WO1994011307A1

WO1994011307A1 - Ozone treatment of landfill waste-water

Info

Publication number: WO1994011307A1
Application number: PCT/US1993/010897
Authority: WO
Inventors: William R. Martin; Robert A. Panza
Original assignee: Pacific Energy
Priority date: 1992-11-16
Filing date: 1993-11-12
Publication date: 1994-05-26
Also published as: AU5600794A

Abstract

The present invention relates to an apparatus and a process for the effective treatment of waste-water from landfills to remove contaminants. The process of the present invention comprises the steps of collecting waste-water from a landfill (16) and mixing (14) the waste water with generated ozone (12). The waste-water/ozone mixture is then reacted by spraying (20) the mixture into a primary ozone/UV reactor (18) where it is reacted to form treated waste-water. An apparatus to carry out the process of the present invention is also provided.

Description

OZONE TREATMENT OF LANDFILL WASTE-WATER

Field of the Invention

This invention is related to a method and apparatus for the treatment of waste-water from landfills.

Background of the Invention

Landfills are typically divided into four classifications based on their intended content: Class One landfills are for the dumping of hazardous waste; Class Two, for non-hazardous waste including liquids; Class Three, for non-hazardous, non-liquid waste; and Class Four, for inert waste such as construction rubble. A primary concern regarding landfill management is the containment of the materials in the landfill, and these concerns are related to.the type of refuse in the landfill and the landfill's exposure to water and liquids. In some cases, leaks of waste-water from landfills have contaminated underground aquifers. Such contamination can require pumping out the entire contents of the aquifer and processing the water to remove the contaminants. Such procedure constitutes an enormous and expensive task.

To prevent fluids and waste-water from mixing with the contents of the landfill and then seeping back into groundwater supplies, modern landfills are constructed with an impermeable lining. In the absence of such a lining, as is the case for older landfills, nearby groundwater supplies must be monitored for contamination indefinitely. However, all landfills pose some risk and require monitoring.

Two forms of waste-water from landfills are commonly distinguished: "leachate" and "condensate." "Leachate" is the waste-water generated from liquids percolating through the landfill (such as from precipitation or irrigation water which fall on or drain into the landfill, and from liquids deposited with the refuse or formed during the decomposition of refuse) . As liquids percolate through the landfill, they wash away soluble and insoluble components of the refuse. The contaminants likely to be collected in the runoff vary with the class of the landfill involved, but may include heavy metals, bacteria, pesticides, organic matter, organic solvents, oils, fats, and the like. Ordinarily,_' a Class One landfill would be expected to discharge more hazardous contaminants into its waste-water than a Class Four landfill. However, consideration of factors such as design, location, climate, the presence of unanticipated chemicals and other factors provide more meaningful information when evaluating the risk of contamination than the landfill's classification.

"Condensate" is waste-water resulting from the collection of water saturated landfill gas. As the gas is cooled, moisture in the warm gas condenses. Landfill gas, which typically contains from 30% to 60% methane and 40% to 50% carbon dioxide, plus small levels of other constituents including nitrogen and volatile organic compounds, is produced in landfills when organic material is anaerobically decomposed by naturally-occurring bacteria. The landfill gas so produced may be collected in piping and used for energy production, or simply disposed of by burning. Gas in the landfill is typically at about 100°F to 120°F and is saturated with water. As the gas is collected and transported, it cools, and the water contained in it condenses and accumulates in the collection system. Also, blowers and compressor systems that are used in plants to transport and compress the gas collected from the landfills, reduce the moisture content of the gas and create condensate. To meet local liquid disposal standards, contaminants in the condensate often must be treated or removed prior to disposal of the water.

One method which has been used previously for the removal of heavy metals, organic material, or other compounds where the waste is of a defined nature, is ozone

(0₃) oxidation. Ozone is tri-atomic oxygen and decomposes into 0₂ with a half-life of about 20 minutes, under ambient conditions. Ozone's instability makes it a powerful oxidizing agent. Ozone is a colorless gas, at ambient conditions, with a strong characteristic odor. It is highly toxic and explosive'above a threshold concentration of 23% by volume, in a gas mixture.

Any oxidizable substance is a potential target of 0₃ oxidation. Such species can include heavy metal ions of copper, iron, nickel, chromium, and other inorganic species such as cyanides. In these cases, the metal ions are oxidized to a high oxidation state, making them insoluble in water and capable of being filtered from solutions containing them.

For disinfection purposes, 0₃ is demonstrably better than chlorination processes and oxidizes the bacteria

Escherichia coli about 3,125 times faster than chlorine.

The combination of UV irradiation with 0₃ treatment substantially increases the effectiveness of the 0₃.

Ozone oxidizes phenol to oxalic and acetic acids. When UV irradiation is used to augment the oxidation, trihalomethanes may also be oxidized, provided the pH is properly adjusted. This combination of UV and 0₃ also has the capacity of degrading pesticides (e.g., DDT) and other persistent organic industrial wastes, such as PCB, PPB, chlorophenols, chloroaijilines, and chlorobenzenes, to nontoxic compounds that may be easily biodegraded. Ozone is used industrially to oxidize free cyanide (KCN) from plating wastes and results in the generation of the nontoxic cyanate (KCNO) , which can be further oxidized to carbon dioxide and the nitrate anion. UV irradiation hastens this oxidation and further allows for the degradation of iron cyanide complexes, glycine, glycerol, ethanol, and acetic acid. Phenolic effluents from paper mills, coke mills, and oil refineries can also be oxidized into simple components. While 0₃ has been used to degrade a single type of contaminant, none of these applications has dealt with the mixtures of different contaminants in high concentrations, i.e., total organic carbons (TOCs) in the range of 500 to 10,000 ppm or more, that would be expected to be found in waste-water from landfills. Also, such methods are often wasteful of the 0₃ generated, frequently at high cost, by disposing of the unreacted 0₃ remaining after the oxidation reaction. This otherwise efficient treatment method can be made unattractive by such costs. It is desirable that an effective method is developed for the decontamination of waste-water which contains a variety of contaminants. It is also desirable that the method, in itself, is nonpolluting and that the quality of the water produced is of at least the minimum required for water for use in, for example, irrigation or for dumping into a publicly-owned treatment works (POTW) for further processing. The cost of the method should also be as economical as possible.

Summary of the Invention

The present invention relates to an apparatus and to a process for the effective treatment of waste-water from landfills to remove contaminants. The process of the present invention comprises the steps of collecting waste- water from a landfill and mixing the waste water with generated 0₃. The waste-water/0₃ mixture is then reacted by spraying the mixture into a primary 0₃/UV reactor where it is reacted to form treated waste-water. An apparatus to carry out the process of the present invention is also provided.

In other embodiments of the present invention pretreatment of the waste-water with flocculents or by processing the water through a secondary reactor may be incorporated into the treatment system. In addition treatment of the waste-water after it has been reacted in the 0₃/UV reactor with filters may also be included.

Brief Description of the Drawings

These and other features and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings, wherein:

FIG. 1 is a schematic representation of a waste-water treatment system, wherein the solid lines represent the path of the waste-water, the dashed lines represent the path of 0₃, and the dotted lines represent the path of waste-water/0₃ mixtures; and

FIG. 2 is a schematic representation of another embodiment of a waste-water treatment system, wherein the lines represent the path of the waste-water.

Detailed Description

The method and the apparatus of the present invention use ozone (0₃) in combination with ultraviolet (UV) light to oxidize contaminants of waste-water from landfills. The contaminants in landfills comprise organic solvents, aromatics, insecticides, heavy metals, bacteria, priority pollutants (as defined by the EPA) , and mixtures thereof.

In one embodiment of the present invention the present invention relates to an apparatus and to a process for the effective treatment of waste-water from landfills to destroy contaminants. The process of the present invention comprises collecting the water from a landfill and adjusting the pH to a suitable range. Typically this can be either slightly acidic (about 6.2 to about 6.6) or basic (above about 8.0) depending on the original pH of the waste-water. The waste-water is then mixed with 0₃. While any concentration of 0₃ is effective in the treatment of the waste-water, preferred concentrations are 1 to 20 mg 0₃/l waste-water. The 0₃/waste-water mixture is then reacted under ultraviolet light in a primary 0₃/UV reactor to form treated waste-water. The treated waste- water further treated with a filter package. This embodiment of the present invention is described in detail below in conjunction with FIG. 2. in another embodiment of the present invention, a secondary 0₃/UV reactor can be used in addition to the primary 0₃/UV reactor. After pH adjustment, and prior to mixing the waste-water with fresh 0₃, the waste-water can be mixed with the exhaust from the primary 0₃/UV reactor, which still contains unreacted 0₃, and transferred to the secondary 0₃/UV reactor to pretreat the waste-water. This embodiment of the present invention is described in detail below in conjunction with FIG. 1.

In one embodiment of the present invention, represented in FIG. 1, the treatment is conducted in a continuous batch-wise manner, with water being collected, processed, and released from the treatment system before more waste-water is collected. Starting in the treatment process by following 0₃ gas production, an air or oxygen supply is fed into an 0₃ generator 12. The oxygen suitable for use in the present invention is either in the form of liquid oxygen compressed in a tank, in the form of air compressed from atmospheric air, or in other forms that are known in the art.

Ozone may be generated by two basic methods: silent electric discharge (or coronal discharge) and UV irradiation. The corona discharge method uses an alternating-current, high-voltage electrical discharge across a gap which contains a steady flow of oxygen. Ozone is produced in the corona as a direct result of power dissipation therein. Without being bound by scientific theory, it is thought that the reaction path for the generation of 0₃ is initiated by free, excited electrons, generated within the gap, dissociating oxygen molecules to produce oxygen atoms : e^"1 + 0₂ → 20 + e^"1 Ozone is then formed through a three-body collision:

0 + 0₂ + → 0₃ + M where M is any other molecule present in the gas. Simultaneously, atomic oxygen and electrons also react with 0₃ to form oxygen: O + 0₃ → 20₂ e^"1 + 0₃ → 0₂ + O + e^"1 The net 0₃ yield is the sum of all the reactions which form and decompose 0₃. However, since the decomposition of 0₃ is accelerated at high temperatures, and the low volume of gas passing between the electrodes is insufficient to provide adequate cooling, it is desirable to provide a heat sink to dissipate the heat .

Ozone generation by UV irradiation is a practical method when small quantities of 0₃ are required. Evidence points to a mechanism whereby an oxygen molecule is dissociated into two oxygen atoms upon the absorption of light. The oxygen atom then reacts with an oxygen molecule to produce 0₃. Ozone is formed from diatomic oxygen with light at a wavelength of 187 nm. While 0₃ can be made in this way, it is not economically feasible for large-scale production, due to the cost of the large power consumption required for the process. In the present invention, the silent electrical discharge method of generating 0₃ is preferred.

The generated 0₃ is fed into a mixer 14 and is mixed, by methods known in the art, with pretreated waste- water (pretreated as described below) . Typically the 0₃ is "fed" into the waste-water at a rate of about 1 to about 20 mg 0₃/l. The pretreated waste-water is supplied from a waste-water holding tank 30. Preferably, the 0₃ feed is at a concentration of about 2% to about 4% by weight. The combined pretreated waste-water/0₃ mixture is fed into a primary 0₃/UV reactor 18. Upon entering the 0₃/UV reactor, the pretreated waste-water/0₃ mixture is atomized through atomizer 20. The atomizer comprises a spray nozzle, and the pretreated waste-water/0₃ mixture is forced through the nozzle at a pressure of about 42,000 kg/m². (Reactors of this type are supplied by Ozone Processes Inc. of San Diego, CA.)

Most 0₃ contacting systems rely on bubbling the 0₃- containing gas through a tank of the liquid to be treated. Even with minute bubbles, channelling takes place, and the effective surface area for reaction with the available 0₃ is small. In the practice of the present invention, the gas and liquid streams are premixed and fed to a spray- nozzle manifold inside the 0₃/UV reactor. The liquid/gas stream is atomized to generate particles of water of an average diameter of about 50 μm. Since the liquid/gas stream is mixed under pressure, prior to atomization, 0₃ is dissolved in the liquid to be treated. The remainder of the 0₃ is present in a gas phase. The atomization of the waste-water/0₃ mix results in a large surface area of waste-water available for contact with the 0₃. The large contact area greatly increases the reaction rate of the 0₃ with contaminants present in the waste-water.

UV irradiation of the waste-water/0₃ also increases reaction rate to about 10,000 times the rate of waste- water/0₃ mix alone. The normally slow reaction of 0₃ with certain organic compounds, i.e., 0₃ with aliphatic hydrocarbons, is increased so that, with excess 0₃, the reaction can be driven to completion (i.e., C0₂, H₂0) in only a few seconds. However, many toxic compounds need only be broken into two or three fragments to render them biodegradable or harmless constituents.

The primary 0₃/UV reactor includes UV sources 22 which generate UV light at a wavelength of about 254 nm. As the "droplets" of waste-water/0₃ fall under gravity, they are exposed to UV irradiation, accelerating the reaction of the 0₃ to oxidize contaminants in the waste- water. While UV light at a wavelength of 187 nm can be used for the synthesis of 0₃, UV light at a wavelength of 254 nm is photolytic toward 0₃ and results in the decomposition of 0₃ to form a reactive oxygen radical 0₂.

The UV-irradiated waste-water condenses in the bottom

26 of the 0₃/UV reactor, where the water is collected and distributed for reuse, as depicted by box 32, or for further purification, if desired, as depicted by block 34. The oxidized waste-water can be further purified by filtering to remove particulate matter generated by the UV irradiation reaction; by processing to remove C0₂ generated by the oxidation of organic matter; by filtering through activated carbon to remove soluble contaminants; or by other suitable methods as may be required to produce water of the desired purity. If the waste-water is not of a desired purity, it can be recycled for treatment in the primary 0₃/UV reactor or in a secondary 0₃/UV reactor, as required. If the purity is at the desired level, it may be distributed for reuse in irrigation, as cooling water, or discharged into the sewer system. In one embodiment of the present invention, the oxidized waste-water is filtered through granulated activated carbon to produce water suitable for non- agricultural irrigation uses. Ozone not decomposed in the primary 0₃/UV reactor, and oxygen generated from the UV irradiation/oxidation reaction, are collected, by pumping, from the gas phase of the primary 0₃/UV reactor and are transferred for pretreatment of waste-water in a secondary 0₃/UV reactor 28, which is identical to the primary 0₃/UV reactor described above. The 0₃ concentration in the collected gas phase stream is typically one-third to one-half that entering the primary 0₃/UV reactor.

Waste-water is collected from a landfill 16, either from runoff water, precipitation or irrigation which percolates through the landfill (leachate) , or from condensation which collects in pipes in which landfill gas generated by the landfill is collected (condensate) . The waste-water is collected from the landfill by conventional collection methods, known by those skilled in the art, into a holding tank 30. When sufficient water is collected, it is fed to the secondary 0₃/UV reactor. Prior to reaching the secondary 0₃/UV reactor, it is mixed with the 0₃ gas phase collected from the exhaust of the primary 0₃/UV reactor in mixer 24. This waste-water/0₃ mixture is introduced into the secondary 0₃/UV reactor, where it is atomized and irradiated with UV light, as described above for the primary 0₃/UV reactor.

The gas phase 0₃ remaining after reaction in the secondary 0₃/UV reactor is collected and transferred to an 0₃ destruct unit 36, where any remaining 0₃ is destroyed by UV irradiation or other suitable method. This gas is then discharged into the atmosphere or recycled for further use of the 0₂ present in the gas, preferably for use in a process such as an aerobic biodegradation process. The partially oxidized pretreated waste-water is collected in storage tank 30, then mixed with freshly generated 0₃. The treatment cycle of the water is started again with the collection of a new batch of waste-water and the production of fresh 0₃.

The pretreatment of the waste-water has the advantage of exposing, at least twice, the contaminants of the waste-water to oxidation, thereby increasing the effectiveness of the oxidation process. Also, the 0₃ generated is used more efficiently than if it were to be destroyed before all or most of the 0₃ were consumed.

Table I sets forth the criteria for water for non- agricultural irrigation purposes produced by the 0₃/UV reactor system of the present invention.

Table I

Criteria Limit

Coliform 7 days Not greater than 2.2 units/100 ml

TSS¹ Not greater than 40 mg/1 daily max. Not greater than 15 mg/1 30 day max.

Settleable solid Not greater than 0.3 mg/1 max.

COD² Not greater than 20 mg/1 30 day max. Not greater than 60 mg/1 daily max.

TDS³ Not greater than 900 mg/1 monthly max. Chloride Not greater than tap water chloride plus 85 mg/1

Sulfate Not greater than 300 mg/1 max.

Boron Not greater than 1.5 mg/1 max.

Total Nitrogen Not greater than 30 mg/1 30 day max.

Fluoride Not greater than 1.2 mg/1

¹ TSS Total Suspended Solids TDS Total Dissolved Solids

³ COD Chemical Oxygen Demand

In a second embodiment of the present invention a single 0₃/UV reactor is used in combination with filters as shown in FIG. 2. In this embodiment waste water is collected from a landfill 40 into a tank 44. When sufficient water is collected, the water may, if desired, be pretreated with flocculents such as high molecular weight polymers such as those sold by American Cyanimide under the tradename 541C or 883A or other flocculents, which are well known in the art.

The precipitated material which forms in the presence of the flocculents is removed by centrifugation or filtration. The pH of the waste water is adjusted. In the case of condensate the pH is preferably adjusted to at least about 8.0. In the case of leachate or leachate/condensate mixtures the pH is adjusted to about 6.2 to about 6.6. In general, if the collected waste- water has an acidic pH it, is adjusted to an alkaline pH prior to treatment and if the collected waste-water has an alkaline pH it is adjusted to an acidic pH prior to treatment. The pH adjusted water is transferred to a 0₃/UV reactor 46. Prior to reaching the 0₃/UV reactor, the waste-water is mixed with the 0₃ in mixer 50. Typically the 0₃ is "fed" into the waste-water at a rate of about 1 to about 20 mg 0₃/l. The 0₃/UV reactor is identical to the 0₃/UV reactors described above and includes atomizer 52 and UV sources 54. The "atomization" of the waste-water in the 0₃/UV reactor results in 0₃ concentrations as low as 1 mg/1 of waste-water being effective for the treatment of the "atomized" waste-water, compared to concentrations as high as 75 to 100 mg/1 which are required for the treatment of a liquid streams. The UV-irradiated waste- water condenses in the bottom 56 of the 0₃/UV reactor, where the water is collected and directed to filters 58, 60 and 62. In one embodiment of the present invention, about one half to one third of the UV-irradiated waste- water which condenses in the bottom of the 0₃/UV reactor is collected and pumped back to tank 44. Some of the UV- irradiated waste-water from the bottom of the 0₃/UV reactor is diverted from the main stream and is sent to filters 58, 60 and 62. Many combinations of filters can be used. The preferred combination is a coarse cartridge filter 58 followed by a fine cartridge filter 60 then a particle filter 62. In one embodiment of the present invention, granular activated carbon is used for the particle filter. Activated carbon, when used in this manner with this type of 0₃/UV reactor has demonstrated the added benefit of an extremely extended adsorption life, by some unique in si tu regeneration effect.

In a preferred embodiment of the present invention the filtering system comprises three filters through which the oxidized waste-water passes, in sequence. The first is a 20 micron filter 58 to remove large particulate matter. Such filters are well known in the art and are of the type used as swimming pool filters. The second filter is a 20 micron/diatomatious earth filter 60, such filters are also of a type used as swimming pool filters and are also well known in the art . The third filter is an activated carbon filter 62. The carbon filter for use in the present invention is preferably a granular composition of a size of about 12 x 30 mesh. Carbon particles that are very small are undesirable for use in the present invention since they are powdery and cannot be easily contained within the filter and tend to be washed through with the flow of waste water. Particles that are too large are undesirable for use in the present invention since at size of about 1/4" x 1/4", the particles have an undesirably low surface area to volume ratio. Carbon filtration is an important step in the process and a ratio of maximum flow to volume

(gpm/ft³) of less than 0.7 and more preferably 0.25-0.35 and flow to area ratio (gpm/ft²) of less than 5, and more preferably 0.75-1.3, are preferred for the treatment of waste-water in the present invention.

After the filtration the water is then transferred back to the tank 44. The water is then discharged into the sewers, represented by box 64, if it is of sufficient purity, or it may again be directed into the 0₃/UV reactor for further treatment.

The gas phase 0₃ remaining after reaction in the 0₃/UV reactor is collected and transferred to an 0₃ destruct unit 66, where any remaining 0₃ is destroyed by UV irradiation or other suitable method. This gas is then discharged into the atmosphere or recycled for further use of the 0₂ present in the gas, preferably for use in a process such as an aerobic biodegradation process.

In another embodiments of the present invention a secondary 0₃/UV reactor (not shown) can be incorporated to use the exhaust gas from the primary 0₃/UV reactor 56. The exhaust gas contains some ozone which can be use as a pretreatment for the waste-water in the secondary 0₃/UV reactor. In this process typically one-third to one-half of the waste-water being supplied to the primary 0₃/UV reactor 56 is fed into mixer and mixed with the waste- water. This combined waste-water/exhaust 0₃ mixture is then reacted in the secondary 0₃/UV reactor. The waste- water is then reacted in the primary 0₃/UV reactor as described above. If desired the waste-water can be cycled between the primary and secondary 0₃/UV reactors until the desired purity is obtained. The pretreatment of the waste-water in the secondary 0₃/UV reactor has the advantages of increasing capacity of the treatment system and increasing the purity of the waste-water without the expense of larger or secondary ozone generator. Table II sets forth different treatment "runs" performed on different source water where the COD of the water was monitored during the treatment. Table II

Treatment

Run No. Source Time (min)

519-1 Landfill 0

Leachate/ 15

Condensate 30 45 60 75

523-2 Landfill 0

Leachate/ 5

Condensate 15 30 45 60 75

528-2 Landfill 0

Leachate/ 15

Condensate 3^'0 45 60 75

527-2 Landfill 0

Leachate/ 5

Condensate 10 15 20 30

731-1 Landfill 0 Condensate 5

15

30

45

120

805-1 Landfill 0 Condensate 5 15 30 45 60 75 120

0908 Landfill 0 Condensate 15

, 30

45

60

The use of filters as described in the embodiment of the present invention described above offers the advantage of providing an efficient means of treating waste water in an inexpensive and small treatment system. As shown in Table II there is a rapid destruction of COD and within 15 to 30 minutes of treatment, with about 60 to 80% of the COD is eliminated.

Table III sets forth the results of an analysis of a waste-water sample before and after treatment in an 0₃/UV reactor/filter system.

Table II cont/d

The results illustrated in Table III show that the waste-water treatment system of the present invention is effective for removing a variety of compounds from the waste-water.

The treatment systems of the present invention is typically of a size that can be skid mounted and easily moved from one site to another as needed. The construction of the treatment systems of the present invention is preferably from materials such as polyvinyl chloride (PVC) , or other suitable material, for the piping and storage tanks. These features of the designs of the present invention make the equipment costs very low and thus the treatment of the waste-water inexpensive. In addition, the process 'of the present invention is very efficient compared to other treatment processes. For example, the irradiation of the waste-water, by spraying an "atomized" stream of waste-water and exposing the spray to a UV light source overcomes many of the difficulties encountered when a stream of water is to be treated. Waste-water of the type treated in the process of the present invention is often dense or opaque and light will not penetrate into the water stream. Therefore, the treatment in such water stream is only effective for the water in contact with, or very close proximity to, the light source. Although the present invention is described in relation to only a few working embodiments, variations will be apparent to those skilled in the art. For example, the number of tanks, and the direction of flow between them and the 0₃/UV reactors, could be varied; the waste-water could be processed multiple times through the 0₃/UV reactors to eliminate contaminants; other forms of purification in addition to or instead of the granulated activated carbon could be used; the waste-water could be further purified by biological oxidation processes; other oxidizing agents, such as H₂0₂, could be added in addition to 0₃; a secondary 0₃/UV reactor/filter system could be operated from the exhaust gas from the primary 0₃/UV reactor to allow two separate waste-water streams to be processed simultaneously; a secondary 0₃/UV reactor/filter system could be run from the exhaust gas of the primary 0₃/UV reactor/filter package with the treated waste-water being sent to the primary 0₃/UV reactor/filter package for further processing; or the waste-water stream can be pretreated to remove solids by centrifugation after treatment with a chemical flocking agent (such as those manufactured by Betz of American Cyanamide or others known in this art) . Therefore, the present invention is not intended to be limited to the working embodiment described above. Also, the invention may be practiced in the absence of any element which is not specifically disclosed in the specification. The scope of the invention is defined in the following claims.

Claims

WHAT IS CLAIMED IS

1. A landfill waste-water treatment system comprising: an 0₃ supply; means for collecting landfill waste-water; a primary 0₃/UV reactor for treating landfill waste-water; and means for transferring the mixed landfill waste- water and 0₃ to the' primary 0₃/UV reactor wherein the landfill waste-water is introduced into the 0₃/UV reactor in the form of a spray.

2. A landfill waste-water treatment system as recited in claim 1 wherein the treatment system further comprising a secondary 0₃/UV reactor for pretreating landfill waste-water.

3. A landfill waste-water treatment system as recited in claim 1 wherein the treatment system further comprises a filter system for filtering solid and soluble components from the treated landfill waste-water.

4. A landfill waste-water treatment system as recited in claim 1 wherein the landfill waste-water contains at least two contaminants selected from the group consisting of organic solvents, insecticides, heavy metals, bacteria, fats, oils, priority pollutants, and mixtures thereof.

5. A landfill waste-water treatment system as recited in claim 1 wherein the landfill waste-water collected from the 0₃/UV reactor is further purified to obtain a desired standard of purity.

6. A process for treating landfill waste-water comprising: collecting waste-water from a landfill; generating 0₃; mixing the generated 0₃ with the collected waste-water; spraying the 0₃/waste-water mixture into a primary reactor; and reacting the 0₃/waste-water spray in the primary 0₃/UV reactor to form treated waste-water.

7. A process for treating landfill waste-water as recited in claim 1 wherein the process further comprises filtering the treated waste-water to remove soluble and particulate contaminants.

8. A process as .recited in claim 6 further comprising: mixing an exhaust 0₃ gas phase from a primary 0₃/UV reactor with the collecting waste-water; reacting the waste-water/0₃ gas mixture in a secondary 0₃/UV reactor to form pretreated waste-water; separating the pretreated waste-water from a gas phase; collecting the pretreated water-water from the secondary 0₃/UV reactor; collecting the reacted 0₃ gas phase from the secondary 0₃/UV reactor; mixing the pretreated waster-water with generated 0₃; and transferring the pretreated waste-water/0₃ mixture to the primary reactor.

9. A process as recited in claim 6 wherein the waste-water contains at least two contaminants selected from the group consisting of organic solvents, aromatics, insecticides, heavy metals, bacteria, priority pollutants, and mixtures thereof.

10. A process as recited in claim 6 wherein the waste-water collected from the primary reactor is further purified to a desired standard.

11. An improved waste-water treatment system of the type in which the waste-water is oxidized by the action of UV light in the presence of 0₃ in a primary 0₃/UV reactor, wherein the improvement comprises filtering the oxidized waste-water through a series of different filter.

12. An improved waste-water treatment system as recited in claim 11 wherein the waste-water contains at least two contaminants selected from the group consisting of organic solvents, aromaticε, insecticides, heavy metals, bacteria, priority pollutants, and mixtures thereof.

13. An improved waste-water treatment system as recited in claim 11 wherein a gas phase collected from the primary reactor is irradiated with UV light to destroy any residual 0₃ remaining in the gas phase.

14. An improved waste-water treatment system as recited in claim 11 wherein at least one of the filters is a carbon filter.

15. In a method of treating waste-water, of the type wherein the waste-water is oxidized by action of UV light in the presence of 0₃, the improvement comprising pretreating the waste-water with 0₃ derived from the exhaust-gas phase of the primary 0₃/UV reactor for the effective treatment of waste-water from landfills.

16. A method as recited in claim 15 wherein the waste-water contains at least two contaminants selected from the group consisting of organic solvents, aromatics, insecticides, heavy metals, bacteria, priority pollutants, and mixtures thereof.

17. A method as recited in claim 15 wherein the waste-water collected from the primary reactor is further purified to a desired standard.