JPH0975976A - Agent for suppressing fault in separation of solid from liquid for activated sludge process system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an agent for suppressing the fault in sepn. of solid from liquid for suppressing the fault in the sepn. of solid from liquid of activated sludge, such as bulking or scumming, in an activated sludge process system, which has a rapid action and does not contaminate treated water by preparing this agent suppressing the fault in sepn. of solid from liquid from a nonionic surfactant and a chlorine-based bactericide or peroxide. SOLUTION: Org. matter is decomposed by the activated sludge in which bacterium, such as Zooglea, are dominant, but filamentous bacterium, such as sphaerotilus, propagate therein according to the characteristics, etc., of raw water and filamentous bulking arises therein. The retardation in the sepn. of the solid in a vessel for sepn. of solid from liquid is resulted in such a case. The agent for suppressing the fault is sepn. of solid from liquid is prepared from the nonionic surfactant and the chlorine-based bactericide or peroxide in order to prevent such filamentous bulking. Alkyl phenol ethylene oxide additive and higher alcohol ethylene oxide additive are used as the nonionic surfactant and bleaching powder, hypochlorite, etc., are used as the chlorine-based bactericide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-liquid separation disorder inhibitor for an activated sludge treatment system for suppressing bulking, scumming and other solid-liquid separation disorders of the 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 and aerated, and the sludge is separated in a solid-liquid separation tank, and the separated liquid is discharged as treated water. A part of the sludge is returned to the aeration tank as return sludge, and the remaining part is discharged as surplus sludge. In such an activated sludge treatment method, organic substances are decomposed by activated sludge in which bacteria such as zooglare have become dominant, but filamentous bacteria such as sphaerotilus grow in the activated sludge depending on the properties of raw water and various treatment conditions. As a result, filamentous bulking may occur. Filamentous bulking is a phenomenon in which activated sludge is lightened by the growth of filamentous bacteria 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 sufficient returned sludge cannot be secured and the treatment performance deteriorates.

Conventionally, as a method for preventing such filamentous bulking, a method of adding an anionic or nonionic surfactant (JP-A-7-116686), a cationic or primary or tertiary amino group or A method of adding an amphoteric surfactant (Japanese Patent Application Laid-Open No. 7-116687) has been proposed. These methods are not harmful to humans and animals and are safe, and do not harm BOD-decomposing bacteria in activated sludge, but when the amount of the surfactant added is large, foaming becomes severe, and addition of an antifoaming agent is added. May be required.

As another method for suppressing filamentous bulking, there is a method for suppressing the growth of filamentous bacteria by adding various bactericidal agents, and as the bactericidal agent, chlorine-based bactericidal agents such as porridge powder and hypochlorite, Peroxides such as, for example, hydroxyl peroxide and sodium percarbonate are used. However, since the bactericidal action of chlorine-based bactericides and peroxides is non-specific, B
In addition to the sterilization of OD-decomposing bacteria, there is a problem that it harms humans and livestock, and the effect of addition does not appear until a certain period of time elapses after the addition of the bactericide, resulting in a problem of rapid effect.

[0005]

The object of the present invention is to reduce the amount of nonionic surfactant used while maintaining the bulking inhibitory effect of nonionic surfactants, and to suppress the scumming caused by actinomycetes, thereby preventing foaming. It can suppress the solid-liquid separation obstacle of sludge and has a fast effect,
It is an object of the present invention to provide a solid-liquid separation disorder inhibitor in an activated sludge treatment system that does not reduce the activated sludge treatment capacity and does not contaminate the treated water.

[0006]

The present invention is a solid-liquid separation disorder inhibitor in an activated sludge treatment system, characterized by containing a nonionic surfactant and a chlorine-based bactericide or peroxide. .

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 by adding the solid-liquid separation disorder inhibitor of the present invention to any position of this treatment system, the solid-liquid separation disorder due to bulking is suppressed. can do. In addition, in the present invention, the term “suppression” means to suppress the occurrence of solid-liquid separation disorder and also to suppress the progress and spread of the already-generated solid-liquid separation disorder.

Examples of the nonionic surfactant used in the present invention 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, and fatty acids. Polyethylene glycol type such as amide ethylene oxide adduct, ethylene oxide adduct of fat and oil, polypropylene glycol ethylene oxide adduct; fatty acid ester of glycerol,
Examples thereof include fatty acid esters of pentaerythritol, fatty acid esters of sorbitol and sorbitan, fatty acid esters of sucrose, alkyl ethers of polyhydric alcohols, and polyhydric alcohol types such as fatty acid amides of alkanolamines. In particular, alkylphenol ethylene oxide adducts and higher alcohol ethylene oxide adducts are preferred. As nonionic surfactants, HLB8 ~
18 are preferable, and especially HLB10-15 are most preferable. The nonionic surfactants can be used alone or in combination of two or more. Nonionic surfactants adsorb well to sludge and transfer less to treated water.

As the chlorine-based bactericide used in combination with the nonionic surfactant in the present invention, those conventionally used as chlorine-based bactericides can be used without limitation, for example, porridge powder, hypochlorite, Examples include chlorine dioxide. These may be used alone or in combination of two or more. As the peroxide, peroxides that have been conventionally used as bactericides can be used without limitation, and examples thereof include hydrogen peroxide, sodium percarbonate and sodium pyrophosphate.
These may be used alone or in combination of two or more. It is also possible to use a chlorine-based bactericide in combination with a peroxide.

The mixing ratio of the nonionic surfactant and the chlorine-based bactericide or peroxide is such that the nonionic surfactant is 10
0 to 20 parts by weight of chlorine-based germicide or peroxide 1 to 20
It is desirable to set the content by weight, preferably 2 to 10% by weight. When the blending ratio is within the above range, the synergistic effect of the nonionic surfactant and the chlorine-based bactericide or hydrogen peroxide reduces the addition amount as compared with the case where the nonionic surfactant is used alone. Also provides the same bulking suppression effect. If the amount of the chlorine-based bactericide or peroxide is smaller than the above lower limit value, the synergistic effect will be reduced. Further, as the amount exceeds the upper limit and increases, the amount of chlorine-based bactericide or peroxide added to the activated sludge treatment system increases, so that the effect on BOD-decomposing bacteria gradually increases.

The solid-liquid separation disorder inhibitor of the present invention may be composed of a nonionic surfactant and a chlorine-based bactericide or a peroxide, or may contain other substances. Further, the solid-liquid separation disorder inhibitor of the present invention can be mixed with a nonionic surfactant and a chlorine-based bactericide or a peroxide in advance before being added to the activated sludge treatment system, or at the time of addition. Or, they can be mixed while being added, or can be added separately.

The solid-liquid separation disorder inhibitor of the present invention can be added to any place of the activated sludge treatment system, but it is particularly preferable to add it to the aeration tank. The addition amount of the solid-liquid separation disorder inhibitor of the present invention varies depending on the addition position, the addition method, the type of components, etc., but is 3 to 500 mg / l, preferably 20 as a nonionic surfactant with respect to the aeration tank mixture. ~ 250
About mg / l is suitable. As the addition method, it may be added continuously, but it is preferable to add intermittently so that the above concentration is obtained at a predetermined time, for example, once a day. In some cases, only the first addition is required.

By adding the solid-liquid separation disorder inhibitor of the present invention in this way, the filamentous bacteria in the activated sludge contract within the sheath body in a short time, or the filamentous bacteria fall off from the sheath body or lyse, Or, the phenomenon that the sheath body is cut off is observed, and the scumming by actinomycetes is suppressed,
Bulking is suppressed in 48 hours. Thereby, the solid-liquid separation obstacle is suppressed in a short time, and the solid-liquid separation can be easily performed. At this time, BOD-degrading bacteria other than filamentous bacteria and actinomycetes in the activated sludge are not affected, the degrading activity for organic substances is maintained, and the activated sludge treatment capacity is not lowered. Further, the added nonionic surfactant is not adsorbed to the activated sludge and does not flow out into the treated water, and since the amount of the chlorine-based bactericide or the peroxide added is small, the treated water is not polluted.

In this case, the amount of the nonionic surfactant added can be reduced as compared with the case where the nonionic surfactant is used alone, so that foaming is also suppressed. When foaming in the aeration tank becomes severe, it is possible to prevent foaming by adding an antifoaming agent such as silicone oil or polypropylene glycol. Even in this case, the solid-liquid separation disorder suppression effect can be obtained.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. Example 1 A filamentous bulking sludge (MLSS = 2000 mg / l) with type 021N filamentous bacteria was placed in a 100 ml beaker, polyoxyethylene nonylphenyl ether (HLB = 14) was 30 mg / l, and sodium hypochlorite was 1 mg. / L, and add 2 at 25 ° C.
Let stand for 4 hours. As a result of observing with a microscope after that, almost all filamentous bacteria were lysed and only the pods remained.

Example 2 Filamentous bulking sludge (MLSS = 2000 mg / l) with type 021N filamentous bacteria was placed in a 1 liter beaker, to which polyoxyethylene nonylphenyl ether (HLB = 14) was added at 30 mg / l, and then Sodium chlorite was added to 1 mg / l. The following artificial drainage was passed through this, aerated at 1 liter / min at 25 ° C., and treated with a TOC load of 0.5 kg / m ³ · day. As the artificial wastewater, a composition of glucose 10%, peptone 10%, potassium phosphate 1% 5%, sodium phosphate 10% and adjusted to pH 7.0 was used.

As a result, lysis of filamentous bacteria was observed after 12 hours. Then, after 3 days, filamentous bacteria were hardly found in the sludge, and as shown in Table 1, the SVI was reduced from 500 ml / g to 100 ml / g, and the filamentous bulking was resolved. During this time, treated water C
The OD was 30 mg / l or less, there was almost no adverse effect, and the wastewater treatment was good.

[Table 1]

Example 3 BO with aeration tank capacity = 800 m ³ and precipitation tank volume = 300 m ³
D = 600 mg / l drainage volume load = 0.63 kg-
An on-site test was carried out in the processing equipment of the S food factory, which treats activated sludge at BOD / m ³ · day. Filamentous bacterium is type 1701, MLSS is 4800 mg / l, SVI is 4
It was 80 ml / g, and the sedimentation property of the activated sludge was deteriorated. In this state, 150 mg / l of polyoxyethylene lauryl ether (HLB = 14) and 5 mg / l of sodium hypochlorite were added from the upper part of the aeration tank. as a result,
Immediately after the addition, the SVI started to decrease, and after 6 days, the MLSS was 5100 mg / l, the SVI was 190 ml / g, and the sedimentation property of the activated sludge was improved. After that, for one month SVI
Of the treated water is good, and the treated water C
The OD was between 10 and 30 mg / l.

Example 4, Comparative Example 1 Activated sludge having filamentous bulking caused by Sphaerotils natans (MLSS = 2500 mg / l,
SV ₃₀ = 95, SVI = 380 ml / g) 1 liter is 2
Put in a liter volume measuring cylinder, add nonionic surfactant (nonylphenol ethylene oxide 5 mol adduct) and sodium hypochlorite in the amounts shown in Table 2, and add 1 l
Aerated at iter / min. Table 2 shows the SV ₃₀ after 3 hours.

[0020]

[Table 2]

From the results shown in Table 2, it can be seen that the effect can be obtained in a small amount by using both of them in combination as compared with the case of using nonylphenol ethylene oxide 5 mol adduct or sodium hypochlorite alone.

[0022]

The solid-liquid separation disorder inhibitor in the activated sludge treatment system of the present invention contains a nonionic surfactant and a chlorine-based bactericide or peroxide. The amount used can be reduced while maintaining the bulking suppression effect of the surface active agent, and the scumming caused by actinomycetes can be suppressed. For this reason, it is possible to suppress foaming due to the nonionic surfactant and to prevent solid-liquid separation obstacles of sludge, and also it has fast-acting property, does not reduce the activated sludge treatment capacity, and does not pollute treated water. .

Claims (1)

[Claims] 1. A solid-liquid separation disorder inhibitor in an activated sludge treatment system, which comprises a nonionic surfactant and a chlorine-based bactericide or a peroxide.