GB Patent 1406888 - ACID COMPOSITION AND PROCESS FOR TREATING DOMESTIC MUNICIPAL AND INDUSTRIAL LIQUID WASTES

Description

PATENT SPECIFICATION

( 21) Application No 36775/72 ( 22) Filed 7 Aug 1972 ( 31) Convention Application No 169 739 ( 32) Filed 6 Aug 1971 in ( 33) United States of America (US) ( 44) Complete Specification published 17 Sept 1975 ( 51) INT CL 2 CO 2 B 1/20 ( 52) Index at acceptance C 1 C 200 202 210 217 253 254 30 X 311 400 40 Y 415 424 426 431 435 43 Y () 1406888 ( 54) AN ACID COMPOSITION AND PROCESS FOR TREATING DOMESTIC, MUNICIPAL AND INDUSTRIAL LIQUID WASTES ( 71) I, GEORGE MATTHEW CHAPPELL, a citizen of the United States of America, of Drakes Island, Wells, State of Maine, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the

following statement:-

The present invention relates to an acid composition and a method for treating domestic, municipal and industrial liquid wastes.

Efficient disposal of domestic, municipal and industrial liquid wastes is important to the health of any community A simple method of waste disposal is by dilution; that is, the waste is dumped into an available body of water such as a river or lake containing oxygen which destroys the organic material in the waste Even though the resulting pollution of the river or lake is only temporary, public condemnation has led to the development of methods of treating the wastes prior to disposal These methods include both mechanical and chemical procedures.

The impurity in a particular liquid waste and the amount of treatment required is usually measured on one of two bases: ( 1) the amount of suspended solids, or ( 2) the biological oxygen demand.

Suspended solids are generally separated from a liquid waste by mechanical methods or chemical treatment Mechanical methods of removing solids include passing the waste or sewage through screens, filters, grit chambers (shallow rectangular tanks in which the velocity of flow is checked so as to cause the grit to settle out, carrying some of the organic material with it), sedimentation basins, and trickling filters Chemical treatment methods include precipitation of solids from the waste by coagulation The coagulated materials are then removed by sedimentation or filtration.

The disposal of the solids removed by any lPrice 33 pl of these processes depends upon the local conditions In some cases they are buried, burned or sold as fertilizer after filtering and drying The liquids remaining after the removal of solids are usually chlorinated to destroy harmful microorganisms, such as aerobic bacteria, and then discharged into near-by streams.

Biological oxygen demand, hereinafter referred to as " B O D ", is a measure of the amount of impurities in a waste as determined by the amount of oxygen required to oxidize these impurities It is desirable that treated liquid wastes have a sufficiently low B O D.

in order that there is sufficient oxygen in the liquid waste to support marine life when the waste is discharged into a lake or stream.

Otherwise, oxygen in the waste and oxygen in the lake or stream water is required to oxidize impurities in the waste.

Many of the processes now being used to treat liquid wastes involve the use of costly equipment and high operating and maintenance costs Furthermore, not all of the prior art processes produce a treated liquid having a low enough B O D suitable for discharge in lakes or streams Also, not all of the processes currently in use are suitable for treating some industrial wastes, such as the liquid waste from a leather tanning operation, a paper mill or a textile plant Thus, there exists a definite need in the art for an effective, low cost means of generally purifying liquid containing wastes and reducing the B O D thereof By practice of the present invention this need in the art may be fulfilled.

According to a first embodiment of the present invention there is provided an acid composition for flocculating domestic, municipal or industrial liquid waste said composition comprising:

a) 30 to 97 9995 weight per cent aluminum sulfate, b) 2-20 weight percent of an alkali metal chloride, and c) 0 0005-0 1 weight percent of sodium V If 1,406,888 or potassium hypochlorite.

According to a second embodiment of the present invention there is provided a process for treating domestic, municipal or industrial liquid waste to reduce B O D of the waste, said process comprising adjusting the p H of said waste to from 2 to 5, thereafter adding a sufficient amount of an acid composition according to the first embodiment of the invention and a sufficient amount of an alkaline composition (as defined herein) to said waste, to thereby cause evolution of heat and cause flocculation of solids in the waste and separating the flocculated solids from the liquid.

1 S An example of waste suitable for treatment in accordance with the present invention is a domestic, municipal or industrial liquid waste containing suspended solids, the temperature of the waste prior to addition of the alkaline and acid compositions being 1100 F.

to 1500 F.

A preferred embodiment of a process in accordance with the present invention involves dividing the waste at a p H of 2 to 5 into a first portion and a second portion.

A sufficient amount of an acid composition of the invention is added to the first portion to obtain a mixture having a p H of 0-3.

A sufficient amount of an acid composition position as hereinafter defined is added to the second portion to obtain a mixture having a p H of 9-14 The first and second portions are then mixed to cause the flocculation and evolution of heat previously referred to.

It is also preferred to aerate the waste prior to separation of solids and liquid The liquid is recovered, and if desired subjected to further processing before being discharged into a lake, river or stream The solids can be discarded or recycled to reduce the cost of the process Depending upon the nature of the waste treated, some solids recovered are useful as fertilizer.

Preferably the acid composition of this invention also includes 0-25 % by weight of an inorganic acid selected from H 3 PO 4, HQCI, H 2 SO 4 and HNO 3 and 0-25 % by weight of an organic acid selected from oxalic, formic, acetic and lactic acid For some effluents it may be desirable to add a small amount of alcohol such as isopropyl alcohol to the composition Generally speaking it may be used up to 9 % by weight Alcohol generally aids in keeping the acid composition in solution form at low temperatures.

The term "alkaline composition" as used herein including the claims is intended to mean a composition for flocculating and oxidizing domestic, municipal and industrial liquid wastes, which comprises:

a) 10-25 weight percent aluminum sulfate, b) 34-60 weight percent sodium aluminate, c) 15-35 weight percent sodium hydroxide, d) 1-10 weight percent of an alkali metal chloride, e) 05-4 weight percent sodium or potassium hypochlorite, f) 1-7 weight percent of one or more alkali metal nitrate(s), g) 0 25-5 weight percent of an alkali metal carbonate, and h) 0 25-5 weight percent of an alkali metal bicarbonate.

As with the acid composition, alcohol, e g.

isopropyl alcohol, may also be employed to keep the alkaline composition in solution form at low temperatures Generally speaking the alcohol may be used up to 9 % by weight.

Further, the alkaline composition can preferably contain 0-2 weight percent calcium carbonate, and 0-2 weight percent calcium chloride.

In this specification including the claims the percentages are calculated on the total weight of the components, other than water, in each acid or alkaline composition.

A process in accordance with this invention provides an effective and low cost means of reducing solids contents and reducing the B.O D in liquid wastes The process can be used to treat liquid wastes from municipalities, private dwelling, commercial dwellings and many industries The desirable results of a process according to the invention may be accomplished by the use of inexpensive chemicals, simplified mechanical processes and optional reuse of treated solids The acid composition of this invention and alkaline composition used in the process may be used to increase the productivity of many existing filter plants by at least 65-75 percent by permitting the eliminating of some currently used mechanical procedures Liquid wastes treated by a process in accordance with the invention can be safely discharged into lakes, rivers or streams Considerable financial savings can be realized by the government, states, municipalities, industry and others.

This invention will now be further described, by way of example with reference to the accompanying drawings wherein the Figures are schematic diagrams of equipment which can be used in the application of this invention to the treatment of domestic, municipal or industrial waste.

The liquid waste is usually water containing aerobic and anaerobic bacteria invisible to the unaided eye A process in accordance with the invention is particularly suitable for treating such waters containing suspended solids The waste is adjusted to the proper p H, i e p H= 2 to 5, for example by the addition of an organic or inorganic acid or base.

Two factors must be considered in determining the proper p H for a particular waste.

1,406,888 First, the type of effluent to be treated, average p H of the effluent and p H range should be determined by means well known to those skilled in the art Second, the p H of the waste should be adjusted to 2-1 X Sulfuric acid, phosphoric acid and sodium hydroxide are particularly preferred chemicals for making p H adjustments in the waste Adjustment and control of the p H are important to minimize premature coagulation of ingredients in the waste, neutralize a great percentage of lime or other highly alkaline ingredients, and maintain the waste as a liquid which will readily flow through the processing equipment Control of the p H permits a reduction in the cost of chemicals required for B O D reduction.

A preferred acid composition comprises the following ingredients:

a) 78-82 weight percent aluminum sulfate, b) 6-8 weight percent of an alkaline metal chloride, c) 10-12 weight percent of one or more inorganic acid(s) selected from phosphoric, hydrochloric, sulfuric and nitric acids, d) 1-3 weight percent of one or more organic acid(s) selected from oxalic, formic, acetic and lactic acids, e) 0 001-0 002 weight percent sodium or potassium hypochlorite.

This acid composition is preferably prepared by boiling components (a) and (b) in the above composition in water until a clear solution is obtained This is conveniently accomplished by adding component (a) slowly during boiling When components (a) and (b) have been dissolved in the water, components (c) and (d) are added and boiling continued After all of the components have been added, the solution is boiled for about 5-10 minutes or until clear The solution is then cooled to about 1600 F Component (e) is gradually added, and the liquid is again brought to a boil The resulting mixture is then cooled to about 68 F yielding a yellow paste One gallon of this acid composition weighs about 105-13 pounds.

A preferred alkaline composition comprises the following ingredients:

a) 15-19 weight percent aluminum sulfate, b) 34-42 weight percent sodium aluminate, c) 22-28 weight percent sodium hydroxide, d) 1 8-2 2 weight percent of an alkaline metal chloride, e) 1 0-2 0 weight percent sodium or potassium hypochlorite, f) 2-6 weight percent sodium and/or potassium nitrate, g) 0 2-1 weight percent calcium carbonate, h) 0 2-1 weight percent calcium chloride, i) 0 4-2 weight percent sodiunm carbonate, and j) 0 4-2 weight percent sodium bicarbonate.

This alkaline composition can conveniently 70 be prepared by dissolving about 5 pounds of components d), g), h), and i) in one gallon of boiling water The resulting solution is boiled until clear Component j) is added slowly to the boiling solution, and boiling con 75 tinued until dissolved Component b) is similarly added slowly until dissolved, followed by component c) Then, the solution is removed from the heat and component a) is added very slowly until dissolved After com 80 ponent a) is dissolved, boiling is continued until all solids are in solution The solution is removed from the heat and components e) and f) are cautiously added The resulting mixture is then heated to boiling until a uni 85 form solution is obtained The solution is then cooled to obtain a yellowish brown paste having a density of about 115-14 lbs /gal.

at about 680 F.

It will be understood that mixtures of the 90 inorganic acids and mixtures of the organic acids can be used in the acid composition.

Similarly, mixtures of the various salts in the alkaline composition can be used, e g both Na and K nitrate 95 In a preferred embodiment the liquid waste at a p H of 2 to 5 is divided into two portions A sufficient amount of the acid composition is added to the first portion to obtain a mixture having a p H of 0-3, pre 100 ferably 15-2 5 When the acid composition contacts the first portion of liquid waste some flocculation occurs Similarly, a sufficient amount of alkaline composition is added to the second portion to obtain a mixture having 105 a p H of 9-14, preferably 95-11 Some flocculation occurs when the alkaline composition contacts the second portion of liquid waste.

The portion containing the acid composition 110 is mixed with the portion containing the alkaline composition resulting in further flocculation The flocculated product is insoluble in water, and can be separated with any solids originally suspended in the liquid waste The 115 reaction of components in the acid and alkaline compositions generates heat of neutralization Chemical reaction occurs instantaneously, and continues over a period of time as the acid and alkaline components in each 120 portion of waste contact each other It has been found that the heat generated by this reaction kills at least a portion of the aerobic bacteria present in the liquid waste thereby reducing the B O D of the waste Further 125 B.O D reduction is accomplished by means of the oxidizing agents in each of the compositions and by the change in p H which results from the neutralization reaction Thus, it is usually not necessary to chlorinate liquids 130 1,406,888 remaining after the removal of solids in order to destroy harmful microorganisms It has also been found that the use of an acid composition and an alkaline composition as described above results in a treated liquid relatively free of undesirable odors.

The flocculated product, in the nature of a solid, is separated from the liquid, carrying with it any suspended solids in the waste.

Separation can be effected by means well known to those skilled in the art; for example, settling, filtration centrifugation and/or evaporation Separation is preferably accomplished by permitting the flocculated material 1 S to settle by the action of gravity This obviates the need for costly separation equipment.

The separated solids frequently contain active chemicals; thus the solids can be recycled to the process to reduce the cost of operation The amount recycled will of course depend upon the required B O D reduction in the treated waste, and the amounts of active chemicals in the solids These factors can readily be determined by those skilled in the art.

The liquid remaining after the separation of solids can be subjected to further processing For example, it is preferred to adjust the p H of the liquid to 6-8 before discharging it into a lake or stream.

A process in accordance with the invention can be operated on either a batch or continuous basis, and will be more clearly understood by reference to Figure 1 which is a flow diagram of a continuous process in accordance with the invention.

A waste material 1 having solid materials suspended therein enters vessel 2 through line 6 Vessel 2 is usually covered to prevent the escape of obnoxious odors Vessel 2 is provided with mixing means 7 Other vessels used in the process are also generally covered for the same reason The p H of the waste 1 in vessel 2 can be measured by sampling or automatically, such as by the p H electrode at The p H is adjusted by adding acid through line 3 or alkali through line 4 The p H of the waste should be 2-5 at the start The liquid waste 1 is removed from vessel 2 via pump 9 through line 8 Valve 10 can be used to control the liquid level in vessel 2 or the feed rate of liquid waste 1 The liquid waste is divided at 11 into a first portion in line 12, and a second portion in line 13 Lines 12 and 13 are equipped with automatic or manual control valves 14 and 15 to control the flow rates of material in each line Also provided are lines 16 and 17 having valves 18 and 19, respectively, through which excess waste can be removed from the system, and recycled to vessel 2 or some other vessel (not shown in the Figure) for storage and later treatment.

It will of course be understood that tank 2 and related equipment need not be used For example, waste can be pumped in 2 separate portions directly from the source of the waste into lines 12 and 13 Adjustments to p H are made directly in the pipelines in such a case.

The embodiment of Figure 1 is particularly 70 advantageous when septic tank wastes are combined with municipal or industrial wastes.

For example, septic tank waste can be added to tank 2 in Figure 1 It is preferred to adjust p H of this waste using H 2 SO 4 or 75 Na OH The septic tank waste can then be combined with other waste, such as waste pumped directly from the source into lines 12 and 13 such that the resultant mixture has a p H of from 2 to 5 80 The first portion of liquid waste flows through line 20 and valve 22 to point 24 where it is mixed with acid composition 26 from vessel 28 Some flocculations occurs when the acid composition contacts the waste 85 Acid composition is prepared as previously described introducing the ingredients into vessel 28 through line 30 Vessel 28 can be provided with heating means, such as a jacket 32 into which steam 34 is introduced Con 90 densate is removed through line 36 Vessel 28 can also be provided with means for mixing the acid composition, such as mixer 38.

It will be understood that the acid composition can be heated by other means 95 The rate of addition of acid composition 26 to the waste in line 20 is a function of the p H of the waste in line 20 The p H of a liquid waste can be measured automatically as at 40, and the pumping rate of pump 100 44 controlled to provide the proper amount of acid composition at point 24 Alternatively, the flow of acid composition 26 can be controlled by automatic control valves such as 42 and 46 and pump 44 in Figure 1 Suffi 105 cient acid composition is added to insure that the waste is acidic preferably having a p H of 0-3, and most preferably 2.

In a similar fashion, the second portion of liquid waste flows through line 21 and valve 110 23 to point 25 where alkaline composition 27 in vessel 29 is added Some flocculation occurs when the alkaline composition contacts the waste Vessel 29 is provided with line 31 for the introduction of components compris 115 ing the alkaline composition Vessel 29 is also provided with heating means, such as jacket 33, steam line 35, condensate line 37 and mixer 39 It will be understood that other suitable heating means can be employed The 120 rate of addition of alkaline composition 27 is similarly a function of the p H of the waste in line 21 The p H can be measured at 41, and the flow rate of alkaline composition 27 controlled by valves 43 and 47 and pump 125 Sufficient alkaline composition is added to insure that the waste is alkaline, preferably having a p H of 9-14, and most preferably 10-11.

Preferably, both the acid and alkaline corn 130 1,406,888 positions are heated to a temperature of F -150 F prior to addition to the first and second portions of the waste It is thereby easier to maintain the consistency of each cornposition and uniformity of flow.

When treating certain types of waste, the p H of the second portion of waste will be 13-14 after the addition of alkaline composition Under these conditions, it is preferable that valve 47 be set to provide a substantially continuous feed rate of alkaline composition of 25-50 parts per million parts of waste to be treated.

The first portion of liquid waste in line 48 is mixed at point 50 with the second portion of liquid waste in line 49 The combined streams pass through line 51 into line 53 and into equipment shown schematically in the lower half of Figure 1, or into line 54 and then into equipment shown schematically in the upper half of Figure 1 Use of these alternate flow paths will be more apparent from the discussion which follows.

When streams 48 and 49 combined at point 50, additional flocculation occurs due to the reaction of ingredients in the acid and alkaline compositions Also, heat of neutralization is generated Assume all of the material at point 50 flows via streams 51 and 54 to vessel 56 The liquid 58 containing flocculant, flows into vessel 56 until the vessel is full, at which time the flow of material from point 52 is diverted to vessel 55 through line 53 Vessel 56 is provided with an overflow line 60 to vessel 86 to avoid spillage in the event the flow in line 54 is not diverted to line 53 at the proper time Vessel 56 can optionally be provided with an overflow line to a storage vessel (not shown).

Vessel 56 is preferably provided with a mixer 62 to mildly agitate the liquid 58 as it is being added through line 54 to vessel 56 The vessel is also provided with a discharge 64 through which liquid 58 is preferably recirculated by pump 66 and line 68 to the top of the vessel in order to more efficiently contact the active chemicals in each composition A line 80 is provided after the discharge of pump 66 to facilitate removal of a portion of the recirculated liquid, such as for sampling Vessel 56 is also provided with a false bottom 70 such as a screen, to permit separation of liquids and solids.

When vessel 56 is filled with liquid 58, air 111 compressed by compressor 112 is fed to vessel 56 through lines 114 and 116.

The compressed air is uniformly distributed around the interior of vessel 56, such as by a perforated hose (not shown in Figure 1).

The compressed air is introduced below false bottom or screen 70 and allowed to bubble through the liquid 58 When the flow of compressed air to vessel 56 is started, recirculation of liquid 58 through pump 66 is stopped.

The mixer 62 and flow of compressed air are shut off and the liquid 58 in vessel 56 is allowed to stand to permit flocculated product and suspended solids to settle to the bottom of the vessel through screen 70 This is complete when the liquid in vessel 56 appears clear to the unaided eye Generally, the time required for the solids to practically completely settle is only about 30 minutes.

At the end of the settling period, the liquid in vessel 56 is transferred through line 72 by pump 78 and line 74 to vessel 86.

When the liquid above the screen 70 in vessel 56 has been practically removed, pump 78 can be stopped and more waste added to vessel 56 through line 54 as before This new charge of waste from point 50 is recirculated, agitated, aerated and allowed to settle as previously described.

The liquid 84 in vessel 86 is free of obnoxious odors and clear, has a low B O D.

and usually has an acceptable p H for disposal, e g 6-8 The p H of liquid 58 can be measured by p H probe 76 and the p H of liquid 84 can be adjusted, if necessary, by adding an acidic or alkaline material, such as an inorganic or organic acid or base, to vessel 86 and mixed by 88 The liquid is then transferred through line 90 by pump 92 and line 94 to vessel 95 Alternatively, the liquid can be pumped through line 90 and pump 92 directly to a lake or stream Vessel permits further treatment of the liquid 96 if required (For example aeration or settling).

The p H of liquid 84 can be measured by p H probe 118 and, if necessary, the p H of liquid 96 can be adjusted by addition of acidic or alkaline material to vessel 95.

Finally, liquid 96 can be pumped through line 97 by pump 98 into a river, lake, stream or reused.

Vessel 95 can also be provided with a screen 99 to permit separation of any remaining solids Solids can be removed from vessel 95 through line 100 and discarded or used as a by-product.

Referring again to vessel 86 in Figure 1, any solids in liquid 84 pass through screen 102 to the bottom of the vessel These solids can be returned to vessel 56 through line 104 by pump 106 and line 108 if the solids contain active chemicals.

Solids can also be removed through line and discarded or recovered as by-products.

As previously noted, when vessel 56 is filled, the flow of combined waste from point 52 in the Figure 1 is diverted to vessel 55 via line 53 as shown in the lower half of the Figure Liquid 57 in vessel 55 is subjected to the same treatment as liquid 58 in vessel 56 Vessel 55 can be provided with an overflow line 59 to vessel 81 or an overflow line to a storage tank (not shown in Figure 1).

Vessel 55 is preferably provided with a 1,406,888 mixer 61 to mildly agitate the liquid 57 as it is being added through line 53 to the vessel The vessel is also provided with a discharge line 63 through which liquid 57 is preferably recirculated by pump 65 and line 67 to the top of the vessel Vessel 55 is also provided with a false bottom 69 such as a screen.

After vessel 55 has been filled with liquid 57 air 111 compressed by compressor 112 is fed to the vessel through lines 113 and 115.

The compressed air is uniformly distributed around the interior of vessel 55, such as by means previously described The compressed air is allowed to bubble through the liquid 57, and recirculation of liquid 57 through pump is stopped.

The mixer 61 and flow of compressed air shut off, and the liquid 57 in vessel 55 is allowed to stand to permit flocculated product and suspended solids to settle to the bottom of the vessel through screen 69 When the liquid in vessel 55 appears substantially clear to the unaided eye, it is transferred by pump 73 through lines 71 and 77 to vessel 81.

When the liquid above the screen 69 in vessel has been practically removed, a new charge of liquid waste can be added to the vessel.

The p H of liquid 57 from vessel 55 can be measured by electrode 75 and the p H of liquid 83 adjusted to the same level as stated relative to the tank 86 discussed hereinabove, by adding an organic or inorganic acidic or alkaline material to vessel 81 through line 85.

The liquid is then transferred by pump 91 through lines 89 and 93 to vessel 95 The p H of liquid 83 can be measured by p H probe 117 and, if necessary, the p H of liquid 96 can be adjusted by the addition of acidic or alkaline material to vessel 95 Alternatively, the liquid can be pump through line 89 by pump 91 directly to a lake or stream.

Solids, if any, in the liquid 83 in vessel 81 pass through screen 101 to the bottom of the vessel These solids can be returned to vessel 55 by pump 105 and lines 103 and 107 Solids can also be removed through lines 79 and 109 and discarded, recovered as byproducts, or recycled to the process.

When vessel 55 has been filled with liquid waste, the flow of combined waste from point 52 in Figure 1 is again diverted to vessel 56 through line 54 It will be apparent that the flow of material from point 52 is alternated between vessels 55 and 56 in Figure 1 It will be apparent to those skilled in the art that more than two treatment stages beyond point 52 can be used depending upon the amount of waste to be treated and the capacity of each stage For convenience, only two stages are shown in Figure 1 for treatment of waste from point 52.

When liquid is being pumped into any vessel described above, it is preferred that the flow of liquid be directed at about a 45 angle relative to a vertical side of the vessel to create a cascading effect down the wall of the vessel This increases the turbulence in the flow of liquid permitting more efficient contact of active chemicals in each composition.

This invention will be more clearly understood by reference to the following example.

EXAMPLE.

In this example, municipal, industrial and domestic waste is treated in a batch process using equipment depicted in Figure 2.

In this process, about 900 gallons of Saco River water is pumped directly from the river through line 201, pump 202 and line 203 into a 1000 gallon capacity tank 204.

To tank 204 are also added about 40 gallons of untreated effluent from the City of Biddeford, Maine, 10 gallons of septic tank waste, and 50 gallons of effluent from a commercial tanning operation By mixing the three types of waste together an adjustment of p H is obtained such that the p H of the mixture is 2 to 5.

A sample of the waste in tank 204 is drawn for testing The results of the tests are reported in Column 4 of Table I.

500 Gallons of waste are pumped from tank 204 to tank 209 in Figure 2 The waste is transferred by pump 206 through lines 205, 207, and 208 Valve 213 is open and valve 214 is closed to prevent the waste from flowing into tank 216 via line 215 The waste from line 208 is directed at a 450 angle against the vertical side of tank 209 to permit the waste to cascade down the vertical wall of the tank.

After about 200 gallons of waste is added to tank 209, about 100 c c of acid composition at about 1400 F is added to the tank through line 211 After all the acid has been added, about 50 c c of alkaline composition at about 1200 F are added to the tank through line 212 A sample is taken, and the degree of flocculation observed and p H measured.

The flocculation is too slow and the p H is about 3 After 50 c c of acid composition is added to tank 209 to reduce the p H to about 2.25 The rate of flocculation improves Before this second addition, mixer 210 is turned on.

After tank 209 is about full, another 50 c.c of alkaline composition are added and another sample is taken The rate of flocculation as visually determined was satisfactory, and the p H of the sample measured about 4.

The following acid composition, prepared as previously described, is used in this example:

7 1,406,888 7 aluminum sulphate crystals A 12 ( 504), 18 H 20 sodium chloride phosphoric acid ( 75 % by wt HI 2 PO) oxalic acid crystals (COOH)2 2 H 20 sodium hypochlorite solution 12 5 % by wt Na O Cl) water Balan paste lb./g The following alkaline compos pared as previously described, is u example:

aluminum sulphate crystals A 12 (SO 4), 18 H 20 sodium aluminate sodium hydroxide sodium chloride sodium hypochlorite solution ( 12 5 % by wt Na O Cl) sodium nitrate calcium carbonate calcium chloride sodium carbonate ( 58 % Light Soda Ash) sodium bicarbonate water Balal past lbs / When the evolution of heat cease 210 is shut off and solids permits to the bottom of the tank A samp drawn for testing, and the results in Column 2 of Table I The w, 209 was not aerated during this process.

Valve 213 is closed and valve 21 The balance of the waste totaling in tank 204 is transferred to t Figure 2 The waste is permitted lbs down the side of the wall of tank 216 in the same manner as described in tank 209.

10.74 While the waste is being added to tank 216, 1 it is aerated by means not shown in Figure 2.

When the waste covers mixing blade 217, the 2 mixer is started About 150 c c of acid composition at 140 F is added via line 218 after 0.3 the mixer is started When all of the acid composition has been added, about 100 c c.

0.1 of alkaline composition at about 110 F is ce to yield added via line 219 A sample is taken, and of 12 2 an additional 35 c c of alkaline composition al are added to tank 216 to increase the rate of flocculations and raise the p H from 4 4 to ition, pre 5 75 Aeration is continued until tank 216 is sed in this filled with the 500 gallons of waste from tank 204 The mixer is stopped and solids perlbs mitted to settle to the bottom of tank 216.

A sample is then drawn for testing, and the 2.5 results are reported in Column 3 of Table I.

5.62 The treated waste in tanks 209 and 216 3.75 are returned to tank 204 by pump 222 and 0.317 lines 220, 221 and 223 After the waste has been blended in tank 204, it is pumped back 1.875 into tank 209 through pump 206 and lines 0.626 205, 207 and 208 Valve 213 is opened and 0.0626 valve 214 is closed As tank 209 is filling, 0.0626 the waste is aerated by means not shown in Figure 2 After the waste covers mixing blade 0.0935 210, the mixer is started The waste in tank 0.0935 209 is permitted to overflow through line nce to yield 224 to tank 216 The waste is aerated as re of 12 5 tank 216 is being filled When all the waste /gal in tank 204 has been transferred to tanks 209 and 216, pump 206 is stopped and all s, the mixer valves closed When the tanks are filled, both ted to settle mixers which were operating during the filldle was then ing operation are shut off.

are reported Solids are permitted to settle to the bottom aste in tank of each tank Samples are then drawn for step of the testing, and the results are reported in Column of Table I.

4 is opened The untreated waste had an extremely 500 gallons obnoxious odor before processing After chemiank 216 in cals were added, all perceptible odor dist to cascade appeared.

1,406,888 Column 1 Dissolved oxygen-ppm p H Temp.

% oxygen increase Nitrates (ammonium)-ppm Polyphosphates-ppm Relative Stability Culture Test for Bacteria per Liter O.D I Test Diluted 50 % (Distilled) P.P M.

% Reduction B O D.

TABLE I

Column 2 Column 3 Column 4 Column 5 Tank 209 Tank 216 Tank 204 Tanks 209 & 216 500 gals 500 gals 1000 gals 1000 gals.

Treated Treated Untreated Treated 5.9 6 7 0 9 6 55 5.8 6 7 6 57 4.4 45 4 4 4 55 4 6 4 4 4 55 62 OF 61 c F 66 F 620 F.

_ _ _ _ _ _ _ __ 847865 86384.7 86 5 86 4 84 86 5 -86 4 _- _ 0 4 0 0 4 0 1 2 1 2 1 2 1 1 144 hrs 48 hrs.

no change clear (methylene blue) 1 liter 1 liter higher than 20,000 0 55 570 56 52 58 87.5 90 5 90 3 87.5 91 90 1 o 00 I-.

0 00 00 00 TO Os oo TABLE I (Continued) Column 1 Column 2 Tank 209 500 gals.

Treated Column 3 Tank 216 500 gals.

Treated Day B O D Test P.P M.

Column 4 Tank 204 1000 gals.

Untreated 300 310 % Reduction B O D.

Column 5 Tanks 209 & 216 1000 gals.

Treated 9 9.5 97 97.5 Oxygen Demand Index Test This is a standard analytical test described on p 63 of the publication entitled "Procedures and Chemical Lists for Water and Waste Water Analysis", 5th edition, Hach Chemical Co, Ames, Iowa.

It will be apparent from the foregoing discussion that there are numerous advantages related to the practice of this invention.

The B O D of liquid wastes treated according to the process of this invention can be reduced at a relatively low cost per gallon treated Treatment time is not excessive, and the treated waste is free from obnoxious odors.

The clear water obtained after waste is treated can be safely discharged into rivers, lakes or streams The chemicals employed in this invention are readily available, relatively inexpensive and can be used to increase the productivity of existing waste treatment plants by elimination of some mechanical procedures The chemical compositions generally contain only naturally occurring materials and are free of synthetic materials such as polyelectrolytes Flocculated solids obtained from a process in accordance with the invention can be used as a fertilizer, or deposited in a polluted body of water, such as a settling pond, to assist in B O D reduction.

Furthermore, flocculated solids can be recirculated to earlier stages in the process to reduce the overall chemical cost and further lower B O D It is to be noted that fish have lived for several months without additional feeding in the clear water obtained from municipal waste treated by a process in accordance with the invention.