WO1995005346A1

WO1995005346A1 - Process for purifying contaminated liquids utilizing ozone

Info

Publication number: WO1995005346A1
Application number: PCT/US1994/009419
Authority: WO
Inventors: John P. Gilboy, Jr.; Keith R. Schneider; Rick Wilber
Original assignee: Gilboy John P Jr; Schneider Keith R; Rick Wilber
Priority date: 1993-08-18
Filing date: 1994-08-18
Publication date: 1995-02-23
Also published as: AU7635194A

Abstract

This process which is designated to accept and treat leachate, or other organic-filled waste water, directly at/from the site. This process utilizes ozone to simultaneously sterilize the liquid and its suspended components, mechanically separate the suspended substances, BOD, from the liquid, and eliminate odors. The separated substances are recovered in the form on an inert sludge. The sterile sludge can be used as a fertilizer food source or replaced in the landfill. The separated liquid is sterile, and can be reused to irrigate the site or discharged to storm water systems.

Description

PROCESS FOR PURIFYING CONTAMINATED LIQUIDS UTILIZING OZONE

FIELD OF THE INVENTION

This invention relates to a process for purifying contaminated liquids. In particular, this invention relates to a method for treating landfill leachate prior to or after conventional anaerobic and aerobic treatment processes. The process utilizes ozone as a flocculent to remove contaminants in the form of a sterile sludge. The sterile sludge may then be utilized as a fertilizer food source.

BACKGROUND OF THE INVENTION

In conventional processes, such as outlined in Fig. 1, leachate from a landfill 12 is collected in a retention pond 10 where the leachate is aerated to minimize odors from the pond. From the retention pond 10, raw leachate is chemically treated to adjust the pH in a primary clarifier 15. The effluent from the primary clarifier 15 is then treated in anaerobic digestors 20 and aerobic digestors 25. The effluent from the anaerobic and aerobic digestors 20, 25 is sent to a secondary clarifier 28 for disinfection and deodorization (final clarification) . The effluent from such a conventional waste treatment system is normally sent to a water treatment facility (WTF) . Sludge created in the clarifiers and digestors is removed and transferred to a sludge collection tank 30. This sludge transport is illustrated generally by dashed lines in the Figures, except where otherwise stated. Sludge collected in the sludge collection tank 30 is then treated by de-watering in a filter press 35 or other methods known in the art .

The process outlined above operates at a level which was basically satisfactory in meeting statutory requirements for landfill effluent discharge at the time of most facilities' construction. However, stricter regulations regarding water release standards have rendered current leachate treatment technologies inadequate. As a landfill's volume increases, water percolating through garbage and waste material included in the landfill absorbs a greater concentration of dissolved waste. Hence, the age of many landfills is a direct contributor to the ineffectiveness of current technologies. For example, as a landfill reaches its peak density, and for a minimum time period of twenty five years after the site ceases receiving waste, the treatment facility must be upgraded or replaced in order to meet current WTF standards under state and/or federal regulations for environmental discharge and to operate successfully under conditions of increased flow rate. Failure to meet minimum guidelines can result in discharge of contaminated water into the environment such as into the water supply and can present severe health hazards.

The standards for environmental discharge are being raised in an effort to preserve the environment and reduce such health hazards. Thus, industrial effluents that previously contained certain quantities of contaminants and met then applicable government standards will not meet today's more stringent requirements.

A further problem with conventional treatment processes lies with odors produced by treatment facilities utilizing these processes. Although the effluent from these standard facilities is frequently disinfected and deodorized prior to release to the WTF, the contaminated liquids still produce odors at all steps prior to disinfection and deodorization.

An additional problem with many current contaminated liquid treatment processes is their failure to remove fats, oils and greases (FOGs) or to allow for treatment of larger volumes of water and/or larger waste loading. These FOGs emulsify under currently used chemical treatment processes and are not removed from the final treatment- effluent. This failure can also result in severe human health hazards. Moreover, these FOG emulsions significantly add to the biological oxygen demand (BOD) and chemical oxygen demand (COD) of the effluent sent to the WTF. The high BOD and COD produced by the FOG emulsions causes removal of dissolved oxygen from the aquatic environment where the effluent from conventional treatment facilities is placed prior to treatment in the WTF.

Moreover, the sludge produced in conventional treatment processes is not sterile. Even though some processes utilize ozone to treat the contaminated liquid, these processes produce microorganism-containing sludge. The non-sterile nature of these sludges cause problems with odors and handling. These problems are of particular concern in those processes using the sludge as a fertilizer food source. Fertilizer foods consist of carbohydrates that have been degraded. This degradation allows the plants to absorb the nutrients from the carbohydrates. Fertilizer composts contain a degradation initiator and a carbohydrate source. Often times horse, chicken, or cow manure is used as the initiator. Hay, wheat and other vegetation are the carbohydrate source.

The live bacteria in manure attacks and. consumes the carbohydrates, degrading the carbohydrates^' and/or hastening their decay. The carbohydrate source and manure are mixed for a pasteurization process. In the pasteurization period, the mixture is continuously watered and mixed. The temperature is maintained at about 125- 130°F. If the temperature reaches above 140°F, the bacteria are destroyed. Several problems exist in current fertilizer food production methods. First, essential nitrogen is displaced from the mixture during pasteurization. The nitrogen comes off in the form of ammonia. Hence, the valuable nutrient is lost and odors are created. Further, bacterial degradation can consume carbohydrates in the mixture. This consumption reduces the food content of the fertilizer and requires supplementation through commercial additives. Even if a satisfactory mix has been produced, the fertilizer has no shelf life and must be used almost immediately.

DESCRIPTION OF THE PRIOR ART

Many systems are currently used to treat contaminated liquids. U.S. Patent No. 4,256,574 discloses a method of treating off-gas from an ozone disinfection tank in an aqueous waste treatment process. In this method, the off-gas is split into two portions, one diverted to sludge treatment and the other fed to an ozone generator. One treatment in this process occurs after secondary clarification.

U.S. Patent No. 4,160,724 discloses ozone treatment of waste water immediately prior to effluent discharge, after the waste water has been chemically treated. By performing ozone disinfection and deodorization later in the treatment process, the methods disclosed in 4,160,724 and 4,256,574 are prone to the odor problems known in conventional treatment processes.

U.S. Patent No. 4,178,239 discloses a process for intermediate treatment of aqueous sewage. This process does not produce a sterile sludge. The sludge produced by the 4,176,239 requires endogenous respiration or aerobic digestion to remove the microorganisms.

U.S. Patent No. 4,214,887 discloses utilizing the sludge from waste water treatment as a fertilizer food source. However, this sludge is not produced by utilizing ozone as the flocculent . In fact, 4,214,887 teaches against using ozone as a flocculent. Moreover, the sludge produced by 4,214,887 is not sterile and requires further treatment before being used as a fertilizer food source.

U.S. Patent No. 4,225,431 discloses a method and apparatus for treating aqueous waste. However, as noted in the patent, the method and apparatus disclosed therein fail to remove FOGs from the contaminated liquid. U.S. Patent No. 5,122,165 discloses utilizing ozone in an air sparging process to treat contaminated liquids. Air sparging consists of pumping liquid to the top of a tower and allowing the liquid to fall in droplet form from the top of the tower. The contaminated liquid droplets are met by a countercurrent of air or other gas which displaces contaminants from the liquid droplets. Air sparging systems require treatment of the contaminant-containing off-gas and require further treatment of the contaminated liquids after sparging to even meet current environmental discharge standards.

OBJECTS OF THE INVENTION It is an object of the invention to provide a process for treating contaminated liquids, in particular landfill leachate, wherein the effluent from the process meets current and proposed environmental standards . Moreover, it is an object of the invention to produce such conforming environmental effluents by a process that is both economical and time efficient and allows currently existing facilities to operate at higher loads.

It is another object of the invention to provide a process for treatment of contaminated liquids which eliminates odors early in the treatment process .

It is a still further object of the invention to provide a process for treating contaminated liquids, in particular landfill leachate, which produces an effluent substantially free of FOG. It is an additional object of the invention to produce a sterile composition that may be utilized • as a fertilizer food source.

Other objects and advantages of the invention will become apparent to those skilled in the art from the drawings in the following description of the invention.

SUMMARY OF THE INVENTION

The invention provides a high efficiency method of treating contaminated liquids, particularly landfill leachate. The process according to the invention comprises contacting the contaminated fluid with ozone in the form of bubbles . The ozone bubbles act as flocculent to remove the contaminants. Such contact methods as dissolved ozone flotation (DOF) and/or induced ozone flotation (IOF) treatment of leachate utilize ozone as a coagulation/flocculation medium to deodorize, disinfect and purify the contaminated liquids. The DOF/IOF treatment can be at a point proximal to and/or tertiary of conventional treatments, or can be a replacement to conventional treatment processes . The resulting effluent meets water release standards. The ozone contact removes the contaminants in the form of a sterile sludge. The sludge can be utilized as a fertilizer food source. Being sterile, the sludge can be stored or transported without the handling problems inherent with microbiologically active fertilizers.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a flow diagram illustrating a conventional contaminated liquid treatment facility.

Fig. 2 is a flow diagram illustrating one method of treating contaminated liquids prior to storage in a retention pond in accordance with the invention.

Fig. 3 is a flow diagram illustrating one method of treating contaminated liquids by DOF prior to conventional treatment in accordance with the invention.

Fig. 4 is a schematic diagram of a dissolved ozone flotation (DOF) device.

Fig. 5 is a schematic diagram of an induced ozone flotation (IOF) device.

Fig. 6 is a flow diagram illustrating one method of treating contaminated liquids by IOF prior to conventional treatment in accordance with the invention.

Fig. 7 is a flow chart illustrating treatment of contaminated liquids by IOF/DOF after conventional treatment in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION Although a particular form for the process has been selected for illustration in the drawings, and although specific terms are used in the specification for the sake of clarity in describing the process shown, the scope of this invention is to be defined in the appended claims and is not intended to be limited either by the drawings selected or the terms used in the specification or abstract .

Ozone is a powerful oxidizing agent. Ozone chemically alters many organic and inorganic substances . Ozone can be used as a disinfecting agent, in algae control, to oxidize inorganic micropollutants (iron and manganese) , to oxidize organic micropollutants (taste and odor compounds, phenolic pollutants, and pesticides) and to oxidize organic macropollutants (bleaching, increasing biodegradability, and reducing trihalomethane formation and chlorine demand) .

Moreover, it has been discovered that ozone can improve coagulation. When treating contaminated liquids with ozone, physicochemical phenomena occur improving subsequent coagulation, flocculation and floatation processes. Ozone breaks down compounds, effecting surface charges and causing aggregation of particles. Ozone acts as a microflocculant . The microflocculant effect of ozone is synergistic with filtration processes which may be used in the fluid treatment. For example, granulated activated carbon (GAC) , sand and mixed-bed filtration units function more efficiently when treating liquids that are pre-treated with ozone. An additional benefit of ozone's ability to break down organic particles in contaminated liquids occurs when breaking down these contaminants : the BOD of the contaminated fluid is temporarily increased. This breakdown creates a larger number of biodegradable particles in the contaminated fluid. The temporary increase results from IOF/DOF treatment of the contaminated fluid. Although known methods teach decreasing the BOD in the final effluent (a result shared by the process of the invention) conventional methods fail to realize the benefit conferred by the temporary increase in BOD. IOF/DOF treatment of contaminated liquids has a synergistic effect on the efficacy of the filtration units. The breakdown of organic particles, (such breakdown causing the temporary increase in BOD) , allows the resultant, broken-down particles to be more quickly digested by anaerobic/aerobic treatments utilized in conventional processes. The temporary increase in BOD from IOF/DOF treatment allows much quicker digestion of the BOD in aerobic/anaerobic treatment. The speed and efficiency of the treatment of contaminated liquids is increased when subjected to conventional treatment systems after the IOF/DOF treatment. Hence, the temporary setback of increased BOD results in a surprising increase in the speed and extent to which the BOD is decreased in the final effluent being discharged.

The resultant sludges from the IOF/DOF processes and any filtrate obtained through synergized filtration- processes have been disinfected by the prior contact with ozone and are therefore more amendable to conventional treatment methods as well. An additional benefit arises from the ability to utilize the resultant sludges as a fertilizer food source. As mentioned earlier, conventional fertilizer foods comprise carbohydrate sources degraded to plant absorbable form by bacteria. It is important to note that it is not the manure that is the food source in fertilizer. The carbohydrates are the food source. The bacteria in the manure merely degrades the carbohydrates to plant absorbable form.

The leachate sludge provides a suitable fertilizer food. A quantitative analysis shows the decayed vegetation found in liquid leachate to be similar to the fertilizer mix after pasteurization. Exposing the contaminants in the liquid to ozone breaks down the contaminants in a manner similar to bacterial degradation of carbohydrates. The broken down contaminants coagulate to form a sludge. Hence, the sludge, by exposure to ozone, presents the food source of the decayed vegetation in a plant absorbable form. Moreover, the leachate is sterile. After drying, the sludge can be packaged and shipped for use as compost at a much later time. As no bacteria is actively degrading the sludge, it has an infinite shelf life.

As the sludge is not subjected to the high temperatures of standard fertilizer pasteurization, the sludge contains inert nitrogen, the principal element necessary in a fertilizer. By keeping the nitrogen in the sludge, and the not the effluent, any further treatment of the effluent is accelerated. Nitrogen and ammonia slow conventional anaerobic processes .

For case of explanation, the following embodiments describe landfill leachate as the treated fluid. However, liquid contaminants other than landfill leachate may be decontaminated. Gray water is one such example. Gray water is not potable because of contaminants but is sufficient for certain uses such as irrigation.

In certain embodiments of the invention, landfill leachate is subjected to a non-flocculating ozone treatment directly upon retrieval from the landfill, prior to storage in a retention pond. Ozone treatment at this point disinfects and deodorizes the effluent stored in the retention pond. This treatment decreases odors resulting from the retention pond. However, in situations where it is impossible to treat the leachate prior to storage in the retention pond, IOF/DOF treatment of the leachate can be accomplished upon removal of the leachate from the retention pond. In certain embodiments, the effluent from the IOF/DOF process is further processed by conventional treatment processes, although certain types of landfill leachate, when treated with IOF/DOF, produce an effluent meeting current and proposed environmental discharge standards without further treatment.

Fig. 2 illustrates a method of proximal ozone treatment of contaminated liquid prior to storing the liquid in a retention pond 10. Ozone treatment is carried out in this step without sludge removal . The ozone treatment at this step can be carried out by a single apparatus or multiple apparatus in parallel. This method pre-treats the contaminated liquid to lessen odors associated with retention ponds 10 and to make the effluent entering a conventional treatment facility more biodegradable. As shown in Fig.2, raw leachate, or other contaminated liquid is taken by way of recirculation pump 59, feed line 53, and tank line 58 from landfill 12 or other contaminated liquid source (such as groundwater, waste water storage, sewage storage, or the like) . The leachate is collected in holding tank 50. The conduit carrying raw leachate from holding tank 50 to retention pond 10 is equipped with process pump 52, venturi 54 and static or mechanical mixer 55. Venturi 54 operates in a known fashion and introduces ozone into the raw leachate stream. Ozone is produced by ozone generator 56 and introduced into venturi 54 through ozone feed line 57. The mixer 55 downstream of venturi 54 ensures thorough mixing of the ozone gas and raw leachate or other contaminated liquid. Recirculation pump 59 may be employed to ensure holding tank 50 maintains a consistent volume allowing continuous operation of venturi 54. Feed_. line 53 carries liquid from retention pond 10 to input side of recirculation pump 59. Tank line 58 carries liquid from recirculation pump 59 to holding tank 50. This also allows re-ozonation of liquids in retention pond 10 when the volume of leachate coming from the landfill drops.

The steps illustrated in Fig. 2 (collection of raw contaminated liquid in a holding tank 50, pumping of the liquid for holding tank 10 to venturi 54, introducing ozone to leachate in venturi 54, mixing the liquid with the ozone in mixer^' 55 and storing the ozonated leachate in retention pond 10) ^' help to eliminate odor problems associated with conventional retention ponds. The liquid from retention pond 10 can be treated by conventional processes (clarification, anaerobic digestion, aerobic digestion, UV light treatment, or the like) immediately after the initial ozone treatment of Fig. 2, or can be further treated by IOF/DOF in accordance with the invention. Fig. 3 illustrates treatment of leachate or other contaminated liquid, wherein contaminants are removed from the liquid. Raw leachate from landfill 12 or from retention pond 10 as described with respect to Fig. 2, is collected in holding tank 50. Liquids from retention pond 10 can be introduced into holding tank 50 via feed line 53, recirculation pump 59, and tank line 58. Similar to the method described in Fig. 2, process pump 52 moves leachate from holding tank 50. Venturi 54 draws ozone gas produced by ozone generator 56, through ozone feed line 57, into contact with the contaminated liquid. Small aliquots of the liquid flow can be bypassed by feedback loop 62 back to the intake side of pump 52 to enhance mixing. Alternatively, mixer 55, as shown in Fig. 2, may be used instead of, or in conjunction with, feedback loop 62 for mixing ozone and leachate.

The ozonated leachate from venturi 54, or optionally mixer 55 of Fig.2, is then fed into a pressure vessel 60, preferably at 40 to 60 psi. The highly pressurized ozone in pressure vessel 60 goes into solution with the leachate entering pressure vessel 60 downstream from venturi 54 or mixer 55. A pressure relief valve 61 controls the pressure in pressure vessel 60 and directs the flow of ozonated leachate from pressure vessel 60 to a DOF device 65. DOF device 65 is at atmospheric pressure and permits the dissolved ozone in the leachate to come out of solution, giving rise to minute bubbles which carry out a floatation and flocculation process. The release of ozone from solution is analogous to carbon dioxide release when a carbonated beverage is allowed to reach standard pressure. As the pressure is decreased, small bubbles of gas form around solute contaminants, also in solution. As more bubbles form, the specific gravity of the solute becomes less than that of the surrounding liquid and the material floats to the top of the treatment vessel forming a sludge. Sludge is removed from DOF device 65 by known sludge removal methods, for example, by a rotating skimmer arm, not shown. The sludge is channeled to a collection area and/or is pumped to sludge collection tank 30 where it can be stored for dewatering or other conventional sludge treatment systems indicated generally as 35. As the sludge is sterile, no sanitizing processes are required. The sterile sludge is suitable for packaging and distribution as a fertilizer food.

The leachate clarified by the flotation and flocculation process then leaves the DOF device 65. The clarified effluent is sterile and can be used for irrigation or discharged to storm sewer systems. If necessary for state and/or federal discharge regulations, the clarified effluent can enter a conventional water treatment facility. Other optional flows may be established , such as reintroduction into retention pond 10 from DOF device 65 by way of line 180 or leachate may be channelled downstream of holding tank 50 through line 170.

Fig. 4 illustrates the flow of contaminated fluid from holding tank 50 into and through DOF device 65.

Contaminated liquid is taken from holding tank 50 and brought into contact with ozone gas in venturi 54. Ozone gas is produced by ozone generator 56 and introduced into venturi 54 through ozone feed line 57. After contact with ozone gas in venturi 54, the ozonated liquid is transmitted via process pump 52 into pressure vessel 60. From pressure vessel 60 ozonated fluid is transferred through pressure relief valve 68 into DOF device 65. Ozonated fluid enters DOF device via an anti-vortex device 79. Anti-vortex device 79 is located at the top central portion of DOF device 65 and reduces mixing currents within DOF device 65. Once in DOF device 65, ozone dissolved in the ozonated fluid is released in the form of bubbles 150, as discussed earlier. A sterile sludge formed from bubbles 150 entraps the contaminant (s) in the liquid. The sterile sludge is removed by means known in the art and not shown or described herein, leaving a clarified effluent to be discharged from DOF device 65. The sterile sludge and clarified effluent can be handled as ^{^}described in^' Fig. 3. Similarly, Fig. 5 illustrates the flow of contaminated fluid from the holding tank 50 into IOF device 66. Contaminated liquid is moved from holding tank 50 by process pump 52 into IOF device 66. Contaminated fluid enters IOF device through an anti-vortex device 79 located at the top central portion of IOF device 66. Ozone produced in ozone generator 56 is pressurized by compressor 80 and introduced into IOF device 66 through diffusing apparatus 67. Bubbles 160 emanating from diffuser 67 act to remove contaminants (s) in the same manner as bubbles 150, the difference being that bubbles 150 are formed in si tu and grow, whereas bubbles 160 are introduced.

Fig. 6 illustrates a method of proximal treatment of leachate similar to that of Fig. 3 except that IOF device 66 instead of DOF device 65 is used. IOF device 66 works on the same principles as DOF device 65, a difference in the two systems being the method of .ozone introduction into the floatation chamber. The contaminated liquid placed in DOF device 65 has ozone introduced therein under pressure, the ozone being released as bubbles in the lower pressure atmosphere of DOF device 65. IOF device 66, on the other hand, forces ozone through diffusing apparatus 67 creating a high number of very fine ozone bubbles in the liquid. The ozone bubbles perform the same function of removing contaminants by flotation in both IOF device 66 and DOF device 65.

Process pump 52 moves the leachate from holding tank 50 directly to IOF device 66. When an IOF device 66 is utilized, there is no need for venturi 54 or pressure vessel 60 of Fig. 3 to maintain ozone in the contaminant solution. Ozone generated by ozone generator 56 must be pressurized to allow direct injection of ozone into IOF device 66 through diffuser apparatus 67. Diffuser apparatus 67 can comprise porous pipe, diffusing disks or frits, ceramic or fabric socks, or any other gas diffusion apparatus capable of handling ozone.

The same sludge removal methods are utilized whether the contaminated liquid is treated by IOF or DOF. In fact, it is possible to incorporate both IOF and DOF methods in a treatment system. IOF device 66 and DOF device 65 can be utilized in series or can be combined in a two or three chamber vessel. In most cases the preferred method includes a single IOF, DOF, or combined IOF/DOF chamber. Although in special cases requiring multiple IOF/DOF treatments, the chambers may be run in parallel to handle larger loads with increased speeds.

The effluent is passed through the DOF/IOF device at a given rate, determined in accordance with the device manufacturer's specifications and site conditions. For example an IOF/DOF device can operate at a preferred rate of 2.5 gallons per minute for every square foot (2.5 gpm/ft²) of surface area of IOF/DOF device 66, 65. The operating rate may also be calculated by examining the total loading of the system and preferably allowing 2 pounds of solids removal for every square foot of surface area.

The ozone dose varies depending on the loading, flow rate and point of entrainment . Ozone dose rates can be calculated for different sites and conditions through analysis of total organic carbon (TOC) . For disinfection purposes, approximately 0.1 to 2.0 mg of ozone per liter leachate can be used and a contact time of 30-60 minutes is preferred. Depending on the levels of total solids to be removed, several units can be run to achieve the water quality needed for environmental discharge.

The ozone bubbles purify the contaminated liquids, and sterilize the resulting sludge. The flocculation and flotation of contaminants can be increased by known means. Depending on the types of suspended and dissolved solids encountered, coagulation and flocculation aids may be added to enhance the microflucculant properties of ozone. For example, polymer flocculation aids can be introduced into the IOF/DOF to increase the rate of flocculation and floatation thereby further increasing the purification rate of the liquids and sludge in the process of the invention.

Fig. 7 represents a tertiary or distal treatment of leachate after being treated by a conventional treatment facility. If the final effluent from a conventionally operated facility (Fig. 1) fails to meet the standards required by the appropriate governing body, a tertiary ozone floatation and flocculation treatment reduces the BOD and COD associated with FOGs that have passed through the system. According to Fig. 7, contaminated liquids are treated in a primary clarifier 15. Effluent from primary clarifier 15 is treated in anaerobic digestors 20 and aerobic digester 25. Conventionally, secondary clarifier 28 processes effluent from aerobic digestors 25. In accordance with the invention, effluent leaving the aerobic digestors 25 or secondary clarifiers 28 is pumped to a DOF or IOF device 65, 66 and treated similarly to the methods illustrated in Figs. 3 and 6. Sludge from clarifier (s) 15, 28, digestors 20,25 and IOF/DOF devices 65,66 is collected in sludge collector 30 for treatment in treatment apparatus 35. Treatment apparatus 35 can be utilized to dry the sludge. Once dried the sludge can be packaged as a fertilizer food. Since the sludge is sterilized in the IOF/DOF treatment, no further sterilization of the sludge is required. Depending on how strict the discharge regulations are, GAC/sand filters 78 may be applied as a final polishing step. It has been discovered that when effluent from the aerobic digestors 25 is treated in a DOF device 65 or IOF device 66, treatment by IOF/DOF eliminates the need for processing the contaminated liquid in the secondary clarifier 28. As a result, the overall contaminated liquid treatment is faster and more cost effective. However, in treatment facilities where it is impossible to avoid the secondary clarifier 28, IOF/DOF can be performed tertiary to secondary clarification.

Although this invention has been described in connection with specific forms thereof, it should be appreciated that a wide array of equivalents may be substituted for the specific elements shown and described herein without departing from the spirit and scope of this invention as described in the appended claims.

Claims

CLAIMSWe claim:

1. A method of treating contaminated liquids comprising: introducing ozone into the contaminated liquid wherein said ozone contacts the contaminated liquid in the form of bubbles, (150, 160) said bubbles removing contaminants from said contaminated liquid to produce an ozone treated effluent and a sterile contaminant sludge; and removing said sterile sludge from said ozone treated effluent.

2. A method of producing a fertilizer food source wherein a contaminated fluid is contacted with ozone in the form of bubbles (150, 160) , said bubbles removing contaminants in the form of a sterile sludge; drying said- sludge; and using said sterile sludge as said fertilizer food source.

3. In a method of treating contaminated liquids containing contaminants wherein said liquids are collected and stored in a treatment reservoir and subsequently subjected to anaerobic and/or aerobic and clarifications processes, the step comprising: introducing ozone into the contaminated liquid prior to storing the contaminated liquid in said retention reservoir, wherein said introduction of ozone sterilizes the liquids and the contaminants, reducing the BOD.

4. The method of claim 1 wherein said bubbles (150) are produced by subjecting the contaminated liquid to pressure in the presence of ozone to produce ozonated contaminated liquid; depressurizing said ozonated contaminated liquid to cause ozone dissolved in said ozonated contaminated liquid to release from said ozonated contaminated liquid to form said bubbles.

5. The method of claim 2 wherein said bubbles (150) are produced by subjecting the contaminated liquid to pressure in the presence of ozone to produce ozonated contaminated liquid; depressurizing said ozonated contaminated liquid to cause ozone dissolved in said ozonated contaminated liquid to release from said ozonated contaminated liquid to form said bubbles.

6. The method of claim 1 wherein said bubbles contact said contaminated liquid by introducing ozone into said contaminated liquid in the form of bubbles (160) and causing said bubbles to stream through said contaminated liquid.

7. The method of claim 2 wherein said bubbles contact said contaminated liquid by introducing ozone into said contaminated liquid in the form .of bubbles (160) and causing said bubbles to stream through said contaminated liquid.

8. A sludge resulting from contact of a contaminated liquid with bubbles comprising ozone, wherein the sludge is sterilized by the ozone bubble contact.

9. A fertilizer food source comprising the sterile sludge of claim 8.

10. A fertilizer food source comprising the sterile sludge produced by the method of claim 1.

11. The method of claim 1 wherein the liquid is contaminated with pollutants chosen from the group consisting of infectuous agents, algae, inorganic micropollutants, organic micropollutants, and organic macropollutants.

12. The sludge of claim 8 produced from liquids contaminated with pollutants chosen from the group consisting of infectuous agents, algae, inorganic micropollutants,organic micropollutants, and organic macropollutants.