JPH0231900A - Treatment of sludge - Google Patents

Abstract

PURPOSE:To make flocks large and to reduce the water content of a cake by adding an amphoteric polymer flocculant consisting of a cationic monomer and an anionic monomer or a nonionic monomer to sludge and by subjecting the sludge to pH adjustment, flocculation and dehydration. CONSTITUTION:A cationic monomer such as dimethylaminoethyl methacrylate is copolymerized with an anionic monomer such as acrylic acid or a nonionic monomer such as acrylamide to obtain an amphoteric polymer flocculant having 4.05-5.50meq/g cation equiv. Cv, 0.15-2.35meq/g anion equiv. Av, 1.7-36.7 ratio of Cv to Av and 3-15dl/g intrinsic viscosity [eta] in 1N NaNO3 soln. at 30 deg.C. The flocculant is added to sludge and this sludge is adjusted to 6.0-10pH, flocculated and dehydrated. Flocks become large and hard and have superior dehydratability and filterability, so the water content of a dehydrated cake is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for treating sludge generated in various industrial wastewater, sewage, human waste treatment, etc. using an amphoteric polymer flocculant.

[Prior Art] The surface potential of sludge generated in various types of industrial wastewater, sewage, and human waste is negatively charged, and it is known that a cationic flocculant with a counterion is effective for sludge treatment. However, the required dewatering performance (recovery rate of suspended solids, moisture content of dehydrated cake) and productivity (separability in belt press dehydration, water repellency in various dehydrators), etc. are insufficient. In order to improve the performance, a method using a mixture of a powdered anionic polymer flocculant such as polyacrylic acid (salt) and a powdered cationic polymer flocculant mixed with an acid (Japanese Patent Application Laid-open No. 58-215454 ), amphoteric polymer electrolytes containing quaternary cationic groups and nonionic amine groups in the molecule (4-'F 149292/1989), and tertiary amine groups as cationic groups in the molecule. 1, 0-4,
0meq/g, anionic group 0.3-2.0meq
/g, and a method for producing an amphoteric polymer flocculant having a ratio in the range of 1.5 to 8.0 (Japanese Patent Application Laid-open No. 205112/1983) has been proposed.

[Problems to be Solved by the Invention] However, in these methods, the aqueous solution to be dissolved during use must be in a strong acid.

Normally, sludge from various industrial wastewater, sewage, and human waste has less than neutral P.
Even if an amphoteric polymer flocculant in the form of a strongly intoxicated aqueous solution with an H value of 0 is used for these sludges, the pH of the sludge will further decrease, and the anionic group monomer in the amphoteric polymer a flocculant will It is not an ionization tendency.

In other words, even if it is a monoampholytic compound, even if it exhibits the activity behavior of a cationic group monomer, it does not exhibit the activity behavior of an anionic monomer. In particular, cationic intermediate (1), anionic monomer (
The activity behavior differs depending on the composition combination of the nonionic monomer (m) or the nonionic monomer (m).

[Means for solving the problem] In order to efficiently demonstrate the various properties of an amphoteric polymer flocculant that has a cationic group, anionic group, or nonionic group in its molecule, various properties were studied in detail. As a result, these amphoteric polymer flocculants have different dependencies depending on the composition combination of cationic monomers, anionic monomers, or nonionic monomers, depending on the pH of the material to be treated such as sludge, and it is difficult to obtain the appropriate composition. combination, and found that in the pH range of sludge 1
This has led to the present invention. That is, 2 the present invention is a strong acid salt monomer (1) of dimethylaminoethyl acrylate or dimethylaminoethyl methacrylate, 1 selected from acrylic acid, methacrylic acid, and salts thereof.
, GTi or higher monomer (■), or the monomer (1
), the rH mer (II) and acrylamide (m)
It is a polymer composed of, and has a cation output value Cv of 4.
05 to 5.50 m eq / g, anion equivalent value Av of 0.15 to 2, 35 m eq / g, and a ratio of Cv / Av of 1.7 to 36.7, Intrinsic viscosity [η]1N-N aNo g (30
The present invention provides a method for treating sludge, which comprises adjusting the pH of the sludge to 6.0 to 10 using an amphoteric polymer flocculant of 3 to 15 dl/g, followed by flocculation and dewatering.

In the present invention, as the monomer (I) of the cationic component, dimethylamine ethyl methacrylate or a strong acid salt of dimethylaminoethyl acrylate is used.
, tertiary salts such as dimethylaminopropyl (meth)acrylate, or quaternary ammonium-based amphoteric polymer flocculants are not preferred because they have significantly poor cake dehydration performance.

The anionic monomer (II) is acrylic acid.

Alternatively, methacrylic acid or a salt thereof is used, and the salt used is an alkali metal salt such as sodium or potassium.

The monomer (IT) is the above-mentioned ? In copolymerization with Ii-mer (I) or acrylamide (m), it was selected in consideration of pH dependence, and in compositions outside the scope of the present invention, p
In the treated liquid (sludge or suspended water) of H6.0 to 10, the presence of anionic species was not substantially confirmed, and excellent effects could not be obtained.

Acrylamide is selected as the nonionic monoabrasive material in the present invention. Others, such as methacrylamide,
N,N-dimethylacrylamide N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,
N-diethylmethacrylamide and the like cannot exhibit the modest effects of the present invention.

Generally, sewage sludge has a pH value below neutrality, and in this case, even if an amphoteric polymer flocculant manufactured under strong acidity is used for sludge or other materials to be treated. , P) of the entire system, and within this desired range, the dissociation of the carboxyl group of the anionic monomer is inhibited and the excellent effects of amphoteric properties cannot be exhibited.

In addition, the present invention adjusts the pH of the material to be treated to a range of 6.0 to 10, and flocculates it with the amphoteric polymer flocculant according to the present invention.
4. Dehydrate. +i sign. When it is lower than this range, dissociation of the carboxyl group of the anionic monomer is inhibited. Further, if the amount is higher than the above range, the activity of the cationic monomer is inhibited, and a sufficient effect as an amphoteric polymer flocculant cannot be expected.

In the amphoteric polymer flocculant according to the present invention, the cation equivalent value Cv is 4.05 to 5.50 meq/g, the anion equivalent value Av is 0.15 to 2.35 meq/g, and the temperature Cv/A V ( 1) In one polymerization, monomer (1) is added while taking into account the cation equivalent value of monomer (CI) and the anion equivalent value of intermediate (IT) so that the ratio is in the range of 1.7 to 36.7. ), monomer (II) and monomer ([) need to be determined in the amounts to be used.

In flocculation treatments such as sludge treatment, the components to be removed are usually loaded, so the amphoteric polymer flocculant of the present invention retains a certain amount of cationic groups as described above, and also contains floc formation aids. It is necessary to reduce the number of anionic groups acting as cationic groups.

If the cation equivalent value Cv is smaller than a, 05 meq/g, dewatering properties will be poor in sludge flocculation treatment and dewatering treatment, which is not preferable.

In addition, if the anion equivalent value Ay is smaller than 0.15 meq/g, amphoteric characteristics are difficult to appear, and 2.35 meq/g
When it exceeds q/g, cloudiness and gelation occur in water, resulting in decreased solubility.

If the Cv/Av value is smaller than 1.7 and the 7-ion equivalent value is too large, the effect of cationic salt will be diminished and the cohesive part will decrease, which is not preferable.
When the /Av value exceeds 36.7, the proportion of anionic groups is too small and sufficient amphoteric action cannot be expected.

The cation equivalent value of the present invention, anion'! ! JrXL
In addition to the value, it is also desirable to appropriately control the molecular weight.

Molecular weight is defined as intrinsic viscosity [η] l N N a N Oa
(30℃), the intrinsic viscosity of the amphoteric polymer flocculant [77] I1N -N a N Oa (30℃)
is in the range of 3.0 to 15 d/g, more preferably 5 to 1
It is desirable to appropriately select the composition of each monomer, polymerization time, etc. so that the polymerization rate is 0di/g.

[η] I N N a N O3 (30°C) is 3.
OJ: If the diameter is small, the strength of the flocs generated during flocculation treatment will be insufficient and dewatering will often be difficult;
If it exceeds the viscosity, the viscosity of the flocculant becomes too high and the flocculating properties and dewatering properties tend to decrease.

In the present invention, the cation equivalent value Cv and anion ff1Q (iffAv+f) of the amphoteric polymer flocculant can be determined by the colloid suitability method shown below.

(Measurement of colloid equivalent value) Preparation of sample: Calculate 0.2g of pure sample and add to water to make a 0.2% aqueous solution. If the sample is completely dissolved, 25m will be covered! ; Take L with a whole pipette and make one sentence with water (50 ppm).

■Measurement of cation equivalent value Take 100m5L of a sample prepared to 50ppm in a conical beaker, and while stirring with a stirrer, add N/10M.
Adjust the pH to 4 with CI solution. Immediately add 2-3 drops of toluidine blue indicator and titrate with N/400 polyvinyl potassium sulfate solution (N/400PVSK). The end point is when the sample water changes color from blue to reddish-purple and remains for 10 seconds or more.

Calculation method Cation equivalent value (meq/g) = N/400PVSK titration m (ml) X P V
S K titer ■Measurement of anion equivalent value Take 100 mJ1 of a sample prepared to 50 ppm in a conical beaker and add 0.5 N/l ON a OH.
Add mJ1. N/200M while stirring with a stirrer
.

G, C3mM added accurately and touch, N/400P, V,
Titrate with S.

The end point of color change is blue, reddish-purple, and the end point is the point where the reddish-purple color does not disappear even after a few seconds. Let the titration value be Am sentence. Separately, perform a blank test using pure water, and let the titration value be 8m.

Calculation method of anion equivalent value (B-A) f Agon equivalent value (meq/g) = f: N/400 PVSKsoln, 7y Kuta First The present invention will be specifically explained with reference to Examples.

Each I'lid shown in Example Table 1 (1) and Table 1 (2)
Ampholytic polymer flocculants were obtained by a general method of solution polymerization in the presence of a 5-polymerization initiator, and their physical properties are shown in Table 1 (1) and Table 1 (2). Ta.

Performance 19 value was determined by arbitrarily adjusting the pH of sludge (7) with HCI and NaOH, and conducting it based on the following press dehydration test method and centrifugation dehydration test method, and the results are shown in Tables 2 and 3. Indicated.

(Press dehydration test method) Test No. 2.4, 7, 12. An aqueous solution in which 0.2% by weight of Comparative Products 2 and 5.6 amphoteric polymer flocculants were dissolved was prepared, and the raw mixed sludge from a sewage treatment plant was adjusted to an arbitrary pH.
PH=5.5.5S=2.2%, organic content in SS=7
6%), the amount of amphoteric polymer flocculant added is 0.6rr
i amount% (vs. SS), stirred rapidly (200 rpm) for 30 seconds using a stirrer, and then placed in a Nutsche (Nutsch) lined with a white nylon cloth (96 mesh).
Pour the flocculated sludge into a tube (with a diameter of 70 mm) and measure the amount of liquid at the mouth after 308+.Put the flocs remaining in the Nutsche between white cloths and put them in a press.

1kg/cm2X1 minute, 4kg/cm2X1 minute and so on,
Apply pressure, then evaluate peelability and measure cake moisture content. (Test results are shown in Table 2) (Centrifugal dehydration test υ;) Addition of an amphoteric polymer flocculant to raw mixed sludge from a sewage treatment plant prepared in the same manner as the press dehydration test method. 8% by weight (relative to SS) and stirred rapidly (800ppm) for 30 seconds with a stirrer. Then, a white nylon cloth (
Pour the flocculated sludge into a Nutsche (diameter: 70 mm) lined with 96 mesh, and measure the amount of liquid at the mouth after 30 seconds.

The flock remaining on Nutsche is made of nylon 60mesh.
Put it in a bag and set it in a centrifuge. Gradually increase the rotation speed and centrifuge for 2 minutes from the point when the rotation speed reaches 3.000 rpm. Next, measure the moisture content of the sludge cake separated at the top of the centrifuge tube. lII! to be determined. (Test results are shown in Table 3) Table 3 [Effects of the invention] The amphoteric polymer flocculant according to the present invention has moderate ionic dissociation of cationic groups and anionic groups, and is excellent due to their mutual effect. Demonstrates excellent performance.

■The flocs produced during flocculation treatment are large and hard, so they have excellent dehydration and mouthfeel properties, and the water content of the dehydrated cake is low.

■Excellent SS removal performance as a coagulant.

■Since the flocs produced during aggregation treatment have low viscosity, they have good pricking properties during belt dehydration and transferability on scree conveyors.

■By lowering the moisture content of the cake, it is expected that the amount of cake generated will be reduced, and that energy costs will be reduced when incinerating the cake.

Claims (1)

[Claims] Strong acid salt monomer of dimethylaminoethyl acrylate or dimethylaminoethyl methacrylate (I)
, acrylic acid, methacrylic acid, and salts thereof (II), or the monomer (I
), is a polymer composed of the monomer (II) and acrylamide (III), and has a cation equivalent value Cv of 4.0.
5 to 5.50 meq/g, anion equivalent value Av is 0.1
5 to 2.35 meq/g, and the Cv/Av ratio is 1.
It is in the range of 7 to 36.7, and the intrinsic viscosity [η]1N-Na
A method for treating sludge, which comprises adjusting the pH of sludge to 6.0 to 10 using an amphoteric polymer flocculant of 3 to 15 dl/g at NO_3 (30°C), followed by flocculation and dewatering.