CA2042162A1 - Cationic polymer for water clarification and sludge dewatering - Google Patents

Abstract

ABSTRACT
Methods of clarifying wastewater and of dewatering sludge are disclosed. The methods comprise adding to the wastewater or the sludge an effective amount for the purpose of a polymer comprising repeat unit moieties of methacryloyloxyethyl trimethyl ammonium chloride, said polymer having an intrinsic viscosity from about 1.0 to about 4.5 dl/g.

Description

~2~2 CATIONIC POLYMER FOR WATER CLARIFICATION
AND SLUDGE DEWATERING

FIELD OF T}IE INVENTION

The present invention pertains to the use of a particular water soluble cationic homopolymers of a specific intrinsic viscosity range for water clarification and for sludge dewatering.
The homopolymers are obtained from the polymerization of cationic monomers, namely quaternization products of dimethylamino-ethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate and N,N-dimethylpropyl methacrylamide.
BACKGROUND OF THE INVENTION

A difficult problem in industry is the clarification of industrial wastewaters. Much too often these waste waters contain finely di~ided solids and when allowed to flow into lakes and streams, add to water pollution.

It is highly desirable to remove these finely divided solids from industrial wastewaters so that these waters can be discharged into the environment without the risk of harmful pollution.

As detailed in Kirk-Othmer: Encyclopedia of Chemical Technology Volume 10, Third Edition, pages 489-5~3, clarification of an aqueous system suffering from finely divided solids consists of three distinct steps: coagulation, flocculation and sedimentation.

Coagulation is the process of neutralizing the charge on the suspended particles, allowing them to be brought together. Floccu-lation is the process of coagulating these neutralized particles to form an agglomeration. Lastly, sedimentation refers to the settling . , ~ ..: , ~ : ~ : , . :: : . :.
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of the coagulated particles which can then be removed by mechanical means if necessary.

Metal coagulants are often used to treat wastewaters but they can cause problems in pH control and carryover of metallic light flocs downstream. Polyelectrolytes are high molecular weight electrolytes in polymer form that do not have these limitations.

It has been found that certain water-soluble organic polymers with numerous sites for coagulation along the polymer chain allow for clarification of an aqueous based system.

The use of cationic polymers for wastewater treatment is known in the art. As cited in "Polyelectrolytes for Water and ~astewater Treatment" chapters 6 and 7 (W.L.K. Schwoyer, CRC Press, 1981), it is gcnerally believed that in settling and flocculation, there is a rela-tionship between molecular weight and effectiveness, with the higher molecular weight polymers of a given type being the most effective.

U.S. Patent 4,699,951 (Allenson, et al) discloses a combination of two cationic polymers with vastly different molecular weights for treating water contaminated with oily waste and dispersed solids. The application and method of treatment differ from the present invention in that it is a polymer admixture that is applied to the wastewater.
Other patents of interest include U.S. Patent Numbers 3,336,269 (Nonagle et al.) and 3,336,270 (Monagle). These disclosures pertain, inter alia, to preparatory routes for acrylamide type water soluble polymers in general and detail the preparation of acrylamidejvinyl quaternary ammonium salt copolymers, such as betamethacryloyloxyethyl-trimethyl ammonium methyl sulfate/acrylamide copolymers. Another patent related to the general field of flocculation is U.S. Patent 3,278,506 (Chamot et al.).

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~ 3 ~ ~ ~ ~2~2 In contrast to the prior art disclosures, we have found that a polymer oE methacryloyloxymethyl trimethyl ammonium chloride (METAC) is surprisingly effective in clarlfying water that has fine solids dispersed in it.

In the sedimentation step, the coagulated particles accumulate as sludge at the bottom of the vessels wherein the water clarification takes place, which sludge is generally removed continuously or at predetermined intervals. However, the sludge removed from the vessels contains large amounts of water and must be dewatered before disposal.

With the increasing concern over pollution problems, sludge dewatering has become an essential part of wastewater treatment pro-grams. No longer can untreated sludge simply be dumped into the nearest river, lagoon or vacant lot. With this environmental interest in mind, improved sludge concentrating and dewatering techniques have become an important task in the water treatment industry.

Generally, sludge is given primary dewatering treatment before belng discharged from any given process system. Primary dewatering is usually accomplished using thickeners/clar~fiers or settling ponds.
Secondary dewatering, including vacuum filtration, centrifugation, belt filters, lagoons, etc., is then commonly employed to further increase the solids content and reduce the water content in the resulting sludge to 50 to 90~ liquid. This can cause sludge dewatering to be a slow process.

In sludge handling ~acilities, problems often encountered in the dewatering process include the formation of sludge cake with high moisture content, poor cake release from dewatering equipment, high disposal costs, slow dewatering and poor equipment ef~iciency.

Improved sludge dewatering can lead to increased savings, especially with respect to the costs associated with transportation of the sludge to be disposed.

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Uater soluble polyelectrolytes, such as anionic and cationic polymers, are often added to the sludge to ald in the production of a drier cake and in the reduction of wear and tear on dewatering equipment.

As detailed in the Betz Handbook of Industrial Water Conditioning, 8th Edition, 1980, Betz Laboratories, Inc., Trevose, PA, pages 253-256, cationic polymers can increase the settling rate of bacterial floc. These polymers further improve capture of the dispersed floc and cell fragments. By concentrating solids more quickly, the volume of recycle flow can be minimized so that the oxygen content of the sludge is not depleted. Further, the waste sludge is usually more concentrated and will require less treatment for eventual dewatering.

U.S. Patent 3,023,162 (Fordyce, et al.) describes a homo-polymer of dimethylaminoethyl methacrylate quaternized with ethylene oxide or propylene oxide for dewatering. The precise structure of the resulting polymers after reaction is not identified. Polyalkylene oxide is usually formed from this type of reaction and may be attached to the amine site. This differs from the present invention in that the quaternization is achieved by the use of alkylene oxides.

U.S. Patents 4,319,013 and 4,396,752 (Cabestany et al.) teach that a cationic copolymer of acrylamide and quaternized dimethylamino-ethyl acrylate can be used for dewatering. The effective copolymer is in powder form and has an intrinsic viscosity higher than 6 dl/g. The present invention differs in that the polymer is a homopolymer in solution form having an intrinsic viscosity less than 6 dl/g. In con-trast to the Prior Art, this polymer shows an unexpected improvement in soluble dewatering.

U.S. Patent 4,395,513 (Haldeman) discloses the use of a cationic copolymer consisting essentially of acrylamide (10-20%) '' : . ' : ::: ` : : :: .:

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/N,N - dimethylaminoethyl methacrylate methyl chloride (90-80%) with a molecular weight about one million and an intrinsic viscosity of at least 5 dl/g for biological sludge dewatering. This patent also states that the copolymer performs better than the 100~ cationic homopolymer in the test conducted.

U.S. Patent 4,699,9Sl (Allenson et al.) discloses a combination of two cationic polymers with vastly different molecular weights for treating water contaminated with oily waste and dispersed solids. The application and method of treatment differ from the present invention in that it is a polymer admixture that is applied to the wastewater.

One problem with these anionic and cationic polymers is that their operating parameters are limited. The addition of too much of these dewatering agents can cause the solids to disperse and defeat the whole purpose of dewatering.

Uith the foregoing in mind, the present inventors embarked upon a comprehensive study in an attempt to dewater sludge in a more efficient fashion.
Accordingly, the present invention is directed to a process of clarifying wastewater by adding to water that has suspended solids present, a clarifying cationic homopolymer of a specific intrinsic viscosity and to the use of particular water soluble cationic homopolymers of a specific intrinsic viscosity range for sludge dewatering.
The cationic homopolymers comprise a repeat unit having the structure: . R
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C = O
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The water clarifying homopolymer is obtained from the polymerization of the cationic monomer, namely quaternization product of dimethylaminoethyl methacrylate and the homopolymers for sludge dewatering are obtained from the quaternization products of dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, dimethylaminoethyl acrylate, and N,N-dimethylpropyl methacrylamide.

DETAILED D~SCRIPTION OF THE INVENTION
In accordance with the invention, a cationic homopolymer comprising the polymerization products of ethylenically unsaturated cationic monomers such as quaternized dimethylaminoethyl methacrylate and dimethylaminoethyl acrylate, at an intrinsic viscosity range of 1.0 to 4.5 dl/g, preferably 1.0 to 4.0 dl/g, more prefera~ly 1.0 to 2.0 dl/g is unexpectedly effectiv~ in water clarification.
The cationic homopolymer which has proven to be most effective as a clarifying aid for water that has suspended solids ln it, comprises repeat unit moieties having the structure:

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C = O
o 2s CH3 - N~ ~ CH3 Cl- - -Furthermore, catlonlc homopolymers comprising the polymerizatlon products of ethylenically unsaturated cationic monomers such as quaternized dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, dimethylaminoethyl acrylate, N,N-dimethylpropyl methaerylamide, and N,N-dimethylpropyl acrylamide, etc. are unexpectedly effective in sludge dewatering at an intrinsic viscosity 35 range of 1.0 to 4.5 dl/g, preferably 1.5 to 4.0 dl/g, more preferably 1.5 to 2.0 dl/g.

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The described cationic monomers are obtained from a quater-nization reaction of the respective monomers with alkyl or aryl halides such as methyl chloride, methyl bromide benzyl chloride, or dimethyl sulfate. The resulting cationic monomers are then polymerized by conventional polymerization techniques. Any of the well known initiators such as azo compounds, peroxides, redox couples and persulfates may be used to polymerize the catlonic monomers.
Radiation, thermal or photochemical polymerization methods may also be used to yield the polymers. Likewise, for those skilled in the art, any method such as chain transfer agents, concentration, temperature and addition rate variations may be used to regulate the viscosity or molecular weight of the resulting polymers. The polymerization may be conducted in solution, suspension, bulk or emulsion. In the emulsion polymerization, a water-in-oil inverse emulsion technique as disclosed in U.S. Patents 3,284,393, Reissue 28,474 and Reissue 28,576 is preferred. The reaction will generally occur between 20 and 100C, pending the initiation system and polymerization medium used. The pH
of the reaction mixture is generally in the range of 2.0 to 7Ø
Higher pH will cause the hydrolysis of the cationic monomers.

The preferred method in accordance to the invention is to polymerize each cationic monomer in an aqueous medium using persulfate as an initiator at 80 to 95C and at a pH of 2.0 to 4Ø The desired viscosity of the polymer is regulated by adding a proper amount of persulfate, cationic monomer and water during polymerization. The resulting polymer is verified by viscosity increase, light scattering measurement and carbon 13 nuclear magnetic resonance (NMR) spectroscopy. Intrinsic viscosity of the polymer is measured in 1 M
sodium chloride solution at 30C. The Huggins equation is used to determine the intrinsic viscosity. According to established theory and equations in the art, intrinsic viscosity values can be correlated with the molecular weight of the polymer. A higher intrinsic viscosity of the polymer will represent a higher molecular weight.
This is illustrated in Billmeyer's "Textbook of Polymer Science" pages - . , ~.- ~ , , .: ~, , : ...... : - : , ;
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208 to 213 (1984). Intrinsic viscosity of the polymers in accordance with this invention is about 1.0 to ~l.5 dl/g, preferably 1.5 to 4.0 dl/g, more preferably 1.0 to 2.0 dl/g.

The poly~er for water clarification ls added to the selected substrate in an amount of about 1 to 50 ppnl active, preferably 2 to 10 ppm active. The polymer may be added to the substrate prior to entering the secondary clarifier, or to the clarifier centerwell.

The specific homopolymer which has proven to be most effective as a dewatering aid comprises repeat unit moieties having the structure r l 1 l- CH~ - C - J
C = 0 lH2 Ctl3 - N~- CH3 Cl wherein R is H or methyl.
The method of preparation of the homopolymer methacryloyl-oxyethyl trimethyl ammonium chloride (METAC) designated as Samp]e Number 1 in Table I is detailed below.

A suitable reaction flask was equipped with a mechanical agitator, a thermometer, a condenser, a nitrogen inlet and addition 30 inlets for reagents. The flask was charged with 40.0 g of 75~ METAC
and 20 g of deionized water. The resulting solution was heated to 90C under a nitrogen ~lanket. An initiator solution containing 0.5%
of sodium persulfate in deionized water was prepared separately and sparged with nitrogen. The initiator solution (7.5 g) was then added 35 to the reaction flask over 270 minutes at 90C. Three 20 g aliquots of deaerated, deionized water were added to the reaction at the 30, 90 , :

2~2~
g and 210 minute addition intervals. The reaction was held at temperature for 60 minutes followed by the addition of 120 g of deionized water. After mixing at 90C for another 30 minutes the reaction mixture was cooled to room temperature.

The homopolymer solution, after being diluted to 10.6% solids, had a Brookfield viscosity of 1160 cps. The resulting product was a clear solution with a pH at 3.3. The structure of the polymer was verified by C 13 NMR. Tlle structure was characteri~ed by a broad polyacrylate type backbone and no evidence of unreacted monomer.
Intrinsic viscosity of the polymer was 1.5 dl/g as measured in 1 M
sodium chloride solution at 30 C.

The polymer is added to the sludge to be treated in an amount of about 80 to 600 ppm active, preferably 100 to 350 ppm active.
These dosages correspond to about 5 to 40 pounds active polymer per ton of dry sludge, based on an average sludge solids of 3~. The polymer may be added directly to the sludge after it has been clarified.
The polymer may also be added after the sludge has been subjected to a thickener, digester or the like. The polymer may also be added to the sludge prior to other dewatering processes such as belt filters, vacuum filters, centrifuges or lagoons.
Compounds such as alum, ferric chloride, anionic polymers such copolymers of acrylamide with acrylic acid, 2-acrylamido-2-methylpropylsulfonic acid or styrene sulfonate etc., and other cationic polymers for example, polydimethyldiallyl ammonium chloride (DMDAC); condensation product of epichlorohydrin with alkylamines;
copolymers of acrylamide with DMDAC, methacryloyloxyethyl trimethyl ammonium methacrylate (METAMS), methacrylamido propyltrimethyl ammonium chloride, (MAPTAC), acrylamido propyltrimethyl ammonium chloride (APTAC), acryloyloxyethyl trimethyl ammonium chloride (AETAC), methacryloyloxyethyl trimethyl ammonium chloride (METAC), "" ~ "

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acryloyloxyethyl diethylmethyl ammonium chloride or their methyl sulfate quats may be used in conjunction with the polymers in this invention for sludge dewatering or for water clarification.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings graphically present the data generated by the examples which are reported hereinbelow. In the Drawings:

Figure #l is a graph showing the settling rate versus the dosage of samples tested in Table I.

Figure #2 is a graph showing the compaction rate versus the dosage of samples tested in Table I.

Figure #3 is a graph showing the supernatant turbidity versus the dosage of samples tested in Table I.

Figure #4 is a graph showing the settling rate versus the dosage of samples tested in Table II.

Figures #5 is a graph showing the comparison rate versus the dosage of samples tested in Table II.
Figure #6 is a graph showing the supernatant turbidity versus the dosage of samples tested in Table II.

Figure #7 is a graph showing the capillary suction time of various conditioned samples tested in Table III.
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Figure #8 is a graph showing the capillary suction time of other conditioned samples tested in Table III.

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Figure #lo is a graph showing the percent solids captured of conditioned samples tested in Tables IV and V.

Figure #11 is a graph showing the percent caked solids of conditioned samples tested in Table VI.

Figure #12 is a graph showing the percent solids captured of conditioned samples tested in Table VI.

Figure #13 is a graph showing the percent cake solids of conditioned samples tested in Table VI.
Figure #14 is a graph showing the percent solids captured of conditioned samples tested in Table VI.

Figure #15 is a graph showing the percent cake solids of conditioned samples tested in Table VII.

Figure #16 is a graph showing the percel~t solids captured of conditioned samples tested in Table VII.

EXAMPLES
The following examples are illustrative only and should not be construed as limiting the invention.

Water Clarification Example 1 Preparation of Methacryloyloxyethyl Trimethyl Ammonium Chloride Homopolymer (METAC) , , ., , ~" , :,, . ~ :
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':. : , ~2~2 To a suitable reactor was charged 339 parts of METAC (75~), 501.5 parts of deionized water and 8.0 parts of ethylene diamine tetraacetic acid solution (6.25%, disodium salt). The reactor was purged with nitrogen and the solution was then heated to 190F. 41.22 parts of a 0.81~ sodium persulfate solution was then added to the solution over three hours at 190F. After that, the resulting viscous solution was diluted with water and cooled down.

The final product was a clear solution with a p~l of 2.92 and a 10 Brookfield viscosity of 9,020 cps (20.2% solids). No residual monomer was detected by carbon 13 nuclear magnetic resonance measurement. An intrinsic viscosity of 1.8 was measured in 1 M sodium chloride solution at 30C.

Table A below presents a summary of the physical properties of the resulting polymer.

TABLE A
Polvmetac Properties Brookfield Viscosity, Intrinsic 25Example% Solids cps, at 25C ~ Viscositv. dl/~

1 20.2 9,020 2.92 1.8 Comparative clarifying tests were also performed using well-~nown cationic polymers described in the prior art. Their properties are described in Table B.

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TA~LE B
Comparative Polymers 5 Comparative Intrinsic Viscosity Polymer Desi~nation Description dl/g A Polydimethyldiallyl 0.8 Ammonium Chloride BEpichlorohydrin/Dimethyl 1.0 Amine CYLINDER SOLIDS SETTLING TEST
The secondary clarification activity of the proposed invention was evaluated by conducting cylinder settling tests with aeration basin effluent obtained from two sources in the Midwestern United States, one chemical and one plastics manufacturer. Substrate used for conducting the cylinder settling tests at each test site was diluted to eliminate cylinder wall effects on settling and compaction rates. For the tests conducted with the substrate from the plastics manufacturer, the dilutions were made with water at a ratio of 1:1.
The substrate obtained from the Chemical Manufacturing facility was diluted 1:3 with the plant's tertiary effluent.

The use of effluent from the waste treatment system for dilution is preferable to tap water since it will affect the least change on test substrate behavior. Treatment performance was evaluated based on solids settling and compaction rates as well as final supernatant turbidity valves. ~le solids settling results would be analogous to the rate at which the solids would separate from the waste stream upon entering the secondary clarifier.

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, . : -:: ' ' .: ' ` 2~2~2 The solids compaction results are an indication of how dense the sludge bed in the secondary clarifier would become with the use of a particular treatment. Supernatant turbidity values would also indicate the performance of the treatment with respect to final secondary clarifier effluent.

Letters A and B represent the comparative polymer results while number l represents the homopolymer of the present invention.

The results of these tests appear in Table I and II.

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C~linder Solids Settling Test Results Substrate Source: Mid-West Chemical Manufacturer Substrate: Aeration Basin EfEluent Substrate Suspended Solids: 5,740 ppm Substrate p~l: 6.42 Substrate Volume: 500 m~ 0 Test Procedure: Premix substrate by inverting sample 3 times.
Add treatment and invert sample 5 times.
Record time for solids interface to travel between the 450 and 300 mL graduations for determining settling rate. Record time for solids interface to travel between the 300 and 200 mL graduations for determining solids compaction rate.
Supernatant Turbidity values were measured after completion of the settling and compaction rate tests.

Dosage Settling Compaction Supernatant Treatment (ppm. active) ~ CC~ Rate mm/sec Turbiditv tNTU) "A" 0.38 1.49 1.05 20.0 0.76 1.87 1.15 13.2 0.95 2.32 1.05 12.6 1.14 2.49 1.25 14.0 1.52 2.23 1.43 26.0 "B" 1.00 2.00 1.40 17.0 2.00 2.67 1.89 12.6 2.51 3.26 2.35 12.0 3.01 3.83 2.79 12.8 4.01 4.00 3.08 13.0 "1" 0.42 1.82 1.28 15.0 0.84 2.51 1.71 10.5 1.06 2.93 2.28 10.2 1.27 3.47 2.55 10.0 1.69 3.83 2.45 9.0 , , , . ~ . ~:: :

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Cylinder Solids Settling Test Results Substrate Source: Mid-West Chemical Manufacturer Substrate: Aeration Basin Effluent Substrate Suspended Solids: 2,650 ppm Substrate p~l: 7.66 lO Substrate Volume: 500 mL
Test Procedure: Premix substrate by inverting sample 3 times.
Add treatment and invert sample 5 times.
Record time for solids interface to travel between the 450 and 300 mL graduations for determining settling rate.
Record time for solids interface to travel between the 300 and 200 mL graduations for determining solids compaction rate.
Supernatant Turbidity values were measured after completion of the settling and compaction rate tests.

DosageSettling Compaction Supernatant Treatment(ppm, active) Rate mm/sec Rate mm/sec Turbidity (NTU) "A" 0.19 0.70 0.35 4.4 0.57 0.98 0.38 2.2 0.76 1.40 0.49 2.4 0.95 1.60 0.56 2.5 1.33 1.76 0.58 2.8 1.71 2.20 0.63 3.8 "B" 0.502 1.22 0.52 7.9 1.506 2.45 1.59 3.8 2.510 4.53 2.83 4.1 3.514 6.38 3.61 4.4 4.518 6.29 3.67 5.1 "1" 0.212 1.28 0.44 2.~l 0.636 1.91 0.67 2.6 0.84~ 2.43 0.91 2.5 1.060 3.39 1.59 2.7 1.484 3.67 1.42 5.0 " ; . : : :: :
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- 17 - ~ 2 The examples demonstrate that the METAC exhibits surprlsingly superior performance when compared to the conventional or well known polymers as described in the prior art. This polymer promotes faster settling rates and compaction rates which have both economic and environmental benefits.

It would be expected that the dimethyl sulfate quat of dimethylamino ethylacrylate homopolymer should perform similarly to the described polymer.
Sludge Dewaterin~

SA~PLES

15 Homopolymers of (meth)acryloyloxyethyl trimethyl ammonium chloride were prepared in aqueous solution using sodium persulfate as an initiator at 80 to 95C. A proper amount of water was added during the reaction to regulate the desired viscosity (molecular weight) of the product. No residual monomer was detected by carbon 13 nuclear magnetic resonance measurement. Intrinsic viscosity of the polymer was measured in lM sodium chloride solution at 30C.

Table I below presents a summary of the physical properties of the resulting polymers produced by the above method.

TABLE C
Polymetac Properties Brookfield Intrinsic Viscosity, Viscosity, Sample Number Composition % Solids cps. at 25C pH dl/~
1 (1555-43) METAC 10.6 1160 3.3 1.5 2 (1555-45) AETAC 9.9 1444 2.9 1.7 3 ~1577-32) METAC 9.6 12040 3.2 2.9 4 (1485-281) METAC 3.5 114 3.5 0.86 METAC = methacryloyloxyethyl trimethyl ammonium chloride AETAC = acryloyloxyethyl trimethyl ammonium chloride ,, ,, , .................... -,., - , , ...... , -., .

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~2~2 Comparative dewatering tests were also performed using the well-known polymers described in the prior art. These are described in Table II.

TABLE D
Comparative Pol~mers Intrinsic 10 Polymer Description Viscositv. dl/g A Copolymer of acrylamide/metac 8.9 B Polymetac 5.4 C Polydimethyldiallyl Ammonium Chloride 1.4 D Polydimethyldiallyl Ammonium Chloride (DMDAC) 0.8 E Polydimethyldiallyl Ammonium Chloride (DMDAC) 1.5 ~EWATERING ACTIVITY TEST
The relative dewatering performance of the polymers was evaluated by two different test methods, capillary suction time (CST) and a laboratory belt filter press. Mixtures of primary and secondary sludge from a pharmaceutical plant in New Jersey taken on four different dates were used for evaluation.

In the CST test, an aliquot of sludge is placed in a cylindrical cell which is placed on top of a piece of chromatography paper. The capillary pressure exerted by the paper draws the water out of the sludge. A timer records the time in seconds required for the water to pass between two fixed points. Shorter times indicate better dewater-ing efficacy. Results are evaluated by preparing a graph of CST
versus treatment dosage. Generally, the treatment which produces the lowest CST value at the lowest dosage is the most effective. The lowest CST value at the lowest dosage is the most effective. The results appear in Figures 1 and 2 and the data used to generate these figures is found in Table III. Letters A through E represent the ,: , , ~ , .::
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2 ~ ~ 2 comparative polymer results, while numbers 1 through 4 represent the homopolymers of the present invention.

A Larox laboratory scale belt filter press was the second method employed to evaluate polymer dewatering performance. The design of this instrument permits modeling of full-scale belt filter press operations by adjustment of conditions such as solids loading, filter media, free drainage time, pressure and press time. The sludge cake produced from the laboratory scale belt filter press is analyzed for percent solids and percent solids capture, with solids capture being defined as the quantity of solids retained by the belt filter media compared to the quantity of solids loaded on the press. Results are evaluated by plotting percent solids and percent solids capture results versus treatmer.t dosage. Higher values of percent sludge cake solids and percent solids capture indicates a higher degree of dewatering and better treatment performance. Dosages for conducting evaluations on the laboratory belt filter press were selected based on the results of the CST tests. Sludge characteristics and test conditions are described in the Tables below. The results have been plotted and appear in Figures 3 to 10. Data used to generate the graphs is presented in Tables IV to VII. Letters A through E
represent the comparative polymer results, while numbers 1 through 4 represent the homopolymers of the present invention.

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Test Conditions Substrate Volume: 200mI.
" Solids: 2.85 " pH: 6.90 Treatment mixing: 5 seconds @ 550RPM prior to treatment addition 30 seconds @ 550RPM after treatment addition TABLE III
Ca~il]arv Suction Time (Seconds~:
Polymer Dosage Treatment:
(ppm, active) _ B C #3 #1 D #2 246.7 144.5 2050 143.5 60.6 304.35114.7 13.7 93.2 54.3 10.8 175.9026.0 100 84.2 64.5 52.9 22.2 6.4 44.6013.7 115 10.2 25120 62.2 125 54.3 30.4 28.6 9.5 6.8 135 22.7 7.0 23.3 150 8.2 8.0 7.3 6.9 8.0 175 7.9 12.8 13.4 7.3 30200 18.4 19.6 23.7011.5 225 25.7 29.2 250 15.908.1 300 10.308.3 350 8.4 35400 8.50 8.0 500 8.4 600 10.55 700 9.5 800 16.9011.6 :: . , ; . ::~ .: . :
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- 21 - 2~21~2 Substrate Solids: 2.79%
" pH: 6.53 Loading Rate: 2~188XlOE-02 grams/cm2 Cycle: 20 seconds of Free Drainage 40 seconds @ 40 psig Belt Cloth: Parkson P-28S (smooth side used for contact with sludge) Blank - no cake formed Treabnent mi~in~: 5 seconds @ 550RPM prior to treatment addition 30 seconds @ 550RPM after treatment addition.

TABLE IV
Laboratorv Scale Belt Filter Press Tests Polymer Dosage Percent Percent Treatment (ppm. active~Cake Solids Solids CaPture A 100 4.85 13.94 150 5.19 21.00 , 200 7.02 36.36 250 8.30 55.00 350 7.99 53.00 D 50 5.04 7.31 100 5.23 11.63 300 8.15 39.86 450 8.77 46.09 600 7.96 44.80 B lOO 4.95 16.47 150 7.15 24.00 200 8.48 39.00 250 9.75 53.50 350 10.21 60.80 C 100 5.49 13.85 125 5.57 18.60 150 5.95 21.50 200 7.06 30.59 300 7.58 41.90 .

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- 22 - 3~}~21~2 TABLE IV (Cont'd~
Laboratorv Scale Belt Filter Press Tests Polymer DosagePercent Percent Treatment(ppm. active)Cake Solids Solids Capture #3 75 5.20 13.28 125 6.25 20.25 150 7.11 27.99 200 9.31 55.35 300 10.15 70.34 #1 50 5.82 17.91 6.90 32.40 lO0 8.60 46.36 150 9.58 57.63 200 9.32 54.16 #2 100 5.73 14.91 150 6.15 21.20 250 ~.01 30.60 350 8.56 43,40 500 9.49 54.66 , ' ': ., ' , , - ' :', ' `: ',: ' ~ ' " . . ' ' `' ;, ' .' : ,: .

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Substrate Solids: 2.71%
Substrate pH: 6.85 Loading Rate: 2.188XlOE-02 grams/cm2 Cycle: 20 seconds of free drainage 40 seconds @ 100 psig Blank - no cake formed Treatment mixing: 5 seconds @ 550RPM prior to treatment addition 30 seconds @ 550RPM after treatment addition.

TABLE V
Laboratory_Scale Belt Filter Press Tests Polymer Dosage Percent Percent Treatment ~ppm active~ Cake Solids Solids Capture C 100 5.671 28.98 150 6.893 34.24 185 7.712 42.63 200 8.164 45.68 250 8.824 52.64 300 10.851 66.05 #4 100 6.757 30.69 150 6.950 34.20 185 7.311 40.01 200 7.510 45.20 250 7.965 47.90 300 8.850 51.15 #1 100 6.367 34.94 150 8.038 49.94 185 9.491 58.57 200 9.702 63.82 250 10.490 58.71 300 11.168 72.49 B 100 6.548 32.41 150 8.707 55.99 185 9.860 67.30 200 10.900 75.72 250 11.850 82.10 300 12.030 82.03 .
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- 24 - ~ ~3 ~ 2 Substrate Solids: 2.71 Substrate pH: 6.85 Loading Rate: 2.188XlOE-02 grams/cm2 Cycle: 20 seconds of free drainage 40 seconds @ 90 psig Blank - no cake formed Treatment mixing: 5 seconds @ 550RPM prior to treatment addition 30 seconds @ 550RPM after treatment addition TABLE VI
LaboratorY Scale Belt Filter Press Tests Polymer Dosage Percent Percent Treatment(ppm. active) Cake Solid~ Solids Capture D 50 5.179 14.39 100 5.867 27.14 200 7.844 45.12 450 11.840 75.89 C 50 4.769 15.29 100 6.519 25.69 200 9.250 53.34 450 12.160 79.99 E 50 5.382 16.88 100 6.280 31.86 200 8.450 49.96 450 12.560 86.68 #1 50 5.356 20.58 100 7.629 40.56 200 10.684 72.64 450 12.960 97.75 #2 50 4.853 16.10 100 7.130 35.69 200 9.450 57.23 450 ll~.060 95.59 ' . ' ' , :. ' ~ ' ' ' ~

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Substrate Solids: 2.71%
Substrate p~: 6.85 Loading Rate: 2.188XlOE-02 grams/cm2 Cycle: 20 seconds of free drainage 40 seconds @ 100 psig Blank - no cake formed Treatment mixin~: 5 seconds @ 550RPM prior to treatment addition 30 seconds @ 550RPM after treatment addition T~BLE VII
LaboratorY ScaLe Belt Filter Press Tests Polymer Dosage Percent Percent Treatment (ppm. active~ Cake Solids Solids Capture D lOO 5.883 19.83 150 6.822 32.85 185 7.610 36.25 200 7.953 38.02 250 8.120 38.35 C 100 5.915 24.20 150 7.138 36.58 185 7.575 43.90 200 8.180 47.80 250 9.386 54.34 30 E lOO 6.257 26.28 150 7.280 38.50 185 8.312 48.26 200 8.601 52.79 250 9.687 62.23 #1 lOO 6.889 40.71 150 8.673 47.55 185 10.253 60.03 200 10.85~ 66.35 250 11.675 75.50 .~ , , , . - . ~ : ~ . .-- : :
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TABLE VII (Cont'd) Laboratory Scale Belt Filter Press Tests Polymer Dosage Percent Percent Treatment (ppm. active) Cake Solids Solids Capture #2 100 6.013 29.39 150 7.867 43.28 185 9.389 52.56 200 10.106 54.95 250 11.762 67.45 15 The examples demonstrate that the polymers in this invention exhibit surprisingly superior performance when compared to the conven-tional or well known polymers as described in the prior art. The polymers according to the invention promote higher cake solids in the sludge dewatering tests which have both environmental and economical benefits. They also have a wider effective dosage range as compared to the prior art polymers making it easier to control the polymer dosage in a treatment plant.

In accordance with the patent statutes, the best mode of practicing the invention has been herein set forth. However, it will be apparent to those skilled in the art that many modifications can be made in the methods herein disclosed without departing from the spirit of the invention.

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Claims (18)

1. Method of clarifying aqueous fluid suspensions of finely divided solids comprising adding to said aqueous fluid suspensions an effective amount for the purpose of a homopolymer, said homopolymer comprising repeat unit moieties having the structure:

and having an intrinsic viscosity from about 1.0 to about 4.5 dl/g.

2. Method as claimed in claim 1 wherein said homopolymer has an intrinsic viscosity from about 1.0 to about 2.0 dl/g.

3. Method as claimed in claim 1 wherein said homopolymer has an intrinsic viscosity of between about 1.5 and 2.0 dl/g.

4. Method as claimed in claim 1 wherein said homopolymer has an intrinsic viscosity of about 1.8 dl/g.

5. Method as claimed in claim 1 wherein said suspension is a wastewater system.

6. Method as claimed in claim 1 wherein said homopolymer is added to said aqueous fluid suspensions in an amount from about 1 to 50 parts per million of said aqueous fluid suspensions.

7. Method as claimed in claim 1 wherein said homopolymer is added to said aqueous fluid suspensions in an amount from about 2 to 10 parts per million of said aqueous fluid suspensions.

8. Method of treating aqueous sludge comprising adding to said sludge an effective amount for the purpose a homopolymer, said homopolymer comprising repeat unit moieties having the structure:

wherein R is H or methyl and having an intrinsic viscosity from about 1.0 to about 4.5 dl/g.

9. Method as defined in claim 8 wherein said homopolymer has an intrinsic viscosity from about 1.0 to about 2.9 dl/g.

10. Method as defined in claim 8 wherein said homopolymer has an intrinsic viscosity from about 1.5 to about 2.0 dl/g.

11. Method as defined in claim 8 wherein R is H.

12. Method as defined in claim 8 wherein R is methyl.

13. Method as defined in claim 8 comprising adding said homopolymer to said sludge in the amount of about 5 to about 40 pounds active polymer per ton of dry sludge.

14. Method as defined in claim 8 wherein said treating aqueous sludge further comprises processing said sludge in a belt filter mechanism.

15. Method as defined in claim 8 wherein said treating aqueous sludge further comprises processing said sludge in a vacuum filter mechanism.

16. Method as defined in claim 8 wherein said treating aqueous sludge further comprises processing said sludge in a centrifuge.

17. Method as defined in claim 8 wherein said treating aqueous sludge further comprises processing said sludge in a lagoon.

18. Method as defined in claim 8 wherein said treating aqueous sludge further comprises processing said sludge in a waste water treatment system.