JP2005319386A - Method for suppressing swelling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating swelling in a system for an activated sludge process solving the swelling by a bactericide, complementing a decrease in process performance caused by damage to activated sludge due to the bactericide by introducing at least one or more kinds of microbes, without reducing a waste water treatment performance, and capable of swiftly and continuously suppressing the swelling. <P>SOLUTION: In the method for suppressing the swelling characterized by introducing the bactericide and at least one or more kinds of microbes to the system for the activated sludge process by leaving a space, it is preferable that the bactericide is a chlorine-based oxidation type bactericide, and further, to dose the bactericide to a sludge separation tank and/or a sludge recirculation line as a dosing place, and introduce the microbes into an aeration tank. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for suppressing swelling in an activated sludge treatment system derived from filamentous bacteria.

The activated sludge treatment system is a system including an aeration tank that keeps at least a concentration of activated sludge and aerated air or oxygen to oxidatively decompose organic matter in wastewater. In the activated sludge treatment system, Organic matter in waste water is decomposed by activated sludge composed of bacteria. The activated sludge may contain protozoa and metazoans. There are various types of activated sludge treatment systems, but the existence form of activated sludge is roughly divided into two types: floc and biofilm. For example, in the standard aeration method in which air is aerated by surface aeration and aeration, the oxygen aeration method in which oxygen is aerated, and the deep layer aeration method in which dissolved oxygen is increased by water pressure, activated sludge is present as floc. In the rotating disk method, the fluid carrier method, and the contact oxidation method, activated sludge exists as a biofilm on the carrier surface such as a ceramic porous material, honeycomb, polymer polymer, or resin.

When the activated sludge is present in the floc form, the activated sludge treatment system includes an aeration tank, a sludge separation tank, and a return line. Usually, a sludge separation tank is placed after the aeration tank. In the sludge separation tank, flocs are gravity settled and separated into solid and liquid, and the supernatant is discharged. Will be returned.

When activated sludge exists in the form of a biofilm, activated sludge hardly flows out, so the sludge separation tank and return line for returning activated sludge are not usually installed, and the activated sludge treatment system is an aeration tank. Consist only of.

Filamentous bacteria are important structural factors that form a firm floc of activated sludge and a biofilm skeleton. However, in the activated sludge treatment system, the filamentous bacteria become abnormally dominant and may cause swelling under certain water conditions and conditions. When swelling occurs, if the activated sludge is flocs, the treated water quality may be deteriorated due to a decrease in bulk density, and in the case of biofilms, the biofilms may become clogged with carriers or grow filamentous bacteria. Troubles such as exfoliation and deterioration of treated water may occur.

Conventional methods of suppressing swelling include a nonionic surfactant and an anionic surfactant (see, for example, Patent Document 1), a method of adding a nonionic surfactant and a cationic surfactant of a quaternary ammonium salt (for example, a patent) Reference 2) has been proposed. In these methods, nonionic surfactants and anionic surfactants themselves may become growth factors for filamentous bacteria such as Type0041 and Nostocoida limicola, and foaming may occur if the amount used is large due to the property as a surfactant. is there.
Japanese Patent Laid-Open No. 11-216484 Japanese Unexamined Patent Publication No. 08-103788

In addition, a method of sterilizing filamentous bacteria using a chlorine-based oxidizing fungicide exemplified by hypochlorite and chlorine dioxide is also known, but the chlorine-based oxidizing fungicide is also applied to activated sludge itself. There was a problem that the treatment performance of the activated sludge treatment system deteriorated due to damage. In addition, filamentous bacteria become dominant again after the treatment with a chlorine-based oxidizing disinfectant and often cause swelling, which is not a fundamental solution.

Furthermore, specific strains of Bacillus genus (see, for example, Patent Document 3) and Acinetobacter genus (for example, see Patent Document 4) having specific lytic ability against filamentous bacteria and cultures thereof There has been proposed a method for suppressing swelling by adding microorganisms. However, such a swelling suppression method is very expensive because the activated sludge treatment system is already occupied by a large amount of dominant microorganisms, and a large amount of microorganisms must be added. It often takes a long time to appear.
Japanese Patent Laid-Open No. 06-007154 Japanese Unexamined Patent Publication No. 06-063587

  The addition of a surfactant, which is a conventional method for suppressing swelling, includes the transparency of treated water of an activated sludge treatment system, SS concentration, biochemical oxygen consumption (BOD), chemical oxygen consumption (COD) due to lysis. The operability may be reduced, such as causing deterioration of the control value and foaming, and the addition of microorganisms is effective from the start of addition because the activated sludge treatment system is already occupied by a large amount of dominant microorganisms. It may take more than one month for a long time. In addition, the addition of the disinfectant improves the expansion and at the same time damages the activated sludge itself, so that the activated sludge collapses and the treatment performance of the activated sludge treatment system may be lowered. For this reason, there is a demand for a method for suppressing swelling that is immediately effective without reducing the operability of the activated sludge treatment system.

(1) A swelling suppression method characterized by adding a bactericide and at least one or more microorganisms to an activated sludge treatment system at intervals,
(2) The swelling suppression method according to the above (1), wherein the bactericide is a chlorine-based oxidized bactericide.
(3) The method for suppressing expansion of (1) or (2), wherein a disinfectant is added to the sludge separation tank and / or the return sludge line.
(4) The swelling suppression method according to any one of (1) to (3), wherein at least one type of microorganism is added to the aeration tank.

The expansion treatment method in the activated sludge treatment system of the present invention eliminates expansion by a disinfectant, and supplements a decrease in treatment performance due to damage to the activated sludge by the disinfectant by adding at least one microorganism. It is possible to quickly and continuously suppress expansion without reducing the wastewater treatment capacity.

Examples of the disinfectant of the present invention include chlorine-based oxidative disinfectants such as chlorine gas, hypochlorous acid, hypochlorite, chlorine dioxide, and salash powder, peroxides such as hydrogen peroxide, ozone, and Polymeric cationic polymers such as quaternized products of dimethylamine epichlorohydrin and polydimethylaminoethyl acrylate with methyl chloride can be mentioned. Chlorine oxidation type disinfectants are preferable, and hypochlorite is particularly preferable. One type of bactericidal agent can be used alone, or two or more types can be used in combination.

The place for adding the disinfectant of the present invention to the activated sludge treatment system may be any place in the activated sludge treatment system as long as the disinfectant and the microorganism are added at intervals, but added to the sludge separation tank and / or the return sludge line. It is preferable to do. Moreover, it is preferable to add so that it may become a density | concentration of 0.03-200 mg / l as an active ingredient with respect to an aeration tank liquid mixture. The number of additions may be continuous or intermittent, and may be once / day.

As the microorganism in the present invention, any microorganisms such as bacteria, bacterial spores, bacterial diapauses, molds, yeasts, protozoa and the like can be used. Among these, it is preferable to use microorganisms belonging to the genus Bacillus and Pseudomonas. These microorganisms are preferably those in which two or more kinds are mixed, and the culture of the microorganisms may be used as it is. Among these microorganisms, it is preferable that the microorganisms have a high growth rate, produce a large amount of enzyme, and contain microorganisms suitable for the quality of wastewater. Microbial preparation MC-002 sold by Seiko PMC Co., Ltd. as such microorganisms. MC-003, MC-004, MC-005, MC-006, MC-008, MC-038, etc. can be mentioned. These microorganisms can be used directly in the activated sludge treatment system in powder form, but they are cultured in a batch or continuous culture tank, and as a culture containing enzymes, polysaccharides, and microorganisms secreted by the microorganism group. It can also be used in an activated sludge treatment system.

The place for adding microorganisms to the activated sludge treatment system in the present invention may be any place in the activated sludge treatment system as long as a disinfectant and microorganisms are added at intervals, but it is preferable to add microorganisms to the aeration tank. It is preferable to add to the sludge dry weight 1 so that the cultured cell or culture weight is 0.005 to 2.0. The number of additions may be continuous or intermittent, and may be once / day.

In the present invention, adding a disinfectant and microorganisms at intervals means that one of these is added first without adding the disinfectant and microorganisms at the same time, and then the other is added. It is preferable to add a disinfectant and leave a sufficient interval so as to add microorganisms in the aeration tank.

Example Tests were carried out in an activated sludge treatment system in which expansion by Thiothrix, Nostocoida limicola has occurred. Sodium hypochlorite as an effective chlorine amount as a disinfectant was added to the return sludge line at 13 mg / L, and a sufficient interval was added so that residual chlorine was not detected in the activated sludge treatment system. The culture of formulation MC-003 was added to the aeration tank at 0.9 to 1 activated sludge dry weight. Volume load, filament shape in the average value for one month before this example (hereinafter abbreviated as “before test”), average value for one month after this example (hereinafter abbreviated as “under test”) Table 2 shows the bacterial level and COD reduction rate. The volumetric load was calculated by multiplying the COD concentration at the inlet of the aeration tank by the flow rate entering the aeration tank for one day and dividing it by the aeration tank volume. The determination of the level of filamentous bacteria in the activated sludge was performed as shown in Table 1 by the Jenkins method. Filamentous bacteria levels 4 to 6 indicate that the activated sludge flocs have poor sedimentation due to swelling, and that filamentous bacteria level 3 can be operated without problems. The COD reduction rate is expressed as a percentage obtained by dividing the difference between the COD value at the time of final drainage from the COD value at the time before entering the activated sludge treatment system by the COD value at the time before entering the activated sludge treatment system. It is. The COD value was measured by the permanganic acid method.

Comparing the data before and during the test, the activated sludge treatment system does not deteriorate in performance even though the volume load is increased during the test, and immediately after the start of the addition of sodium hypochlorite The tendency of the decrease in the level of filamentous bacteria as an index of swelling was observed, and the level decreased to the level of filamentous bacteria 2 days after the start of the addition. Four days after the start of the addition, the level of filamentous bacteria was lowered to level 3 which did not affect the sedimentation property, and swelling was eliminated. After the test, the addition of the culture solution of the microorganism preparation MC-003 was continued, and no swelling was observed over one month, and the treatment performance of the activated sludge treatment system was stable.

Claims (4)

A method for suppressing swelling, comprising adding a disinfectant and at least one microorganism to the activated sludge treatment system at intervals. The method according to claim 1, wherein the bactericide is a chlorine-based oxidized bactericide. The method according to claim 1 or 2, wherein a disinfectant is added to the sludge separation tank and / or the return sludge line. The expansion method according to any one of claims 1 to 3, wherein at least one kind of microorganism is added to the aeration tank.