JP2006159130A - Method for suppressing generation of excess sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for suppressing the generation of excess sludge by subjecting organic waste water to biological treatment in the presence of an uncoupler, where, under the maintenance of the quality of treated water, the leakage of the uncoupler to the outside of the system is prevented, and the amount of the excess sludge to be generated is safely reduced at a low cost. <P>SOLUTION: Organic waste water is subjected to biological treatment in the presence of a carrier carrying an uncoupler. By carrying the uncoupler on the carrier, it can be stably held to the inside of the system. The carrier carrying the uncoupler exhibits a satisfactory uncoupling action by the contacting of its surface with a microbial cell, and suppresses the generation of excess sludge. According to the method where, by subjecting organic waste water to biological treatment in the presence of the uncoupler, the generation of excess sludge is suppressed, under the maintenance of the quality of treated water, the leakage of the uncoupler to the outside of the system is prevented, and the amount of the excess sludge to be generated can be safely reduced at a low cost. As the carrier, a polylactic acid based plastic carrier is preferable. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for suppressing the generation of excess sludge, and in particular, in a method for suppressing the generation of excess sludge by biologically treating organic wastewater in the presence of a uncoupling agent, while maintaining the treated water quality, The present invention relates to a method for reducing excess sludge generation safely and at low cost by preventing leakage of a conjugate agent from the system.

  Currently, the activated sludge treatment method is widely used for the treatment of sewage and organic wastewater discharged from factories and business establishments. This method is excellent in treatment efficiency and economy, but has a big problem that excess sludge is generated as waste. Excess sludge is said to occupy about half of industrial waste, and its processing and disposal requires a great deal of cost.

  Conventionally, this excess sludge has been treated by incineration or landfill after dehydration. However, in recent years, it has become an important issue to control the generation of excess sludge due to issues such as the regulation of incineration of surplus sludge by strengthening environmental regulations for dioxins and the difficulty of securing a final disposal site and an increase in treatment costs. It has become.

  On the other hand, the use of surplus sludge as solid fuel, composting, construction materials, etc. has been studied, but there is still no practical utility, and it is even more necessary for such a recycling system to function effectively. Since time is required, development of an effective technique for reducing excess sludge is awaited.

  As a technique for reducing the amount of excess sludge, there are a method for reducing the amount of generated excess sludge until final treatment and a method for suppressing the generation of sludge in the original wastewater treatment tank itself. In addition, there are a physicochemical method and a biological (biochemical) method depending on the means used, and the latter is a method mainly used for suppressing sludge generation in the treatment tank.

  The method for suppressing the generation of sludge in the wastewater treatment tank is a means for preventing the generation of excess sludge itself, so that secondary waste is not generated, and it is excellent in terms of economy. In this case, biological and biochemical methods such as a fast oxidation method, a predation method, and an uncoupling (proton transfer) method are used (Non-Patent Document 1).

  Among these, the fast oxidation method is a method of promoting the oxidation of organic matter including the self-oxidation of sludge, but means such as increasing the aeration amount or taking a longer aeration time must be used for stability, There are problems in terms of cost and labor. The predation method is a method using sludge predation by protozoa and minute metazoans, but has not yet been established as a practical technique. The uncoupling method is a method of adding an agent that suppresses generation of chemical energy ATP of microorganisms, and can be easily performed at a relatively low cost. The uncoupler suppresses energy generation without significantly inhibiting the respiratory electron transfer associated with substrate oxidation of microorganisms, so the addition of chemicals suppresses only the growth of bacteria without impairing respiration or the decomposition of organic matter, As a result, it is considered that the generation of excess sludge can be suppressed while enabling normal treatment.

  As uncoupling agents used in biochemical experiments and the like, carbonyl cyanide, m-chlorophenol hydrazone and 2,4-dinitrophenol are well known. On the other hand, in an example in which the uncoupling method is applied to suppress the generation of excess sludge, chlorophenol, nitrophenol and the like having weaker uncoupling action, tetrachlorosalicylanilide, etc. are used (Non-patent Document 2). , 3).

  Examples of using chlorophenols as uncoupling agents so far include 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,4,5 -Trichlorophenol has been reported, and in particular, it has been reported that the effect of 3,5-dichlorophenol is high (Patent Document 1).

On the other hand, it is known that petroleum-based plastics and biodegradable plastics adsorb various hydrophobic chemical substances, and a technique for removing pollutant chemical substances using these properties has been reported (Patent Document 2).
Japanese Patent Application No. 2004-65989 JP 2004-8967 A Akira Hiraishi: “Biological principles and application of excess sludge reduction in activated sludge treatment”, Water and wastewater, Vol.44, pp.853-860 (2002). Liu, A .: “Chemically reduced excess sludge production in the activated sludge process”, Chemosphere, Vol. 50, pp. 1-7 (2003). Wei, Y., Van Houten, RT, Burger, AR, Eikelboom, DH, and Fan, Y .: “Minimization of excess sludge production for biological wastewater treatment”, Water Research, Vol. 37, pp. 4453-4467 (2003 ).

  As described above, the uncoupling method is an excellent technique for suppressing excessive sludge generation in terms of cost and simplicity, but the uncoupling agent itself is a substance that is toxic to living organisms. If it leaks out of the system, there are concerns about adverse environmental effects. Therefore, in the practical application of the uncoupling method, it is required for safety that the uncoupling agent to be used does not leak out of the system, but an effective technique for preventing the uncoupling agent from leaking out of the system is still established. The current situation is not.

  The present invention solves the above-mentioned conventional problems, and in the method of suppressing the generation of excess sludge by biologically treating organic wastewater in the presence of the uncoupler, while maintaining the treated water quality, the uncoupler It aims at providing the generation | occurrence | production suppression method of the excess sludge which prevents the outside leakage of this system and reduces the excess sludge generation amount safely and at low cost.

  The surplus sludge generation suppression method of the present invention (Claim 1) is characterized in that organic wastewater is biologically treated in the presence of a carrier carrying a uncoupler.

  That is, as a result of intensive studies on the leakage prevention technology of uncoupling agents outside the system, the present inventors have found that petroleum-based plastics and biodegradable plastics can adsorb various hydrophobic substances, while uncoupling Since the agent is a proton-releasing hydrophobic substance, there is a possibility that the uncoupling agent can be immobilized by using the adsorption action of this plastic. By immobilizing the uncoupling agent, the uncoupling agent system The inventors have found that leakage can be prevented and completed the present invention.

  The surplus sludge generation suppression method according to claim 2 is characterized in that, in claim 1, the carrier is made of plastic.

  The surplus sludge generation suppression method according to claim 3 is characterized in that, in claim 2, the carrier is made of a biodegradable plastic.

  According to a fourth aspect of the present invention, there is provided a surplus sludge generation suppressing method according to the third aspect, wherein the carrier is made of a polylactic acid plastic.

  The surplus sludge generation suppression method according to claim 5 is the uncoupling agent according to any one of claims 2 to 4, wherein the carrier is used under the temperature condition equal to or higher than the glass transition temperature of the plastic constituting the carrier. It is characterized in that the uncoupling agent is supported on the carrier by contact.

  The method for suppressing the generation of excess sludge according to claim 6 is the method according to claim 5, wherein the carrier is immersed in a saturated solution of the uncoupling agent under a temperature condition equal to or higher than the glass transition temperature of the plastic constituting the carrier. Thus, the uncoupling agent is supported on the carrier.

  According to the method for suppressing the generation of excess sludge according to the present invention, in the method for suppressing the generation of excess sludge by biologically treating organic waste water in the presence of the uncoupling agent, by supporting the uncoupling agent on a carrier. It can be stably held in the system. This uncoupling agent-carrying carrier exhibits a good uncoupling action when bacterial cells come into contact with the surface thereof, and suppresses the generation of excess sludge. Therefore, according to the present invention, the amount of excess sludge generated can be reduced safely and at low cost by maintaining the quality of the treated water and preventing the uncoupling agent from leaking out of the system.

  In the present invention, the carrier is preferably made of plastic, and the uncoupling agent can be stably immobilized by utilizing its excellent hydrophobic substance adsorption ability.

  In particular, the plastic constituting the carrier is preferably a biodegradable plastic. If the biodegradable plastic is used, the uncoupling agent can be stably adsorbed in the adsorption treatment of the uncoupling agent at a glass transition temperature or higher described later. It is possible and preferable. In particular, among the biodegradable plastics, polylactic acid-based plastics are preferable because they are excellent in resistance to biodegradability and have a long life.

  As a method for supporting the uncoupler on such a plastic carrier, it is preferable to bring the carrier into contact with the uncoupler, preferably a saturated solution of the uncoupler, under a temperature condition higher than the glass transition temperature of the plastic. In other words, the uncoupler adsorbed on the plastic carrier under the temperature condition higher than the glass transition temperature enters the non-crystalline region of the plastic and is not easily desorbed. Since this property is particularly remarkable in biodegradable plastics, it is preferable to use a biodegradable plastic carrier as the carrier in the present invention.

  The embodiment of the surplus sludge generation suppression method of the present invention will be described in detail below.

<Target processing system>
The treatment system to be used for the uncoupling method of the present invention is activated sludge treatment such as municipal sewage and industrial wastewater, combined purification treatment such as domestic sewage, oxidation ditch, lagoon oxidation treatment, biofilm treatment, spray filter bed Any aerobic wastewater treatment system. There are no limitations on the processing mode such as anaerobic-aerobic processing and intermittent aeration.

<Uncoupler>
The uncoupler is not particularly limited, but 3,5-dichlorophenol is preferably used. That is, as described above, examples of the uncoupler used so far include analogues such as chlorophenol and nitrophenol, and tetrachlorosalicylanilide. Among these, chlorophenol analogues include 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, and 2,4,5-trichlorophenol. . Among these, those excellent in uncoupling action are included, but those having a high uncoupling effect have a disadvantage that they also inhibit the decomposition of the organic substrate. On the other hand, 3,5-dichlorophenol has little influence on the oxidation activity of organic substrates and has a strong inhibitory effect on cell growth accompanying energy generation. is there. However, an uncoupling agent other than 3,5-dichlorophenol may be used in combination with 3,5-dichlorophenol or alternately after adjusting the effective concentration. This cocktail-type uncoupling method is effective in maintaining the efficacy of the drug. As the uncoupling agent that can be used in combination with 3,5-dichlorophenol, basically, any one having a modifying group other than positions 3 and 5 of phenol, or any compound that is not a similar compound may be used. Particularly effective are, for example, 3,4-dichlorophenol, all trichlorophenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, all trichlorophenol, tetra Examples include chlorosalicylanilide.

<Carrier>
In the present invention, the uncoupling agent as described above is supported on a carrier and used.

  The carrier for supporting and immobilizing the uncoupling agent basically has an adsorption action on the uncoupling agent and does not desorb after adsorption, and is not particularly limited. Some polyethylene, polypropylene, polyethylene terephthalate, etc. are mentioned. In addition, a biodegradable plastic is preferable because it has excellent immobilization performance for the uncoupler.

  Examples of biodegradable plastics include α-hydroxypropionate (lactic acid), hydroxybutyrate, butylene succinate, ethylene succinate, caprolactone, butylene succinate adipate modified product, butylene succinate carbonate modified product, butylene adipate terephthalate, etc. A homopolymer composed of one kind, or a copolymer composed of two or more kinds thereof, derivatives or modified products thereof, such as polylactic acid, polyhydroxybutyrate, polybutylene succinate, polyethylene succinate, polycaprolactone, poly Butylene succinate adipate modification, polybutylene succinate carbonate modification, polybutylene adipate terephthalate, copolymers of hydroxybutyrate and 3-hydroxyvaleric acid, etc. Among these, polylactic acid (poly α-hydroxypropionate), polyhydroxybutyrate (polyhydroxybutyric acid), polycaprolactone, polybutylene succinate and the like are preferable, and among these, biodegradability is particularly preferable. Polylactic acid-based plastics such as polylactic acid and its derivatives or modified products are preferred because of their excellent resistance to heat and long life.

  The form of these carriers may be any form as long as it does not leak out of the system. For example, it can be in various other shapes such as granular, pellet, fiber, filament, and film. . The dimensions of the carrier are appropriately designed according to the form, taking into consideration leakage prevention and handling, contact efficiency with organic waste water, adsorption efficiency of uncoupler, and the like.

<Supporting uncoupling agent on carrier>
The method for supporting the uncoupler on the carrier is not particularly limited and can be carried out according to a conventional method. However, a preferred method for supporting a plastic carrier as a carrier will be described below.

  One of the properties of plastics including biodegradable plastics is the glass transition temperature. Adsorption of the uncoupler to the plastics depends on the glass transition temperature. That is, the adsorption of the uncoupling agent to the plastic easily proceeds at a temperature higher than the glass transition temperature of the plastic, and the uncoupling agent adsorbed to the plastic under this temperature condition can easily enter the non-crystalline region of the plastic. It will not be desorbed. Since this property is particularly remarkable for biodegradable plastics, it is considered that biodegradable plastics are particularly effective as uncoupling carriers. In addition, as described above, polylactic acid, polybutylene succinate and derivatives thereof, or a mixture thereof are excellent from the viewpoints of resistance to biodegradability and long life.

  The temperature condition at the time of the supporting treatment may be higher than the glass transition temperature of the plastic, and if it is excessively high, it causes thermal degradation of the plastic. Is done.

  In general, biodegradable plastics have a glass transition temperature below room temperature, so that the uncoupler can be easily adsorbed at room temperature. However, since the glass transition temperature of polylactic acid is 65 ° C., decoupling at room temperature is possible. Adsorption of the conjugating agent is difficult, and for that purpose, it is necessary to heat to 65 ° C. or higher, preferably 70 to 75 ° C.

  More specifically, the uncoupling agent is adsorbed by immersing the carrier in a saturated aqueous solution of the uncoupling agent, and stirring for about 1 to 2 days under a predetermined temperature condition as necessary. .

<Method of adding uncoupler-carrying carrier>
The uncoupler-carrying carrier may be added continuously in the treatment system, but added at intervals of 3-7 days to prevent the sludge from gaining resistance to the uncoupler. Is desirable. Further, for example, a pattern in which 3,5-dichlorophenol-carrying carrier is added for 3 to 7 days and then a carrier carrying another uncoupling agent is added for 3 to 7 days, and this can be repeated thereafter.

  The place where the uncoupler-carrying carrier is added may be any of inflow wastewater, storage tank, pretreatment tank, or aeration tank, but if added at a stage before the main treatment tank, dissolution will be faster. It is effective.

  When the uncoupler-carrying carrier is added to a water tank such as an aeration tank, it is preferable to add about 1 to 5% by volume of the tank capacity.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

  The method for supporting the uncoupler on the carrier and the method for preparing the sludge mixed solution are as follows.

<Method of supporting uncoupling agent on carrier>
As the carrier, a pellet made of polylactic acid having a diameter of 5 mm and a thickness of 1.5 to 2.0 mm was used, and 3,5-dichlorophenol was used as the uncoupling agent.

  The uncoupling agent is supported on the carrier by immersing the polylactic acid carrier in a saturated aqueous solution of 3,5-dichlorophenol (concentration: 4000 mg / L), holding it at a temperature of 75 ° C. and a stirring speed of 100 rpm for 2 days, and removing it. It was performed by washing with pure water and drying.

  Hereinafter, the polylactic acid carrier not supporting 3,5-dichlorophenol is referred to as “PLA”, and the polylactic acid carrier supporting 3,5-dichlorophenol by the above-described method is referred to as “3,5-DCP adsorption PLA”. Called.

<Method for preparing sludge mixture>
1L scale jacket after adjusting 1L of the collected sewage sludge mixture to a sludge concentration (MLSS) of 700mg / L using the sewage sludge mixture collected from the main aeration tank of Nakajima Treatment Plant (Toyohashi City) as seed sludge It added to the attached calster flask (made by Shibata Kagakusha). Acclimatization was started by adding artificial wastewater having the composition shown in Table 1 to this reactor so that the biological oxygen demand (BOD) loading was 0.35 g / g-MLSS / day. 500 ml of the supernatant was extracted and adjusted to 1 L again by adding autoclave-sterilized artificial waste water and tap water. The sludge concentration was adjusted to MLSS 700 mg / L once a week, and then the amount of artificial wastewater added was determined according to the increase in sludge. The temperature in the tank was 25 ° C., the stirring speed was 150 rpm, and aeration (3 L / min) was performed with a pump.

  After acclimatization for 2 months, as a result of the analysis of the community structure by PCR-DGGE method, it was confirmed that the dominant species was stable. Using.

Example 1
The above-mentioned artificial wastewater is added to the sludge mixed liquid prepared above so that the BOD load is 0.35 g / g-MLSS / day, and 3,5-DCP adsorption PLA is added to 5 volume% of the reactor internal volume ( 50 g), and the treatment was performed under the same conditions as in the method for preparing the sludge mixed solution.

  The change with time of the sludge concentration in the tank at this time was examined, and the results are shown in FIG.

The sludge concentration was determined by temporarily stopping the operation and measuring the turbidity (OD ₆₆₀ ) of the sludge in the reactor at a wavelength of 660 nm using a spectrophotometer.

Comparative Example 1
In Example 1, the treatment was carried out in the same manner except that the reactor was not charged with 3,5-DCP adsorption PLA, and the sludge turbidity (OD ₆₆₀ ) was similarly examined. The results are shown in FIG.

Comparative Example 2
In Example 1, treatment was conducted in the same manner except that 5 vol% (50 g) of the reactor internal volume was added to the reactor in place of 3,5-DCP adsorption PLA, and the sludge turbidity (OD ₆₆₀ ) was similarly obtained. The results are shown in FIG.

  From FIG. 1, the sludge concentration gradually increased in Comparative Examples 1 and 2, whereas in Example 1 in which the uncoupler-carrying carrier was introduced, the sludge concentration was reduced, and therefore excess sludge was generated. It can be seen that the amount can be suppressed.

In Example 1 and Comparative Examples 1 and 2, the reactor supernatant was collected periodically during operation, centrifuged, filtered through a 0.45 μm membrane filter, and further filtered through a 0.25 μm membrane filter. When the TOC concentration was measured with a TOC measuring device “TOC-V _CPH / TOC-V _CPN ” manufactured by Shimadzu Corporation, the TOC concentration was 10 to 10 in each case during the operation period of about 1 month. In the range of 15 mg / L, Example 1 using the uncoupler-carrying carrier has no problem of deterioration in the quality of treated water compared to Comparative Examples 1 and 2, and the equivalent treated water quality can be obtained. Was confirmed.

  When the 3,5-DCP-adsorbed PLA was put into an aeration tank of an actual food wastewater treatment facility in an amount of 5% by volume with respect to the tank volume, the quality of the treated water was similarly lowered. Thus, it was confirmed that the amount of surplus sludge generated could be reduced, and that there was no problem of outflow of 3,5-DCP adsorption PLA.

Is a graph showing changes with time of the sludge turbidity _{(OD 660)} of Example 1 and Comparative Examples 1 and 2.

Claims (6)

  A method for suppressing the generation of excess sludge, characterized in that organic wastewater is biologically treated in the presence of a carrier carrying an uncoupling agent.   The method for suppressing the generation of excess sludge according to claim 1, wherein the carrier is made of plastic.   The method for suppressing the generation of excess sludge according to claim 2, wherein the carrier is made of a biodegradable plastic.   4. The method for suppressing the generation of excess sludge according to claim 3, wherein the carrier is made of polylactic acid plastic.   5. The carrier according to claim 2, wherein the carrier is brought into contact with the uncoupler under a temperature condition equal to or higher than the glass transition temperature of the plastic constituting the carrier. A method for suppressing the generation of excess sludge, which is characterized in that it is supported.   6. The carrier according to claim 5, wherein the carrier is supported on the carrier by immersing the carrier in a saturated solution of the uncoupler under a temperature condition equal to or higher than the glass transition temperature of the plastic constituting the carrier. A method for suppressing the generation of excess sludge.

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