ITTO941100A1 - PROCEDURE AND EQUIPMENT FOR THE TREATMENT OF FLUID - Google Patents

Abstract

The present invention provides a process for the treatment of waste water containing particulate material and free oil, said process comprising the removal of the free oil from the waste water, the passage of the waste water through a first filtration means having real dimensions of the pores of about 200? m or less, subjecting the waste water to dynamic filtration using a second filter medium having a real pore size of about 5? m or less, and bringing the waste water into contact with an absorbent bed to form a stream of purified water. The present invention also provides an apparatus which can be used to carry out the process of the present invention.

Description

DESCRIPTION of the industrial invention entitled: "Process and apparatus for the treatment of fluid"

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a process for treating a fluid. More particularly, the present invention relates to an improved process for treating waste water, particularly gray water, for recovering purified water and reducing effluents, and to an apparatus for carrying out this waste water treatment.

BACKGROUND OF THE INVENTION

Wastewater treatment tier reducing effluents and recycling reusable water is a matter of utmost importance in the overall pollution reduction and water conservation effort. A field of particular interest is the treatment of gray water on board boats and ships, i.e. marine gray water. Gray water refers to the combined effluent from kitchens, sinks, dishwashers, laundries, showers, on-board bilges, as well as from wells (including those in work areas such as engine rooms and medical areas). Contaminants are typically food particles of even large sizes (e.g. slices of food), sick fats, vegetable oils, soaps, detergents, body oils, human hair, metal particles from sinks and machines, solvents, and small items of clothing (e.g. socks), which may have been unloaded from laundries. Gray water is normally differentiated from both black water, which is a salt water residue of physiological discharges and paper materials from onboard services, and bilge water, which is a mass of salt water with all other on-board drains and which may contain chemical solvents and the like,

Although it is very variable in composition and origin. as well as with regard to the concentration and type of contaminants, gray water is produced on board ships. in an average amount of about 15-20 gallons (about 55-75 liters) per person and per day. Thus, for example, the production of gray water can be of the order of 4,000 gallons / day (about 15,000 liters / day) for a frigate with a crew of 200 people, and even reach 120,000 gallons / day (about 450,000 liters / day). / day) for an aircraft carrier with a crew of 6,000 people. The average gray water flow aboard such vessels can range from approximately 2.8 gallons / minute (approximately 10 liters / minute) to approximately 83.3 gallons / minute (approximately 315 liters / minute) with peaks ranging from approximately 8, 4 gallons / minute (approximately 32 liters / minute to approximately 250 gallons / minute (approximately 950 liters / minute).

Normal coalescing plants and centrifugal separators are inadequate for the treatment and purification of gray water, since, for example, the viscosity and surface tension of soaps and water are too close to allow satisfactory separation. Many ships discharge gray water directly. without treatments. in navigable waters, including lakes and waters near the coast. Some ships are equipped with a concentration tank. accumulation and transfer for the purpose of retaining gray water until it can be pumped into an onshore treatment plant. These ships use the concentration tank system. accumulation and transfer in an attempt to avoid discharging gray water into lakes and waters near the coast, but normally discharging gray water into the high seas o. when the reservoirs are full, even in other navigable waters. In increasingly widespread areas where the discharge of gray water is prohibited, expensive and demanding solutions are used, such as the transfer of gray water stored in tankers, or the prohibitions are simply ignored,

However, there remains a need for an effective and economical system to reduce waste water, particularly the discharge of gray water from ships. An object of the present invention is to provide such treatment systems. Another object of the present invention consists in concentrating the contaminants of the waste water in order to be able to store and discharge them more easily, at the same time allowing the discharge of recovered purified water. It is also an object of the present invention to provide a means for treating waste water, particularly gray water, so as to recycle the reusable water and thus save water. These and other objects and advantages of the present invention. as well as further inventive features. will be made clear by the description that follows.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a process and apparatus for treating waste water. The process and apparatus of the present invention are particularly suitable for the treatment of waste water containing particulate matter and free oil, particularly marine gray water.

The process of the present invention for the treatment of waste water containing particulate matter and free oil, comprises the removal of the free oil from the waste water, the passage of the waste water through a first filter medium having an actual pore size of about 200 µm or less, subjecting the wastewater to dynamic filtration using a second filtration medium having an actual pore size of about 5 pm or less, and bringing the wastewater into contact with an absorbent bed to get a stream of purified water.

The apparatus of the present invention for treating wastewater containing particulate matter and free oil comprises: (a) means for removing free oil from wastewater, (b) means for transferring wastewater. after removal of the free oil, to a first filtration medium, (c) a first filtration medium having an actual pore size of about 200 µm or less, (d) means for transferring 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 actual pore size of approximately 5 µm or less, (f) means for transferring the water after passing through the second filter medium to an absorbent bed and (f) an absorbent bed.

DESCRIPTION OF THE FAVORITE REALIZATIONS

The present invention is based on the discovery that wastewater can be treated to concentrate contaminants in wastewater and provide a stream of purified water, reprocessing wastewater to remove larger particles and free oil, subjecting the dynamic filtration wastewater using the filtration medium having an actual pore size of about 5 pm or less, and then bringing the wastewater into contact with a suitable absorbent bed to remove any remaining contaminants. The waste water stream can then be further treated, recycled and / or discharged as appropriate, while the concentrated streams can be further treated or stored for discharge in a suitable place.

Although the present invention is particularly suitable for treating gray water, especially marine gray water, the process and apparatus of the present invention can be used to treat other types of waste water. Other suitable uses of the present invention include the treatment of waste water coming from plants for the processing of food products, such as breweries, bakeries. dairies, sweet potato starch treatment plants, poultry processing plants, laundries, textile plants, pharmaceutical plants and the like. The present invention is described herein in the context of sea gray water treatment, although it can be understood that it is easily within the competence of a person skilled in the art to use the present invention in other contexts.

Characteristics of reef waters and purified waters

The function of the present invention, applied to the treatment of marine gray waters, consists in reducing the quantity and / or the concentration of the various contaminants to values lower than the standards indicated for the waters that receive them, i.e. those natural waters in which the gray waters can be unloaded from a ship. The typical characteristics of gray water and receiving water are shown in the following table.

And

The value of the total solids (TS) is the sum of

total suspended solids (TSS) and discio Iti solids

totals. The total solids correspond to the residue which

remains after evaporation. The oxygen demand

biochemical (BOD) represents the amount of oxygen

dissolved required during stabilization of

organic substances decomposable by action

aerobic biochemistry in water. The request for

chemical oxygen (COD) is a measure of quantity

of oxidizable components present in the water.

The present invention is therefore particularly

suitable for waste water treatment

comprising at least about 150 mg / l of total solids.

at least about 100 mg / l of total suspended solids, at least about 100 mg / l of B00, at least about 200 mg / l of COD, and at least about 15 mg / l of oils and fats. Such wastewater may also contain fecal coliforms, for example in a concentration up to about 10 <6>. 10 <8> or more fecal coliforms per 100 ml. Wastewater may also contain residual chlorine, for example in a concentration of up to about 20 mg / l or more, and may contain less than 5 mg / l of dissolved oxygen. possibly also not to contain practically dissolved oxygen. The pH of such wastewater can generally have any value (depends on the stability of the equipment being used), although the present invention works best with pH values between about 5 and 12.

The treatment of waste water according to the present invention involves. in part, the subsequent separation of smaller particles from the wastewater stream. While such a separation process may be effective in removing suspended particles from wastewater, it will normally be desirable to pre-treat wastewater to remove free oil and post-treat effluent to remove other contaminants. The preferred embodiment of the present invention includes such pre- and post-treatments.

The present invention preferably treats waste water such that the purified water stream contains less than about 150 mg / l, preferably less than about 30 mg / l, of total solids, less than about 100 mg / l, preferably less than about 30 mg / l of total suspended solids, less than about 100 mg / l, preferably less than about 30 mg / l, of B00, less than about 100 mg / l, preferably less than about 90 mg / l, of COD, and less about 15 mg / l of oils and fats. The purified water stream also preferably contains less than about 14 fecal coliforms / 100ml. less than about 0.0002 mg / l of residual chlorine and at least about 5 mg / l of 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 discharging into restricted receiving waters according to U.S. provisions, i.e. the purified water stream contains less than about 30 mg / L of total suspended solids, less than about 30 mg / L of BOD. . less than about 14 fecal coliforms / 100ml. 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 pre-treatment of the waste water before subjecting it to dynamic filtration preferably comprises removing the free oil from the waste water and then passing the waste water through a first filtration medium. The free oil can be removed from the waste water by any suitable means, preferably by bringing the waste water into contact with a material, such as cotton, preferably in the form of a spongy fabric. It absorbs free oil. The first filter medium preferably has an actual pore size of about 200 µm or less, more preferably about 160 µm or less. The removal of free oil and relatively larger particles from the waste water before subjecting it to dynamic filtration is provided to ensure the smooth operation of the subsequent dynamic filtration process and to avoid premature clogging of the filtration medium used in the dynamic filtration.

To further facilitate the efficient treatment of the waste water, it is preferably passed through a separator prior to passing through the first filtration medium (and also preferably before removal of the free oil, although this is not significant). Any separator can be used, for example a duplex separator, and the separator is intended to separate larger particles (such as hair, laundry residues and the like) and, as such, can typically be a perforated plate, or. more preferably a mesh screen. A suitable separator screen can have any suitable configuration, but will preferably have about 10-50 threads per linear inch (about 4-20 threads per linear cm) in each direction, with any suitable wire diameter, for example between about 0.002 and 0.02 inch (about 50 - 500 um). More preferably, such a separation mesh will have about 20-40 threads per linear inch (about 8-16 threads per linear cm) more preferably about 30 threads per linear inch (about 12 threads per linear cm), in each direction. , with any suitable diameter of the wires, for example between about 0.002 and 0.02 inches (about 50-500 inches).

preferably between about 0.005 and 0.01 inches (about 125-250 µm). The separator desirably removes particles with a diameter greater than about 1000 µm, preferably with a diameter of at least about 600 µm.

The separator is preferably sized so as to reduce the clogging frequency. while separating as much particulate material as possible, particularly particulate material which could disturb the satisfactory operation of the first filtration medium. To permit continuous operation, a switchable duplex separator is preferably employed and, when one of the separators becomes clogged, it can be excluded from the cycle by switching the flow to the second separator. The separator excluded from the cycle is then washed against the current by any suitable means, for example with a relatively small volume of waste water or purified water or with air pulses, in order to clean it for reuse. The effluent can be transferred to a dedicated concentrate tank to be subsequently discharged. Backwashing can be carried out automatically to avoid the need for an operator to intervene in this operation. The waste water is also preferably passed into an accumulation tank prior to passing through the first filtration medium (and preferably also before passing through the separator, if vineyard used, and before removal of the free oil although, also in this case, this is not particularly important). The storage tank is preferably constructed in such a way as to allow the high-density products entrained by the waste water to deposit on the bottom of the tank itself, so as to separate from the waste water. For example, the storage tank can be equipped with deflectors and / or the drain can be placed at a short distance, for example a few cm, above the bottom of the tank itself. so that the high-density material contained in the waste water can deposit on the bottom of the tank. In this respect. the bottom of the storage tank may have a removable access cover to facilitate the occasional periodic removal of high density contaminants. The separator and / or means for carrying out the separation of the free oil can be, and are preferably, contained within the storage tank. In particular, the storage tank preferably contains inclined surfaces such that the wastewater can flow alternately upward and downward, and such inclined surfaces not only contribute to the removal of high-density materials from the wastewater but also contribute to the separation of the free oil from the waters themselves.

In addition to facilitating the removal of high-density materials from waste water, the storage tank ensures a certain regularization of the incoming waste water. The volume and concentration of contaminants in wastewater can vary throughout the day depending on the particular end use, such as on board boats, and, therefore, the subsequent treatment will produce better results if the variations in flow and concentrations are mediated. or regularized in the storage tank. Such regularization can have a particular effect on the possible excursions of the BOD of the pH and other parameters. Also, in many end uses, particularly on board boats. the storage tank is desirably sized to collect and hold a volume equivalent to the peak flow for a reasonable period of time. For example from about 1 hour to a few hours, in order to ensure that the treatment system is not overloaded in times of excessive waste water generation (although the volume of the storage tank may be larger or smaller depending on the generation specification of waste water and the capacity of the treatment system).

At any stage of the pre-treatment process, desirably before the passage of the wastewater through the first filtration medium and preferably after the passage through a suitable storage tank to remove the high-density materials, the wastewater can be subjected to any suitable action that reduces the size of the particulates in the water itself, for example contact with rotating blades, in order to facilitate the removal of such particulates without unduly adversely affecting the subsequent filtration means. The means by which the particulate size is reduced may also be means by which wastewater is transferred from the storage tank and passed downstream for further treatment, for example through the separator and the first filtration medium. . Thus, for example, the discharge of the storage tank can be connected with a suitable piping to a macerator pump. The macerator pump draws wastewater from the storage tank, reduces solids to smaller particles, and ensures the pressure to force the wastewater through the rest of the treatment system. The macerator pump can be positioned outside the storage tank or inside the tank itself. If using a macerator pump. this is preferably equipped with an integral inlet screen, which is inserted into the discharge tank, so that the fragments collected on the screen can be washed against the current in the necessary way on the bottom of the storage tank for subsequent removal. The inlet screen is preferably sized so as to reduce the frequency of cleaning, while eliminating all particulates of sufficient size which would otherwise create problems for the macerator pump.

During the pre-treatment process, suitable treatment chemicals can be added to the wastewater, although this is generally not necessary. Such chemicals can be added to wastewater by any suitable means, for example with a supply system for such products. The chemical product feed systems preferably comprise a piston pump and an electronic control device such that the sensors installed downstream are capable of sending signals to the electronic controllers to automatically adjust the feed rate of the chemical product. The pumps for the chemical product can be connected directly to suitable storage containers and vessels containing the chemical products to be added to the waste water, with suitable means, for example with flexible suction pipes. In particular, acid can be added to the wastewater to neutralize it, and coagulants can be added to improve the separation efficiency in the dynamic filtration unit.

Dynamic filtration

After pretreatment, the wastewater is dynamically filtered using a second filtration medium having an actual pore size of about 5 µm or less. A dynamic filtration process has the purpose of removing practically all the remaining particulate in the waste water, preferably without the need for further filtration, i.e. ultrafiltration.

At this level of filtration, in an efficient and practical gray water treatment on board vessels, it has been found that effective filtration can only be done with the use of dynamic filtration. Specifically, the actual pore size of the filter medium is so small, and the effective surface area of the filter medium is so small, that the clogging of the filter medium pores and the formation of filter cake layers adjacent the surface of the filter medium present problems with the use of ordinary barrier-type filter elements.

For gray water treatment, direct barrier filtration is not as satisfactory as dynamic filtration for a number of reasons. Some of these reasons lie in the fact that contaminant volumes and concentrations are generally too high for the effective use of direct filters, an effective counter-current system would be prohibitively large, and the pre-coating (which is necessary to keep the contaminants compressible) or sticky away from the filter medium) requires the introduction of other chemical products which must then be discharged with the concentrated discharges.

Dynamic filtration is an extension of the concept of cross flow filtration. The operating principle is to maintain a filter medium free from clogging or clogging by repelling the particulate material from the filter element and preventing the formation of cake layers near the filter medium. These results are achieved by causing the fluid to be filtered to move at sufficient speed relative to the filtration medium to produce high shear loads as well as high lifting forces on the particles. as for example with the use of rotating means. swinging. with reciprocating or vibratory movement. The shear speed at the interface between the fluid and the filter medium is almost independent of the transverse velocity of the fluid, as opposed to what happens in tangential or cross-flow filtration techniques (which present, among other things, problems such as premature clogging of the filter due to compound absorption and high and uneven pressure drop, associated with high tangential velocities throughout the filter, potentially causing counter-current flows in the filtration medium and reducing filtration).

Dynamic filtration exhibits a number of advantageous features in the context of the present invention. Very high shear rates can be achieved in dynamic filtration assemblies to provide improved lift to repel small particles and / or permit high permeate flow rates. It has been observed that the increase in permeate flow rate is approximately proportional to the increase in shear rate in some systems. This means that the required filter surface can be greatly reduced compared to other filtration media. Since the shear can be evenly distributed throughout the system, uniformly high flow rates can be achieved and maintained in the system such that progressive clogging is eliminated and longer filtration times can be realized. Furthermore, by adopting dynamic filtration, it is possible to obtain high concentrations of agglomerated particulates for removal from the treated fluid.

A dynamic filtration unit has the ability to treat a wide range of contaminants, obtain an appreciably high concentration of retained solids, operate continuously for prolonged periods of time without the need for filtration aids and / or backwashing, and obtain uniformly high filtration characteristics to minimize overall system size. The dynamic filtration assembly may have any suitable configuration and will typically comprise a housing which contains a filter assembly comprising one or more filtration media and means for accomplishing relative movement between the filtration media and wastewater. The filtration medium of the filtering assembly and the means for effecting the relative movement between the fluid to be filtered and the filtration medium can have a variety of suitable conformations. A variety of suitable means can be used to accomplish such relative movements. how. for example, rotational, oscillating, reciprocating or vibrating motion.

The dynamic filtration assembly can consist of any suitable device. Suitable cylindrical dynamic filtration systems are disclosed in U.S. Pat.

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 disclosed in U.S. Pat. 3,997,447 and 5,037,562. as well as in U.S. Pat. No. 07 / 812.123. Suitable oscillating, reciprocating or vibrating groups for dynamic filtration are generally described in U.S. Pat. No. 4,872,988. 4,952,317 and 5,014,564. Other dynamic filtration devices are described in Murkes "Fundamental of Crossflow Filtration." Separation and Purification Methods. 19 (1), 1-29 (1990). In addition, many dynamic filtration assemblies are commercially available. For example, suitable dynamic filtration groups include the CROT Pai1-BDF-LAB, A5EA Brown Bovery rotary filter. and the New Logic V-SEP. While the desired removal of the particulate matter can be achieved with any suitable dynamic filtration group, it has been found that the use of dynamic vibration filtration, as generally exemplified by the New Logic V-SEP filter, is particularly suitable in the context of the present invention.

Dynamic filtration desirably creates shear forces of at least 20,000 seconds <-1> preferably of at least about 100,000 seconds <-1>. Optimal filtration rates will be achieved at high shear rates e. Since concentrate shear damage is not a problem in wastewater treatment, higher shear loads are preferred, within the constraints of the equipment used.

Any suitable filtration medium can be used in the dynamic filtration assembly. Generally, filtration media with smaller actual pore sizes are preferred, in order to minimize or avoid the need for post-treatment of the waste water. Thus, while the filter medium has an actual pore size of about 5 µm or less, the filter medium preferably has an actual pore size of about 1 µm or less, more preferably about 0.5 µm or less. The dynamic filtration medium most preferably has a molecular weight cutoff of about 200 Daltons or less, e. as is especially desirable, it is a dynamic filtration medium consisting of a reverse osmosis membrane capable of rejecting at least 97% of the salts (which is considered equivalent to a membrane having a molecular weight cut of about 50 Daltons). The reverse osmosis membrane capable of rejecting at least 97% of the salts is the membrane with the finest porosity that can be practically used in the context of the present invention. After the passage of the waste water through the dynamic filtration unit, the water desirably does not need to be subjected to further filtration by passing through a filter medium. but rather they can simply be subjected to a treatment with an absorbent bed, (and possibly another post filtration treatment such as ozonation and UV exposure) to eliminate any remaining contaminants. The dynamic filtration unit is connected by means of suitable fluid lines. to a suitable concentrate tank. Concentrated contaminants from the dynamic filtration assembly are preferably periodically discharged into the concentrate tank. Any suitable means, such as any usable counter-current means, may be employed to control the dynamic filtration assembly. It is preferred that the back current control be employed in correlation with the driving mechanism of the dynamic filter assembly. to sense the increase in torque associated with the increased viscosity of concentrated contaminants and operate the control valves to automatically drain the concentrated contaminants into the concentrate reservoir. In wastewater treatment, the dynamic filtration assembly will eliminate much of the particulate load. Specifically, the dynamic filtration group will eliminate most of the total suspended solids and reduce the shares of BOD and COD associated with particulates. The dynamic filtration assembly will also preferably eliminate undesirable molecules and agglomerates, for example those whose molecular weight is at least about 5oo Daltons (up to about 30,000 Daltons or more), more preferably those with molecular weights of at least about 200 Daltons, and more more preferably those with molecular weights of at least about 50 Daltons. In waste water treatment. the dynamic filtration group preferably removes many smaller organic compounds, particularly those bound to soap micelles, which has the effect of reducing the BOD and lowering the pH, although the increase in pH is caused by the soap solutions. The dynamic filtration assembly also preferably has the effect of eliminating almost all suspended solids and fecal coliforms.

While the concentrate from the dynamic filtration assembly is finally passed through suitable fluid lines into a suitable concentrate tank, this can be done after the concentrate has been recycled for further concentration. Since the dynamic filtration process is improved by high fluid velocities which tend to reduce the clogging rate of the filter medium, it is preferred that the dynamic filtration assembly use a recirculation pump to suck from the discharge ends of the dynamic filtration assembly and discharge at the inlet end of the group itself. Recirculation rates between 1 and 10 times the waste flow rate are preferred, with a preference for higher flow rates when handling highly contaminated fluids. Two or more dynamic filtration groups can be connected in a multiplex system to ensure the possibility of switching to a fresh dynamic filtration group when one of the groups becomes clogged.

Post-treatment

The filtrate from the dynamic filtration unit can essentially be sterilized water depending on the nature and precise quantity of contaminants present in the waste water and the particular pore size of the dynamic filtration unit. The dynamic filtration assembly can remove bacteria, yeasts, fungi and the like from wastewater and can reduce, if not eliminate, endotoxins. He lied and the filtrate from the dynamic filtration group does not necessarily need further treatment, the filtrate is preferably still treated to reduce and preferably eliminate all microorganisms.

viruses and residual organic and inorganic compounds. Thus, after the waste water has been subjected to dynamic filtration, it is brought into contact with an absorbent bed suitable to remove all such possible contaminants remaining in the water itself, particularly organic and inorganic contaminants, such as chlorine and metal ions (especially arsenic which is used aboard boats as a rat poison and can end up in gray marine waters). as well as certain microbial contaminants. which can be passed through the dynamic filtration medium.

The absorbent bed may comprise any suitable absorbent material (s), and will typically comprise one or more components selected from the group consisting of carbon absorbent, activated alumina, silica hydrogel. zeolite and metal components that generate metal cations. Carbon absorbents can be charcoal based, fruit shells such as coconut shells, wood based, activated petroleum carbon based, synthetic carbon and mixtures thereof. The carbonaceous absorber is more preferably activated carbon. The metal components which generate metal cations are preferably selected from the group consisting of copper, zinc, brass, manganese, silver and their mixtures, and more preferably are brass particles.

Since the precise nature of the wastewater may be unknown and may vary from day to day, the absorbent bed is preferably a mixed absorbent bed containing a variety of absorbent materials capable of acting on a variety of potential contaminants. Such a preferred mixed absorbent bed may contain, for example, about 40-80% by weight of carbonaceous absorbent, about 5-20% by weight of 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 form metal cations, The absorbent bed more preferably comprises activated carbon, activated alumina , silica hydrogel, zeolite and brass particles. Preferred absorbent beds are described, for example, in U.S. Pat. 5,178,768 and in U.S. Pat. No. 08 / 118.998. After the absorbent bed has been loaded with contaminants such that its ability to remove further contaminants is adversely affected, the absorbent bed can be replaced, or more preferably, regenerated and reused. The absorbent bed can be regenerated by any suitable means, for example with water at about 200 "F (about 93 DEG C.) according to the process described in U.S. Pat. 5,281,344.

While the filtrate coming from the dynamic filtration unit is preferably made to pass, through suitable pipes, directly to the absorbent bed. the filtrate coming from the dynamic filtration unit can be passed through suitable pipes to an ozonation system before being brought into contact with the absorbent bed. The ozone system generates ozone to clean the filtered waste water as ozone is able to sterilize waste water and oxidize many organic compounds. as well as eliminating microorganisms and viruses that may have passed through the upstream filters. This disinfectant action can typically be carried out with an ozone concentration of at least about 0.5 mg / l, preferably at least about 1 mg / l, in the water. Ozone produces no negative side effects and quickly disappears from the treated water.

Ozone can be supplied with any suitable system.

The ozonation system preferably comprises a pressurized air dryer with oscillating absorption, an ozone generator, a contact medium for ozone, and, more preferably. a UV lamp and another contact medium for ozone. The ozone generator can be any suitable device, for example a conventional device that produces ozone by accelerating electrons between two electrodes. The power supply for the ozone generator is either filtered and dry air or oxygen. An oxygen supply produces more ozone and has a higher concentration. Concentrations typically vary between 1 and 8% by weight, with concentrations of 2% by weight typical of the air supply and concentrations of 3% by weight typical of the oxygen supply.

In the case of an air supply, the compressed air is dried by means of an oscillating absorption double bed pressurized air dryer. Along with appropriate filters. this unit supplies air of the required quality by treating the air, preferably compressed air, which passes through an intake opening suitable for the oscillating absorption pressurized dryer. In the case of an oxygen supply, the oxygen in the compressed air is concentrated by means of a deflection purification absorber. This system is similar to that for the oscillating absorption pressurized air dryer, with the exception of details for the absorbent and the cycle. The use of the oxygen supply system requires much more air and a larger absorption system, and therefore the air supply system is preferred. The oscillating absorption pressurized air dryer is used to purify and dry the air down to a low dew point, for example -70 ° C (about -57 ° C). so that the ozone generator receives very dry filtered air to be able to work well and produce high concentrations of ozone for long periods.

The ozone mixer ensures sufficient contact time for the reaction of the organic residue in the filtered wastewater with the ozone generated by the ozone generator. Ozone is generated in the gaseous phase and must be dissolved in the filtered waste water. Various procedures are available for the transfer or contact to dissolve the ozone in the waste water. For example, ozone can be bubbled through a wastewater column with or without backfill material. The ozone can also be injected into a pipe that carries the waste water. The ozone transfer into the waste water is improved by using a static mixer in series.

The wastewater treatment system also preferably comprises a second ozone mixer with a UV light source. Ultraviolet light, particularly 254nm long, will produce hydroxyl radicals in ozonated water, and these radicals. together with ozone, they will be able to oxidize most organic compounds. The second ozone mixer with ultraviolet light source ensures the completion of any desirable or necessary oxidation in wastewater by ozone.

Residual ozone can be allowed to naturally decompose to oxygen, since its half-life is approximately 20 minutes in water at 70 “F (approximately 21 ° C). The decomposition of ozone can be accelerated by heating. An alternative procedure, which has the other benefits mentioned above. Is the use of irradiation with ultraviolet light. An absorbent bed may also be employed for ozone removal, particularly since the surface of the absorbent bed can provide a site for the decomposition of the ozone. Therefore, as regards the treatment of the waste water with ozone, this contact preferably occurs before the waste water comes into contact with the absorbent bed. An ozone analyzer can be used to analyze treated wastewater or exhaust gas to check the complete removal of ozone from the water. The treated wastewater is then withdrawn from the wastewater treatment system as a stream of purified water.

A concentrate reservoir can be provided to hold the concentrate generated in the treatment process so that it can subsequently be discharged at a suitable point. For example, in the case of marine greywater generated on board a vessel, the concentrate can be pumped when the vessel is in port with disposal facilities or transport vessels close at hand, or in the open sea outside the controlled waters.

Treated wastewater can be further treated, recycled and / or discharged, as appropriate. The treatment system is preferably provided in such a way as to purify the gray water up to a point where it can be discharged into waters in which there are discharge limits.

The efficiency of the treatment system is such that with a footprint of approximately 20 feet (approximately 6 meters) long x 10 feet (approximately 3 meters) wide x 10 feet (approximately 3 meters) high, it is capable of treating up to 5 gallons (19 liters) of gray water per minute on board, with minimal maintenance.

Equipment

Any suitable apparatus may be employed to carry out the present invention. Generally, such equipment for treating waste water containing particulate matter and free oil will include (a) means to remove free oil from waste water (b) means to start waste water, after removal of free oil , to a first filtration medium. (c) a first filtration medium having an actual pore size of approximately 200 µm or less, (d) means for initiating 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 5 µm or less, (f) means for initiating the wastewater after passing after the second filtration medium to an absorbent bed and (g) an absorbent bed.

The apparatus will preferably further comprise a separator through which the waste water is passed prior to passing through the first filter medium. This separator will preferably consist of a mesh screen, as described above. in the context of the process of the present invention. The first filter medium preferably has an effective pore size of about 160 µm or less, and the means for removing free oil preferably comprises means for contacting the waste water with a material that absorbs free oil, such as cotton ( for example spongy tissues).

As explained in more detail with reference to the process of the present invention, the dynamic filtration assembly is preferably capable of creating shear forces of at least about 20,000 seconds <-1>, more preferably shear forces of at least about 100,000 seconds <- 1>. The dynamic filtration assembly is more preferably a vibration dynamic filtration assembly. The second filter medium preferably has a molecular weight cutoff of about 200 Daltons or less, and more preferably is a reverse osmosis membrane capable of rejecting at least 97% of the salts.

As has also been explained in more detail above with reference to the process of the present invention, the absorbent bed may contain any suitable absorbent material intended to remove contaminants that could pass through the dynamic filtration medium. The absorbent bed preferably comprises a carbonaceous absorbent, particularly activated carbon, activated alumina, silica hydrogel, zeolite and metal components which can release metal cations (such as copper, zinc, brass, manganese, silver and their mixtures, particularly brass particles).

The equipment may further comprise an ozone mixer to bring the wastewater into contact with ozone before passing it through the absorbent bed (which can be used to remove residual ozone and / or facilitate its decomposition, as well as to remove the reaction products of ozone). The equipment can also include an ultraviolet light irradiation source to subject the ozonated wastewater to ultraviolet irradiation, preferably before bringing the wastewater into contact with the absorbent bed.

In most applications, as previously described with reference to the process of the present invention, the apparatus will also comprise a collection tank which allows to retain the high density material present in the waste water by making it deposit on the bottom of the tank itself before the transfer of waste water through the separator. The apparatus may also comprise means for reducing the size of the particulates in the waste water prior to its passage through the first filter medium. The equipment will typically further comprise suitable valves (to control the flow of waste water), a concentrate tank (for temporary storage of the concentrate), drains (such as a carbon exhaust filter to deodorize the gases discharged from the storage tank waste water and to the concentrate tank), and the like, as is known in the art.

Examples

The following examples further illustrate the present invention, particularly the use of dynamic filtration in the treatment of fluids. These examples, of course, are not to be considered in any way as limiting the scope of the present invention.

Example 1

Two 55-gallon drums of gray water are taken from the David Taylor Research Center and the adjacent Naval Academy. It is believed that 45% of gray water originates from showers and washbasins, 33% from kitchens and sinks and 22% from the laundry. Tests are completed within 72 hours of sample taking.

The sample just received does not appear to contain large particles. 25 gallons (approximately 210 liters) of the gray water is passed through a 24 x 24 x 0.014 stainless steel screen (threads / linear inch x threads / linear inch x thread diameter (inches)) (approximately 9 threads per linear cm in both directions, with a wire diameter of about 356 pm). To further reduce the size of any large particles, a household waste discharge device is used. About 15 gallons (about 57 liters) of the drawn water are filtered using a BDF-LAB (Pali Corporation) dynamic microfilter. The filter element is a porous stainless steel balanced cylinder type Pali S50-3PSS grade H, S series, with an absolute pore size of 5 pm.

Half of the outflow is concentrated, and half of the outflow is filtered. The filter is started using clean water to set the operating parameters. We then move on to feeding with gray water, and the operating parameters are appropriately adjusted. Flow rates are kept constant during the test by slightly increasing the operating pressure during the course of the test. Although the filter has only been tested for a short time, it is evident that the filter does not clog as quickly as a standard type filter. The apparent turbidity of the filtrate is significantly lower than that of the incoming liquid. while the turbidity of the concentrate is higher than that of the incoming liquid. The permeate flow rates and annular pressures at 10 and 30 minutes of the test are shown in the following table.

About two gallons (about 8 liters) of filtrate are ozonated for 200 minutes. The ozonator adopts a recirculation circuit with 30 feet (about 9.1 meters) of copper tubing. An ozone generator from Clean Air Corporation is used to supply the ozone, producing 8 g / hour (about 30 1 hour of ozone). An aspirator is used to supply the ozone. The contact and mixing of the ozonated air with the water is achieved with a turbulence of 6-8 feet / minute (about 180-240 cm / minute).

The characteristics of gray water in various stages of treatment are shown in the following table.

Although total suspended solids (TSS) was not measured after filtration, it is believed that dynamic filtration alone can be credited with decreasing TSS from 26 mg / L to 6 mg / L. The increase in BOD from filtered water to ozonation is believed to be the result of the fact that ozonation converts non-biodegradable material into biodegradable material. After 200 minutes of ozonation the water remains foamy, indicating that the soaps have not been broken down. The pH remains unchanged through dynamic filtration and ozonation.

It is clear from the evidence that ozone is effective in reducing the COD of gray water. Although only a small amount of ozone was used, there was an appreciable reduction in COD. Ozone was added at a concentration of 72 ppm for 200 minutes. During this time. Samples were taken from the tank, reducing the total volume of gray water and increasing the ozone concentration at each new time period. At the end of the predicted time, the ozone concentration would have been 43 mg / l, had no ozone been consumed in the reaction. If all the ozone supplied had reacted with COO compounds, the COO would have been reduced by 43 mg / l. The value of COO. however, it decreased from 490 mg / l to 360 mg / l. with a decrease of 130 mg / l. This decrease is three times higher than the reduction of COD which can be attributed to the effect of the ozone alone.

Ozone was introduced into the water by means of an an a current. There was about 3,000 times more oxygen in the air than ozone. Oxygen could be effective in oxidizing those compounds that are easily oxidized, and the air flowing through the water could also carry away volatile organic compounds. These mechanisms may have a bearing on the added effectiveness of the ozonation process.

Although ozone has been shown to be effective in reducing COD, and perhaps BOD, it is clear that a significant amount of ozone would be required to reduce COD and BOD to acceptable values. after dynamic filtration alone, using a filtration medium that has a pore size of 5 µm. While this test demonstrates the feasibility of dynamic filtration and ozonation in the treatment of gray water. this test also demonstrates that it is desirable to use dynamic filtration with a filtration medium having pores less than about 5 µm in size.

Example 2

A 55-gallon (approximately 2101) drum of gray water is taken from the David Taylor Research Center and filtered through a series of filters characterized by decreasing pore size. The first filter is a mesh screen that simulates a separator. The second, third and fourth filters simulate the filtration of the dynamic filtration group. The second filter is an Ultipor GF filter with 3pm pores (Pali Corporation!), While the third filter is a Sanitary Filler with a nylon membrane and 0.04 pm pores (Pali Corporation) and the fourth filter is an Ultrafilter model VIP-3017 (Asahi). with a cut of the molecular pe? o at 6,000 Daltons.

The fourth filter was rinsed with deionized water at 3 pm absolute for about 20 hours, and then drained before testing. The gray water drum was pressurized to approximately 5 psig (approximately 34 kPa) with air, which forced the gray water through the filters with a total flow rate of less than 0.5 g / minute (approximately 1.9 liters /minute). The flow rate of the concentrate from the fourth filter is approximately 1/4 of that of the filtrate (purified water). Samples of the filtrate are taken at three different points on the test system: (i) downstream of the first filter, (ii) downstream of the second and third filters, and (iii) downstream of the fourth filter. The filtrate is allowed to flow from the first two sampling taps for 30 seconds before taking the sample, and the fourth filter is washed with the fluid to be treated for 10 minutes before taking samples.

The filtration system significantly improves the clarity of gray water, and also reduces the odor and foaming of gray water. The flow rate gradually decreases along the test if a constant pressure is maintained in the drum. Examination of the system indicates that the second or third filter, or both, are clogged. The use of a dynamic filtration unit excludes this clogging. Examination of the concentrate in the contents of the second filter reveals that it is much darker than the original gray water fluid. The test results are shown in the following table.

The results of the test indicate that the combination of the various filters can meet the requirements for suspended solids and faecal coliforms. while the addition of an acid may be necessary to correct strongly alkaline conditions. The use of an upstream coagulant can improve the filtration effect obtained through dynamic filtration. The test results also indicate that ozone and ultraviolet light irradiation are useful for further reducing the BOD value.

Example 3

Two 55-gallon (approximately 2101) drums of gray water are obtained from the U. S. Naval Academy in Annapolis. Maryland. Each gray water drum contains 27 gallons (approximately 102 liters) of laundry water. 18 gallons (about 68 1) of kitchen water, and 5 gallons (about 19 1) of shower water.

Using a transfer pump. gray water is passed through a 30 x 30 x 0.0065 screen (threads / linear inch x threads x linear inch x diameter of the threads (inches)) (approximately 12 threads / linear cm in both directions. with diameter of the threads about 165 pm) by transferring them to buckets to remove larger debris. The debris removed consisted of hair. filiform material, flakes, and other soft means. At the bottom of each of the stems, the last 2-3 inches (about 5-8 which) consisted of a thick, dark oily substance.

The gray water in the buckets was then poured through a 160-shock metal filter. The gray water thus filtered are opaque, dark inky and contain no traces of soap or soapy water. Freshly poured gray waters emit a strong and pungent odor, which however decays in a few hours.

The gray water is then subjected to dynamic filtration using the Pali SEP VMF series L (Pali Corporation) dynamic vibration filtration group and one of the two filtration media, i.e. a nano filtration membrane with a molecular weight cutting capacity of 200 ( with a minimum retention percentage of 80% of the salts) or with a retention percentage of 97% of the salts, through a reverse osmosis membrane. The operating conditions of the dynamic filtration group are as follows:

Using the nanofiltration membrane, approximately 80 gallons (approximately 300 liters) of gray water are treated over a 3 week period. At the end of this period, 99.31% of the fluid was removed from the system as permeate. The total permeate collected, i.e. 75.91 gallons (287.53 1). indicates a loss of 3.52 gallons (13.3 1) of gray water. The loss in gray water is attributable to the evaporation of the volatile organic compounds that are released and of the water vapor. The total quantities of gray water recorded are reduced by 4.4% to take into account evaporative losses. As the percentage permeate / total gray water ratio approaches 99.31%. the permeate flow rate decreases from approximately 73ml / minute to approximately 47ml / minute.

Using the reverse osmosis membrane. it is about 72 1 of gray water with a permeate recovery of about 68 1, ie about 94.31%. As the permeate / total percentage of gray water goes from about 89% to about 94%, the permeate flow rate decreases from about 24.4 ml / minute to about 21.3 ml / minute.

The characteristics of gray water before and after being subjected to dynamic filtration are indicated in the following table:

The permeate obtained through the nanofiltration membrane has a sweet and pungent odor and has a pale yellow color. The permeate obtained through the reverse osmosis membrane is clear and does not emit any odor. Both permeates meet U.S. requirements. for discharge into open waters. However, the permeate obtained from the reverse osmosis membrane is generally poorer in contaminants than the permeate obtained from the nanofiltration membrane. The permeate obtained from the nanofiltration membrane should preferably still be treated by bringing the permeate into contact with a suitable absorbent bed to ensure compliance with the laws applicable to water discharge, while the permeate obtained from the reverse osmosis membrane can probably avoid the need for such further processing.

All references cited, including patents, patent applications, publications and the like, are incorporated herein in their entirety by reference.

Although this invention has been described with emphasis on preferred embodiments, it is evident to those of ordinary skill in this art that variations can be made to the preferred method and apparatus and that it is intended that the invention may be embodied other than as specifically described. here. The invention therefore includes all the modifications that fall within the spirit and scope of the invention itself, as defined by the following claims.

Claims (24)

CLAIMS 1. A process for the treatment of waste water containing particulate matter and free oil, said process comprising the removal of free oil from said waste water, the passage of said waste water through a first filtration medium having a dimension pore size of about 200 µm or less, subjecting said waste water to dynamic filtration using a second filtration medium having a real pore size of about 5 pm or less, and bringing said waste water into contact with a bed absorbent to obtain a stream of purified water. 2. The process of claim 1 wherein said wastewater is passed through a separator before passing it through said first filtration medium. 3. Process according to claim 2, wherein said separator is a mesh screen comprising about 4-20 threads per linear cm in each direction, such threads having a diameter of about 50-500 µm. A process according to any one of claims 1 to 3, wherein said first filter medium has an actual pore size of about 160 µm or less. 5. Process according to any one of claims 1 to 4, in which free oil is removed from said waste water by bringing said waste water into contact with a material that absorbs free oil. Method according to any one of claims 1 to 5, wherein said dynamic filtration is a dynamic vibration filtration. 7. A process according to any one of claims 1 to 6. wherein said second filtration medium has a molecular weight cutting capacity of about 200 Daltons or less. 8. Process according to claim 7, wherein said second filtration medium is a reverse osmosis membrane capable of blocking at least 97% of the salts. 9. Process according to any one of claims 1 to 8. wherein said absorbent bed comprises one or more components selected from the group consisting of carbonaceous absorbents, activated alumina, silica hydrogel, zeoite, and metal components which release metal cations. 10. Process according to any one of claims 1 to 9, wherein said waste water is passed into an accumulation tank before the passage of said water through said separator. 11. Process according to any one of claims 1 to 10. wherein said wastewater is subjected to an action which reduces the size of the particulates in said wastewater prior to their passage through said first filtration medium. 12. Process according to any one of claims 1 to 11. wherein said waste water is marine gray water. 13. Process according to any one of claims 1 to 12. wherein said waste water comprises at least about 150 mg / l of total solids, at least about 100 mg / l of total suspended solids. at least about 100 mg / l of B00, at least about 200 mg / l of COD. at least about 15 mg / l of oils and fats, fecal coliforms, residual chlorine and / or less than about 5 mg / l of dissolved oxygen. The process according to any one of claims 1-13, wherein said purified water stream contains less than about 150 mg / l of total solids. less than about 100 mg / l of total suspended solids, less than about 100 mg / l of B00, less than about 200 mg / l of COO. less than about 15 mg / l of oils and fats, less than about 14 fecal coliforms / 100 ml, less than about 0.0002 mg / l of residual chlorine, and at least about 5 mg / l of dissolved oxygen. 15. Waste water treatment equipment containing particulate matter and free oil, comprising: (a) means for removing free oil from such waste water, (b) means for transferring said wastewater after the removal of said free oil to a first filtration medium, (c) a first filtration medium having an actual pore size of about 200 µm or less, (d) means for transferring said wastewater after passing through said first filtration medium to a dynamic filtration apparatus. (e) dynamic filtration assembly comprising a second filtration medium having an actual pore size of about 5 µm or less. (f) means for transferring said wastewater after passing through said second filtration medium to an absorbent bed, and (g) an absorbent bed. 16. Apparatus according to claim 15, wherein said apparatus further comprises a separator through which said wastewater is passed prior to passing through said first filtration medium, wherein said separator is a mesh screen comprising about 4-20 threads per linear cm in each direction, with such wires having a diameter of about 50-500 µm. 17. Apparatus according to claim 15 or 16, wherein said first filtration medium has actual pore size of about 160 µm or less. 18. Apparatus according to any one of claims 15-17, wherein the means for removing free oil comprises means for bringing said wastewater into contact with a material which absorbs free oil. 19. Apparatus according to any one of claims 15 to 18, wherein said dynamic filtration assembly is a vibrating dynamic filtration assembly. 20. Apparatus according to any one of claims 15 to 19 wherein said second filtration medium has a molecular weight cutting capacity of about ZOO Daltons or less. 21. Apparatus according to claim 20, wherein said second filtration medium is a reverse osmosis membrane capable of retaining at least 97% of the salts. Apparatus according to any one of claims 15 to 21, wherein said absorbent bed comprises one or more components selected from the group consisting of carbon absorbent, activated alumina, silica hydrogel, zeolite, and metal components which generate metal cations. 23. Apparatus according to any one of claims 15 to 22, wherein said apparatus further comprises an ozone mixer for bringing said wastewater into contact with ozone before bringing it into contact with said absorbent bed, and a light irradiation source ultraviolet to subject said ozonated waste water to irradiation with ultraviolet light. 24. Apparatus according to any one of claims 15 to 23, wherein said apparatus further comprises an accumulation tank which allows the material of high density retained in said waste waters to deposit on the bottom of said accumulation tank before the passage of said waters through said separator, and means for reducing the size of the particulates in said wastewater before passing said wastewater through said first filtration medium.