WO1983002240A1

WO1983002240A1 - Apparatus and method for renewing coolant fluid

Info

Publication number: WO1983002240A1
Application number: PCT/US1982/001720
Authority: WO
Inventors: Inc. Economics Laboratory; Henry A. Rowan; William Hamilton
Original assignee: Economics Lab
Priority date: 1981-12-30
Filing date: 1982-12-09
Publication date: 1983-07-07
Also published as: EP0097696A1; IT1152926B; IT8223843A0

Abstract

An apparatus (10) for renewing coolant fluid and other similar liquids. The fluid is fed into an entry compartment (28) of the apparatus housing (12) and made to pass, thereafter, through a plate separator (30) disposed obliquely within the housing (12). The liquid passes between a plurality of plates (34) and exits from the separator (30) at a bottom end thereof. The liquid exits from the separator (30) into a processing compartment (32). Thereafter, it flows over the upper edge (58) of a weir wall (60) into a clean tank (56). While being processed, the liquid is treated by a biochemical bacteria retardant agent metered into the liquid from a source (82) through a line (84) by which it is conducted. Renewed fluid is recovered and held in a service tank (74) or returned to a sump.

Description

APPARATUS AND METHOD FOR

RENEWING COOLANT FLUID

Technical Field

The invention of the present application is broadly related to systems for treating and recovering liquid coolants used in machine metal working processes. Specifically, the invention is directed to an apparatus and method for renewing such coolants by removing solid wastes and contaminating oils therefrom and inhibiting bacterial growth by aerating the coolant through recir- culation and adding biochemicals to deter bacteriolog¬ ical build up.

Background of the Invention Machining of metal components for use in machine assemblies is a common practice in industry. An essen¬ tial operation in conducting such manufacturing is cooling the cutting tool and lubricating the cutting edge.

It is a common industrial practice to use cutting fluids during the production process in order to effect cooling. Such liquid coolants have, typically, been low in price and, until recently, have been able to be disposed of easily and inexpensively. Many industrial concerns have, where not precluded by local legislation, disposed of the coolant waste substances by pumping them directly into rivers or the ground.

As has become evident during recent years, however, such practices have deleterious effects upon the land and waters of the geographical locale in which the particular plant is located. In the case of discharge into rivers, pollutants can be carried a significant distance, whereby adverse consequences are effected upon locales removed from the point of discharge.

Many state and local governments, in recognizing these adverse consequences, have enacted legislation prohibiting the direct discharge of waste substances,

^. --* r- -^ _- _ _^ , / ^"0 _.-_.._ ^OKF such as metal working cutting fluids, directly into rivers or the ground. Similarly, the federal government has enacted laws prohibiting such waste disposal, and the Environmental Protection Agency (EPA) has implement- 5 ed regulations making any business entity directly accountable for the safe usage and disposal of all wastes generated during its manufacturing processes. Compliance with these laws and implementing regulations has been sought to be achieved by providing for both

__ civil and criminal penalties for non-compliance.

An alternative available to businesses in their efforts to comply with these mandates is bulk disposal of the used coolants. Costs involved in taking such steps, however, frequently prove prohibitive.

__ At least one additional factor has given impetus to programs for renewing rather than disposing of used cutting fluids. During recent years, the costs involved in buying such fluids have escalated dramatically.

In consequence, most manufacturing companies have

20 directed their attentions to developing systems for recovering used coolant fluids. Typically, such systems take the form of custom engineered waste management systems which are designed specifically for installation and use in one particular plant. Such custom designed

25 systems are, however, very expensive, making their installation and use cost prohibitive.

Attempts have been made to design a truly universal coolant fluid renewal system, but all these systems are lacking in some respect. No designer offers more than a

30 partial solution to the probLems in renewing such coolant fluid. Some extant systems will precipitate and remove solid sludge but will not remove contaminating liquids such as oils and solvents. Conversely, some systems might remove the liquids but will not filter

35 solid wastes.

- An additional feature which a desirable system need possess is one wherein bacterial growth in the coolant

is inhibited. This feature is particularly desirable in view of the atmosphere conducive to bacterial growth that cutting fluids provide. Prior systems which have been devised are particularly lacking in solving this problem.

The invention of the present application provides a system, including both an apparatus and method, which is directed to these problems. It is a system which provides methods for eliminating both solid and liquid contaminants and for treating the coolant in order to reduce the likelihood of bacterial growth therein.

Summary of the Invention The invention of the present application is an apparatus and method for removing solid and liquid contaminants in a liquid such as coolant fluid in order to allow the liquid to be reused. The method includes steps of filling an entry compartment, in a filtration device, with the contaminated liquid and passing the liquid through a plate separator which extends down- wardly and obliquely. As the liquid passes through the plate separator, lighter contaminating liquids rise to downwardly facing sides of plates extending obliquely within the separator. These lighter contaminating fluids are, thereafter, allowed to rise back into the entry compartment where they are recovered and disposed of. Solid contaminants settle to upwardly facing sides of the plates and pass downwardly along the plates onto the bottom of a processing compartment with which the lower end of the separator communicates. The coolant, thus having been divested of solid and liquid contami¬ nants flows from the processing compartment into which it is passed after leaving the separator over a weir into a clean fluid collection tank. The fluid is, thereafter, pumped from the collection tank to a service tank or back into a sump for reuse. Biochemical agents are added to the liquid during its passage through the various compartments and tanks in order to

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The method can include additional steps to retard bacterial growth. One of such steps can include the recirculation of clean fluid, after it has been pumped out of the clean fluid collection tank, back through the processing compartment and collection tank.

The apparatus invention of the application is a device by which the method invention can be accom¬ plished. The device includes a process tank which is further subdivided into a liquid entry compartment and a processing compartment. The plate separator extends obliquely within the process tank and a first, upper end of the separator communicates with the entry compart¬ ment. The second, lower end, communicates with the processing compartment, so that contaminated fluid introduced into the entry compartment will be passed downwardly through the separator and enter the process¬ ing compartment of the process tank. A clean tank is separated from the processing compartment by a weir, over the upper edge of which fluid passed into the processing compartment overflows. The fluid is, there¬ after, collected in the clean tank. The device can, further, include means for introducing the anti¬ bacterial treating agent into the liquid. The means by which the agent is added can provide that the agent will be introduced into either the process tank or the clean tank.

A preferred embodiment of the invention includes means for controlling flow of the liquid to be renewed through the various compartments and tanks. A conduit by which the liquid is channeled into the entry compart¬ ment can have a solenoid actuated valve interposed therein. The valve is normally biased to an open position so that, unless the solenoid is actuated, the liquid will pass from a contaminated reservoir into the entry compartment. A float actuated switch can be mounted within the clean tank in order to sense whether

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' Gi.PI the fluid therein has exceeded a desired level. Such a switch includes a float member which, when the level of fluid is below the desired maximum, is in a position wherein the switch is deactivated and the solenoid is not energized to close the solenoid actuated valve. If the fluid in the clean tank rises to a level above the desired maximum, the float member of the switch will be driven to a position to effect switching of the switch in order to activate the solenoid controlling the valve. The valve will, thereby, be closed to prevent entry of contaminated fluid for processing until the level of processed fluid in the clean tank recedes.

Similarly, the device can include a pump for transferring processed fluid from the clean tank to a service tank or back into a sump. A second float switch having a float member similar to that of the first switch can be disposed in the clean tank to sense a minimum desired level of fluid within the tank. The pump would normally be actuated unless the switch, through its float member, sensed the level of fluid in the clean tank receding to a point below the desired minimum level. At that point, the float switch would function to deactivate the pump in order to allow the level of fluid in the clean tank, assuming a continuous input to the tank, to rise.

Although the majority of contamina ing oils and other liquids in the processed fluid are removed by the plate separator, some of the liquid contaminants are drawn through the separator and into the processing compartment. The weir wall can be so structured, and a baffle can be provided relative to the weir wall, so that only liquid _virtually devoid of such tramp oils passes over the weir separating the clean tank from the processing compartment. The weir wall can be structured having a lower generally vertically extending portion and an upper generally vertically extending portion spaced laterally from the lower portion and toward

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<___"_ _-._k_. I the clean tank. An interconnecting portion of the weir wall disposed either generally horizontally or obliquely interconnects the upper and lower portions in order to complete the wall. The baffle member is positioned above the interconnecting portion of the wall so that any tramp oil which does manage to pass through the separator will rise to the surface of the liquid being processed on a side of the baffle away from the side facing the weir. Overflow of the tramp oil into the clean tank will, thereby, be virtually precluded.

The invention of the present application is, thus, an apparatus and method for renewing liquids such as coolant fluid. More specific features and advantages obtained in view of those features will become apparent with reference to the detailed description of the invention, appended claims, and drawing figures.

Brief Description of the Drawings

Fig. 1 is a perspective view of an apparatus in accordance -with the invention of the present applica- tion, some portions thereof being broken away;

Fig. 2 is a view taken generally along the line 2-2 of Fig. 1;

Fig. 3 is a view taken generally along the line 3-3 of Fig. 1;

Fig. 4 is a view taken generally along the line 4-4 of Fig. 1;

Fig. 5 is a side elevational view, showing some elements schematically, of the apparatus illustrated in Fig. 1; and

Fig. 6 is a top plan view of the apparatus illus¬ trated in Fig. 5.

Detailed Description of the Invention

Referring now the drawings wherein like reference numerals denote like elements throughout the several views. Fig. 1 illustrates an apparatus 10 in accordance with the invention of the present application for renewing coolant fluids and other similar liquids. The

the clean tank. An interconnecting portion of the weir wall disposed either generally horizontally or obliquely interconnects the upper and lower portions in order to complete the wall. The baffle member is positioned above the interconnecting portion of the wall so that any tramp oil which does manage to pass through the separator will rise to the surface of the liquid being processed on a side of the baffle can be disconnected from a line 20 running between it and the surge tank 16. The reservoir 14 can, thereby, be transported to loca¬ tions at which contaminated fluids are deposited therein and, thereafter, be returned to the renewing apparatus 10 for discharge of its contents. Although the figures illustrate a transportable reservoir 14, it will be understood that coolant liquid can, in certain embodiments of the apparatus invention, be pumped directly from a sump to housing 12.

As seen in Fig. 1, the line 20 by which the reser¬ voir is connected to the surge tank 16 can include a solenoid actuated valve 22. The purpose of the valve 22 will be discussed hereinafter.

Contaminated fluids from the reservoir 14 can be pumped through the line 20 connecting it to the surge tank 16 and, thereafter, through a line 24 to a port 26 through which it enters into the housing 12. The surge tank 16 insures that any air which might be pumped through line 20 by becoming entrained in the contam¬ inated liquid when the liquid level in reservoir 14 recedes below the level of the connection of line 20 therewith does not pass through line 24.

The fluid passes through the port 26 into the housing 12 and, specifically, into a liquid entry compartment 28. Positioned beneath the compartment 28, and sealing the bottom thereof, is a plate separator 30 extending downwardly and obliquely from the bottom of the entry compartment 28. An upper end of the separator 30, thereby, communicates with the entry compartment

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A lower end of the separator 30 communicates with a processing compartment 32 which, in cross-section taken in one direction, is generally triangular in shape. In one embodiment, a plurality of corrugated plates 34 5 extend longitudinally from the upper end of the separa¬ tor 30 to the bottom end thereof. The plates 34, as best seen in Fig. 4, are corrugated to define upper and lower vertices 36. Although Fig. 4 illustrates only four plates, it will be understood that significantly

__Q larger numbers of plates are specifically contemplated, and it is not intended to exclude such larger numbers by illustrating only four plates in Fig. 4.

Contaminated liquid pumped into the liquid entry compartment 28 will be made to pass downwardly through

__ the separator 30 and between the plates 34. During this passage, heavier sedimentary solid contaminants will settle to the bottoms of lower vertices 36 of a down¬ wardly disposed plate from the particular solid sedimen¬ tary particles. A sludge thereby formed will slide

20 downwardly in these corrugated channels to the bottom of the processing compartment 28.

Tramp oil contaminants in the liquid, tending to be lighter than the bulk of the liquid, will rise to upwardly disposed vertices 36 formed by the convolutions

25 in a plate disposed immediately above the particular tramp oil particles. They will, thereafter, return upwardly within the separator 30 and back into the liquid entry compartment 28. This tramp oil will accumulate and form the upper stratum of liquid within

30 the entry compartment 28. .A duct 38 can be mounted to a sidewall 40 of the entry compartment 28 for removing this tramp oil and transferring it to a location where it is collected for disposal.

Duct 38 can be positioned at a height above the

35 normal level of liquid in the processing compartment 32. As seen in Fig. 1, the liquid level in the entry com-

partment 28 is somewhat higher than the level in pro¬ cessing compartment 32. This is due to the relative specific gravities of the processed liquid and the tramp oil, that of the tramp oil being lower. Consequently, since the level of fluid in compartment 28 is higher than that in compartment 32, the tramp oil in compart¬ ment 28 will spill over through duct 38 for collection without any coolant fluid being removed from the system. A conveyor 42 can be provided for removing solid contaminants which have settled out of the liquid coolant being processed and deposited on the bottom of the processing compartment 32. The conveyor 42 can be structured and positioned so that the solid contami¬ nants, as they exit from the separator 30, are deposited onto the conveyor 42. Typically, the conveyor 42 would be a drag type conveyor consisting of a plurality of angle irons oriented generally transversely to the direction of movement of the conveyor 42, and open between the angle irons 44. The solid contaminant would be allowed to pass through the conveyor 42 and down to a bottom 46 of the processing compartment 32. As the endless conveyor 42 is moved, the angle irons 44 would scrape the contaminant along the bottom surface 46 and up an oblique wall 48 of the compartment 32, which wall 48 forms the bottom of a rear leg extension 50 of the main portion of the compartment 32. The solid contamin¬ ant would be dragged along this oblique wall 48 and through an aperture 52 formed in a side wall of the leg 50 into a sludge elimination subsystem. Although the subsystem is illustrated as a collection tank 54 in the figures, it will be understood that any type of sludge disposal system could approp iately be used. The particular operation of the conveyor 42 can be best understood with reference to Fig. 5. A clean tank 56 is separated from the processing compartment 32 by a weir type structure. An upper edge 58 of the wall 60 separating the two chambers 32, 56

*_[- - m_^ _ _ _ *__> - .__ «_._______ . / v '.r., defines a lip over which liquid having passed through the separator 30 will flow as it rises in the processing compartment 32. As will be apparent, the side walls of the processing compartment 32 will extend above the upper edge 58 of the weir wall 60 in order to contain the liquid within the processing compartment 32 even when the level rises to a height at which it will flow over the weir.

Theoretically, then, the weir will allow collection of completely decontaminated liquid in the clean tank 56 since all of the tramp oil should have been retained in the liquid entry compartment 28 and all of the solid contaminants should have been deposited on the conveyor 42 for removal from the processing compartment 32. As a practical matter, however, some of the tramp oil will be carried through the separator 30 and will rise to the surface of the liquid within the processing compartment 32 since it tends to be lighter. For purposes of illustration, this tramp oil has been illustrated as a flecked stratum in Figs. 1 through 3.

Referring now to Figs. 2 and 3, contamination of the liquid passing over the weir by the tramp oil which has risen to the surface of the liquid in the processing compartment 32 can be prevented by providing a baffle 62 extending generally along the weir wall 60 but spaced laterally from the top edge 58 thereof a distance into the processing compartment 32. As this tramp oil rises, therefore, its flowing over the weir will be obstructed by the baffle 62.

Rather than providing a completely platen like weir wall 60, the wall 60 can be formed having a lower generally vertically extending portion 64 and an upper generally vertically extending portion 66 spaced some- what laterally toward the clean tank 56 from the ^'lower portion 64. An interconnecting portion 68 of the wall 60, seen as being generally horizontal in Figs. 2 and 3,

makes the wall 60 continuous to isolate the contents of the processing compartment 32 from those in the clean tank 56. By positioning the baffle 62 generally verti¬ cally and above the interconnecting portion 68 of the weir wall 60 with an upper edge of the baffle above the upper edge 58 of the weir wall 60 and a lower edge of the baffle 60 below the upper edge 58 of the weir wall 60, all of the tramp oil which rises within the liquid should be contained on the processing compartment side of the baffle 62. All of the liquid contaminants should, therefore, be eliminated from the liquid which ultimately passes over the weir into the clean tank 56.

Appropriate means can be provided for collecting and removing the stratum of tramp oil in the processing compartment 32. A skimmer (not shown) can be used in conjunction with apparatus 10 for this purpose.

Referring to Fig. 5, a line 70 exiting from the bottom of the clean tank 56 is shown as passing through a final filter 72 to a transportable service tank 74. The final filter 72 can serve to remove any non-soluble contaminants from the liquid which is passed to the service tank 74. As in the case of the input end of the system, wherein liquid can be passed directly from a sump to the renewing device, renewed coolant can be returned directly to a sump rather than through an intermediate service tank.

A shut-off valve 76 is shown as being interposed in the line 70 between the final filter 72 and the service tank 74. The shut-off valve 76 can be made to be operable manually or in any other manner. Flow of renewed fluid from the clean tank 56 to the service tank 74 can, thereby, be precluded as desired.

A branch line 78 can be tapped off the main line 70 between a main pump 79 and the service tank 74. With the shut-off valve 76 in its closed position, means (not shown) can be operated to allow flow through this line

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Sϋ^SST.TUTE SHEZ 78 and back into either the processing compartment 32 or the clean tank 56, as desired. A circulation pump 80, positioned on the opposite side of the housing 12 from the final filter 72, can facilitate flow through the branch line 78. Such flow may be desirable for a number of reasons. Most significantly, such flow can be used for backflushing to clean the processing compartment 32 and for recirculation to provide additional aeration of the processed liquid in order to inhibit bacterial growth.

Further means can be provided to achieve the end of bacterial growth inhibition. As best seen in Fig. 1, a biochemical source, generally indicated schematically by the reference numeral 82, can be mounted to the housing 12. A line 84 from the biochemical source 82 can run to the line 24 passing from the surge tank 16 to the liquid entry compartment 28. A biochemical agent can, thereby, be either automatically metered or selec¬ tively dispensed into the contaminated liquid in order . to retard growth of bacteria. If necessary, a number of biochemical agents can be injected into the system.

Newly combined coolant can also be fed into either the processing compartment 32 or the clean tank 56. A coolant concentrate source 86 can be channeled into a dispenser 88 wherein the concentrate is mixed with water provided through another line 90. The mixture is, thereafter, dispensed into the desired chamber through appropriately constructed piping 92.

Flow of the liquid through the various chambers can be controlled by appropriate means. As seen in Fig. 5, a first float actuated switch 94 having a float member 96 is mounted within the clean tank 56 near the upper levels thereof. The float member 96 is cantilevered outwardly from the switch housing 93 by a shaft 100. The shaft 100 is pivotally mounted to the housing 98 so that, as the level of liquid within the clean tank 56 rises and falls, the float member 96 will remain on the

surface thereof. The switch 94 is configured so that, when the level of liquid within the clean tank 56 rises above a desired maximum level, the switch 94 will activate a solenoid controlling the normally open valve 22 interposed in the line 20 between the reservoir 14 and the surge tank 16. Activation of the solenoid will, in turn, close the valve 22 to preclude further flow of fluid into the liquid entry compartment 28. When the level of liquid in the clean tank 56 drops below the maximum desired level, the switch 94 will be deactivated, thereby deactivating the solenoid. The valve 22 will, in turn, be allowed to open, and flow of liquid will again be initiated.

A second float actuated switch 102 is mounted to the wall of the clean tank 56 proximate a desired minimum level. As in the case of the first switch 94, the second switch 102 includes a float member 104 cantilevered from a switch housing 106 by a shaft 108 pivotally mounted at the housing 106. The float member carried by the second switch 102 will seek to attain the level of the surface of liquid within the clean tank 56. This will, however, often be precluded if the liquid level is too high.

The pump 79 is operatively connected to the second switch 102 and is normally activated when the level of fluid in the clean tank 56 sensed by the second switch

102 is above a desired minimum level. When the level in the tank 56 recedes to below the desired minimum level, the switch 102 will cause the pump to deactivate, thereby allowing the level of fluid in the tank 56 to rise if liquid is flowing continuously over weir wall

60. The level of liquid in the clean tank 56 can, thereby, be automatically maintained between optimum, maximum and minimum levels. Numerous characteristics and advantages of the invention for which this application has been submitted have been set forth in the foregoing description. It

will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the invention. The invention's scope is, of course, defined in the language in which the appended claims are ex¬ pressed.

Claims

WHAT IS CLAIMED IS:

1. Apparatus for renewing contaminated liquid comprising:

(a) a process tank having a liquid entry compart- ment segregated from the rest of said tank;

(b) a plate separator obliquely disposed within said process tank, said separator having an upper end communicating with said liquid entry compart¬ ment, a lower end communicating with the rest of said tank, and a plurality of plates, each extend¬ ing substantially from said upper end to said lower end of said separator;

(c) a clean tank adjacent said process tank and separated from that portion of said process tank from which said liquid entry compartment is segre¬ gated, by a weir, wherein liquid channeled into said entry compartment and passed through said separator into said portion of said process tank from which said entry compartment is segregated flows over said weir into said clean tank; and (d)" means for adding an anti-bacterial treating agent to the liquid while it is in one of said process tank and said clean tank.

2. Apparatus in accordance with claim 1 further comprising conveyor means in said process tank, disposed beneath said lower end of said plate separator to have solid contaminants removed from the liquid by said separator, deposited thereon, for removing said solid contaminants from said process tank.

3. Apparatus in accordance with claim 1 further comprising:

(a) first means for channeling liquid from a contaminated liquid reservoir to said liquid entry compartment; (b) first means for sensing a high level of liquid in said clean tank; and (c) means, responsive to said first sensing means,

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OH?I _ for regulating volumetric flow of liquid through said first channeling means.

4. Apparatus in accordance with claim 3 wherein said regulating means comprises a normally open solenoid actuated valve.

5. Apparatus in accordance with claim 3 or 4 wherein said first sensing means comprises a float actuated switch positioned in said clean tank with a float member thereof disposed for movement from below a desired maximum level of liquid in said clean tank, wherein flow of liquid through said first channeling means is permitted, to above said desired maximum level, wherein flow of liquid through said first channeling means is precluded.

6. Apparatus in accordance with claim 1 further comprising:

(a) second means for channeling liquid from said clean tank to a clean liquid service tank;

(b) second means for sensing a low level of liquid in said clean tank; and

(c) means, responsive to said second sensing means, for pumping liquid from said clean tank to said service tank through said second channeling means.

7. Apparatus in accordance with claim 6 wherein said second sensing means comprises a float actuated switch positioned in said clean tank with a float member thereof disposed for movement from above a desired minimum level of liquid in said clean tank, wherein said pumping means is actuated, to below said desired minimum level, wherein said pumping means is deactivated.

8. A system for extracting solid and tramp oil contaminants from coolant to renew the coolant for subsequent use, comprising in combination: (a) a coolant entry compartment;

(b) means for feeding contaminated coolant into said entry compartment;

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(c) a processing compartment having a weir wall;

(d) an obliquely disposed corrugated plate separa¬ tor having an upper end communicating with said entry compartment and a lower end communicating with said processing compartment;

(e) a clean tank disposed adjacent said weir wall;

(f) means for pumping renewed coolant from said clean tank to a clean coolant service tank; and (g) means for treating the coolant with a reagent for inhibiting bacterial growth while it is in one of said entry compartment, said processing compart¬ ment, and said clean tank.

9. A system in accordance with claim 8 further comprising means for recirculating clean, treated coolant pumped from said clean tank back into one of said entry compartment, said processing compartment and said clean tank.

10. A system in accordance with claim 8 further comprising a final filter through which clean, treated coolant is pumped prior to entering said service tank.

11. A system in accordance with claim 8 wherein said weir wall has an upper edge over which coolant in said processing compartment can overflow into said clean tank, said system further comprising a baffle member in said processing compartment and proximate said upper edge of said weir wall.

12. A system in accordance with claim 11 wherein said baffle member extends generally vertically and has an upper edge above said upper edge of said weir wall and a lower edge below said upper edge of said weir wall.

13. A system in accordance with claim 11 or 12 wherein said weir wall has a lower generally vertically extending portion, an upper generally vertically extend¬ ing portion laterally offset from said lower portion toward said clean tank, and a portion interconnecting

Cϊ? S j .'____;__, i said upper and lower portions, and wherein said baffle member is disposed above said interconnecting portion.

14. A method for removing solid and liquid con¬ taminants from a liquid such as a coolant fluid to renew the liquid for subsequent reuse, comprising the steps of:

(a) introducing contaminated liquid into an entry compartment;

(b) passing the liquid downward and obliquely through a corrugated plate separator into a pro¬ cessing compartment;

(c) allowing liquid contaminants to rise upwardly through said separator and return to said entry compartment for recovery and disposal; (<3) allowing solid contaminants to settle to the bottom of said processing compartment; (e) removing said solid contaminants from said processing compartment and disposing of said solid contaminants; (f) adding a biochemical agent to the liquid to retard bacterial growth;

(g) passing the liquid over a weir from the processing compartment into a clean fluid collec¬ tion tank; and (h) pumping the liquid from the clean fluid collection tank to a service tank.

15. A method in accordance with claim 14 further comprising a step of recirculating clean liquid, after it has left the clean fluid collection tank, back through the processing compartment and clean fluid collection tank.

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