# Patent

## Title
Self-diluting feedwell for thickener dilution

## Abstract

This is a continuation-in-part of Ser. No. 08/080,909 filed Jun. 22, 1993, now abandoned.

## Background
The present invention relates to compositions of tannin containing polymers and methods of using the same for water clarification.

Raw water such as water from rivers, lakes or underground usually contains suspended matter. The suspended matter must be removed by clarification in order to provide water suitable for use in domestic and industrial applications. The suspended matter can consist of large solids, settleable by gravity alone without any external aid, and nonsettleable material, often colloidal in nature. Removal of the suspended material is generally accomplished by coagulation, flocculation, and sedimentation. in combination, these processes are referred to as conventional clarification. (see Betz Handbook of Industrial Water Conditioning, 9th Edition, 1991, Betz Laboratories, Inc., Trevose, Pa., pages 23 through 30).

Naturally occurring suspended particles are predominantly negatively charged. Water-soluble organic cationic polymers, such as polyamine and polydiallyldimethyl ammonium chloride, are normally used to clarify water having high turbidity (greater than 60 NTU, nephelometric turbidity units). In low turbidity water (less than 60 NTU), there are generally not enough particulates to form a settleable floc when the water is treated with cationic polymer alone. Inorganic coagulants such as aluminum sulfate, polyaluminum chloride, ferric sulfate, ferric chloride and sodium aluminate are used instead. These inorganic coagulants are relatively inexpensive and generally effective for water clarification. However, they tend to generate voluminous sludge which is difficult to dewater. Also, such inorganic coagulants are only effective within a particular pH range and therefore require proper pH adjustment of the water during treatment. In addition, residual iron and aluminum ions in the water treated may affect downstream operations such as cooling and boiler treatments and may also cause health and environmental concerns when the water is finally discharged.

Water soluble/dispersible melamine formaldehyde resins have been used for clarification of low turbidity waters, but the residual formaldehyde in the resin can give rise to handling and disposal difficulties. It is the object of the present invention to provide an effective method of clarifying water without incurring the disadvantages of inorganic coagulants and melamine formaldehyde resins.

The present invention provides for a composition, the method of preparing the same and a method of using the composition for water clarification. The composition comprises a water soluble/dispersible tannin containing polymer obtained by polymerizing ethylenically unsaturated monomers with tannin.

U.S. Pat. Nos. 4,558,080; 4,734,216 and 4,781,839 disclose a tannin based polymer obtained by reacting tannin with an amino compound and an aldehyde under acidic conditions for use as a flocculant. The manufacturing process requires careful monitoring of the pH and intermediate viscosity during the reaction to prevent the batch from gelling. The long term stability of the product and the amount of residual amine and formaldehyde in the solution may cause handling concerns.

U.S. Pat. No. 4,990,270 discloses a thickening agent prepared by graft copolymerizing acrylamide and cationic monomer with water insoluble lignin in a calcium chloride/dimethylsulfoxide solution. The procedure is quite complicated and requires precipitation in acetone and filtration, and dialysis to isolate the product. The resulting material is used for enhanced oil recovery.

This invention provides for a composition comprising a tannin containing polymeric material. The invention also provides for methods for preparing the tannin containing polymers and methods of using the polymers for various water treatments.

Tannin, also called tannic acid, occurs in the leaf, branch, bark and fruit of many plants. As disclosed by A. Pizzi in "Condensed Tannin for Adhesives", Ind. Eng. Chem. Prod. Res. Dev. 1982, 21, pages 359-369, the natural tannins can be categorized as "hydrolyzable" tannin and "condensed" tannin. The composition and structure of tannin will vary with the source and the method of extraction, but the empirical structure is given as C.sub.76 H.sub.52 O.sub.46 with many OH groups attached to the aromatic rings. The tannin used in the present invention is a condensed tannin type including but not limited to those derived from Quebracho, Mimosa and Sumac. However, hydrolyzable tannins are also contemplated to be within the scope of this invention.

The present invention relates to a water soluble or dispersible tannin containing polymer composition comprising a copolymer of a tannin and a cationic monomer. In another embodiment of the present invention, the water soluble or dispersible tannin containing polymer composition comprises a polymer of tannin; a cationic monomer and at least one monomer selected from the group consisting of an anionic monomer and a nonionic monomer.

The cationic monomer is selected from a group containing ethylenically unsaturated quaternary ammonium, phosphonium or sulfonium ions. Typical cationic monomers are quaternary ammonium salts of dialkylaminoalkyl(meth)acrylamides, dialkylaminoalkyl(meth)acrylates and diallyl dialkyl ammonium chloride.

The preferred cationic monomers are selected from the group include but are not limited to methyl chloride quaternary salt of diethylaminoethyl acrylate, dimethyl sulfate salt of diethylaminoethyl acrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide, dimethylaminopropyl acrylamide, diallyldimethyl ammonium chloride and diallyldiethyl ammonium chloride. The most preferred cationic monomer is methyl chloride quaternary salt of diethylaminoethyl acrylate.

The anionic monomer is selected from the group containing ethylenically unsaturated carboxylic acid or sulfonic acid functional groups. These monomers include but are not limited to acrylic acid, methacrylic acid, vinyl acetic acid, itaconic acid, maleic acid, allylacetic acid, styrene sulfonic acid, 2-acrylamido-2-methyl propane sulfonic acid (AMPS.RTM.) and 3-allyloxy-2-hydroxypropane sulfonic acids and salts thereof. The preferred anionic monomer is acrylic acid.

The nonionic monomer is selected from the group of ethylenically unsaturated nonionic monomers which comprise but are not limited to acrylamide, methacrylamide, N-methylolacrylamide, N,N-dimethyl-acrylamide; lower alkyl (C.sub.1 -C.sub.6) esters including vinyl acetate, methyl acrylate, ethyl acrylate, and methyl methacrylate; hydroxylated lower alkyl (C.sub.1 -C.sub.6) esters including hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate; allyl glycidyl ether; and ethoxylated allyl ethers of polyethylene glycol, polypropylene glycol and propoxylated acrylates. The preferred nonionic monomers are allyl glycidyl ether and acrylamide.

The resulting tannin containing polymer contains from 10 to 80% by weight of tannin, 20 to 90% by weight of cationic monomer, 0 to 30% by weight of nonionic monomer and 0 to 20% by weight of anionic monomer, provided that the resulting tannin containing polymer is still water soluble or dispersible and the total weight % of cationic, nonionic and anionic monomers and tannin adds up to 100%. Preferably, when the cationic monomer and anionic monomer are present together in the tannin containing polymer, the cationic monomer comprises a greater weight percentage than the anionic monomer.

The preferred copolymer of tannin and cationic monomer contains 20 to 80 weight % of tannin. More preferably, the copolymer contains from 30 to 60 weight % of tannin and most preferably, from 30 to 50 weight % of the tannin in the copolymer, provided the total weight of tannin and cationic monomer totals 100 weight %. More preferably still, the copolymers have a weight % of 30% tannin and 70% cationic monomer and 50% tannin and 50% cationic monomer. These particular copolymers are most preferred when the tannin is a Mimosa type tannin and the cationic monomer is methyl chloride quaternary salt of dimethylaminoethyl acrylate.

The number average molecular weight of the resulting tannin containing polymer is not critical, as it is still water soluble or dispersible. The tannin containing polymers may be prepared by mixing the desired monomers with tannin and initiating by a free radical initiator via solution, precipitation or emulsion polymerization techniques. Conventional initiators such as azo compounds, persulfates, peroxides and redox couples may be used. The preferred initiators are 2,2'azobis(2-amidinopropane) dihydrochloride, available as V-50 from Wako Chemicals and t-butylhydroperoxide/sodium metabisulfite (t-BHP/NaMBS). These or other initiators may be added at the end of polymerization to further react with any residual monomers.

Chain transfer agents such as alcohol, amine, formic acid or mercapto compounds may be used to regulate the molecular weight of the polymer. The resulting polymer may be isolated by well known techniques including precipitation, etc., or the polymer may simply be used in its aqueous solution.

The reaction temperature is not critical and generally occurs between 20.degree. and 100.degree. C., preferably 40.degree. to 70.degree. C. The pH of the reaction mixture is also not critical and is generally in the range of 2.0 to 8.0. The resulting tannin containing polymers are characterized by C-13 NMR, Brookfield viscosity and percent solids.

The resulting tannin containing polymers should be added to the aqueous system to be treated in an amount sufficient for its intended purpose. For the most part, this amount will vary depending upon the particular aqueous system for which treatment is desired and can be influenced by such variables as turbidity, pH, temperature, water quantity and type of contaminants present in the system. The tannin containing polymers are effective at a wide range of pHs and should prove effective at the pH of any aqueous system for which water treatment is sought.

The tannin containing polymers of the present invention prove useful in a variety of aqueous systems suffering from different contaminants but are well suited to the reduction of turbidity, color and the clarification of aqueous systems such as influent waters and waste water systems. Clay, silt, finely divided organic and inorganic matter, and microscopic organisms can all contribute to turbidity. Color is most often colloidal in nature and results from organic materials such as humic acids and other compounds leached from vegetative matter.

The tannin containing polymers can be added to the aqueous system where water clarification is sought in amounts ranging from about 0.1 parts to about 100 parts per million parts water. The polymers may be added to the aqueous system neat or in an aqueous solution either continuously or intermittently.

Polymeric flocculants such as polyacrylamide and copolymers of acrylamide with acrylic acid and other coagulants such as alum, ferric chloride, clays, zeolites, activated carbon and the like may be used in conjunction with the tannin containing polymers to reduce turbidity and color and improve clarity.

Those skilled in the art will recognize the many applications in which these tannin containing polymers will find utility. These utilities include, but are not limited to, wastewater treatment applications such as wastewater from chemical plants, refineries and pulp and paper mills, influent water clarification, color reduction, secondary water clarification, oily waste water treatment, proteinaceous containing waste water, papermaking (e.g., retention and drainage aids), protein recovery, emulsion breaking, sludge dewatering, upflow filter clarification, horizontal flow clarification, and the like.

Wastewater systems that are envisioned to be within the scope of the present invention include primary and oily wastewater streams from industries including but not limited to the refinery, petrochemical, chemical, steel, rolling mill, automobile, textile and meat and food processing industries. The contaminants in these systems are organic and inorganic contaminants which include but are not limited to settleable and unsettleable solids, oil, grease, precipitated metals, and fatty and proteinaceous substances.

In order to more clearly illustrate this invention, the data set forth below were developed. The following examples are included as illustrations of the invention and should not be construed as limiting the scope thereof.

A reaction flask equipped with a condenser, a thermometer, a nitrogen inlet and a mechanical stirrer was charged with 51.0 g of condensed tannin (Quebracho type) and 204.0 g of deionized water. 3.5 g of 50% caustic and 3.76 g of allylglycidyl ether (AGE) were then added to the tannin solution. This solution was heated to 50.degree. C. and maintained for 7 hours. FT-IR showed that there were no adsorption bands corresponding to the residual epoxy group of AGE.

The resulting tannin/AGE solution of Example 1 was adjusted to pH 6.8 by sulfuric acid. An initiator solution containing 0.39 g of 2,2'azo bis(2-amidino propane)dihydrochloride (V-50) in 2.4 g of deionized water was then added to 124 g of the solution at 60.degree. C. A monomer solution containing 57.2 g of dimethylaminoethyl acrylate methyl chloride quat (AETAC, 80%) and 1.1 g of acrylic acid (AA) was then gradually added to the flask in 5 hours.

Additional initiator solution was added before the completion of the monomer addition. After that, the polymerization was allowed to proceed overnight. More initiator was added to complete the reaction. The structure of the resulting polymer was verified by C-13 NMR. The resulting tannin containing polymer solution had a Brookfield viscosity of 1070 cps at 27.3% solids (25C).

Utilizing the apparatus and procedure as described in Example 2, 60.5 g of 80% AETAC and 1.2 g of AA were used for polymerization with 79 g of the tannin/AGE solution. The resulting tannin containing polymer solution had a Brookfield viscosity of 243 cps at 24.5% solids (25C).

Utilizing the apparatus, procedure and reagent charge as described in Example 3, 32.50 g of the AGE/tannin solution was used for the polymerization with AETAC and AA. The resulting solution had a Brookfield viscosity of 81 cps at 21.8% solids (25C).

The apparatus and procedure similar to that described in Example 3 were used, except this time, AA was not used for the reaction. The solution pH was adjusted to 6.5 by sulfuric acid before polymerization. 60.5 g of 80% AETAC and 79 g of the tannin/AGE solution were used for polymerization. The resulting polymer solution had a Brookfield viscosity of 1050 cps at 26.9% solids (25C).

A procedure as described in Example 5 was used to prepare a different weight ratio of tannin/AETAC polymers. The composition and physical properties of the resulting polymer solutions are shown in Tables I and II.

60.5 g of AETAC (80%) and 1.2 g of AA were gradually charged into 127.5 g of tannin solution (20% solids) at 60.degree. C. in 4.5 hours. V-50 was shot fed into the reactor vessel to initiate the polymerization process

The structure of the resulting tannin containing polymer solution was verified by C-13 NMR. The resulting polymer solution had a Brookfield viscosity of 583 cps at 35.5% solids (25C).

A similar process as described in Example 8 was used to prepare a tannin/AETAC/AA polymer solution. The resulting polymer solution had a Brookfield viscosity of 754 cps at 35.6% solids (25C).

A similar process as described in Example 8 was used to prepare a tannin/AETAC solution. 64.5 g of AETAC (80%) was reacted with 127.5 g of tannin solution (20% solids) using V-50 as the initiator. The resulting polymer solution had a Brookfield viscosity of 625 cps at 35.2% solids (2SC).

Utilizing a procedure similar to that described in Example 10, 47.8 g of 80% AETAC was reacted with 127.5 g of tannin solution (20% solids) using V-50 as the initiator. The structure of the resulting polymer was verified by C-13 NMR. The polymer solution had a Brookfield viscosity of 323 cps at 33.3% solids (25C).

Utilizing an apparatus and procedure similar to that described in Example 11, Mimosa type of tannin was used in the reaction. The resulting solution had a Brookfield viscosity of 109 cps at 36.3% solids (25C).

Utilizing a similar apparatus and procedure as described in Example 11, Mimosa type of tannin from a different source was used in the reaction.

In this example, a redox pair of t-butylhydroperoxide (t-BHP)/sodium metabisulfite (NaMBS)was used as the initiator. 22.1 g of tannin (Mimosa type), 64.5 g of 80% AETAC were charged to a reaction vessel containing 42.7 g of Dl water at 55C. 20 g of 4% t-BHP and 20 g of 6% NaMBS were then gradually charged to the solution in 5.5 hours at 50.degree.-55.degree. C. The solution was held at 50.degree. C. for 30 minutes before cooling down. After final dilution, the resulting polymer solution had a Brookfield viscosity of 173 cps at 31.2% solids (25C).

Utilizing a similar procedure as described in Example 15, Quebracho tannin was used in the reaction. The resulting solution had a Brookfield viscosity of 133 cps at 32.5% solids (25C).

A similar procedure as described in Example 15 was used to prepare a different weight ratio of tannin/AETAC polymer.

Utilizing a procedure similar to that described in Example 15 however, 31.0 g of 80% AETAC and 7.7 g of 52% acrylamide (AM) were used to copolymerize with 38.7 g of tannin. The resulting solution had a Brookfield viscosity of 459 cps at 31.2% solids (25C).

Utilizing a procedure similar to Example 15, 1439 parts of AETAC (80%) was reacted with 1151 parts of tannin (Mimosa type) in an aqueous solution at 45.degree. C. 68 parts of t-BHP and 189 parts of sodium metabisulfite (20%) was used as the initiator. The resulting solution had a Brookfield viscosity of 1150 cps at 37.2% solids (25C).

Utilizing a procedure similar to Example 22, 4400 parts of AETAC (80%) was reacted with 3520 parts of tannin (Mimosa type) in an aqueous solution. The resulting solution had a Brookfield viscosity of 409 cps at 38.2% solids (25C).

A tannin/monoethanolamine/formaldehyde material was prepared in substantial conformity to the procedure of Example 1 in U.S. Pat. No. 4,558,080. The resulting product had a viscosity of 200 cps (40.5% solids) at pH of 2.4.

Tables I and II summarize the composition and physical properties of the resulting tannin containing polymers. ______________________________________ Composition of tannin containing polymers Examples 1-11 and 15-21 are Quebracho tannin Examples 12-14 and 22-23 are Mimosa tannin Example No. Composition       Weight % ______________________________________ 2        tannin/(AETAC/AA/AGE) 33.1/(62.9/1.6/2.4) 3        tannin/(AETAC/AA/AGE) 23.2/(73.3/1.8/1.7) 4        tannin/(AETAC/AA/AGE) 11.1/(86.0/2.1/0.8) 5        tannin/(AETAC/AGE) 32.2/(65.4/2.4) 6        tannin/(AETAC/AGE) 22.5/(75.8/1.7) 7        tannin/(AETAC/AGE) 10.8/(88.4/0.8) 8        tannin/(AETAC/AGE) 34/(64.4/1.6) 9        tannin/(AETAC/AA) 34/(64.4/1.6) 10        tannin/AETAC      33.1/66.9 11        tannin/AETAC      40/60 12        tannin/AETAC      33.1/66.9 13        tannin/AETAC      33.1/66.9 14        tannin/AETAC      33.1/66.9 15        tannin/AETAC      30/70 16        tannin/AETAC      30/70 17        tannin/AETAC      40/60 18        tannin/AETAC      50/50 19        tannin/AETAC      50/50 20        tannin/AETAC      55/45 21        tannin/(AETAC/AM) 50/(40/10) 22        tannin/AETAC      50/50 23        tannin/AETAC      50/50 ______________________________________ AETAC is dimethylaminoethyl acrylate methyl chloride QUAT AA is acrylic acid AGE is allyl glycidyl ether AM is acrylamide ______________________________________ Physical properties of tannin-containing polymers Brookfield Solids      Viscosity Examples Composition       %       pH  (cps) ______________________________________ 2     tannin/(AETAC/AA/AGE) 27.3    4.0 1070 3     tannin/(AETAC/AA/AGE) 24.5    3.5 243 4     tannin/(AETAC/AA/AGE) 21.8    3.1 81 5     tannin/(AETAC/AGE) 26.9    4.6 1050 6     tannin/(AETAC/AGE) 24.4    4.4 151 7     tannin/(AETAC/AGE) 21.8    4.0 89 8     tannin/(AETAC/AGE) 35.5    3.4 583 9     tannin/(AETAC/AA) 35.6    3.2 754 10     tannin/AETAC      35.2    4.0 625 11     tannin/AETAC      33.3    4.0 323 12     tannin/AETAC      36.3    3.6 109 13     tannin/AETAC      36.4    3.6 204 14     tannin/AETAC      36.3    3.5 238 15     tannin/AETAC      31.2    1.8 173 16     tannin/AETAC      32.5    2.2 133 17     tannin/AETAC      33.2    2.3 148 18     tannin/AETAC      31.8    2.4 118 19     tannin/AETAC      33.5    2.8 180 20     tannin/AETAC      32.1    2.2 189 21     tannin/(AETAC/AM) 31.2    2.4 459 22     tannin/AETAC      37.2    2.2 1150 23     tannin/AETAC      38.2    2.5 407 Comparative: tannin/amine/formaldehyde 40.5    2.4   200 ______________________________________ AETAC = methyl chloride quaternary salt of dimethylaminoethyl acrylate AA = acrylic acid AGE = allyl glycidyl ether AM = acrylamide Comparative = polymer of U.S. Pat. No. 4,558,080, Example 1

To demonstrate the efficacy of tannin-based polymers for clarification of wastewaters, tests were conducted in the laboratory on several wastewater samples from different industries. Descriptions of the test substrates, test procedures and test results are given in the examples below.

Jar tests were conducted using a sample of oily wastewater from a Texas refinery as a test substrate. The clarity of the wastewater was determined by measuring the turbidity. Untreated the water had a turbidity of 32 ntu. Samples of untreated oily wastewater were placed in 400 ml beakers then treated with varying dosages of each coagulant. Coagulants evaluated included aluminum sulfate (as a Control treatment representing traditional technology) and solutions of the tannin-based polymers.

The following procedure was used for mixing each treated sample of oily wastewater: separation of oil; Model 18900 Ratio Turbidimeter.

Results of these tests are shown in Table III below. ______________________________________ Oily Wastewater Clarification Southwest Oil Refinery Poly- Resid- Dosage  mer   ual Exam-   (mg active 1115L Tur- Test Al2(SO4)3-14H2O ple     polymer/ (mg/  bidity #    (mg/liter)    No.     liter)  liter) (ntu) ______________________________________ 1   0             -       -       1.5   33 2   50            -       -       1.5   4.7 3   75            -       -       1.5   2.8 4   100           -       -       1.5   2.9 5   125           -       -       1.5   1.8 6   150           -       -       1.5   2.3 7   0             20      10      1.5   6.2 8   0             20      15      1.5   4.4 9   0             20      20      1.5   7.8 10   0             20      25      1.5   5.5 11   0             21      10      1.5   5.2 12   0             21      15      1.5   5.3 13   0             21      20      1.5   6.1 14   0             21      25      1.5   2.2 15   0             18      10      1.5   6.7 16   0             18      15      1.5   10.4 17   0             18      20      1.5   6.3 18   0             18      25      1.5   8.7 ______________________________________

As can be seen from the turbidity data, all three of the experimental polymers were capable of achieving significant improvements in the clarity of the oily wastewater. Of particular note was the polymer of Example 21, which reduced turbidity to 2.2 ntu at a dosage of 25 mg/l (Test #14). This treatment was comparable to the aluminum sulfate treatment at 125 mg/l which reduced residual turbidity to 1.8 ntu (Test #5). A comparison of the theoretical amounts of sludge solids that would be generated by these treatments indicates that 125 mg/l of aluminum sulfate would generate 65 mg/l of solids due to aluminum hydroxide precipitation while 25 mg/l of Example 21 would generate approximately 25 mg/l of solids. This represents a 62% reduction in waste sludge, a significant reduction that would result in substantial savings in sludge disposal costs for the waste treatment plant.

Jar tests were conducted using a sample of oily wastewater from an aluminum processing plant. The clarity of the water was determined by measuring the turbidity and oil content. Untreated, the wastewater turbidity was 71.6 ntu and the freon-extractable oil content was 252 ppm.

Samples of oily wastewater were placed in 400 ml beakers and treated with varying dosages of aluminum sulfate and Example 23. The following procedure, designed to simulate the mixing conditions in the full-scale waste treatment system, was used for the jar test evaluations. adjusted to 7.0 to 7.5 with NaOH) sec. @ 125 rpm; mixed 24 sec. @ 74 rpm; separation of oil; Analyzer.

Results of these tests are shown in Table IV below. ______________________________________ Oily Wastewater Clarification Aluminum Manufacturing Plant Supernatant Water Quality Resid- Example  Polymer ual   Resid- 23       1125L  Tur-  ual Test Al2(SO4)3-14H2O (mg/     (mg/   bidity Oil #    (mg/liter)    liter)   liter) (ntu) (ppm) ______________________________________ 1    0             0        4      75.5  60 2    50            0        4      39.2  140 3    100           0        4      21.4  42 4    150           0        4      10.7  24 5    200           0        4      11.6  37 6    250           0        4      10.2  50 7    0             100      4      38.3  36 8    0             200      4      15.2  44 9    0             300      4      12.8  30 ______________________________________

As can be seen from the turbidity and residual oil data, the tannin/AETAC copolymer of Example 23 treatments resulted in significant improvements in the clarity of this wastewater.

A sample of mixed liquor from a corn processing plant was used to evaluate the dewaterability of Example 23. Capillary Suction Times (CST) were used to assess performance. Untreated, the sludge contained 0.6% solids with a pH of 6.5. Varying polymer dosages were added to a 200 ml sample of sludge, the treated sludge was mixed for 30 seconds at 500 rpm, and then 7 ml aliquots were removed for CST analysis.

Results of these tests are shown in Table V below. ______________________________________ Corn Processing Plant Wastewater Dewatering Test         Example 23  CST #            (ppm product) (sec) ______________________________________ 1             0          157.1 2            250         63.8 3            500         46.3 4            750         49.9 ______________________________________

The data show that at a dosage of 500 ppm, CST drainage time was reduced by 70%, indicative of reasonable dewatering ability for the tannin/AETAC copolymer, Example 23.

Jar tests were conducted on a sample of wastewater from a municipal waste treatment plant that receives most of its wastewater from textile mills. This wastewater contained a high concentration of color, caused by dyes in the textile mill wastewaters. The concentration of contaminants in treated and untreated water samples was determined using a Perkin-Elmer Lambda 4B UV/VIS Spectrophotometer following the analytical procedure for color measurement recommended by the American Dye Manufacturer's Institute (ADMI). The ADMI color of the untreated wastewater was 434 ADMI units.

The tannin-based product evaluated in this example was Example 23. Aluminum sulfate was also evaluated as a control treatment representative of traditional coagulant technology.

The following procedure was used to evaluate the efficacy of the polymer and aluminum sulfate treatments: using 1".times.2" paddles; solids to settle; procedure.

Results of these tests are shown in Table VI below. ______________________________________ Textile Mill Wastewater Removal of Dye Chemical Treatment Additives Supernatant Water Test  Al2(SO4)3-14H2O Example 23 Residual Color #     (mg/liter)    (mg/liter) (ADMI color units) ______________________________________ 1     0             0          461 2     10            0          459 3     20            0          456 4     50            0          443 5     100           0          446 6     200           0          435 7     500           0          389 8     0             10         371 9     0             20         352 10    0             50         329 11    0             100        326 12    0             200        428 13    0             500        682 ______________________________________

As shown by the residual color data, tannin-AETAC copolymer Example 23 was capable of removing approximately 25% of the color from this wastewater. This was better than the removal achieved with aluminum sulfate.

Jar tests were conducted on a sample of wastewater from a municipal waste treatment plant that receives 80-90% of its wastewater from a textile mill. Analytical and jar test procedures were identical to those described in the previous test. Untreated, the wastewater had an ADMI color of 768. Products evaluated in this example included aluminum sulfate and Example 23. Test results are given in Table VII below. ______________________________________ Chemical Treatment Additives Supernatant Water Test  Al2(SO4)3-14H2O Example 23 Residual Color #     (mg/liter)    (mg/liter) (ADMI color units) ______________________________________ 1     0             0          754 2     10            0          773 3     20            0          774 4     50            0          752 5     100           0          696 6     200           0          620 7     500           0          698 8     0             10         721 9     0             20         720 10    0             50         565 11    0             100        320 12    0             200        240 13    0             500        179 ______________________________________

As the residual color data in this example indicate, the tannin/AETAC copolymer achieved significant reductions in the color of this wastewater, while aluminum sulfate achieved only slight reductions in color.

Jar tests were conducted on two samples of wastewater from a textile mill that treats its own wastewater. Analytical procedures and jar test procedures were again identical to those described in the previous test. The color of the untreated wastewaters were 619 for Sample A and 626 for Sample B.

Products evaluated in this example included aluminum sulfate and tannin/AETAC copolymer, Example 23.

Results of tests with both substrates are given in Tables VIII and IX below: ______________________________________ Textile Mill Wastewater Dye Removal Sample A Results: Chemical Treatment Additives Supernatant Water Test  Al2(SO4)3-14H2O Example 23 Residual Color #     (mg/liter)    (mg/liter) (ADMI color units) ______________________________________ 1     0             0          619 2     10            0          607 3     20            0          610 4     50            0          607 5     100           0          588 6     200           0          556 7     500           0          474 8     0             10         579 9     0             20         577 10    0             50         523 11    0             100        489 12    0             200        332 13    0             500        145 ______________________________________ ______________________________________ Textile Mill Wastewater Dye Removal Sample B Results: Chemical Treatment Additives Supernatant Water Test  Al2(SO4)3-14H2O Example 23 Residual Color #     (mg/liter)    (mg/liter) (ADMI color units) ______________________________________ 1     0             0          626 2     10            0          650 3     20            0          674 4     50            0          671 5     100           0          650 6     200           0          617 7     500           0          517 8     0             10         612 9     0             20         597 10    0             50         485 11    0             100        408 12    0             200        331 13    0             500        176 ______________________________________

As shown by the residual color data, tannin-AETAC copolymer achieved significant color removal from both samples of wastewater from this textile mill.

While this invention has been described with respect to particular embodiment thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.

## Claims

1. A method for removing contaminants from wastewater comprising adding to said wastewater a water soluble or dispersible copolymer of a tannin and a cationic monomer selected from the group consisting of methyl chloride or dimethyl sulfate quaternary salt of dimethyl aminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide, dimethylaminopropyl acrylamide, and diallyl dimethyl ammonium chloride.

2. The method as claimed in claim 1 wherein said cationic monomer is methyl chloride quaternary salt of dimethylaminoethyl acrylate.

3. A method for removing contaminants from wastewater comprising adding to said wastewater a water soluble or dispersible polymer of a tannin, a cationic monomer selected from the group consisting of methyl chloride or dimethyl sulfate quaternary salt of dimethyl aminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide, dimethylaminopropyl acrylamide and diallyl dimethyl ammonium chloride and at least one monomer selected from the group consisting of an anionic monomer and a nonionic monomer.

4. The method as claimed in claim 3 wherein said cationic monomer is methyl chloride quaternary salt of dimethylaminoethyl acrylate.

5. The method as claimed in claim 3 wherein said nonionic monomer is selected from the group consisting of acrylamide, methacrylamide, N-methylolacrylamide, N,N-dimethylacrylamide, vinyl acetate, methyl acrylate, ethyl acrylate, methyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, allyl glycidyl ether, and ethoxylated allyl ether of polyethylene glycol and polypropylene glycol.

6. The method as claimed in claim 5 wherein said nonionic monomer is acrylamide or allyl glycidyl ether.

7. The method as claimed in claim 3 wherein said anionic monomer is selected from the group consisting of acrylic acid, methacrylic acid, vinyl acetic acid, itaconic acid, maleic acid, allylacetic acid, styrene sulfonic acid, 2-acrylamido-2-methyl propane sulfonic acid, and 3-allyloxy-2-hydroxypropane sulfonic acid.

8. The method as claimed in claim 7 wherein said anionic monomer is acrylic acid.