JPH11147801A - Bactericide for active sludge, sterilization of active sludge by using the same and treatment of organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and economical method for treating an organic waste water capable of reducing the generated amount of an excessive sludge widely by a simple method, without deteriorating the quality of treated water in the final stage, to obtain a bactericide used for the above method, and to provide a method of the sterilization of an active sludge by using the same agent. SOLUTION: This bactericide for an activated sludge consists of at least one kind compound selected from among cationic surfactant, an amphoteric surfactant, chlorinated compounds, polyamines, aliphatic amines, phenols, nitrofurans, compounds having a trichloroalkylthio group, dithiocarbamates, aldehydes, alcohols, a protease, a glucanase, an amylase, magnesium monoperoxyphthalate as a main component, and the method of a sterilization by using the same and the method for treating an organic waste water, are also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disinfectant for activated sludge and a method for treating organic wastewater using the same, and more particularly, to treating organic wastewater with activated sludge.
Activated sludge disinfectant capable of suppressing the growth of bacteria constituting activated sludge and significantly reducing the amount of excess sludge generated, a method for disinfecting activated sludge using the same, and a method for treating organic wastewater It is.

[0002]

2. Description of the Related Art Pollutants in water are decomposed and purified in nature such as rivers and lakes by physicochemical and biological actions such as precipitation, aggregation, oxidation and reduction. In particular, pollution containing organic matter is easily purified by microorganisms by biological action. As a method of purifying organic wastewater utilizing this, there is an activated sludge method of treating organic wastewater with activated sludge containing aerobic microorganisms, but this method has a high purification ability and a relatively low treatment cost. Therefore, various methods utilizing this have been proposed and widely used in sewage treatment, industrial wastewater treatment and the like.

In the above-mentioned activated sludge method, the wastewater p
After performing pretreatments such as H adjustment and homogenization, the organic wastewater is led to an aeration tank (aeration tank) in which the activated sludge decomposes organic pollutants in the wastewater represented by BOD by activated sludge. Purification is in progress. At this time, 50 to 70% of the decomposed BOD is consumed as living energy of the microorganism, but the remaining 30 to 50% is used for the growth of cells, so that the amount of activated sludge gradually increases. . For this reason, generally, as shown in FIG. 4, the wastewater treated in the aeration tank is guided to a settling tank, and the returned activated sludge is removed from the settled activated sludge by an amount required for the organic wastewater purification treatment. To the inside of the aeration tank, and other activated sludge is removed as surplus sludge. As described above, a large amount of excess sludge is generated in the purification treatment of organic wastewater using activated sludge, but this excess sludge contains a substance that is hard to decompose biologically and has disadvantages such as high viscosity and difficulty in handling. In the case of purifying organic wastewater by the activated sludge method, excess sludge treatment is always a problem.

[0004] On the other hand, the method of treating excess sludge, which is generally performed at present, includes a method of dehydrating excess sludge to separate water and incinerating solids or landfilling as industrial waste. Alternatively, the excess sludge is subjected to anaerobic digestion treatment, decomposed into methane gas, carbon dioxide, hydrogen, hydrogen sulfide, etc. to reduce the volume, and then the excess sludge that has not been decomposed and other solids are separated by dehydration, and the solids are separated. Methods include incineration or disposal as industrial waste. Furthermore, in recent years, for the purpose of reducing excess sludge, a method has been known in which a part of the excess sludge is treated with ozone and then the ozone-treated sludge is introduced into an aeration tank to perform aerobic treatment. See JP-B-57-19719 and JP-A-7-88495.

However, the above-mentioned conventional method for treating excess sludge has various problems as described below.
First, when the excess sludge is concentrated by a dehydrator without performing anaerobic digestion treatment and incinerated or disposed of as industrial waste, there is a problem that the processing cost is significantly increased due to a large amount of excess sludge. Current sludge disposal cost is 20,000 yen / 30,000 yen
m ³ and higher, further, the disposal costs tend to rise even more in the future. In addition, the impact on the global environment such as the problem of securing landfill disposal sites and the problem of increased energy consumption due to sludge incineration cannot be overlooked.

The above-described method for reducing excess sludge by anaerobic digestion has the advantage that energy is recovered as methane gas. However, the number of days required for digestion is as long as 20 to 40 days, and excess sludge is required. Since the decomposition rate is as low as about 60%, a large site area is required. Further, undecomposed excess sludge and other solids must be separated by a dehydrator and incinerated or disposed of as industrial waste. There is a problem that the processing cost increases due to inefficiency. Further, as described above, there is a problem of influence on the global environment.

The method of treating a part of the excess sludge with ozone can considerably reduce the volume of the excess sludge, but requires a special ozone generator. Therefore, it is not suitable for small-scale facilities, and there is a practical problem that equipment costs are high, operating costs are increased, processing costs are increased, and economic efficiency is poor.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for treating organic wastewater using activated sludge, wherein the amount of surplus sludge generated without deteriorating the quality of treated water discharged in the final stage is reduced. Activated sludge disinfectant that can greatly reduce the cost of excess sludge treatment, a method for disinfecting activated sludge using the same,
An object of the present invention is to provide a simple and economical method for treating organic wastewater using the same.

[0009]

The above objects are achieved by the present invention described below. That is, the present invention provides cationic surfactants, amphoteric surfactants, chlorine compounds, polyamines, aliphatic amines, phenols, nitrofurans, compounds having a trichloroalkylthio group, dithiocarbamates, aldehydes, Activated sludge disinfectant characterized by containing at least one compound selected from alcohols, proteases, glucanase, amylase, and monoperoxyphthalate magnesium as a main component, a method for disinfecting activated sludge using the same, and This is a method for treating organic wastewater.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to preferred embodiments of the method for treating organic wastewater of the present invention.
The present inventors have conducted intensive studies to solve the above-mentioned problems of the prior art, and as a result, in the conventional method of treating organic wastewater using activated sludge as shown in FIG.
If some of the activated sludge removed from the aeration tank or sedimentation tank is sterilized, the treated sludge is returned to the aeration tank, and the activated sludge treatment is performed. It has been found that the amount of generated excess sludge can be made extremely small without impairing the water quality of the present invention. Further, without being limited to the above method, when purifying organic wastewater using activated sludge, in any of the treatment steps, sterilizing some of the bacteria constituting the activated sludge. Thus, if the amount of activated sludge during the treatment process can be maintained at a necessary and sufficient amount for the purification treatment, the amount of excess sludge generated can be extremely small without impairing the quality of the final treated water. Was. For example, when the treatment is performed using an agent that destroys the cell wall of bacteria constituting the activated sludge, polysaccharides, proteins, and the like in the cell wall are dissolved (this state is referred to as lysis in the present specification).
The bacteria themselves become organic pollutants in the wastewater represented by the BOD, and become a good food for the bacteria. For this reason, as described below, excessive growth of activated sludge is suppressed, so that the amount of excess sludge generated can be reduced.

First, in biological treatment of wastewater with activated sludge, organic substances in the water to be treated are oxidatively decomposed by bacteria. Then, along with this, the bacteria themselves grow using organic matter as a nutrient source. Therefore, it can be said that the organic matter in the wastewater was converted into bacteria by looking only at the phenomenon caused by the bacterial treatment.According to the study of the present inventors, it was found that the conversion rate of organic matter to bacteria was about About 40 to 50%, and 100 parts by weight of organic matter is converted into about 40 to 50 parts by weight of bacteria. On the other hand, when viewed from the bacteria side, it means that the amount of bacteria has increased by 40 to 50 parts by weight. These bacteria cannibalize with each other, or are preyed on by protozoa to precipitate as activated sludge having good coagulability and sedimentation.

[0012] Therefore, the present inventors can promote the so-called cannibalism of bacteria, which can reduce the amount of bacteria (activated sludge) that gradually grows by using organic matter as feed and generate excess sludge. We thought that it could solve the problem, and developed a drug that could promote bacterial cannibalism. That is, if some bacteria constituting the activated sludge can be sterilized and the bacteria themselves can be used as organic pollutants in wastewater represented by BOD, these become good foods for bacteria and protozoa, Bacterial growth can be suppressed (see FIG. 1).

[0013] The present inventors have conducted various studies on agents effective as a bactericide for bacteria constituting activated sludge, and found that excess sludge is reduced in a method for treating organic wastewater using activated sludge. Drugs that can achieve the intended purpose include those that have the function of causing cell wall (membrane) damage and destroying it to lyse bacteria, and those that hydrolyze the cytoplasm that constitutes bacteria to impair dysfunction. Those having a function of causing, those having a function of causing bacterial dysfunction by oxidative decomposition of organic components, those having a function of causing functional dysfunction by binding to bacterial cell proteins, or denaturing or coagulating proteins, It was found that those having a function of causing a functional disorder in activated sludge by causing inactivation or destruction of an enzyme system, metabolic disorder or the like were effective. Among these, in particular, agents having a function of breaking down cell walls and lysing to dissolve polysaccharides, proteins, and the like in the cell wall, as shown in FIG. 1, transform the bacteria themselves into organic pollutants represented by BOD. This is effective because it can be changed efficiently. On the other hand, even if the agent has an excellent bactericidal effect, for example, a highly toxic agent, an agent whose chemical effect affects properties such as pH dependence and temperature dependence of sludge, and an agent which requires too much chemical cost Cannot be applied as a disinfectant for the activated sludge of the present invention.

The agent having the function of disrupting and lysing the cell wall of bacteria, which is mentioned as an example of the bactericide of the activated sludge of the present invention, is not particularly limited as long as it has such a function. When a sludge sample is used and a chemical is added thereto and treated under a certain condition, the concentration of the reducing sugar in the sample is preferably a specific value or more. That is, when the cell wall is destroyed by acting on the cell wall of the bacterium, polysaccharides and the like in the cell wall are dissolved, and the value of the reducing sugar in the sample before and after the treatment with the drug is measured. It is possible to quantify the (lysis rate) to some extent.

As a specific method for measuring the bacteriolytic action on the bacteria used at this time, for example, when activated sludge is used and stirred at pH 7, 3
%, And a treatment is performed at 20 ° C. for about 6 hours, and then the content of reducing sugar in the sample is measured by a somogi method. As the activated sludge used at this time, activated sludge treating dairy wastewater was used. Drug concentration 3
% Means that 3% by weight is added to the SS amount of the sludge. As a method for measuring the content of reducing sugars in a sample by the somogi method, a method for measuring reducing sugars described in “The Chemistry of Carbohydrates” edited by the Biochemical Society of Japan (Biochemical Experiment Course 4 Tokyo Kagaku Dojin (1976)) The method used for was used.
According to the study of the present inventors, a reducing sugar value when measured as described above is 50 mg or more, more preferably 100 mg or more, as a drug capable of achieving the intended purpose of the present invention. Was effective.

Examples of the agent suitable as a disinfectant for the activated sludge of the present invention include a cationic surfactant.
Specific examples include di- or mono-long-chain alkyl di- or tri-lower alkyl or benzyl ammonium salts of quaternary ammonium salt type cationic surfactants, such as dialkyl dimethyl ammonium salt , alkyl dimethyl Ethyl ammonium salt, alkyltrimethylammonium salt, alkyldimethylbenzylammonium salt, alkylamidopropyldimethylbenzylammonium salt and the like can be mentioned. More specifically, for example, didecyldimethylammonium chloride, dioctyldimethylammonium chloride, benzethonium chloride, trimethoxysilylpropyldimethyloctadecylammonium chloride, and decylisononyldimethylammonium chloride can be used. Of course, other salts may be used. Further, pyridinium-type cationic surfactants such as alkylpyridinium salts and alkylquinolinium salts are also preferably used.
2, alkyl quinolinium chloride can be used. Further, amphoteric surfactants such as alkyldi (aminoethyl) glycine hydrochloride and di (alkylaminodiethyl) glycine hydrochloride may be used. Also, polyamines such as chlorhexidine hydrochloride and chlorhexidine gluconate (these are also organic chlorine compounds), chlorine dioxide,
Inorganic chlorine compounds such as sodium hypochlorite are also effective. Furthermore, proteases such as papain and enzymes such as glucanase and amylase can also be suitably used. In addition, aliphatic amines such as N-alkylenealkyldiamine, aldehydes such as glutaraldehyde, phenols such as cresol, and magnesium monoperoxyphthalate can also be used. The fungicide for activated sludge of the present invention may be composed of any one of the above compounds as a main component, or may be composed of two or more compounds in combination.

In order to verify the effects of the chemicals comprising the above-mentioned compounds, experiments were conducted in which activated sludge was treated using various chemicals, and the amount of excess sludge generated was measured. As a test method, first, a 2-liter measuring cylinder was prepared, and the activated sludge was adjusted to 5000 mg / liter and put into the cylinder. Furthermore, milk was used as artificial wastewater, and added thereto once a day at a BOD load of 1.0 kg / m ³ day. After stirring well each time, the mixture was allowed to stand at room temperature for 100 days. Done. During that time, once a day, 1500 mg of activated sludge was taken out and treated with a chemical, the treated sludge was returned to the activated sludge, and the above treatment was continued. For comparison, the system without the drug treatment was also performed in parallel. At this time, the optimal condition for the chemical treatment differs depending on the chemical used, so the optimal condition was selected for each chemical. In Table 1,
The range of the condition of the chemical treatment performed at that time is shown. At the end of the day's treatment, the amount of activated sludge was measured, the amount of proliferated activated sludge was calculated, and the amount of activated sludge increased per day was determined. Table 2 shows the average value. As a result, in particular, quaternary ammonium salt-type cationic surfactants such as didecyldimethylammonium salt and decylisononyldimethylammonium salt, and polyamines such as chlorhexidine hydrochloride and chlorhexidine gluconate were used as disinfectants. In this case, it was found that the effect of suppressing the growth of the activated sludge was large.

Table 1 Chemical treatment conditions

Table 2 Comparison of sludge production

In the method for treating organic wastewater of the present invention, when the organic wastewater is purified using activated sludge, the bacteria constituting the activated sludge as described above may be used in any of the treatment steps. By disinfecting a part of the activated sludge by adding a disinfectant, the growth of the activated sludge during the treatment process is suppressed. Hereinafter, a method for treating organic wastewater of the present invention obtained by adding a treatment with a disinfectant to the activated sludge of the present invention to a system for purifying organic wastewater by a normal activated sludge method will be described.

FIG. 2 shows a preferred system diagram of the organic wastewater treatment method of the present invention. As shown in FIG. 2, after the organic wastewater is introduced into the treatment tank and aerated together with the activated sludge. In the treatment tank, or at least a part of the activated sludge is extracted from the sedimentation tank provided downstream of the treatment tank and introduced into the chemical treatment tank, and the chemical treatment tank is formed of the above-described chemical. After disinfecting the activated sludge by adding the disinfectant of the activated sludge, the treated activated sludge is introduced into the treatment tank, and the aeration treatment is continued again. As a result, compared to the conventional organic wastewater purification system shown in FIG. 4, the amount of generated excess sludge can be reduced to 1/2 to 1/100.

The activated sludge to be sterilized in the chemical treatment tank may be at any stage. For example, as in the example shown in FIG. 2, a part of the returned sludge returned from the sedimentation tank to the aeration tank is extracted and led to a chemical reaction tank, where the activated sludge is sterilized together with the activated sludge disinfectant of the present invention. The sludge may be sterilized, and thereafter, the treated sludge may be returned to the aeration tank to continue the processing. Alternatively, as shown in FIG. 3, a batch without a sedimentation tank may be used. In the case of the activated sludge method of the formula, a part of the treated water in the aeration tank may be extracted and led to a chemical reaction tank for sterilization. Further, in both of the examples shown in FIGS. 2 and 3, a chemical reaction tank is separately provided. For example, in the case of a household septic tank, the activated sludge disinfectant of the present invention is placed in an aeration tank. It is possible to reduce the amount of surplus sludge generated even if it is used by charging.

[0023]

Next, the present invention will be described in more detail with reference to examples of the present invention. Example 1 800 m ³ / da constructed according to the flow shown in FIG.
0.8k BOD load using y-scale processing equipment
Activated sludge treatment of organic wastewater was performed using organic wastewater from a food factory handling g / m ³ dairy products as raw water. Table 3 shows the properties of the raw water.

Table 3 Raw water quality (food factory wastewater)

In the present embodiment, a part of the returned sludge was withdrawn and introduced into a chemical reaction tank, and decyl isononyldimethylammonium salt was charged into the reaction tank and sterilized.
Each time, 3 m ³ of activated sludge is introduced into the chemical reaction tank, and 1.5 kg of a chemical is added thereto (corresponding to 15% of the activated sludge), followed by stirring at 20 ° C. for 6 hours. Was performed. Thereafter, the treated activated sludge was introduced into the pipeline of returned sludge, and returned to the aeration tank having a capacity of 800 m ³ again. In this way, the activated sludge in an amount of 45 m ³ / day was subjected to chemical treatment. As a result, the amount of excess sludge generated was about 20 kg / day. In addition, when the final treated water was examined, as shown in Table 4, the purification capacity was reduced at all, as compared with the case treated by the method described in the following Comparative Example 1 treated by the conventional method. It was confirmed that it was difficult to do.

Example 2 In this example, the sterilization treatment performed in Example 1 was performed under heating and alkaline conditions. First, a part of the returned sludge was withdrawn and introduced into a chemical reaction tank in the same manner as in Example 1, and decylisononyldimethylammonium salt was charged into the reaction tank and sterilized. Then, the pH of the chemical reaction tank was adjusted to 9, and the treatment was performed at a constant temperature of 50 ° C. Activated sludge in an amount of 3 m ³ is introduced into the chemical reaction tank at a time, and 0.5 kg of a chemical is added thereto (corresponding to 5% of the activated sludge), followed by stirring at 20 ° C. for 6 hours. Was performed. Thereafter, the treated activated sludge was introduced into the pipeline of returned sludge, and returned to the aeration tank having a capacity of 800 m ³ again. Thus, 45 m ³ /
The day amount of activated sludge was treated with chemicals. As a result, the amount of excess sludge generated was about 20 kg / day.
In addition, when the final treated water was examined, as shown in Table 4, the purification capacity was reduced at all, as compared with the case treated by the method described in the following Comparative Example 1 treated by the conventional method. It was confirmed that it was difficult to do. or,
Compared with the case of Example 1, it was found that by performing the sterilization treatment under heating and alkaline conditions, the required amount of the sterilizing agent was reduced to ３. In the present embodiment, the pH of the reaction tank is set to 9, but may be set to 8 to 11. In particular, it is preferable to adjust the temperature to about 8.5 to 10. Also, the temperature of the reaction tank may be set at 40 to 100 ° C. In particular, it is preferable to perform a sterilization treatment under the condition of 40 to 60 ° C.

Comparative Example 1 Activated sludge treatment of organic wastewater was performed in the same manner as in Example 1 except that a part of the returned sludge was not treated with a chemical. As a result, the amount of the generated excess sludge was 200 kg / day, and the amount of the excess sludge was 10 times as large as that in Example 1. Table 4 shows the water quality of the final treated water.
Raised.

Example 3 In the activated sludge treatment system without a settling tank shown in FIG. 3, the activated sludge was introduced into the chemical reaction tank at a time of 40 m ³ at the time of the wastewater process, and was treated in the same manner as in Example 1. Activated sludge treatment of organic wastewater was performed in the same manner. As a result, the amount of excess sludge generated was about 20 kg / day.
Further, when the treated water to be discharged was examined, it was confirmed, as shown in Table 4, that the treated water was purified to the same extent as when treated by the conventional activated sludge method.

Comparative Example 2 Except that part of the activated sludge from the aeration tank was not treated with a chemical,
Activated sludge treatment of organic wastewater was performed in the same manner as in Example 2. As a result, the amount of excess sludge generated was 200 kg /
As compared with the case of Example 2, the amount of excess sludge was 10 times as large as that of Example 2. Table 4 shows the quality of the final treated water.

Table 4 Processing results

[0031]

As described above, according to the present invention, in the method for treating organic wastewater using the activated sludge method, the quality of the treated water discharged in the final stage is not deteriorated.
The amount of surplus sludge can be greatly reduced, and the purification treatment of organic wastewater can be performed easily and economically.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an example of the action of a bactericide for activated sludge of the present invention.

FIG. 2 is a schematic system diagram showing an example of a method for treating organic wastewater of the present invention.

FIG. 3 is a schematic system diagram showing another example of the method for treating organic wastewater of the present invention.

FIG. 4 is an example of a processing flow of a conventional method for treating organic wastewater.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naofumi Yamachi 1-9-8 Higashikanda, Chiyoda-ku, Tokyo Environmental Engineering Co., Ltd. (72) Inventor Taketoshi Asakawa 1-9- Higashikanda, Chiyoda-ku, Tokyo 8 Environmental Engineering Co., Ltd.

Claims (4)

[Claims] 1. Cationic surfactants, amphoteric surfactants, chlorine compounds, polyamines, aliphatic amines, phenols, nitrofurans, compounds having a trichloroalkylthio group, dithiocarbamates, aldehydes, alcohols A bactericide for activated sludge, comprising as a main component at least one compound selected from the group consisting of a kind, a protease, a glucanase, an amylase, and magnesium monoperoxyphthalate. 2. Cationic surfactants, amphoteric surfactants, chlorine compounds, polyamines, aliphatic amines, phenols, nitrofurans, compounds having a trichloroalkylthio group, dithiocarbamates, aldehydes, alcohols Activated sludge, wherein the activated sludge is sterilized with at least one compound selected from the group consisting of magnesium, protease, glucanase, amylase and monoperoxyphthalate, and the sterilization is carried out under heating and alkaline conditions. Fungicide method. 3. The sterilization of activated sludge according to claim 1, wherein, when the organic wastewater is purified using activated sludge, a part of the bacteria constituting the activated sludge is removed in any of the treatment steps. A method for treating organic wastewater, comprising sterilizing with an agent and suppressing the growth of activated sludge during the treatment process. 4. An organic wastewater is introduced into a treatment tank and aerated together with activated sludge, and then at least a part of the activated sludge is extracted from the treatment tank or a settling tank provided downstream of the treatment tank. And introducing the activated sludge into the treatment tank by disinfecting the activated sludge by introducing a disinfectant of the activated sludge into the treatment tank and introducing the treated activated sludge into the treatment tank. A method for treating organic wastewater as described in the above.