Methods for treating organic wastewater

Abstract

To provide a method for treating organic wastewater using a non-aerated biological treatment device that can simply and effectively suppress a generation of flies.SOLUTION: There is provided a method for treating organic wastewater, including: supplying organic wastewater to a water receiving tank of a non-aerated biological treatment device comprising a water receiving tank and a filter bed tank; spreading organic wastewater from the water receiving tank to the filter bed tank for biological treatment; and adding an insect growth control agent that suppresses a growth of fly larvae to the organic wastewater in the biological treatment device, in which the addition of the insect growth control agent is carried out while the supply of organic wastewater to the water tank is stopped and a discharge of the organic wastewater from the biological treatment device is stopped, and the biological treatment is carried out while circulating the organic wastewater between the water receiving tank and the filter bed tank and while the supply of the organic wastewater to the water receiving tank is stopped and the discharge of organic wastewater from the biological treatment device is stopped.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating organic wastewater using a non-aeration type biological treatment device to prevent the infestation of flies. [Background technology]

[0002] Non-aeration biological treatment methods such as the trickling filter method do not require aeration, so compared to the standard activated sludge method, they have the advantage of consuming less electricity, producing less sludge, and reducing the cost of disposing of excess sludge. For this reason, in recent years, their application to sewage treatment in developing countries such as Southeast Asia, where infrastructure such as electricity is not well developed, has been considered.

[0003] On the other hand, in the non-aeration type biological treatment method, sludge adheres to the filter media of the trickling filter, and the sludge decays, generating a foul odor. It is known that this sludge causes the emergence of a type of moth fly called filter bed fly. In particular, during the period from May to June and from September to October, when the temperature is 20°C to 25°C depending on the region, filter bed flies are often found to be generated in non-aeration type biological treatment devices, such as trickling filter bed treatment devices. There is a problem that the generation of filter bed flies deteriorates the working environment when maintaining the device. The following technologies are known as countermeasures to the above problem.

[0004] Patent Document 1 (International Publication No. 2015 / 001708) discloses a method for removing eggs and larvae of filter bed flies, biofilm excessively attached to the surface of the filter media, and solid matter trapped between the filter media from the trickling filter bed by using a cleaning means. The cleaning means includes a cleaning water storage mechanism that stores cleaning water in the trickling filter bed and floods the filter media layer, an agitation and cleaning mechanism that agitates and cleans the filter media to which nitrifying bacteria are attached in the flooded filter media layer, and a drainage mechanism that discharges the cleaning water after agitation and cleaning. The document describes that the cleaning means can efficiently treat the water to be treated while suppressing the generation of filter bed flies and bad odors.

[0005] Patent Document 2 (JP 2020-157237 A) describes that when water is poured into an aquarium, the entire filter layer is immersed in water, and the state is maintained for a certain period of time to suffocate the larvae and eggs of harmful organisms attached to the filter layer, the harmful organisms living in the aquarium often remain even after the cleaning operation is completed and become contaminated again because the harmful organisms living in the aquarium retreat upward along the wall of the aquarium. Therefore, this document proposes a method of irradiating the inner wall of the aquarium with light of a wavelength that repels harmful organisms living in the aquarium filled with the filter layer when filling the aquarium with water. This method prevents harmful organisms such as fly larvae from retreating upward along the inner wall of the aquarium, and they sink below the water surface and suffocate to death, or are discharged together with the wastewater when the water is drained, making it possible to more effectively kill or remove harmful organisms.

[0006] Patent Document 3 (JP Patent Publication 7-147875 A) discloses a method for controlling pests in which an aerosol consisting of an insecticidal component, an oil-based solvent, and a flammable propellant is sprayed at a pest infested area without fire at a rate of 5 g or more per second, although this is not a technology related to a non-aeration type biological treatment method. This document describes that by spraying the required amount of the aerosol contents in a short period of time, pests can be controlled extremely efficiently, despite being sprayed randomly, and the operation time can be significantly reduced.

[0007] Patent Document 4 (JP Patent Publication No. 2003-95811) discloses a pesticide for insects living in manholes, which is characterized by the ability to spray an insecticide in foam form, although it is not a technology related to a non-aeration type biological treatment method. This document describes that by using the pesticide for insects living in manholes, it is possible to efficiently control moth flies, Culex pipiens molestus, and flea flies that occur in manholes, and also to suppress re-infestation for a long period of time. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2015 / 001708 [Patent Document 2] JP 2020-157237 A [Patent Document 3] Japanese Unexamined Patent Publication No. 7-147875 [Patent Document 4] JP 2003-95811 A Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, in order to suppress the occurrence of flies on the filter bed, a cleaning means is required that has a cleaning water storage mechanism that stores cleaning water in the filter bed and floods the filter layer, an agitation and cleaning mechanism that agitates and cleans the filter layer to which nitrifying bacteria are attached, and a drainage mechanism that discharges the cleaning water after agitation and cleaning. Therefore, when installing the cleaning means in an existing facility, the facility needs to be renovated, and the cleaning operation of flooding and agitating the filter media is required, which is not convenient. Furthermore, the wastewater generated by the cleaning needs to be treated.

[0010] Patent Document 2 requires a light emitting device that irradiates the inner wall of the tank with light of a repelling wavelength. The invention of Patent Document 2 is premised on the adoption of a method in which the tank is filled with water, the entire filter layer is immersed in the water, and this state is maintained for a certain period of time to suffocate and kill the larvae and eggs of harmful organisms attached to the filter layer. For this reason, as with Patent Document 1, equipment renovation is required, and the method is not simple because it requires filling the tank with water and irradiating light for a certain period of time, and further requires wastewater treatment.

[0011] Patent Document 3 requires that the aerosol be sprayed at the location where pests occur. If the location where pests occur is connected to the outside air and not closed, as in the case of a trickling filter treatment device, the aerosol will diffuse into the atmosphere, making this an ineffective pest control method. In addition, although the suppression effect on adult flies living in the air can be expected, the suppression effect on fly larvae living in water, on the inner walls of aquariums, in biofilms, etc. is unclear. In order to effectively suppress the occurrence of flies, it is desirable to be able to suppress the growth of fly larvae.

[0012] Patent Document 4 is an invention characterized by spraying a foam-like insecticide into a closed space such as a manhole. Therefore, even if the insecticide is sprayed in foam form, if the location where pests are found is open to the outside air and not closed, as in a trickling filter treatment device, the insecticide will diffuse into the atmosphere, causing the same problem as Patent Document 3.

[0013] In view of the above circumstances, an object of the present invention is, in one embodiment, to provide a method for treating organic wastewater using a non-aeration type biological treatment device that can easily and effectively suppress the occurrence of flies. Also, an object of the present invention is, in another embodiment, to provide a non-aeration type biological treatment device that can easily and effectively suppress the occurrence of flies. [Means for solving the problem]

[0014] As a result of intensive research aimed at solving the above problems, the present inventors discovered that adding an insect growth regulator to organic wastewater is significantly effective in suppressing the occurrence of flies, and thus created the present invention, which is exemplified below.

[0015] [1] Supplying the organic wastewater to a non-aeration type biological treatment device; A step of biologically treating the supplied organic wastewater in the biological treatment device; adding an insect growth regulator to the organic wastewater before, after, or both of the organic wastewater being fed to the biological treatment device; A method for treating organic wastewater comprising: [2] The method for treating organic wastewater described in [1], wherein there is a period when an insect growth regulator is added to the organic wastewater and a period when an insect growth regulator is not added to the organic wastewater, and the amount of organic wastewater supplied per unit time to the biological treatment device is lower during the period when an insect growth regulator is added to the organic wastewater than during the period when an insect growth regulator is not added to the organic wastewater. [3] The method for treating organic wastewater described in [1], further comprising the step of adding an insect growth regulator to the organic wastewater in the biological treatment device while the supply of the organic wastewater to the biological treatment device is stopped and the discharge of the organic wastewater from the biological treatment device is stopped. [4] The method for treating organic wastewater according to [3], wherein the supply of organic wastewater to the biological treatment device is stopped and the discharge of organic wastewater from the biological treatment device is stopped for a period of 12 hours or more. [5] The method for treating organic wastewater according to [3] or [4], wherein while the supply of organic wastewater to the biological treatment device is stopped and the discharge of organic wastewater from the biological treatment device is stopped, the biological treatment device biologically treats the organic wastewater while circulating it within the biological treatment device. [6] The method for treating organic wastewater according to any one of [3] to [5], wherein no insect growth regulator is added to the organic wastewater while the organic wastewater is being supplied to the biological treatment device. [7] A water tank for storing organic wastewater; A biofilm for biologically treating organic wastewater; a means for supplying an insect growth regulator to the organic wastewater in the receiving tank; A non-aeration type biological treatment device equipped with [8] At least one filter bed tank that contains a carrier supporting the biofilm and communicates with the atmosphere; A sprinkler for sprinkling the organic wastewater in the water receiving tank into the filter bed tank; The non-aeration type biological treatment device described in [7] is provided with: [9] The non-aeration type biological treatment device according to [7] or [8], wherein the means for supplying the insect growth regulator is a water-permeable container for holding the insect growth regulator in tablet form and immersing it in the organic wastewater in the receiving tank.

[10] The non-aeration type biological treatment device described in [9], wherein the container is hung on the wall on the inlet side of the water tank. Effect of the Invention

[0016] According to the organic wastewater treatment method and biological treatment device of the present invention, it is possible to suppress the occurrence of flies by a simple operation of adding an insect growth regulator to the organic wastewater. In addition, since the insect growth regulator is added to the organic wastewater, not to the air, the insect growth regulator spreads at a desired concentration throughout the wastewater in the biological treatment device, and the insect growth regulator can reach the biofilm in which the fly larvae live. Therefore, the growth inhibition effect on the fly larvae is high, and as a result, the effect of suppressing the occurrence of adult flies is also high. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing a configuration example of a biological treatment device according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic diagram showing a configuration example of a biological treatment device according to a second embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing an example of a water-permeable container for containing an insect growth regulator. [Figure 4] FIG. 1 is a schematic diagram illustrating an example of the configuration of a membrane carrier that can be used in a biological treatment device according to a first embodiment and a second embodiment of the present invention. [Diagram 5] FIG. 4 is a schematic plan view of one of the membrane carriers shown in FIG. [Figure 6] FIG. 1 is a flow diagram of a sewage treatment system using a non-aeration type biological treatment device according to one embodiment of the present invention. [Figure 7] 1 is a graph showing the progress of emergence of fly larvae in Examples 1 to 3 and a Comparative Example. [Figure 8]1 is a graph showing the progress of emergence of adult flies in Examples 1 to 3 and a Comparative Example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment shown below is an example of an apparatus and a method for embodying the technical idea of ​​the present invention, and it should be understood that the design may be appropriately changed or improved based on the ordinary knowledge of a person skilled in the art without departing from the spirit of the present invention.

[0019] [1. Organic wastewater treatment method and biological treatment system overview] A method for treating organic wastewater according to one embodiment of the present invention includes the steps of: Supplying the organic wastewater to a non-aeration type biological treatment device; A step of biologically treating the supplied organic wastewater in a biological treatment device; adding an insect growth regulator to the organic wastewater before, after, or both of the organic wastewater being fed to a biological treatment device; Includes.

[0020] The organic wastewater targeted by the treatment method according to the present embodiment is not particularly limited, and examples thereof include sewage, human waste, and industrial wastewater. Examples of industrial wastewater include wastewater from food factories, chemical factories, and paper factories. According to one embodiment of the present invention, the organic wastewater is supplied to a non-aeration type biological treatment device and undergoes biological treatment. In this specification, the non-aeration type biological treatment device refers to a biological treatment device having a biofilm that can come into contact with air without performing an operation of blowing compressed air as fine bubbles into the organic wastewater, which is the water to be treated, using an aeration tube, an aerator, or the like.

[0021] The majority of flies that occur in non-aeration biological treatment equipment are moth flies. While moth flies develop and live using putrid water as nutrients, moth flies cannot live in water because they supply oxygen to their bodies through breathing. For this reason, they rarely occur in biological treatment equipment that uses a submerged aerobic biological treatment method (activated sludge method, contact oxidation method, etc.). They often occur in non-aeration biological treatment equipment that can secure a space that comes into contact with air other than water, such as a trickling filter, and grow in a cycle of egg → larva → pupa → adult → egg. In particular, larvae feed on the sludge of the biofilm as food, so they are often found in the biofilm. For this reason, the treatment method according to this embodiment is intended for non-aeration biological treatment equipment.

[0022] A non-aeration type biological treatment device according to one embodiment of the present invention includes a receiving tank for storing organic wastewater, a biofilm for biologically treating the organic wastewater, and a means for supplying an insect growth regulator to the organic wastewater in the receiving tank. Examples of non-aeration type biological treatment devices include, but are not limited to, trickling filters and rotating disk devices. A trickling filter device according to one embodiment of the present invention comprises at least one filter bed tank that contains a carrier carrying a biofilm and is connected to the atmosphere, and a sprinkler for spraying organic wastewater in a receiving tank into the filter bed tank. A rotating disc device according to one embodiment of the present invention comprises at least one, and preferably multiple, discs supporting a biofilm, which rotate around a horizontally extending axis of rotation, thereby allowing the supported biofilm to alternately come into contact with organic wastewater in a receiving tank and with the atmosphere.

[0023] The biological treatment may be either aerobic biological treatment or anaerobic biological treatment, but as described above, fly infestation is likely to be a problem in non-aeration type biological treatment devices that can secure space for contact with air. For this reason, the treatment method according to this embodiment is particularly suitable for use when organic wastewater is biologically treated at least partially aerobically. In non-aeration type biological treatment devices, aerobic bacteria can grow outside the carrier, and anaerobic bacteria can grow inside the carrier. For this reason, aerobic and anaerobic bacteria grow in the biological treatment device, making it possible to perform both aerobic and anaerobic biological treatment.

[0024] Chemicals for controlling fly infestations are classified into (1) those that are effective against adult flies, (2) those that are effective against larvae, and (3) those that are effective against both. (1) There are many commercially available insecticides that are effective against adult flies. (2) There are insect growth regulators (IGRs) that are effective against larvae. Insect growth regulators (IGRs) are insecticides that disrupt the balance of hormones that control insect metamorphosis and molting, thereby inhibiting the molting and emergence of insects, and ultimately causing their death.

[0025] Fly larvae feed on the sludge in the biofilm and reproduce. Therefore, if the growth of the larvae can be suppressed, the emergence of adult flies can also be suppressed. Insect growth regulators are effective in suppressing the growth of larvae, and the easiest method is to add them to the organic wastewater to be treated and deliver them to the biofilm.

[0026] Therefore, in the treatment method according to the present embodiment, a step of adding an insect growth regulator to the organic wastewater is carried out before or after the organic wastewater is supplied to the biological treatment device, or both. By simply carrying out the simple operation of adding the insect growth regulator, it is possible to distribute the insect growth regulator at a desired effective concentration in the organic wastewater and biofilm in the biological treatment device, and it is possible to effectively suppress the occurrence of flies. The operation of adding the insect growth regulator to the organic wastewater is simple, and does not require extensive equipment modification. The concentration of the active ingredient of the insect growth regulator added to the wastewater may be appropriately set to an effective concentration according to the type of active ingredient in the insect growth regulator, and there is no particular restriction.

[0027] Before the organic wastewater is supplied to the biological treatment device, typically, means before the organic wastewater flows into the receiving tank of the biological treatment device. After the organic wastewater is supplied to the biological treatment device, typically, means after the organic wastewater flows into the receiving tank of the biological treatment device. The step of adding an insect growth regulator to the organic wastewater may be performed either before or after the organic wastewater is supplied to the biological treatment device, or may be performed both. Since the step can be performed even when the supply of the organic wastewater to the biological treatment device is stopped, it is preferable to perform the step of adding an insect growth regulator to the organic wastewater in the receiving tank after the organic wastewater is supplied to the biological treatment device.

[0028] Examples of active ingredients used in insect growth regulators include, but are not limited to, pyriproxyfen and diflubenzuron. In the case of pyriproxyfen, good effects can be obtained by adding the insect growth regulator so that the pyriproxyfen concentration in the organic wastewater is 2 to 20 μg / L, preferably 5 to 10 μg / L. In the case of diflubenzuron, good effects can be obtained by adding the insect growth regulator so that the diflubenzuron concentration in the organic wastewater is 0.2 to 2.0 mg / L, preferably 0.75 mg / L to 1.5 mg / L.

[0029] Flies grow well when the temperature is between 15°C and 30°C, especially between 20°C and 25°C, but grow poorly at low temperatures in winter (below 15°C) and high temperatures in summer (above 30°C). For this reason, flies tend to appear more frequently in May to June and September to November, depending on the region. Therefore, it is effective to add the insect growth regulator to the organic wastewater when the temperature of the organic wastewater is between 15°C and 30°C, preferably between 20°C and 25°C.

[0030] There is no particular limitation on the formulation of the insect growth regulator, and it may be liquid or solid, but from the viewpoint of handling, solid forms such as granules, wettable powders, tablets (including effervescent tablets), etc. are preferred, and tablets are more preferred. When a solid insect growth regulator is added to organic wastewater, it dissolves and the active ingredient can be distributed throughout the wastewater in the biological treatment device. Table 1 shows examples of representative insect growth regulators (Chemical A, Chemical B, and Chemical C) that are commercially available. The insect growth regulator may be dissolved in water to make it liquid, and then supplied to the biological treatment device by a chemical liquid addition device having a reservoir tank for the insect growth regulator and an injection pump, etc.

[0031] [Table 1]

[0032] The insect growth regulator may be added to the organic wastewater in a required amount manually, or an automatic adder may be installed to automatically add the required amount at a predetermined timing. A method of manually adding a solid insect growth regulator to the organic wastewater includes a method of putting a solid insect growth regulator into a container and contacting the insect growth regulator in the container with the organic wastewater. The container containing the insect growth regulator is suitable as a means for supplying the insect growth regulator to the organic wastewater in the water receiving tank. The container is preferably a water-permeable container, for example, a container having a plurality of water-permeable holes such as a mesh-shaped container. There is no particular restriction on the material of the water-permeable container, but metal, plastic, ceramics, etc. can be used. In the case of a metal container, a wire mesh (mesh metal), punched metal, or expanded metal can be suitably used for the container storage section. FIG. 3 shows a schematic example of a water-permeable container for storing the insect growth regulator.

[0033] The container shown in Fig. 3(A) is a lidless container 310, and includes a storage section 311 made of wire mesh (mesh metal) and a hanging section 312 connected to storage section 311. In container 310 in Fig. 3(A), storage section 311 has an input port 313 for inputting an insect growth regulator into storage section 311, but there is no lid for closing input port 313.

[0034] The container shown in Fig. 3(B) is a lidded container 320, which includes a storage section 321 made of wire mesh (mesh metal), a hanging section 322 connected to storage section 321, and a lid 324. In the container 320 in Fig. 3(B), storage section 321 has an input port 323 for inputting an insect growth regulator into storage section 321, and is provided with a lid 324 for closing input port 323. In order to prevent the input insect growth regulator from accidentally leaking out of the container, a lidded container 320 is preferred. There is no particular limitation on the method for fixing lid 324 to storage section 321, but examples include a screw type, a clamp type, and the like.

[0035] The hanging parts 312, 322 are not particularly limited as long as they have the function of suspending and holding the storage parts 311, 321. For example, the hanging part 312 may be a rigid hanging part such as a rod-like part as shown in FIG. 3A, or the hanging part 322 may be a flexible hanging part such as a chain-like part as shown in FIG. 3B. It is convenient for the hanging parts 312, 322 to have hook parts 315, 325 for locking at a predetermined location. There is no particular limit to the installation location of the water-permeable containers 310, 320, but it is preferable to hang them on the wall on the inlet side of the water receiving tank of the biological treatment device from the viewpoint of increasing the residence time of the insect growth regulator in the biological treatment device. Furthermore, when the water-permeable containers 310, 320 are hung on the wall on the inlet side of the water tank of the biological treatment device, it is preferable to hang the water-permeable containers 310, 320 at a position higher than half the water level in the water tank, from the viewpoint that the insect growth regulator will easily spread in a short period of time together with the inflowing organic wastewater.

[0036] There is no particular restriction on the timing of adding the insect growth regulator, but from the viewpoint of effectively suppressing the occurrence of flies while suppressing chemical costs, it is preferable to add the insect growth regulator to the organic wastewater when the residence time of the insect growth regulator in the biological treatment device is long. Therefore, in a preferred embodiment, there is a time when the insect growth regulator is added to the organic wastewater and a time when the insect growth regulator is not added to the organic wastewater, and the supply amount per unit time of the organic wastewater supplied to the biological treatment device is lower during the time when the insect growth regulator is added to the organic wastewater than during the time when the insect growth regulator is not added to the organic wastewater. For example, when the water level of the raw water tank that stores the organic wastewater supplied to the biological treatment device falls below a set value (e.g., below 20% of the effective water depth of the tank), the raw water pump stops and the raw water supply is stopped. If the supply of raw water to the raw water tank is low, the operation of the raw water pump is likely to become intermittent, and the supply amount per unit time of the organic wastewater also decreases.

[0037] In fact, the amount of organic wastewater supplied to the biological treatment device per unit time is not constant, but fluctuates, and even the supply may stop. For example, in the case of human waste treatment, human waste and septic tank sludge are not accepted on weekends, and the raw water supply is stopped. In some areas, human waste and septic tank sludge are collected on weekdays (Monday to Friday) in human waste treatment, and the separated water after filtration and dehydration is stored in a separation tank (for 1 to 2 days). For this reason, the amount of separated water decreases on weekends, and the raw water supply to the biological treatment device is stopped. While the amount of organic wastewater supplied per unit time is decreasing, the amount of the added insect growth regulator discharged from the biological treatment device together with the organic wastewater after biological treatment also decreases or stops, so the residence time of the insect growth regulator in the biological treatment device is extended, and the amount of insect growth regulator required to be added to maintain the concentration of the active ingredient of the insect growth regulator in the wastewater at a predetermined value can be reduced, allowing the active ingredient of the insect growth regulator to act for a sufficient period of time.

[0038] In a more preferred embodiment, the insect growth regulator is added to the organic wastewater in the biological treatment device while the supply of the organic wastewater to the biological treatment device is stopped and the discharge of the organic wastewater from the biological treatment device is stopped. During normal operation, the insect growth regulator added to the organic wastewater gradually overflows from the biological treatment device together with the organic wastewater after biological treatment, but while the supply of the organic wastewater to the biological treatment device is stopped and the discharge of the organic wastewater from the biological treatment device is stopped, the insect growth regulator added to the organic wastewater does not flow out from the biological treatment device, so that the amount of insect growth regulator added required to maintain the concentration of the active ingredient of the insect growth regulator in the organic wastewater at a predetermined value can be reduced and the added insect growth regulator can be used without waste.

[0039] The longer the time during which the supply of organic wastewater to the biological treatment device and the discharge of the organic wastewater from the biological treatment device are stopped, the greater the effect of the insect growth regulator added to the organic wastewater in suppressing the occurrence of flies, so the time is preferably 12 hours or more, more preferably 16 hours or more, and even more preferably 20 hours or more. However, if the time is too long, wastewater treatment will be delayed, so the time is preferably 48 hours or less, and more preferably 24 hours or less.

[0040] The timing of adding the insect growth regulator to the organic wastewater in the biological treatment device is preferably within 12 hours, more preferably within 3 hours, and even more preferably within 1 hour after the start of a state in which the supply of organic wastewater to the biological treatment device is stopped due to the stop of the raw water pump that supplies the organic wastewater to the biological treatment device, and the discharge of the organic wastewater from the biological treatment device is stopped. After the first addition of the insect growth regulator after the start of the stopped state, the insect growth regulator may be additionally added once or multiple times while the stopped state continues, as necessary. In addition, the time from the first addition of the insect growth regulator after the start of the stopped state until the supply of organic wastewater to the biological treatment device is resumed due to the restart of the raw water pump, etc., is preferably 6 hours or more, more preferably 12 hours or more, and even more preferably 24 hours or more. When using a liquid insect growth regulator, the liquid addition device, such as an injection pump, can be set to start operating a specified amount of insect growth regulator automatically a specified time (e.g., 6 to 24 hours) after receiving a stop signal from the raw water pump.

[0041] During the time when the supply of organic wastewater to the biological treatment device is stopped and the discharge of organic wastewater from the biological treatment device is stopped, the biological treatment device preferably performs biological treatment while circulating the organic wastewater within the biological treatment device. By adding an insect growth regulator while circulating the organic wastewater within the biological treatment device, the added insect growth regulator can be easily distributed throughout the organic wastewater and biofilm within the biological treatment device, and the insect growth regulator can be effectively used against fly larvae that feed on the sludge of the biofilm. "While circulating the organic wastewater within the biological treatment device" refers to, for example, in the case of a trickling filter bed device, a state in which the organic wastewater is circulated between the water receiving tank and the filter bed tank, and in the case of a rotating disk device, a state in which a circulating flow is generated in the water receiving tank by rotating the disk. Circulation may be performed continuously or intermittently.

[0042] From the viewpoint of reducing chemical costs, it is advantageous to operate the biological treatment device such that the insect growth regulator is not added to the organic wastewater while the organic wastewater is being supplied to the biological treatment device. Even in this case, in order to distribute the insect growth regulator throughout the device, for example, the addition of the insect growth regulator may be started just before the supply of the organic wastewater is stopped, or the insect growth regulator may be added while temporarily supplying the organic wastewater.

[0043] There is no particular restriction on the frequency of adding the insect growth regulator to the organic wastewater, but a smaller amount can save costs and management labor, while a larger amount will be more effective in suppressing fly infestations. From a cost-effective perspective, it is preferable to add the insect growth regulator to the organic wastewater once or twice a week. Here, if tablets are added when the amount of raw water decreases and the raw water supply is stopped, the process of adding the insect growth regulator is counted as one addition per day in principle. When raw water is continuously supplied to the raw water tank and raw water flows into the receiving tank in response to the operation of the raw water pump, the raw water pump flow rate, the chemical pump flow rate, and the concentration of the active ingredient of the insect growth regulator in the chemical tank are adjusted so that the concentration of the active ingredient in the raw water is a predetermined concentration. Therefore, the concept of the number of times of addition does not apply in this case.

[0044] Flies multiply in large numbers in a short period of time, fly around indoors day and night, and are easily seen by people, causing discomfort and a feeling of uncleanliness, so it is important to prevent adult flies from escaping from the biological treatment device. Although the above-mentioned insect growth regulator can be added to suppress the occurrence of flies, if the amount added is insufficient or the frequency of addition is low, flies may occur. In order to prevent adult flies from escaping, it is important to increase the airtightness of the biological treatment device. For example, in the case of a trickling filter device, measures can be taken to cover the ventilation opening 116 with a wire mesh 118 to prevent flies from entering or exiting, or to install an airtight lid 114 on the top of the sprinkler 110.

[0045] [2. Example of biological treatment equipment configuration] 1 shows a schematic diagram showing a configuration example of a biological treatment device 100 according to a first embodiment of the present invention. The biological treatment device 100 is a trickling filter device including a water receiving tank 102 for storing organic wastewater, at least one filter bed tank 103 arranged above the water receiving tank 102 and communicating with the atmosphere, a stand 106 supporting the filter bed tank 103, a carrier 104 housed in the filter bed tank 103 and carrying a biofilm for biologically treating the organic wastewater, a sprinkler 110 for sprinkling the organic wastewater in the water receiving tank 102 to the filter bed tank 103, a circulation line 108 for supplying the organic wastewater in the water receiving tank 102 to the sprinkler 110, a circulation pump 105 installed in the middle of the circulation line 108, and a container 109 for storing an insect growth regulator.

[0046] A raw water tank 206 is provided upstream of the receiving tank 102 to store raw water flowing in from a raw water line 216, and the raw water stored in the raw water tank 206 is supplied to the receiving tank 102 by a raw water pump 202 through an inflow line 204. Examples of raw water include organic wastewater (night soil, sewage, food factory wastewater, etc.) that contains a large amount of BOD components.

[0047] The raw water flowing into the receiving tank 102 is mixed with treated water from the filter bed tank 103. The mixed liquid in the receiving tank 102 is transferred to the upper part of the filter bed tank 103 through a circulation line 108 by a circulation pump 105. The mixed liquid is then sprayed by a sprinkler 110 onto the carrier 104 carrying a biofilm. Organic matter such as BOD components in the mixed liquid is decomposed and removed by the biofilm formed by microorganisms proliferating on the surface of the carrier, and the mixed liquid returns to the receiving tank 102.

[0048] In the first embodiment, a container 109 containing an insect growth regulator is used as a means for supplying the insect growth regulator. The container 109 is preferably a water-permeable container such as a wire mesh cage. The container 109 includes a storage section 109a and a hanging section 109h connected to the storage section 109a. A hook 112 is installed on the wall 102w on the inlet side of the water receiving tank 102, and the container 109 is hung from the wall 102w on the inlet side of the water receiving tank 102 by engaging the hanging section 109h with the hook 112. The container 109 is immersed in the mixed liquid (organic wastewater) in the water receiving tank 102 with a predetermined amount of solid insect growth regulator such as a tablet stored in the storage section 109a. The insect growth regulator in the water-permeable container dissolves and spreads in the water receiving tank 102, and also reaches the biofilm supported on the carrier 104 through the circulation line 108. As a result, the insect growth regulator can reach the fly larvae living in the biofilm, effectively inhibiting the growth of the fly larvae and inhibiting the emergence of adult flies.

[0049] The sprinkler 110 preferably sprinkles the mixed liquid evenly onto the carrier 104 in the filter bed tank 103. There are no particular limitations on the sprinkler 110, and any sprinkler such as a perforated plate, a sprinkler type, a spiral type nozzle, or a self-propelled rotary sprinkler can be used.

[0050] A treated water tank 208 for storing treated water is provided downstream of the receiving tank 102, and the treated water overflowing from the biological treatment device 100 is supplied to the treated water tank 208 through an outflow line 207. The treated water in the treated water tank 208 is then discharged (in most cases, it is discharged into a sewer system).

[0051] 2 shows a schematic diagram showing a configuration example of a biological treatment device 200 according to a second embodiment of the present invention. The biological treatment device 200 is a trickling filter device including a water receiving tank 102 for storing organic wastewater, at least one filter bed tank 103 arranged above the water receiving tank 102 and communicating with the atmosphere, a stand 106 supporting the filter bed tank 103, a carrier 104 housed in the filter bed tank 103 and carrying a biofilm for biologically treating the organic wastewater, a sprinkler 110 for sprinkling the organic wastewater in the water receiving tank 102 to the filter bed tank 103, a circulation line 108 for supplying the organic wastewater in the water receiving tank 102 to the sprinkler 110 and a circulation pump 105 installed in the middle of the circulation line 108, a chemical storage tank 210 for storing an insect growth regulator, and a chemical injection pump 214 for sending the insect growth regulator in the chemical storage tank 210 to the raw water line 216.

[0052] The only difference between the biological treatment device 200 according to the second embodiment and the biological treatment device 100 according to the first embodiment is the means for adding an insect growth regulator. The other components of the biological treatment device 200 according to the second embodiment are the same as those of the biological treatment device 100 according to the first embodiment. Therefore, explanations of the components denoted by the same reference numerals as those of the biological treatment device 100 according to the first embodiment will be omitted.

[0053] In the second embodiment, a liquid medicine injection pump 214 is used as a means for supplying the insect growth regulator. The liquid insect growth regulator stored in the liquid medicine storage tank 210 is supplied to the raw water line 216 through the liquid medicine injection line 212 by operating the liquid medicine injection pump 214. The liquid medicine injection pump 214 may be configured to automatically add a predetermined amount of the insect growth regulator at a predetermined timing by using a metering pump or the like. The supply destination of the insect growth regulator is not limited to the raw water line 216, but may be the inflow line 204, or may be directly supplied to the mixed liquid (organic wastewater) in the water receiving tank 102. From the viewpoint of being able to supply the insect growth regulator when the raw water pump 202 is stopped, it is preferable to supply it directly to the mixed liquid (organic wastewater) in the water receiving tank 102.

[0054] The trickling filter device used in the first and second embodiments is a device that treats organic wastewater using the trickling filter method. The trickling filter method is one of the aerobic biological treatment methods, and is a method of obtaining biologically treated water by decomposing organic matter in the water to be treated that is sprayed by the action of microorganisms attached to the surface of the carrier. In the trickling filter method, it is generally known that the surface of the biofilm becomes aerobic and the inside of the biofilm becomes anaerobic. For this reason, when the trickling filter is operated at a low BOD load that allows nitrification to proceed, the nitrification reaction proceeds on the surface of the biofilm and the denitrification reaction proceeds inside the biofilm, which is characterized by its excellent nitrogen removal efficiency. The trickling filter method is characterized by a BOD volume load of 1 kg-BOD / m 3 / d or more, it is possible to operate stably, which is particularly effective when the site area is limited.

[0055] There is no particular restriction on the specific structure of the carrier used in the trickling filter method. The material of the carrier may be any material to which microorganisms can adhere, and representative examples include plastic and crushed stone. The shape of the carrier may be any shape, such as membrane, plate, sphere, cylinder, rectangular parallelepiped, and hollow. The carrier filling rate relative to the volume of the filter bed tank is preferably 40 to 80%, and more preferably 50 to 70%. In the case of a membrane carrier, the membrane volume relative to the volume of the filter bed tank (the membrane volume is calculated based on the outer dimensions of the membrane) is 0.05 to 0.15 m 3 / m 3 It is preferable to fill the mixture so that

[0056] In order to perform biological treatment more efficiently and stably, it is preferable to place a membrane carrier 20 in the filter bed tank, as shown in Figures 4 and 5, which has a structure in which the water to be treated (organic wastewater) supplied to the filter bed tank and the oxygen in the filter bed tank permeate opposite each other across the membrane surface.

[0057] 4 and 5, the membrane carrier 20 includes a support 21 and a membrane 22 supported by the support 21, the membrane 22 has a loop shape that covers the support 21, and is configured so that untreated water permeates from the outer surface of the loop-shaped membrane 22, and oxygen permeates from a space 23 formed on the inner surface of the loop-shaped membrane 22 to the outer surface of the membrane 22. The membrane 22 includes a curved portion 22a that curves outside the support 21, and extension portions 22b and 22c that extend approximately parallel to each other from both ends of the curved portion 22a, and an opening 22d is formed on the lower end side of the membrane 22, i.e., on the side facing the bottom surface of the filter bed tank that houses the membrane 22, for discharging sludge (not shown) that accumulates on the inner surface of the membrane 22 and is subsequently peeled off, out of the space 23.

[0058] The membrane carrier has an area rich in BOD and poor in oxygen on the supply side of the water to be treated, while the oxygen supply side is an area poor in BOD and rich in oxygen. Therefore, it is possible to create conditions suitable for the progress of denitrification reactions on the supply side of the water to be treated, while creating conditions suitable for nitrification reactions on the oxygen supply side, making it more suitable than other carriers in terms of its excellent nitrogen removal performance.

[0059] In contrast, in the case of a normal granular carrier, BOD, nitrogen, and oxygen are supplied to the biofilm on the carrier surface from the same direction, resulting in a BOD of 1.0 to 1.5 kg-BOD / m 3 At a load of 1.5 kg-BOD / m2 / day, oxygen is consumed by the oxidation of BOD, and the nitrification-denitrification reaction may not proceed smoothly. In addition, the membrane carrier has a 1.5 kg-BOD / m2 load compared to treatment methods using other types of carriers. 3 This has the advantage that it can operate stably without clogging even under high load conditions of 1000m3 or more / d. This is because each membrane carrier extends vertically, and biofilms that detach from the carriers are discharged outside the tank without clogging between the carriers.

[0060] In the above embodiment, a trickling filter device is used, but a rotating disk device can also be used as a biological treatment device of the non-aeration type. The rotating disk device is a device that treats organic wastewater using the rotating disk method. The rotating disk method is a method in which a part of a rotating disk is alternately exposed to the water to be treated and the air, forming a biofilm on the surface of the disk, and decomposing the organic matter in the water to be treated to obtain biologically treated water. Since aeration is not performed, there is no need to install a blower that requires air volume adjustment, and there is no need to supply return sludge as in the activated sludge method, etc., so there is an advantage in that simpler equipment can be provided. The BOD load of the rotating disk method is 0.1 to 1.5 kg-BOD / m 3 / d is preferable, and if an excessive load is applied, problems may occur in which excessive microorganisms adhere to the disk and the rotating shaft is damaged.

[0061] There is no particular restriction on the material and specific shape of the disk, and any device can be used. For example, the disk can be made of polystyrene foam, plastic, polyvinyl chloride, waterproof plywood, or metal plate such as aluminum, and can be made into a disk shape with a diameter of 1 to 3 m and a thickness of 0.7 to 20 mm.

[0062] [3. Sewage treatment system] In organic wastewater treatment, depending on the amount of wastewater discharged and the size of the raw water tank, raw water may be supplied continuously (sewage treatment, etc.) or intermittently (night soil treatment, industrial wastewater treatment, etc.). FIG. 6 shows a flow diagram of a night soil treatment system using a non-aeration type biological treatment device according to one embodiment of the present invention, taking as an example a simplified night soil treatment process that is premised on discharge into a sewerage system. The urine treatment system 30 includes a solid-liquid separation device 31, a non-aeration type biological treatment device 32, and a dilution tank 33. In the urine treatment system 30, the water to be treated is separated into separated sludge and separated liquid by solid-liquid separation in the solid-liquid separation device 31, and at least a part of the separated liquid is sent to the non-aeration type biological treatment device 32 for biological treatment. The obtained biologically treated water is sent to the dilution tank 33, diluted with dilution water so as to meet the sewage discharge standard, and then discharged.

[0063] (Water to be treated) The water to be treated is not particularly limited as long as it contains at least one of septic tank sludge and sewage sludge.

[0064] (Solid-liquid separator) In the case where a mixture of sewage sludge and septic tank sludge is used as the water to be treated, it is preferable to separate the sewage sludge and the septic tank sludge. Various solid-liquid separation devices can be used for the solid-liquid separation process, but it is preferable to separate the separated sludge and the separated liquid using a dehydrator, for example, in terms of equipment and operating costs. Furthermore, it is more preferable to perform a concentration process on the water to be treated before solid-liquid separation. As for the concentration method, both gravity concentration and mechanical concentration are effective concentration methods.

[0065] By performing a concentration process in which a polymer flocculant is added before solid-liquid separation, the sludge concentration (TS) of the concentrated sludge can be increased to a maximum of approximately 10 to 12 mass%. If the concentrated sludge is further dehydrated using a dehydrator, dehydrated sludge (separated sludge) with a low moisture content of 70% or less can be obtained, resulting in a more significant sludge volume reduction effect. As this dehydrated sludge with a low moisture content has a high calorie content, it can be self-burned without auxiliary fuel during incineration, resulting in energy savings and low costs.

[0066] (Biological treatment equipment without aeration) Biological treatment methods using the biofilm process can be broadly divided into those that require a periodic cleaning process for the carrier, and those in which the amount of biofilm is autonomously controlled during treatment. The former includes the biofilm filtration method, etc. The latter includes the trickling filter method, the fluidized carrier method, the rotating disk method, and the fixed bed method (contact oxidation method). As described above, fly infestation is prominent in non-aeration type biological treatment methods such as the trickling filter method and the rotating disk method. Therefore, the fly infestation countermeasures in the organic wastewater treatment method according to the above embodiment are particularly effective when a non-aeration type biological treatment device is used. EXAMPLES

[0067] Examples of the present invention will be described below together with comparative examples. These examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

[0068] The raw water (organic wastewater) used was the dehydrated separated liquid from a sewage treatment facility. Table 2 shows the properties of the representative dehydrated separated liquid during the experiment. pH, BOD, SS, NH4-N, and PO4-P were all measured in accordance with JIS K0102:2019.

[0069] [Table 2]

[0070] [Example 1 (drug added once on the weekend) and Example 2 (drug added twice on the weekend)] The raw water was biologically treated in a trickling filter apparatus having the configuration shown in Figure 1. A self-propelled rotary trickling machine was used as the trickling machine 110. The outer dimensions of each filter bed tank 103 were 1.0mW x 1.0mD x 2.5mH, and the effective volume was 2m 3 Two of these were installed in parallel on top of the water tank 102. The effective capacity of the water tank 102 is approximately 2 m 3 The membrane carrier made of cloth as shown in Figures 4 and 5 was installed as the carrier 104. The membrane capacity relative to the capacity of the filter bed tank 103 was 0.06 m 3 / m 3 It was.

[0071] As the insect growth regulator, Chemical-B (pyriproxyfen effervescent tablets) in Table 1 was used. In Example 1, two tablets (Friday) or one tablet (Saturday) of Chemical-B were added to a stainless steel wire mesh cage hanging on the wall 102w on the inlet side of the water receiving tank 102 on Friday evening (with raw water supply) or Saturday evening (with raw water supply). In Example 2, one tablet of Chemical-B was further added to the same stainless steel wire mesh cage on Monday morning (12 to 24 hours before the raw water supply was resumed). When calculated based on the amount of organic wastewater in the water receiving tank 102, when one tablet dissolves, the pyriproxyfen concentration in the organic wastewater is about 6 μg / L. When the supply of raw water to the trickling filter is stopped, the discharge of organic wastewater from the trickling filter is also stopped, and the trickling filter is installed at a volume of 5 to 7 m per filter bed tank 103. 3 The test conditions for Examples 1 and 2 are summarized in Table 3.

[0072] [Example 3 (continuous drug administration on weekdays)] The raw water was biologically treated in a trickling filter having the configuration shown in Fig. 2. The configuration of the trickling filter in Example 3 is the same as that in Examples 1 and 2, except for the means for adding the insect growth regulator. In Example 3, a chemical solution in which Chemical-B is dissolved in water is stored in the chemical solution storage tank 210, and the chemical solution is continuously supplied to the raw water line 216 using the chemical solution injection pump 214 so that the pyriproxyfen concentration is 6 µg / L relative to the amount of raw water in the raw water tank 206, except on weekends when the raw water supply is stopped. When the supply of raw water to the trickling filter is stopped, not only the supply of the chemical solution but also the discharge of organic wastewater from the trickling filter is stopped, and the trickling filter is installed in a volume of 5 to 7 m per filter bed tank 103. 3 The test conditions for Example 3 are summarized in Table 3.

[0073] [Comparative Example (no drug added)] The raw water was biologically treated in a trickling filter (without the addition of an insect growth regulator) having the configuration shown in Figure 1. The configuration and operating conditions of the trickling filter in the comparative example were the same as those in Examples 1 and 2, except that no insect growth regulator was added. The test conditions for the comparative example are summarized in Table 3.

[0074] [Table 3]

[0075] [Evaluation of fly infestation] During the experiments of the above Examples 1 to 3 and Comparative Example, the temperature of the organic wastewater in the water tank 102 was about 15 to 25°C. The experiments were conducted continuously from September to November, and the number of fly larvae and adults that emerged was visually confirmed and recorded periodically. Figure 7 shows the change in the emergence of fly larvae. Figure 8 shows the change in the emergence of adult flies. The emergence of fly larvae and adults was divided into four stages of emergence intensity as shown in Table 4 according to the number of individuals confirmed. The results are summarized in Table 5.

[0076] [Table 4]

[0077] [Table 5]

[0078] In the comparative example, where no insecticide (insect growth regulator) was added, fly larvae appeared on the walls of the water tank and on the upper part of the filter bed from mid-September onwards, and then rapidly increased in number. The number of adult flies also increased in line with the increase in larvae. In Example 3, the drug was continuously injected on weekdays, and no fly larvae or adults were observed throughout the entire period. In Example 1, the drug was applied once a weekend. A small number of fly larvae appeared from late September to October, but no adult flies were observed. This is because the drug suppressed the emergence of larvae into adults. In Example 2, the agent was added twice a week on weekends, and no fly larvae or adults were observed to emerge throughout the entire period.

[0079] [Evaluation of drug consumption] Table 6 shows the amount of pesticide used during the experiment period (September to November). The amount of pesticide was calculated in tablet units (6 g / tablet, containing 0.5% by mass of active ingredient). Examples 1 and 2, in which the pesticide was added on weekends, had almost no difference in the effect of suppressing fly emergence, but the amount used was 1 / 4 to 1 / 7 of that in Example 3, in which the pesticide was added continuously on weekdays.

[0080] [Table 6] [Explanation of symbols]

[0081] 20: Membrane carrier 21:Support 22: Membrane 22a: Curved section 22b: Stretching part 22c: Stretching part 22d: opening 23: Space 30: Sewage treatment system 31:Solid-liquid separator 32: Biological treatment equipment 33: Dilution tank 100: Biological treatment equipment 102: Water tank 102w: Wall 103: Filter bed tank 104: Carrier 105: Circulation pump 106: Stand 108:Circulation Line 109: Container 109a: Storage unit 109h: Hanging part 110: Sprinkler 112: Hook 200: Biological treatment equipment 202: Raw water pump 204: Inlet line 206: Raw water tank 207: Outflow line 208: Treatment tank 210: Chemical storage tank 212: Chemical injection line 214: Chemical injection pump 216: Raw water line 310: Container 311: Storage unit 312: Hanging part 313: Inlet 315: Hook part 320: Container 321: Storage unit 322: Hanging part 323: Inlet 324: Lid 325: Hook part

Claims

1. A method for treating organic wastewater, comprising the steps of: supplying organic wastewater to a receiving tank of a non-aeration type biological treatment device having a receiving tank and a filter bed tank; spraying the organic wastewater from the receiving tank into the filter bed tank for biological treatment; and adding an insect growth regulator for suppressing the growth of fly larvae to the organic wastewater in the biological treatment device, The step of adding the insect growth regulator is carried out while the supply of organic wastewater to the water receiving tank is stopped and the discharge of the organic wastewater from the biological treatment device is stopped; The method for treating organic wastewater, wherein the biological treatment step is carried out while circulating the organic wastewater between the receiving water tank and the filter bed tank while the supply of the organic wastewater to the receiving water tank is stopped and the discharge of the organic wastewater from the biological treatment device is stopped.

2. 2. The method for treating organic wastewater as described in claim 1, wherein the time during which the supply of organic wastewater to the receiving tank is stopped and the discharge of organic wastewater from the biological treatment device is stopped is 12 hours or more.

3. 3. The method for treating organic wastewater according to claim 1 or 2, wherein the step of adding the insect growth regulator comprises placing the insect growth regulator in the form of a tablet in a water-permeable container and immersing the tablet in the organic wastewater in the water tank.

4. 4. The method for treating organic wastewater according to claim 3, wherein the container is hung on a wall on the inlet side of the water receiving tank.

5. The method for treating organic wastewater according to any one of claims 1 to 4, wherein the step of adding the insect growth regulator is not carried out while the organic wastewater is being supplied to the receiving tank.

6. 6. The method for treating organic wastewater according to claim 1, wherein the organic wastewater is human waste.

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