CA1236939A - Dewaterability of alum sludges using high molecular weight anionic terpolymer flocculants - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method for dewatering alum sludges obtained from waste water treatment processes which comprises treating said sludges prior to or during their formation with a water-soluble anionic polymer of acrylamide and/or acrylic acid with 2-acrylamido methyl propane sulfonic acid (AMPS), said polymer having a molecular weight of at least 5 million.

Description

Many industrial and municipal wastes are clarified using flocculants and coagulants. In certain processes these wastes are treated with alum or other metal salts such as iron salts. These materials tend to produce voluminous sludges, which are difficult to handle and to dewater by mechanical means such as filters, centrifuges, filter presses, and the like.
It is common practice today to use high molecular weight anionic polymers such as sodium polyacrylate or acrylamide-sodium polyacrylate copolymers to improve the density of these sludges, thereby increasing the water removal efficiency when they are subjected to mechanical dewatering.
If it were possible to provide an improved polymeric material which would have the ability to treat alum and other metal salt produced sludges to render them more dense and more susceptible to mechanical dewatering operations, an advance in the art would be made.
This invention provides an improvement in waste water treatment processes whereby such alum sludges may be more readily dewatered mechanically. Thus in its broadest aspect this inven-tion provides a method for dewatering alum sludges obtained fromwaste water treatment processes which comprises treating said sludges prior to or during their formation with an anionically charged water-soluble polymer of 2-acrylamido methyl propane sulfonic acid (AMPS) copolymerized with at least 1 monomer selected from the group consisting of acrylamide and acrylic acid or water-soluble alkali metal salts thereof, said polymer having a molecular weight of greater than 5 million, and being further 12369;~9 characterized as containing between 60-98% by weight of acrylamide and/or acrylic acid and between 2-30% by weight of AMPS. Prefer-ably these polymers have molecular weights greater than 5,000,000 and, most preferably, greater than 10,000,000. Preferred composi-tions include a copolymer of AMPS with acrylamide and terpolymers of AMPS with acrylamide and acrylic acid.
These polymers are far more effective as sludge dewater-ing flocculants than the high molecular weight sodium polyacrylate materials described above.
To illustrate the advantages of using the invention, Table I is set forth below.

. _~
O In l 1 1 0 1 0 _, . .
I; I, . Ul t, O O 1`
g NUl l ED
N ED N O Of O l l l ooooo I O O O O O
H do I_I~`1 ') En ~31 Z I I
do o l oooooo H ~9 0 0 0 0 0 H ED 6~ CO 1` 1-- 1`
O
06~ 0 0 0 O
o u n l O
O _~
dP H
H H H
H H H H

O O O O O O
U~,)C.) C)C

~23~939 In the Table above, the percent polymer indicates the amount of polymer present in the composition being tested;
AcAm is acrylamide;
NaAA is sodium acrylic acid;
RSV is reduced specific viscosity and is a known method of characteri7ing the molecular weight of water-soluble polymers;
Spc Drn refers to the specific drainage characteristic of the sludge being treated. This is a test method which is described below.
Specific drainage is calculated from Buchner funnel test results by dividing the volume of filtrate at 30 seconds by the pounds of active polymer per ton of sludge solids. In the Buchner funnel test, a diluted polymer solution is mixed with 200 milli-liters of sludge, then the conditioned sludge is poured into a Buchner funnel and the volume of water drained from the sludge is measured at 15-second intervals.
RR means replacement ratio. This refers to the amount of material required to produce a result comparable to that obtained with a standard polymeric treatment.
In the above, Composition 1 is a high molecular weight commercial sodium polyacrylate having a molecular weight slightly greater than 10 million. It was used as a standard in the tests.
The amount of polymers that may be used vary over a wide range. A typical dosage is 5 to 50 pounds per ton of active poly-mer based on the weight of the sludge. Preferably, 10 to 20 pounds per ton are used.

123~939 A convenient form in which to use the polymers and to prepare them is described in Anderson/Frisque, United States Re.
28,474 and Re. 28,576. Basically, the monomers are polymerized in the form of a water-in-oil emulsion as described in Vanderhoff, United States 3,284,393. These emulsions are then capable of being inverted into water to produce rapidly solutions of the polymers.
It is understood that dry polymeric substances may also be used in the practice of the invention.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for dewatering alum sludges obtained from waste treatment processes which comprises treating said sludges prior to or during the formation with an anionically charged water-soluble polymer containing, on a weight percent basis, from 2-30% of 2-acrylamido methyl propane sulfonic acid and from 70-98% of a mono-mer selected from the group consisting of acrylamide and/or acry-lic acid or water-soluble alkali metal salts thereof, said polymer having a molecular weight of at least 5 million.

2. The method of Claim 1 wherein the polymer is a terpoly-mer of 2-acrylamido methyl propane sulfonic acid, acrylamide and acrylic acid or water-soluble alkali metal salts thereof having from 2-30 weight percent of 2-acrylamido methyl propane sulfonic acid.

3. The method of Claim 1 wherein the polymer is a copoly-mer of 2-acrylamido methyl propane sulfonic acid and acrylamide, said polymer having from 2-30 weight percent of 2-acrylamido methyl propane sulfonic acid.