JP2002001356A - Method and apparatus for treating service water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating by which acryl amide is not residued in service water by almost completely removing the acryl amide in a synthetic organic high molecular flocculating agent changed in the service water. SOLUTION: After acryl amide monomer is biologically degraded and adsorbed on activated carbon to be removed by coexisting an acryl amide monomer degradable bacteria sticking powdery activated carbon and stirring at the time of preparing the high molecular flocculating agent aqueous solution having a prescribed concentration by adding the polyacryl amide based synthetic organic high molecular flocculating agent into water and stirring, the high molecular flocculating agent aqueous solution, in which the powdery activated carbon is suspended, is charged into a flocculation separation process flow-in water in the service water treatment to perform the flocculation separation of the service water to be treated and the adsorption of organic materials in the raw water simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to the removal of harmful acrylamide monomers in a polyacrylamide-based synthetic organic polymer flocculant used for coagulation treatment of water treatment, and to remove musty odor substances and humic acid in raw water treated with water treatment. The present invention relates to a novel water treatment method and a treatment device capable of simultaneously removing organic substances such as agricultural chemicals.

[0002]

2. Description of the Related Art In order to remove suspended solids and dissolved organic matter in raw water to be treated for water treatment, agglomeration treatment has been widely performed. In the coagulation treatment in the tap water treatment, aluminum sulfate (sulfuric acid band) and polyaluminum chloride (PAC) are used as coagulants. These inorganic coagulants are
Because a sufficiently large floc is not formed when used alone,
There is a disadvantage that the solid-liquid separation speed in the coagulation sedimentation step and the sand filtration step is low. In particular, eutrophication of raw water in water treatment is advanced, and in raw water containing a large amount of algae such as microcystis, addition of PAC or sulfate band forms only flocs with extremely poor sedimentation, and flocs float. In some cases, there was a big problem that the algae could not be effectively removed. There is also a disadvantage that sludge discharged from the coagulation separation step has poor sedimentation concentration and dewatering properties.

In order to solve these drawbacks, use of a polyacrylamide-based synthetic organic polymer flocculant is considered to promote floc formation. Due to the toxicity of the acrylamide monomer contained in the synthetic organic polymer flocculant, its use in water treatment in Japan has not been officially approved. The use of a polyacrylamide polymer flocculant was officially approved in April 2000 under strict conditions for water purification treatment in Japan. The condition is
"The residual amount of acrylamide monomer in the treated water is 0.
00005 mg / liter or less ", and the condition of this regulation is that unless the content of the monomer in the polymer flocculant is extremely low," the monomer content per 1 g of the polymer active ingredient is 0.01% or less ". In fact, the conditions are so severe that the polymer flocculant cannot be used for water treatment.

[0004] The reason why a small amount of acrylamide monomer inevitably remains in a polyacrylamide-based synthetic organic polymer flocculant (hereinafter abbreviated as "synthetic polymer") product is as follows. That is, in the polymerization step of polymerizing the acrylamide monomer to produce polyacrylamide, the polyacrylamide polymer becomes a gel in the latter stage of the reaction, so the molecular diffusion rate is deteriorated, and the number of collisions between the acrylamide monomers is deteriorated. It is difficult to polymerize 100% of the monomer. As a result, when polyacrylamide is added to raw water, toxic acrylamide monomers inevitably remain in tap water. In addition, sodium alginate (a kind of dietary fiber extracted from kelp), which is a natural polymer flocculant with no safety problems, has a higher chemical cost than synthetic organic polymer flocculants and has a floc-forming effect of poly. Since it is significantly smaller than acrylamide polymer flocculants, it is not used in water treatment in Japan.

[0005]

SUMMARY OF THE INVENTION The present invention provides a synthetic organic polymer flocculant (hereinafter sometimes abbreviated as "polymer flocculant" or "polymer") to solve the above-mentioned conventional problems. After completely removing the acrylamide monomer when using it (below the detection limit), the synthetic organic polymer flocculant is injected into the water to be treated for drinking water, and the acrylamide monomer does not remain in the treated water (drinking water) The purpose is to be. The present invention thus solves the problem of monomer residue in a polymer flocculant, thereby enabling a synthetic polymer having an excellent floc-forming effect to be used safely in water treatment. It is an object of the present invention to provide an agglomeration treatment technique.

[0006]

The present invention has solved the above-mentioned problems by the following technical concept. That is, the present invention includes the following configurations. (1) When a polyacrylamide-based synthetic organic polymer flocculant is added to water and stirred to prepare a polymer flocculant aqueous solution having a predetermined concentration, the acrylamide monomer-decomposing bacterium-attached powder activated carbon is coexistent and stirred, and the acrylamide monomer is stirred. After biodegradation and removal by adsorption on activated carbon, the aqueous solution of the polymer flocculant in which the powdered activated carbon is suspended is poured into the influent water of the coagulation / separation step of water treatment, and the coagulation separation and raw A water treatment method characterized by simultaneously adsorbing organic matter in water to activated carbon. (2) The water treatment method according to the above (1), wherein the powdered activated carbon adhering to acrylamide monomer-degrading bacteria is obtained by suspending powdered activated carbon in water containing acrylamide monomer and aerating the suspension. (3) A polymer flocculant dissolving tank equipped with a stirrer and provided with a supply pipe for a polyacrylamide-based synthetic organic polymer flocculant, a supply pipe for acrylamide monomer-degrading bacteria-adhered powdered activated carbon, and a discharge pipe for a polymer flocculant solution. Water treatment equipment characterized by the above-mentioned.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of a treatment apparatus for carrying out the water treatment method of the present invention. Hereinafter, the case of using powdered polyacrylamide, which is the most typical synthetic organic polymer flocculant, will be described with reference to FIG.
Water 2 is supplied to a polymer flocculant dissolving tank 1 disposed in a water purification plant until a predetermined water level is reached, and a motor 3 is driven to agitate the stirring blades 4.
While rotating, a powder of polyacrylamide polymer flocculant as the polymer flocculant 5 is supplied and dissolved, and a predetermined amount of powdered activated carbon 6 adhering to monomer-degrading bacteria is further added. The obtained polymer flocculant solution 7 is taken out and sent to a flocculation treatment tank (not shown). It was found that among the various solids, the monomer-degrading bacteria were most easily adhered and immobilized on powdered activated carbon. Acrylamide monomer-degrading bacteria are microorganisms that degrade acrylamide monomers. So far, Brevibacterium (Brevibacterium) has been used as a decomposing bacterium.
akuterium, Nocardi
a) The genus, Pseudomonas genus bacteria and actinomycetes are known, and the acrylamide monomer-degrading bacteria referred to in the present invention may be any of these bacteria, provided that they have the ability to degrade acrylamide monomers. However, the present invention is not particularly limited to these bacteria.

[0008] While stirring the suspension of the activated carbon suspension powder adhering to the monomer-decomposed bacteria thus mixed, a powder of polyacrylamide (polymer flocculant) is added little by little so as not to form mamako (split powder). , 0.1% (w / v). In the above-mentioned sufficiently dispersed state, when stirring is further continued, the powder of the polymer flocculant gradually starts to dissolve, the white powder absorbs water to form transparent gel-like particles, and the acrylamide monomer is gradually removed from the gel. Begin to melt into the water. The eluted acrylamide monomer is rapidly biodegraded by activated carbon-adhering bacteria, and a part of the acrylamide monomer is adsorbed on activated carbon.

In such a state, when stirring is continued for about 1 to 2 hours, the polymer flocculant is completely dissolved, the transparent gel particles disappear, and the acrylamide monomer is almost completely decomposed and disappears. Alternatively, powdered activated carbon immobilized with the monomer-degrading bacteria may be mixed in advance with the polymer flocculant product, and this may be suspended in water in a waterworks to dissolve the polymer. The time required for the biodegradation of the acrylamide monomer varies depending on the content of the acrylamide monomer in the polymer flocculant, the dissolution concentration of the polymer flocculant, the water temperature, and the amount of the activated carbon added to the microorganism-adhered powder.

According to the experiment of the present inventor, after dispersing polyacrylamide powder in water at a water temperature of 20 ° C. at a concentration of 0.1% (w / v), 10,000 mg / w
When about 1 liter was added and stirred for 1 to 2 hours, it was confirmed that the acrylamide monomer was completely decomposed. The smaller the amount of the microorganism-attached activated carbon, the lower the cost. However, a certain amount is required in order to make sufficient contact with the raw water, and the amount is preferably in the range of 1,000 to 20,000 mg / liter. From this result, in the case of the present invention, the polymer flocculant and the powdered activated carbon from which the acrylamide monomer has been completely or highly removed can be injected into the raw water. In the aqueous solution of the polymer flocculant from which the acrylamide monomer has been completely or highly removed, powdered activated carbon coexists.
There is a combined effect that musty odor besides trihalomethane precursors, pesticides, environmental hormones and the like in raw water treated water is absorbed by powdered activated carbon.

[0011]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 (Production of powdered activated carbon adhering to monomer-decomposing bacteria) To tap water to which acrylamide monomer was added and mixed at 30 mg / l, powdered activated carbon was added at 10,000 mg / l, and phosphorus was added at 10 mg / l, and mixed.
The activated sludge collected from the sewage treatment plant was added and mixed at 100 mg / liter, and air aeration was continued for 4 weeks. At this point, the concentration of the monomer in the separated water from which the powdered activated carbon had been removed by centrifugation was 0.13 mg / liter. Further, as a result of observing the separated powdered activated carbon with a microscope, a slightly yellow microorganism was attached.

Example 2 (Monomer removal test in aqueous solution of polyacrylamide) [0013] Anionic polyacrylamide powder was added to tap water (water temperature: 22 ° C) containing 10,000 mg / liter of activated carbon to which monomer-decomposed bacteria obtained by the method of Example 1 was added. (Monomer content 0.17%) was added little by little to a concentration of 0.1% (w / v) and stirred for 2 hours to prepare a dissolved polymer aqueous solution. The monomer concentration in the obtained aqueous solution in the polymer dissolving tank was not more than the detection limit (0.2 ppm) of the acrylamide monomer analysis method by ECD gas chromatography described in the drinking water test method. On the other hand, the above-mentioned polyacrylamide powder was added in 0.1% (w /
v) The concentration of the acrylamide monomer in the aqueous solution of the polymer flocculant obtained by adding it to a concentration and dissolving it with continuous stirring for 2 hours was 7.7 mg / liter, and it was hardly removed.

Example 3 (Water treatment test) Raw water from water purification plant A was sampled, PAC was added at 30 mg / L, and the mixture was stirred for 1 minute, and then the powdered activated carbon suspended polymer flocculant of the present invention (Example 2) ) Was added, and the mixture was stirred for 1 minute to perform an aggregation treatment. As a result, a floc having extremely large sedimentation property is formed, and the sedimentation speed is 56
It was 0 m / min. In addition, the solubility chromaticity in raw water 13
The degree decreased to 3 degrees after the treatment with the polymer flocculant of the present invention. Furthermore, when the acrylamide monomer in the coagulated water was analyzed according to the ECD gas chromatography described in the water supply test method, no detection was possible. The chromaticity of the coagulated water to which only PAC was added at 3 mg / liter was 6 degrees. In addition, the sedimentation speed of the formed floc is 22 mm /
Min was extremely small.

[0015]

According to the method and apparatus for treating clean water of the present invention, the following remarkable effects can be obtained. (A) Since the monomer can be easily and highly removed from the synthetic polymer flocculant containing the acrylamide monomer, the synthetic polymer can be safely used for water treatment. (B) Since an acrylamide polymer flocculant having an excellent floc-forming effect can be used for water treatment, the solid-liquid separation speed in the flocculation settling and filtration processes is significantly higher than when using the conventional inorganic flocculant alone. And the water treatment process can be greatly streamlined. (C) Since the powdered activated carbon coexists in the aqueous solution of the polymer flocculant that has been subjected to the treatment for removing the monomer, even if the aqueous solution of the polymer flocculant is added as it is to the raw water to be treated for water treatment, At this time, a combined effect is obtained in which various trace organic substances, for example, musty odor, color, pesticides, humic acid and the like in the raw water to be treated for water treatment can be removed in the coagulation step. This indicates that activated carbon functions as a carrier for acrylamide monomer-degrading bacteria, musty odor from raw water,
It has a combined function of removing color, pesticides and humic acid.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration example of an apparatus for performing a processing method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 polymer flocculant dissolution tank 2 water 3 motor 4 stirring blade 5 polymer flocculant 6 powdered activated carbon adhering to monomer decomposing bacteria 7 polymer flocculant solution

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C12M 1/40 C12M 1/40 Z 4D062 C12N 1/00 C12N 1/00 R 11/14 11/14 F term (reference) 4B029 AA21 BB02 CC04 CC10 4B033 NA12 NA19 NB23 NB62 NB68 NC04 ND04 ND20 NE02 4B065 AA22X AA38X AA41X AC20 BA23 BB12 BC42 BD15 CA56 4D024 AA01 AB04 BA02 BB01 BC05 DB15 DB29 BA03BA03 BA03 DA03 DD04 DD03 DD03 DD14 DD03 DD03 DD14 DD03 DD14 DD03

Claims (3)

[Claims] 1. When a polyacrylamide-based synthetic organic polymer flocculant is added to water and stirred to prepare a polymer flocculant aqueous solution of a predetermined concentration, stirring is carried out in the presence of activated carbon adhering to acrylamide monomer-degrading bacteria, After the acrylamide monomer is biodegraded and removed by adsorption to activated carbon, the aqueous solution of the polymer flocculant in which the powdered activated carbon is suspended is injected into the influent water of the coagulation / separation step of water treatment, and the coagulation / separation of raw water to be treated with water is carried out. And a method of treating organic water in raw water with activated carbon at the same time. 2. The water treatment method according to claim 1, wherein the powdered activated carbon adhering to acrylamide monomer-degrading bacteria is obtained by suspending powdered activated carbon in water containing acrylamide monomer and aerating the suspension. . 3. A polymer flocculant dissolving tank equipped with a stirrer and provided with a supply pipe for a polyacrylamide-based synthetic organic polymer flocculant, a supply pipe for powdered activated carbon adhering to acrylamide monomer-degrading bacteria, and a discharge pipe for a polymer flocculant solution. A water treatment device comprising: