further include appropriate valves (for controlling the flow of wastewater), a concentrate tank (for temporary storage of the concentrate), vents (such as a carbon vent filter for deodorizing the stale gases from the wastewater). reservoir for the maintenance of waste water and the reservoir of

  concentrated), and the like, as is known.

  Examples The following examples will further illustrate the present invention, particularly the use of dynamic filtration to treat fluids. These examples should not, of course, be considered as limiting a

  any way within the scope of the present invention.

24 2723934

Example 1

  Two balloons of about 210 liters of greywater were collected at the David Taylor Research Center at the nearby Naval Academy. It was thought that gray water came from 45% of the showers and wash tubs, 33% from the kitchen tubs and washers and 22% from the laundry. The tests were completed within 72 hours from the moment o

the sample was taken.

  The sample, as received, did not appear to contain large particles. About 210 liters of greywater were collected through a stainless steel mesh screen of about 9 strands / linear cm in both directions with a wire diameter of about 356 Mm. large particles, an installation of domestic garbage cans. About 57 liters of the filtered water was filtered using a BDF-LAB dynamic microfilter (Pall Corporation). The filter element was a Pall S050- 3 PSS quality H balanced cylinder, made of porous stainless steel, series

  S, with an absolute nominal size of 5 Mm.

  Half of the outflow was concentrated and

  half of the outflow was formed from the filtrate.

  The filter was started using clear water to establish the operating parameters. The input was then switched to greywater and the parameters of

  functioning have been adjusted as appropriate.

  The flow rates were kept constant throughout the test by slightly increasing the operating pressure during the course of the test. Although the filter was only tested for a short time it was obvious that the filter did not get dirty as quickly as a standard filter. The apparent turbidity in the filtrate was considerably lower than that of the influent, whereas turbidity

  concentrate was more important than that of the influent.

  The permeate flow rates and ring pressures at 10 and

  30 minutes in the test are given below.

2723934

  Filtration flow time Ring pressure (mn) (1 / min) (kPa)

0.34 47

0.42 52

  About 8 liters of the filtrate were ozonized for 200 minutes. The ozonator used a recirculation loop with 9.1 meters of copper tube. A Clean Air Corporation ozone generator, producing about 30 1 / h of ozone, was used to supply ozone. A vacuum cleaner was used to introduce ozone. Turbulence around 180-240 cm / min produced contact

  and mixing the ozonized air and water.

  The characteristics of greywater in various stages

  of the treatment are given below.

26 2723934

  filter filtered ozone ozone ozone ozone ozone ozone (1 mn) (3 mn) (10 mn) (30 mn) (100 mn) (200 mn)

TS 1900 1700

(Mg / 1)

TSS 26 6

(Mg / 1)

BOD 170 120 100 130 140 130 110 150

(Mg / 1)

COD 560 490 450 460 450 420 430 360

(Mg / 1)

O & G <1 <1

(Mg / 1)

FC 1 1

(# / 100

ml) pH 10.3 10.3

* RC <0.1 <0.1

  (mg / 1) While total suspended solids (TSS) were not measured after filtration, dynamic microfiltration was assumed to be solely responsible for reducing TSS from 26 mg / l to 6 mg / l . The increase in BOD of the ozonized filtered water was considered to be the result of ozonation which converted the non-biodegradable material into a biodegradable material. After 200 minutes of ozonisation, the water remained foamy, indicating that the soaps were not removed. The pH remained no

  affected by dynamic microfiltration and ozonization.

27239394

  It is clear from this test that ozone is effective in reducing DOC from greywater. Although only a small amount of ozone was applied, there was an appreciable reduction in DOC. Ozone was added at a concentration of 72 ppm for 200 minutes. During this time, samples were taken from the reservoir, reducing the total volume of greywater and increasing the

  ozone concentration with each new period of time.

  At the end of this time, the ozone concentration would have been reduced by 43 mg / l if there had been no ozone consumption by the reaction. If all of the applied ozone had reacted with the DOC compounds, COD would have been reduced by 43 mg / l. However, the DOC level was reduced from 490 mg / l to 360 mg / l, a decrease of 130 mg / l. This decrease is three times greater than the reduction of DOC

  could be attributed to the action of ozone alone.

  Ozone was transferred to the water by a stream of air.

  It was about 3,000 times more oxygen than ozone in the air. Oxygen would be effective in oxidizing compounds that oxidize easily and air flowing through the water could also extract volatile organic compounds. These mechanisms can be taken into

  account for the added efficiency of the ozonization process.

  Although ozone has been shown to be effective in reducing DOC and can be BOD, it is clear that a significant amount of ozone will be needed to reduce DOC and BOD to acceptable levels after simple dynamic filtration using a filtration medium. having nominal Pores of Mm. While this test has demonstrated the possibility of dynamic filtration and ozonisation in greywater treatment, this test also demonstrated the need for dynamic filtration using a filtration medium

  having nominal pores of less than about 5 Mm.

  Example 2 A flask of about 210 liters of greywater was taken from the David Taylor Reserarch Center and filtered through

28 2723934

  a series of filters characterized by a decreasing size of the pores. The first filter was a knitted mesh screen simulating a duplex sieve. The second, third and fourth filters simulated the filtration of the dynamic microfiltration assembly. The second filter was an Ultipor GF absolute filter of 3 Mm (Pall Corportion), while the third filter was a Sanitary Filter with a nylon membrane and an absolute standard of 0.04 pm (Pall Corporation), and the fourth filter was ultrafilter model VIP-3017 (Asahi) with molecular weight cutoff

of 6,000 daltons.

  The fourth filter was rinsed with absolute deionized water at 3 pm for about 20 hours and then drained before testing. The greywater drum was pressurized to approximately 34 kPa with air, forcing greywater through the filters at a total flow rate of less than 1.9 l / m. The flow rate of the ultrafilter concentrate was about one-quarter that of the filtrate (purified water). Samples of the filtrate were taken at three different locations on the test system: (i) downstream of the screen filter, (ii) downstream of the two filters simulating dynamic microfiltration, and (iii) downstream of the fourth filter. The filtrate is allowed to flow from the first two sample taps for 30 seconds before the samples are taken and then the fourth filter is rinsed with the process fluid for 10 minutes.

  before collecting the samples.

  The filtration system has definitely improved the clarity of the greywater and the smell and greywater foam formation have also been reduced. The flow gradually decreased through the test while a constant pressure was maintained in the drum. Examination of the system indicated that the second or third filter or both were clogged. Using an assembly

  actual dynamic microfiltration will prevent this clogging.

  Examination of the concentrate in the housing of the second filter

29 2723934

  revealed that it was much darker than in greywater

  original. The test results are given below.

  1st filter 2nd and 3rd filter 4th filter TS (mg / l) 1100 980 580 TSS (mg / l) 26 2 1 BOD (mg / l) 220 74 47 COD (mg / l) 540 210 120 O & G (mg / l) 110 9 1 FC (# / 100 ml) 19 <1 <1 pH 10.1 10.1 9.9 The test results indicate that various filters meet the requirements for total suspended solids and faecal coliforms, while the addition of an acidic feed may be required to correct the strongly alkaline condition. The use of an upstream coagulant will improve the filtration effect achieved by dynamic microfiltration. The test results also indicate that ozone and irradiation with ultraviolet light will be useful to further reduce the

BOD level.

  Example 3 Two balloons of about 210 liters of greywater from the U.S. Naval Academy were obtained in Annapolis, Maryland. Each gray water flask contained about 102 liters of laundry water, about 68 liters of water from the tanks and about 19 liters of water.

showers.

2723934

  Using a barrel pump, greywater was passed through a screen of about 12 wires / linear cm in both directions with a wire diameter of about pm, to buckets to remove large debris. Removed debris consisted of hair, thick filamentary materials, glitter and other soft agents. The bottom of about 5-8 cm of each gray water flask

  contained a thick oily and black substance.

  The gray water in the buckets was then poured through a 160 μm metal screen filter. The gray water thus filtered was opaque, black as ink, and contained no trace of soap or soap water. A strong, acrid smell was emitted by the fresh gray water

  paid, but disappeared in a few hours.

  The greywater was then dynamically filtered using the PALL-SEP VMF Vibration Dynamic Vibration Filtration Series L (Pall Corporation) and one of two filtration media, a nanofiltration membrane of one cut-off with a molecular weight of 200 (with a minimum salt rejection rate of 80%) or a reverse osmosis membrane calibrated with a salt rejection of%. The operating conditions of the dynamic filtration assembly were as follows:

31 2723934

  Membrane Membrane osmosis reverse nanofiltration Supply pressure 1380 kPa 35 kPa 1380 kPa 7 kPa gray water Supply temperature 22 CO, 8 C 22 C 0.2 C gray water Gray water flow rate of 1.5 1 / m 0.04 1 / m 1, 5 1 / m 0,11 1 / m back Displacement oscillating 3,18 cm 3,18 cm

PALL-SEP VMF

  Oscillation frequency 63.25 cps 0.10 cps 63.25 cps 0.05 cps

PALL-SEP VMF

  Using the nanofiltration membrane, about 300 liters of greywater were treated over a period of three weeks. At the end of this period, 99.31% of the fluid had been removed from the system as a permeate. Total permeate collected, i.e., 287.53 1, reported a loss of 13.3 1 greywater. The loss of greywater was attributed to the evaporation of volatile organic compounds that were emitted and to water vapor. The total amount of greywater recorded was reduced by 4.4% to account for evaporative loss. While the permeate / total greywater percentage increased to 99.31%, the permeate flow decreased from about 73 ml / min to

about 47 ml / min.

  Using the reverse osmosis membrane, about 72 l of greywater was treated with a permeate recovery of about 68 l, or about 94.31 percent. While the permeate / total greywater percentage increased from about 89% to about 94%, the permeate flow decreased by about

24.4 ml / min at about 21.3 ml / min.

  The characteristics of greywater before and after the dynamic filtration are given below:

32 2723934

  Greywater Greywater Gray water before filtration after filtration dynamic filtration (Dynamic membrane (dynamic nanofiltration membrane) of reverse osmosis) Total solids 14,600 {6833 [15] (mg / i) Total solids in 85.8 [1.5 ] [2] Suspended (mg / l) Demand ND (<60) [11] [8.8] biochemical oxygen (mg / l) Chemical application 111 40.2 ND (<2) oxygen (mg / 1) Oils & Fats 33.1 1.7 2.7 (mg / 1) Fecal coliforms ND (<4) NT NT (# / 100 ml) pH 8.55 8, 41 6.56 ND: nothing detected NT: no tested []: probably basic level - samples collected in unsterilized plastic containers {}: doubtful results (real value probably lower) The permeate derived from the nanofiltration membrane presented an acrid and sweet odor and had a very slightly yellow. The permeate derived from the reverse osmosis membrane was crystal clear and emitted no odor. Both permeates met U.S. requirements for evacuation in deep water; however, the permeate derived from the reverse osmosis membrane was generally more free of contaminants than the permeate derived from the nanofiltration membrane. The permeate derived from the nanofiltration membrane will preferably further be treated by contacting the permeate with a suitable adsorbent bed to ensure agreement with applicable disposal laws, while permeate derived from the reverse osmosis membrane. would possibly avoid the need for such

other treatment.

33 2723934

  All cited references including patents, patent applications, publications and the like are

  incorporated herein by reference.

34 2723934

Claims (24)

  1. A method for treating wastewater containing particulate matter and free oil, characterized in that it consists in removing the free oil from said waste water, to pass said waste water through a first filtration medium having an effective nominal pore size of about 200 Mm or less, to subject said wastewater to dynamic filtration using a second filter medium having an effective nominal pore size of about 5 mm or less and to provide said waters residuals in contact with   an adsorbent bed to form a stream of purified water.   2. Method according to claim 1, characterized in that the waste water is passed through a sieve before passing said waste water through said first filtration medium.   3. Method according to claim 2, characterized in that the screen is a mesh screen comprising 4-20 son per linear cm in each direction, said son having a diameter of about 5-500 um.   4. Method according to any one of claims 1   at 3, characterized in that the first filtration medium has a nominal effective pore size of about 160 μm or less.   5. Method according to any one of claims 1   at 4, characterized in that the free oil is removed from said waste water by contacting said water   waste with a material that absorbs free oil.   6. Method according to any one of claims 1   to 5, characterized in that the dynamic filtration is a vibratory dynamic filtration.   7. Method according to any one of claims 1   at 6, characterized in that the second filtration medium has a molecular weight cutoff of about 200 daltons or less. 2723934   8. Process according to claim 7, characterized in that said second filtration medium is a membrane   reverse osmosis capable of a salt rejection of at least 97%.   9. Process according to any one of claims 1   at 8, characterized in that the adsorbent bed comprises one or more components selected from the group consisting of carbonaceous sorbent, activated alumina, silica hydrogel, zeolite and metal components that produce metal cations.   10. Process according to any one of the claims   previous, characterized in that the wastewater passes into a holding tank before moving to through said sieve.   11. Method according to any one of claims 1   at 10, characterized in that the waste water is subjected to an action which reduces the size of the particulate matter in said waste water before passing said waste water through said first filtration medium.   12. Process according to any one of the claims   precedents, characterized in that the waste water is marine wastewater.   13. Method according to any one of claims 1   at 12, characterized in that the waste water comprises at least about 150 mg / l of total solids, at least about 1 mg / l of total solids in suspension, at least about 1 mg / l of BOD, at least about 200 mg / l of COD, at least about 15 mg / l of oils and fats, faecal coliforms, residual chlorine, and / or less than about 5 mg / l of oxygen dissolved.   14. Method according to any one of claims 1   at 13, characterized in that the stream of purified water contains less than about 150 mg / l of total solids, less than about 100 mg / l of total solids in suspension, less than about 100 mg / l of BOD , less than about 200 mg / l DOC, less than about 15 mg / l of oils and fats, less than about 14 faecal coliforms / 100 ml, less than about 0.0002 mg / l of 36 2723934   residual chlorine, and at least about 5 mg / l of dissolved oxygen. 15. Apparatus for the treatment of wastewater containing particulate matter and free oil, characterized in that it comprises: (a) means for removing free oil from said waste water, (b) means for making passing said wastewater, after removal of the free oil, to a first filtration medium, (c) a first filtration medium having an effective nominal pore size of about 200 μm or less, (d) a means for making passing said wastewater, after passing through said first filtration medium, to a dynamic filtration apparatus, (e) a dynamic filtration assembly comprising a second filtration medium having an effective nominal pore size of about 5 μm or less (f) means for passing said waste water, after passing through the second filtration medium, to an adsorbent bed, and (g) an adsorbent bed.   16. Device according to claim 15, characterized in that it further comprises a sieve through which the waste water passes before passing through said first filtration medium, said screen being a mesh screen comprising about 4-20 son by linear cm in each direction, said wires having a diameter of about -500 pm.   17. Device according to any one of   claims 15 or 16, characterized in that the first   filtration medium has an effective nominal size of the pores of about 160 μm or less.   18. Device according to any one of   Claims 15 to 17, characterized in that the means for   eliminate the free oil includes a way to put the waters 37 2723934   in contact with a material that absorbs free oil. 19. Device according to any one of   Claims 15 to 18, characterized in that the assembly of   dynamic filtration is a filtration assembly vibratory dynamics.   20. Device according to any one of   claims 15 to 19, characterized in that the second   Filtration medium has a molecular weight cut about 200 daltons or less.   21. Device according to claim 20, characterized in that the second filtration medium is a membrane   reverse osmosis capable of a salt rejection of at least 97%.   22. Device according to any one of   Claims 15 to 21, characterized in that the bed   adsorbent comprises one or more components selected from the group consisting of carbon sorbent, activated alumina, silica hydrogel, zeolite and metal components which   produce metal cations.   23. Device according to any one of   Claims 15 to 22, characterized in that it comprises   plus an ozone contactor for contacting said wastewater with ozone prior to contact with said adsorbent bed and an ultraviolet light irradiation source for subjecting said contacted water   ozone at irradiation with ultraviolet light.   24. Device according to any one of   Claims 15 to 23, characterized in that it comprises   plus a holding tank which allows the high density material entrained in said waste water to settle to the bottom of said holding tank, before said wastewater passes through said sieve, and a means for reducing the size of the particulate matter in the waste water before the passage of waste water   through said first filtration medium.