JP3385746B2 - Method for controlling solid-liquid separation of activated sludge - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing solid-liquid separation trouble of activated sludge such as bulking and scumming in an activated sludge treatment system.

[0002]

2. Description of the Related Art In an activated sludge treatment method for organic wastewater, wastewater is mixed with activated sludge in an aeration tank to be aerated, the sludge is separated in a solid-liquid separation tank, and the separated liquid is discharged as treated water while being separated. A part of the generated sludge is returned to the aeration tank as return sludge, and the rest is discharged as excess sludge. In such an activated sludge treatment method, organic matter is decomposed by activated sludge in which bacteria such as zooglare are predominant, but depending on the properties of raw water and various treatment conditions, filamentous fungi such as sphaerotils or nos. Cardiac actinomycetes may multiply and cause bulking.

Bulking is a phenomenon in which activated sludge is lightened by the growth of filamentous fungi or actinomycetes to be in a dispersed state and the separability is deteriorated. When such bulking occurs, it becomes difficult to separate the sludge in the solid-liquid separation tank, and the sludge flows out together with the treated water, so that it is not possible to secure sufficient return sludge and the treatment performance deteriorates. When Actinomyces of the genus Nocardia grows, the above-mentioned bulking occurs, and scumming occurs in which activated sludge rises to form scum due to foaming generated by mycolic acid, which is an ultra-higher fatty acid produced, and solid-liquid separation Will get worse.

Conventionally, in order to prevent the bulking caused by the filamentous fungus, there is a method of suppressing the growth of the filamentous fungus by adding various fungicides, and a quaternary ammonium salt is used as the germicide. JP-A-59-112902 shows that benzalkonium chloride, benzethonium chloride and a mixture thereof sterilize only filamentous fungi and can suppress bulking without affecting other bacteria. However, because quaternary ammonium salts are fungicides,
It is said to be unfavorable because it suppresses the growth of bacteria other than filamentous fungi and also affects humans and animals (for example, JP-A-61-35895).

Since chlorhexidine hydrochloride and the like are also powerful bactericides, it is difficult to control the amount used, and excessive use sterilizes bacteria other than filamentous fungi. If the amount used is small, the sterilization of filamentous fungi becomes insufficient. For this reason, the usable amount is extremely limited, and the amount varies depending on the type of filamentous fungus and the condition of the individual aeration tank, and the operation for obtaining the predetermined effect is very complicated. In general, when a bulking agent is eliminated by using a bactericidal agent, the filamentous fungus is sterilized. Therefore, the effect does not appear until a certain period of time elapses after the addition of the agent, and there is a problem in rapid-acting.

On the other hand, a method of preventing bulking by adding a bacteriostatic bactericidal agent and a cationic polymer flocculant has been proposed (JP-A-6-71286). However, since the bacteriostatic fungicide is the main agent, there are the same problems as described above. A cationic polymer flocculant itself is also used for preventing bulking (Japanese Patent Laid-Open No. 49-3468), but since it is a substance that prevents bulking by aggregating sludge, it exerts an effect immediately after addition of a chemical. However, it has a problem of sustainability, and it loses its effect after repeated use. And even if these are combined, an unexpected effect cannot be obtained.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to effectively suppress the bulking caused by filamentous fungi and actinomycetes with a small amount of a drug without harming bacteria other than filamentous fungi and actinomycetes and humans and animals. The object of the present invention is to propose a method for suppressing solid-liquid separation disorder of activated sludge, which is capable of suppressing scumming caused by actinomycetes. Another object of the present invention is to propose a method for suppressing solid-liquid separation disorder of activated sludge, which has fast-acting and long-lasting properties.

[0008]

The present invention is the following method for suppressing solid-liquid separation disorder of activated sludge. (1) A method for suppressing solid-liquid separation disorder of activated sludge, which comprises adding a nonionic surfactant and a quaternary ammonium salt type cationic surfactant to the activated sludge treatment system. (2) A method for suppressing solid-liquid separation trouble of activated sludge, which comprises adding a nonionic surfactant, a quaternary ammonium salt type cationic surfactant and a cationic polymer flocculant to the activated sludge treatment system.

In the present invention, the activated sludge treatment system refers to a treatment system in any method of performing aerobic treatment using activated sludge, and in addition to the standard activated sludge treatment method, its variants and other treatment methods. It includes the processing system in the processing method by combination. Here, the treatment system means the entire system for performing the above treatment, and bulking or scumming can be suppressed by adding a surfactant or the like to any position of the treatment system. In addition, in the present invention, the suppression means suppressing the occurrence of bulking and scumming, and suppressing the progress and expansion of bulking and scumming that have already occurred.

The type of nonionic surfactant that can be used in the present invention is not limited, and may be of natural origin or synthetic. Nonionic surfactants are also used for household use, and are safe without causing any harm to bacteria other than filamentous fungi and actinomycetes and humans and animals. Nonionic surfactants adsorb sludge better than anionic ones and transfer less to treated water. Examples of the nonionic surfactant include higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, higher alkylamine ethylene oxide adducts, fatty acid amide ethylene oxide adducts, and ethylene oxide of fats and oils. Polyethylene glycol type such as adducts, polypropylene glycol ethylene oxide adducts; fatty acid ester of glycerol, fatty acid ester of pentaerythritol, fatty acid ester of sorbitol and sorbitan, fatty acid ester of sucrose,
Examples include polyhydric alcohols such as alkyl ethers of polyhydric alcohols and fatty acid amides of alkanolamines. Particularly, an alkylphenol ethylene oxide adduct and a higher alcohol ethylene oxide adduct are preferable. As the nonionic surfactant, those having HLB 8 to 18 are preferable, and those having HLB 10 to 15 are most preferable.

The cationic surfactant used in the present invention is in the quaternary ammonium salt form. Such a cationic surfactant is generally used as a bacteriostatic bactericidal agent, but when used in combination with a nonionic surfactant, in a low concentration region where bacteriostatic bactericidal effect is not substantially observed. It is possible to suppress solid-liquid separation obstacles such as bulking and scumming. Examples of the quaternary ammonium salt type cationic surfactant include alkyl trimethyl ammonium salts such as lauryl trimethyl ammonium chloride, myristyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride and stearyl trimethyl ammonium chloride; alkyl pyridinium such as cetyl pyridinium chloride and cetyl pyridinium bromide. Salt or the like is preferable. These have a slightly weaker bactericidal activity than chlorhexidine hydrochloride and benzalkonium chloride, have less effect on bacteria other than filamentous fungi and actinomycetes, and expand the usable range.

Examples of the cationic polymer flocculant used in the present invention include aminated (meth) acrylic acid ester-based polymers, aminated (meth) acrylamide-based polymers, Hoffmann degradation products of poly (meth) acrylamide, polyethyleneimine, and polyalkylenes. There are no restrictions on the type of polyamine. The aminated (meth) acrylic acid ester-based polymer includes a homopolymer of the following aminated (meth) acrylic acid ester-based cationic monomer or a copolymer with a nonionic vinyl-based monomer described later.

Examples of the aminated (meth) acrylic acid ester type cationic monomer include dimethylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diethylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, di- n-propylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diisopropylamino (methyl, ethyl,
Propyl or butyl) acrylate or methacrylate, di-n-butylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, di-sec-butylamino (methyl, ethyl, propyl or butyl) acrylate or methacrylate, diisobutylamino (methyl , Ethyl, propyl or butyl) acrylate or methacrylate or methacrylate or other aminated (meth) acrylic acid ester neutralized with an acid such as hydrogen halide, sulfuric acid, nitric acid or acetic acid; Examples thereof include quaternized compounds obtained by quaternizing acid esters with a quaternizing agent such as alkyl halides, dimethylsulfate, and diethylsulfate, but are not limited thereto. Examples of hydrogen halides include hydrogen chloride and hydrogen bromide, and examples of alkyl halides include methyl chloride and methyl bromide.
Methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, benzyl chloride and the like can be mentioned.

The aminated (meth) acrylamide-based polymer is a homopolymer of the following monomers or a copolymer with a nonionic vinyl-based monomer described below.
Examples of the aminated (meth) acrylamide-based cationic monomer include dimethylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, diethylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, di-n-propyl. Amino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, diisopropylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, di-n-butylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide , Di-sec-butylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide, diiso Neutralized salt obtained by neutralizing aminated (meth) acrylamide such as tylamino (methyl, ethyl, propyl or butyl) acrylamide or methacrylamide with acid such as hydrogen halide, sulfuric acid, nitric acid, acetic acid; the aminated (meth) acrylamide Examples thereof include, but are not limited to, quaternized products obtained by quaternizing with a quaternizing agent such as alkyl halide, dimethylsulfate and diethylsulfate. Examples of the hydrogen halide include hydrogen chloride and hydrogen bromide, and examples of the alkyl halide include methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, benzyl chloride and the like.

Examples of the nonionic vinyl-type monomer to be copolymerized with the cationic monomer include vinyl group-containing amides such as acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide; acrylonitrile, methacrylic acid. Vinyl cyanide compounds such as ronitrile; alkyl esters of (meth) acrylic acid such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate; vinyl esters of carboxylic acids such as vinyl acetate; styrene
Examples thereof include aromatic vinyl compounds such as α-methylstyrene and p-methylstyrene, but are not limited thereto.

These cationic polymer flocculants have a pH of
4, the colloid equivalent value is 1.5 meq / g or more, preferably 2.5 meq / g or more, and the molecular weight is 100,000 to 10
One million, preferably one million to ten million is suitable.

In the first method for suppressing solid-liquid separation disorder of activated sludge in the present invention, a nonionic surfactant and a quaternary ammonium salt type cationic surfactant are added to an activated sludge treatment system so that the activated sludge is solidified. Suppresses liquid separation disorders. The addition amount of the nonionic surfactant and the quaternary ammonium salt type cationic surfactant varies depending on the type, the addition position, the addition method, etc., but the nonionic surfactant is 5 to 1000 mg / amount with respect to the aeration tank mixed solution. 1, preferably 10-500
mg / l, the quaternary ammonium salt type cationic surfactant is 0.5 to 100 mg / l, preferably 1 to 50 mg / l.
About l is suitable.

In the second method for suppressing solid-liquid separation disorder of activated sludge in the present invention, a cationic polymer flocculant is added to the nonionic surfactant and the quaternary ammonium salt type cationic surfactant to activate the sludge. Suppress solid-liquid separation failure of sludge. In this case, the addition amount of each component varies depending on its type, addition position, addition method, etc., but the nonionic surfactant is 5 to 1000 mg / l, preferably 10 to 500 mg / l to the liquid containing activated sludge. The tetraammonium salt type cationic surfactant is 0.5 to 100 mg / l, preferably 1 to 50 mg / l, and the cationic polymer flocculant is 10 to 1
It is suitable to be about 00 mg / l, preferably about 2 to 150 mg / l.

Each of these surfactants and coagulants is 1
They can be added alone or in combination of several kinds at the same time or separately at any place in the activated sludge treatment system, but it is generally preferable to add them to the aeration tank. When the chemical is added to the aeration tank, the addition amount of the chemical is calculated with respect to the entire aeration tank mixed liquid. If filamentous fungi or actinomycetes are proliferating in the aeration tank, if a large amount of filamentous fungi or actinomycetes are injected into the aeration tank, a large amount of filamentous fungi or actinomycetes will lyse. Since it may increase and affect the treatment effect, by adding the drug to the returning sludge line, it is possible to continuously sterilize the filamentous fungi and actinomycetes in small amounts without completely killing the filamentous bacteria at once. This makes it possible to effectively suppress bulking and scumming without deteriorating the quality of treated water such as COD and SS. When a chemical is added to the returned sludge line, the addition amount of the chemical is calculated with respect to the amount of returned sludge. The drug may be added continuously, but it is preferable to add it intermittently so that the above concentration is obtained at a predetermined time, for example, once a day. In addition, when bulking or scumming is slight, there are cases where only the first addition is required.

Thus, by adding the nonionic surfactant and the quaternary ammonium salt type cationic surfactant to the activated sludge treatment system, the filamentous fungus in the activated sludge contracts in the sheath body, or The phenomenon of shedding or lysis from the filamentous body, or the phenomenon that the sheath body is cut off,
Bulking is suppressed. In addition, actinomycetes in the activated sludge disappear, the sludge settling property is improved, the substance causing scum is not produced, and scumming and bulking are suppressed. The effect of preventing solid-liquid separation disorder lasts for a long period of time. Further, since a synergistic effect can be obtained by using the surfactant together, the addition amount of the nonionic surfactant and the quaternary ammonium salt type cationic surfactant may be small. Therefore, other bacteria in the activated sludge are not affected and the decomposition activity for organic matter is maintained.

When a cationic polymer flocculant is used in addition to the nonionic surfactant and the quaternary ammonium salt type cationic surfactant, the settling property of the activated sludge is immediately improved, and solid-liquid separation obstacle is suppressed. The effect appears quickly and at the same time, sustainability is obtained. At this time, flocculation occurs due to the action of the cationic polymer flocculant, and the settling property is improved by sedimentation of the activated sludge, but at the same time, contact with the surfactant promotes the bacteriolytic effect on filamentous fungi and actinomycetes. , The suppression effect lasts. In this case, since the combination of the nonionic or cationic surfactant and the cationic polymer flocculant is used, the influence of each charge on the flocculation is small.

The bacterial cells that have fallen off, lysed, or died as described above are B
Since it becomes an OD component and is assimilated into activated sludge, it is possible to prevent the treated water from being contaminated. When filamentous fungi or actinomycetes are proliferating in large quantities, by adding a chemical agent to the returned sludge as described above, filamentous fungi or actinomycetes in the returned sludge are lysed or killed little by little to become BOD, When this is returned to the aeration tank, it is assimilated into activated sludge and does not elute into the treated water.

When foaming in the aeration tank becomes vigorous due to the addition of the surfactant, an antifoaming agent can be added to prevent foaming. As the defoaming agent that can be used here,
Examples include silicone oil and polypropylene glycol. Even in this case, the bulking suppressing effect is not impaired.

[0024]

As described above, in the present invention, since the nonionic surfactant and the quaternary ammonium salt type cationic surfactant are used in combination, the synergistic effect effectively enables bulking by filamentous fungi and actinomycetes with a small amount of drug. Also, it is possible to prevent scumming due to actinomycetes and to prevent solid-liquid separation obstacles of activated sludge, and to maintain the inhibitory effect without harming other bacteria and humans and animals, and to perform efficient activated sludge treatment. You can continue.

Further, by using the nonionic surfactant and the quaternary ammonium salt type cationic surfactant in combination with the cationic polymer flocculant, a rapid effect of inhibiting solid-liquid separation obstacle is obtained, and this effect is maintained. Can be made.

[0026]

EXAMPLES Examples of the present invention will be described below. In each example,% is% by weight.

Test Example 1 Filamentous bulking sludge (M
LSS 2000 mg / l) was placed in a 100 ml beaker and polyoxyethylene nonyl phenyl ether (H
LB14) at 30 mg / l and cetyltrimethylammonium chloride at 1 mg / l, and added at 25 ° C.
It was left still for 20 hours. As a result of microscopic examination, most filamentous fungi were lysed, and only sheath bodies remained.

Example 1 Filamentous bulking sludge (M
LSS 2000 mg / l) was placed in a 1 liter beaker, and once a day, polyoxyethylene nonylphenyl ether (HLB14) was added at 30 mg / l and cetyltrimethylammonium chloride at 1 mg / l to make artificial drainage. Through water, 1 liter at 25 ° C
The waste water was treated by aeration at iter / min. Artificial wastewater is 10% glucose, 10% peptone, 1 potassium phosphate 5
%, Monosodium phosphate 10%, and adjusted to pH 7.0. The TOC load was 0.5 kg / m ³ · day. As a result, lysis of filamentous fungi was observed after 12 hours, and filamentous fungi were hardly found in the sludge after 3 days.

Example 2 BOD was carried out with an aeration tank volume of 800 m ³ and a precipitation tank volume of 300 m ³ .
600 mg / l wastewater volumetric load 0.63 kg-BO
The test was carried out in an activated sludge treatment device of a food factory that is treated at D / m ³ · day. Filamentous fungus is type 1701, MLS
S was 4800 mg / l and SVI was 480. From the top of the aeration tank, polyoxyethylene lauryl ether (HL
150 mg / l of B14) and 10 mg / l of lauryltrimethylammonium chloride were added. Immediately after addition, SVI started to decrease, and 6 days later, MLSS was 5100 mg.
/ L, SVI became 190. After that, one month SV
There was almost no change in I.

Example 3 Filamentous bulking sludge (M
LSS 2000mg / l) aeration tank capacity 5 lite
r, placed in an aerobic biological treatment apparatus having a settling tank capacity of 2 liters, through which the artificial waste water of Example 1 was passed, and at 5 ° C. for 5 hours.
The waste water was treated by aeration at a rate of liter / minute. The TOC load was 0.5 kg / m ³ · day. Inflow rate is 15 li
ter / day, and returned sludge rate was 80%. Polyoxyethylene nonylphenyl ether (HLB14) and cetyltrimethylammonium chloride were continuously added to the returning sludge line so as to be 50 mg / l and 2 mg / l for 24 hours. As a result, lysis of filamentous fungi was observed,
After 3 days, almost no filamentous fungi could be found in the sludge. SVI dropped from 600 ml / g to 150 ml / g. The TOC of treated water did not change at 15 mg / l.

Test Example 2 Bulking sludge (MLSS) in which Nocardia is generated
2000 mg / l) in a 100 ml beaker,
Polyoxyethylene nonyl phenyl ether (HLB1
4) was added at 30 mg / l and cetyltrimethylammonium chloride at 3 mg / l, and the mixture was added at 25 ° C. to 20 mg / l.
Let stand for hours. As a result of microscopic examination, most filamentous fungi were lysed,
Only the pods remained.

Example 4 Bulking sludge (MLSS) in which Nocardia is generated
2000 mg / l) was placed in a 1 liter beaker, and polyoxyethylene nonylphenyl ether (HLB14) was added to this in an amount of 30 mg / l and cetyltrimethylammonium chloride to 3 mg / l once a day. The artificial waste water of No. 1 was passed through, and the waste water was treated by aeration at 25 ° C. at 1 liter / min. The TOC load was 0.5 kg / m ³ · day. As a result, the SVI was reduced from 300 ml / g to 100 ml / g, and the sedimentation property was improved. Lysis of Nocardia was observed after 2 hours, and Nocardia was hardly found in the sludge after 1 day.

Test Example 3 Filamentous bulking sludge (M
LSS 2000 mg / l) was placed in a 100 ml beaker and polyoxyethylene nonyl phenyl ether (H
LB14) 30 mg / l, cetyltrimethylammonium chloride 3 mg / l, polyethyleneimine 10
It was added so as to be mg / l, and the mixture was allowed to stand at 25 ° C. for 20 hours. As a result of microscopic examination, most filamentous fungi were lysed, and only sheath bodies remained.

Example 5 Filamentous bulking sludge (M
LSS 2000 mg / l) was placed in a 1 liter beaker, and once a day, polyoxyethylene nonylphenyl ether (HLB14) 30 mg / l, cetyltrimethylammonium chloride 3 mg / l, and polyethylenimine 10 mg / l were added. And the artificial waste water of Example 1 is allowed to pass through and 1 lit at 25 ° C.
The waste water was treated by aeration at er / min. TOC load is 0.5
It was set to kg / m ³ · day. As a result, SVI is 600 ml
/ G to 100 ml / g, the sedimentation property was immediately improved, lysis of filamentous fungi was observed after 12 hours, and filamentous fungi were hardly found in the sludge after 3 days.

Example 6 BOD with an aeration tank capacity of 720 m ³ and a precipitation tank capacity of 150 m ³ .
600 mg / l drainage volume load 0.3 kg-BOD
/ Testing was performed with activated sludge treatment apparatus we are processing dyeing factories in m ³ · day. Filamentous fungus is Thiothlix, MLSS
Was 3500 mg / l and SVI was 530. From the top of the aeration tank, polyoxyethylene lauryl ether (HLB
14) 150 mg / l, lauryl trimethyl ammonium chloride 10 mg / l, polyethyleneimine 3
0 mg / l was added. Immediately after the addition, SVI started to rapidly decrease, and 2 days later, MLSS was 3200 mg / l, SVI
Became 190. After that, there was almost no change in SVI for one month.

Example 7 Activated sludge (MLSS 3) in which filamentous fungi were not observed under a microscope
290 mg / l), 800 mg / l lauryl alcohol ethylene oxide 7 mol adduct (HLB14) and 80 mg lauryl trimethyl ammonium chloride.
/ L was added and peptone and glucose as carbon sources were 1:
A liquid containing 1 (weight ratio) was added so that the TOC was 290 mg / l, and aeration was performed to examine the change in TOC. The results are shown in Fig. 1. For comparison, 800 mg of 7 mol lauryl alcohol ethylene oxide adduct (HLB14)
The results are shown in FIG. 1 with and without addition of 1 / l.

From the results of FIG. 1, it can be seen that the TOC decrease rate (gradient of the graph) is hardly affected by the addition of 80 mg / l of lauryltrimethylammonium chloride, and does not harm bacteria other than filamentous fungi.

[Brief description of drawings]

FIG. 1 is a graph showing changes in TOC in Example 7.

─────────────────────────────────────────────────── --- Continuation of front page (56) Reference JP-A-7-116686 (JP, A) JP-A-7-24490 (JP, A) JP-A-6-233994 (JP, A) JP-A-49- 3468 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C02F 3/12

Claims (2)

(57) [Claims] 1. A method for suppressing solid-liquid separation trouble of activated sludge, which comprises adding a nonionic surfactant and a quaternary ammonium salt type cationic surfactant to the activated sludge treatment system. 2. A method for suppressing solid-liquid separation obstacle of activated sludge, which comprises adding a nonionic surfactant, a quaternary ammonium salt type cationic surfactant and a cationic polymer flocculant to the activated sludge treatment system. .