JP7481383B2 - Organic wastewater treatment method and biological treatment device - Google Patents

Description

The present invention relates to a method for treating organic wastewater using a non-aeration type biological treatment device to prevent fly infestations.

Trickling filter and other non-aeration biological treatment methods have the advantage that they do not require aeration compared to standard activated sludge processes, consuming less electricity, producing less sludge, and reducing the cost of disposing of excess sludge. For this reason, in recent years, there has been consideration of applying these methods to sewage treatment in developing countries such as Southeast Asia, where infrastructure such as electricity is not well developed.

On the other hand, in non-aeration biological treatment methods, sludge adheres to the filter media of the trickling filter bed, and as the sludge decays, it generates a foul odor. It is known that this sludge causes the emergence of a type of moth fly known as filter bed flies. In particular, filter bed flies are often seen to emerge in non-aeration biological treatment devices, such as trickling filter bed treatment devices, during the periods from May to June and September to October, when temperatures are between 20°C and 25°C, depending on the region. There is a problem in that the emergence of filter bed flies worsens the working environment when maintaining the device. The following technologies are known as countermeasures to the above problem.

Patent Document 1 (WO 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 to clean the trickling filter bed. The cleaning means described includes a cleaning water storage mechanism that stores cleaning water in the trickling filter bed to flood 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.

Patent Document 2 (JP Patent Publication No. 2020-157237A) describes that when a 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 the larvae and eggs of harmful organisms attached to the filter layer, the harmful organisms living in the tank often remain even after the cleaning operation is completed, and the tank is again contaminated by harmful organisms, because the harmful organisms living in the tank retreat upward along the tank wall, and the tank often becomes contaminated again. Therefore, this document proposes a method of irradiating the inner wall of the tank with light of a wavelength that repels harmful organisms living in the tank filled with the filter layer when the tank is filled with water. This method prevents harmful organisms such as fly larvae from retreating upward along the inner wall of the tank, 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.

Patent Document 3 (JP Patent Publication 7-147875A) does not relate to a non-aeration biological treatment method, but it does disclose a method of 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 where there is no fire at 5 g or more per second. This document describes how spraying the required amount of aerosol contents in a short period of time makes it possible to control pests extremely efficiently, despite the spraying being random, and also greatly shortens the operation time.

Patent Document 4 (JP Patent Publication No. 2003-95811) is not a technology related to a non-aeration biological treatment method, but it does disclose an agent for controlling pests that live in manholes, characterized by the ability to spray an insecticide in foam form. This document describes how the use of the agent for controlling pests that live in manholes makes it possible to efficiently control moth flies, Culex pipiens molestus, and flea flies that occur in manholes, and also to suppress re-infestations for a long period of time.

International Publication No. 2015/001708 JP 2020-157237 A Japanese Patent Application Laid-Open No. 7-147875 JP 2003-95811 A

In Patent Document 1, in order to suppress the occurrence of filter bed flies, a cleaning means is required that has a cleaning water storage mechanism that stores cleaning water in the filter bed and floods the filter media layer, an agitation and cleaning mechanism that agitates and cleans the flooded filter media layer to which nitrifying bacteria have adhered, and a drainage mechanism that discharges the cleaning water after agitation and cleaning. For this reason, when installing the cleaning means in an existing facility, the facility must be renovated, and the cleaning operation of flooding and agitating the filter media is required, which makes it less convenient. Furthermore, the wastewater generated by the cleaning must be treated.

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, thereby suffocating and killing the larvae and eggs of harmful organisms attached to the filter layer. For this reason, like Patent Document 1, there is a need for equipment renovation, and it is also not simple since it requires filling the tank with water and irradiating light for a certain period of time, and furthermore, wastewater treatment is also required.

Patent Document 3 requires that the aerosol be sprayed at the location where pests occur. If the location where pests occur is open to the outside air and not closed, as in the case of a trickling filter treatment device, the aerosol will diffuse into the atmosphere, and this is not an effective pest control method. Furthermore, while it is possible to expect an inhibitory effect on adult flies that live in the air, it is unclear whether it will be effective in inhibiting fly larvae that live in water, on the inner walls of aquariums, or in biofilms. To effectively suppress the occurrence of flies, it is desirable to be able to inhibit the growth of fly larvae.

Patent document 4 is an invention characterized by spraying insecticide in foam form into closed spaces such as manholes. 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, resulting in the same problems as those in patent document 3.

In view of the above circumstances, in one embodiment, the present invention aims 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. In another embodiment, the present invention aims to provide a non-aeration type biological treatment device that can easily and effectively suppress the occurrence of flies.

The inventors conducted extensive research to solve the above problems and discovered that adding an insect growth regulator to organic wastewater is highly effective in suppressing the occurrence of flies, leading to the creation of the present invention, which is illustrated below.

[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 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 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 according to [7],
[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 storing the insect growth regulator in tablet form and for immersing it in the organic wastewater in the receiving tank.
[10]
The non-aeration type biological treatment device according to [9], wherein the container is hung on the wall on the inlet side of the water receiving tank.

According to the organic wastewater treatment method and biological treatment device of one embodiment of the present invention, it is possible to suppress the occurrence of flies by the simple operation of adding an insect growth regulator to the organic wastewater. Furthermore, since the insect growth regulator is added to the organic wastewater, not to the air, the insect growth regulator spreads at the desired concentration throughout the wastewater in the biological treatment device, and the insect growth regulator can reach the biofilm inhabited by fly larvae. Therefore, the growth inhibition effect on fly larvae is high, and as a result, the effect of suppressing the occurrence of adult flies is also high.

FIG. 1 is a schematic diagram showing a configuration example of a biological treatment device according to a first embodiment of the present invention. FIG. 4 is a schematic diagram showing a configuration example of a biological treatment device according to a second embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a water-permeable container for containing an insect growth regulator. 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. FIG. 4 is a schematic plan view of one of the membrane carriers shown in FIG. 3. 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. 1 is a graph showing the progress of emergence of fly larvae in Examples 1 to 3 and the Comparative Example. 1 is a graph showing the progress of emergence of adult flies in Examples 1 to 3 and the Comparative Example.

The following describes embodiments of the present invention with reference to the drawings. The embodiments shown below are examples of devices and methods for embodying the technical ideas of this invention, and it should be understood that appropriate design changes and improvements may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[1. Overview of organic wastewater treatment method and biological treatment device]
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;
including.

The organic wastewater targeted by the treatment method according to this embodiment is not particularly limited, but examples 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, a non-aeration type biological treatment device refers to a biological treatment device that has a biofilm that can come into contact with air without the need to blow compressed air into the organic wastewater, which is the water to be treated, as fine bubbles using an aeration tube or aerator.

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 breathe and supply oxygen to their bodies. 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 occur frequently in non-aeration biological treatment equipment, such as trickling filter equipment, which can secure space for contact with air other than water, and grow in a cycle of egg → larva → pupa → adult → egg. Larvae in particular feed on the sludge in the biofilm, 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.

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.

The biological treatment may be either aerobic biological treatment or anaerobic biological treatment, but as mentioned above, fly infestations are 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 biologically treating organic wastewater 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.

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.

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 being treated and deliver them to the biofilm.

Therefore, in the treatment method according to this 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 are no particular restrictions.

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 carried out either before or after the organic wastewater is supplied to the biological treatment device, or may be carried out both. Since this can be carried out even when the supply of organic wastewater to the biological treatment device is stopped, it is preferable to carry out 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.

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.

Flies develop well when temperatures are between 15°C and 30°C, especially between 20°C and 25°C, but develop 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 from May to June and from September to November, depending on the region. Therefore, it is effective to add an insect growth regulator to organic wastewater when the temperature of the organic wastewater is between 15°C and 30°C, preferably between 20°C and 25°C.

There are no particular limitations 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, and tablets (including effervescent tablets) are preferred, with tablets being 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 an insect growth regulator storage tank, an injection pump, etc.

The insect growth regulator may be added to the organic wastewater manually in the required amount, 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. As the container, a water-permeable container is preferable, and for example, a container having multiple water-permeable holes such as a mesh-shaped container is included. 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 preferably used for the container storage section. Figure 3 shows a schematic example of a water-permeable container for storing the insect growth regulator.

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 the storage section 311. In the container 310 in FIG. 3(A), the storage section 311 has an input port 313 for inputting the insect growth regulator into the storage section 311, but there is no lid for closing the input port 313.

The container shown in FIG. 3B is a lidded container 320, which includes a storage section 321 made of wire mesh (mesh metal), a hanging section 322 connected to the storage section 321, and a lid 324. In the container 320 in FIG. 3B, the storage section 321 has an input port 323 for inputting the insect growth regulator into the storage section 321, and is provided with a lid 324 for closing the 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 are no particular limitations on the method for fixing the lid 324 to the storage section 321, but examples include a screw type and a clamp type.

There are no particular limitations on the hanging parts 312, 322 as long as they have the function of suspending and holding the storage parts 311, 321. For example, the hanging parts 312 may be rigid, such as rod-shaped, as shown in FIG. 3A, or the hanging parts 322 may be flexible, such as chain-shaped, 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 are no particular limitations on 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 tank of the biological treatment device in order to increase the retention 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-receiving 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-receiving tank, from the viewpoint that the insect growth regulator is likely to spread in a short time together with the inflowing organic wastewater.

There are no particular restrictions 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., 20% or less 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.

In reality, the amount of organic wastewater supplied to the biological treatment device per unit time is not constant, but fluctuates, and may even be stopped. For example, in human waste treatment, human waste and septic tank sludge are not accepted on weekends, and raw water supply is stopped. In some areas, human waste and septic tank sludge are collected on weekdays (Monday to Friday) and the separated water after dewatering and dehydration is stored in a separation tank (for 1-2 days). For this reason, the amount of separated water decreases on weekends, and 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 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 added required 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.

In a more preferred embodiment, the insect growth regulator is added to the organic wastewater in the biological treatment device 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. 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. However, 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 insect growth regulator added to the organic wastewater does not flow out from the biological treatment device. Therefore, the amount of insect growth regulator 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.

The longer the time during which the supply of organic wastewater to the biological treatment device and the discharge of organic wastewater from said biological treatment device are stopped, the greater the effect of the insect growth regulator added to the organic wastewater in suppressing the emergence of flies, so it 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 it is preferably 48 hours or less, and more preferably 24 hours or less.

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 raw water pump that supplies organic wastewater to the biological treatment device being stopped, and the discharge of 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, if necessary, additional insect growth regulator may be added once or multiple times while the stopped state continues. In addition, the time until the supply of organic wastewater to the biological treatment device is resumed due to the raw water pump being restarted after the first addition of the insect growth regulator after the start of the stopped state 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 operate a liquid addition device a predetermined time (e.g., 6 to 24 hours) after receiving a stop signal from the raw water pump, and automatically add a predetermined amount of insect growth regulator.

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 preferably biologically treats the organic wastewater while circulating it within the biological treatment device. By adding an insect growth regulator while the organic wastewater is circulating 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 in 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, the state in which the organic wastewater is circulating between the water receiving tank and the filter bed tank, and in the case of a rotating disk device, the state in which a circulating flow is generated in the water receiving tank by rotating the disk. Circulation may be performed continuously or intermittently.

From the viewpoint of reducing chemical costs, it is advantageous to operate the biological treatment device without adding an insect growth regulator 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, it is possible to start adding the insect growth regulator just before the supply of the organic wastewater stops, or to temporarily add the insect growth regulator while supplying the organic wastewater.

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 have a higher effect of suppressing fly infestation. From the viewpoint of cost-effectiveness, it is preferable to add the insect growth regulator to the organic wastewater once or twice a week. Here, when tablets are added when the amount of raw water is reduced and the raw water supply is stopped, the step 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.

Flies multiply in large numbers in a short period of time, flying around indoors at all times of the day and night, and are easily noticeable to people, causing discomfort and a feeling of uncleanliness. Therefore, it is important to prevent adult flies from escaping from the biological treatment device. Although the addition of the above-mentioned insect growth regulator is expected to have an inhibitory effect on fly occurrence, flies may occur if the amount added is insufficient or the frequency of addition is insufficient. In order to prevent adult flies from escaping once they have occurred, it is important to increase the airtightness of the biological treatment device. For example, in the case of a trickling filter device, measures that can be considered include covering the ventilation opening 116 with wire mesh 118 to prevent flies from entering or exiting, or installing an airtight lid 114 on the top of the sprinkler 110.

[2. Example of the configuration of the biological treatment device]
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 containing an insect growth regulator.

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. 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 inlet line 204. Examples of raw water include organic wastewater (night soil, sewage, food factory wastewater, etc.) that contains a large amount of BOD components.

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 top of the filter bed tank 103 through the circulation line 108 by the circulation pump 105. The mixed liquid is then sprayed by the sprinkler 110 onto the carrier 104 carrying the biofilm. The biofilm formed by the microorganisms that have proliferated on the surface of the carrier decomposes and removes organic matter such as BOD components in the mixed liquid, and the mixed liquid then returns to the receiving tank 102.

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 has 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 on 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 reaches the fly larvae living in the biofilm, effectively inhibiting the growth of the fly larvae and preventing the emergence of adult flies.

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 type of sprinkler 110, but any type of sprinkler can be used, such as a perforated plate, a sprinkler type, a spiral type nozzle, or a self-propelled rotating sprinkler.

Downstream of the receiving tank 102, a treated water tank 208 is provided to store treated water, 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 the sewer system).

Figure 2 shows a schematic diagram showing an example of the configuration 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 that includes 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 for 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.

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 the 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, the explanation of the components indicated with the same reference numerals as those of the biological treatment device 100 according to the first embodiment will be omitted.

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 contained 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, for example, by using a metering pump. 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.

The trickling filter device used in the first and second embodiments is a device that treats organic wastewater using a 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 a 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 excellent nitrogen removal efficiency. The trickling filter method can be stably operated even with a BOD volume load of 1 kg-BOD/m ³ /d or more, and is particularly effective when the site area is limited.

There is no particular restriction on the specific structure of the carrier used in the trickling filter bed 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, it is preferable to fill the membrane so that the volume of the membrane (the volume of the membrane is calculated based on the outer dimensions of the membrane) relative to the volume of the filter bed tank is 0.05 to 0.15 ^m3 / ^m3 .

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, for example, 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.

As shown in Figures 4 and 5, the membrane carrier 20 includes a support 21 and a membrane 22 supported by the support 21, and the membrane 22 has a loop shape that covers the support 21. The 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 on the outside of the support 21, and extension portions 22b and 22c that extend approximately parallel to each other from both ends of the curved portion 22a. 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 then peels off, out of the space 23.

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 denitrification reaction to proceed on the supply side of the water to be treated, while creating conditions suitable for the nitrification reaction on the oxygen supply side, making it more suitable than the various carriers in terms of its excellent nitrogen removal performance.

In contrast, in the case of normal granular carriers, BOD, nitrogen, and oxygen are supplied to the biofilm on the carrier surface from the same direction, so at a load of 1.0 to 1.5 kg-BOD/ ^m3 /d, oxygen is consumed by the oxidation of BOD, and the nitrification-denitrification reaction may not proceed easily. In addition, compared to treatment methods that use carriers of other shapes, membrane carriers have the advantage that they can be operated stably without clogging even under high load conditions of 1.5 kg-BOD/ ^m3 /d or more. This is because in membrane carriers, each carrier extends vertically, and biofilms that peel off from the carriers are discharged outside the tank without clogging between the carriers.

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, so it is advantageous in that simpler equipment can be provided. The BOD load for the rotating disk method is preferably 0.1 to 1.5 kg-BOD/m ³ /d, and if an excessive load is applied, problems such as excessive microorganisms attaching to the disk and damage to the rotating shaft may occur.

There are no particular limitations on the material or 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 plates 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.

[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 solid-liquid separation into separated sludge and separated liquid 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.

(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.

(Solid-liquid separation device)
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.

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 10-12% by mass. If the concentrated sludge that has been highly concentrated 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 spontaneously combusted without auxiliary fuel during incineration, resulting in energy savings and low costs.

(Biological treatment equipment without aeration)
Biological treatment methods using the biofilm process can be roughly 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 mentioned above, the occurrence of flies is prominent in biological treatment methods that do not use aeration, such as the trickling filter method and the rotating disk method. Therefore, the fly occurrence countermeasures in the organic wastewater treatment method according to the above embodiment are particularly effective when a biological treatment device that does not use aeration is used.

The following examples of the present invention are presented together with comparative examples, but these examples are provided to provide a better understanding of the present invention and its advantages, and are not intended to limit the invention.

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

[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 trickler was used as the trickler 110. The filter bed tanks 103 each had outer dimensions of 1.0 mW x 1.0 mD x 2.5 mH, and ^two units with an effective volume of 2 m3 were installed in parallel on the water receiving tank 102. The effective capacity of the water receiving tank 102 was approximately 2 ^m3 . A cloth membrane carrier 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 ^m3 / ^m3 .

As the insect growth regulator, Chemical-B (pyriproxyfen effervescent tablet) 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 basket 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 basket 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, the pyriproxyfen concentration in the organic wastewater is about 6 μg/L when one tablet is dissolved. When the supply of raw water to the trickling filter device was stopped, the discharge of organic wastewater from the trickling filter device was also stopped, and the trickling filter device was operated in a circulating manner so that water was sprinkled at an average flow rate of 5 to 7 m ³ /h per filter bed tank 103. The test conditions for Examples 1 and 2 are summarized in Table 3.

[Example 3 (continuous drug addition on weekdays)]
The raw water was biologically treated by 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 storage tank 210, and the chemical solution was continuously supplied to the raw water line 216 using the chemical injection pump 214 so that the pyriproxyfen concentration was 6 μg/L relative to the amount of raw water in the raw water tank 206, except on weekends when the raw water supply was stopped. When the supply of raw water to the trickling filter was stopped, the supply of the chemical solution and the discharge of organic wastewater from the trickling filter were also stopped, and the trickling filter was operated in a circulating manner so that water was sprayed at an average flow rate of 5 to 7 m ³ /h per filter tank 103. The test conditions for Example 3 are summarized in Table 3.

[Comparative Example (No Addition of Drugs)]
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.

[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.

In the comparative example, no insect growth regulator was added, so 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 were generated from late September to October, but no adult flies were observed. This is because the drug inhibited the emergence of larvae into adults.
In Example 2, the agent was applied twice a week on the weekend, and no fly larvae or adults were observed to emerge throughout the entire period.

[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 the same effect on suppressing fly emergence, but the amount used was 1/4 to 1/7 of that used in Example 3, in which the pesticide was added continuously on weekdays.

20: Membrane carrier 21: Support 22: Membrane 22a: Curved portion 22b: Extension portion 22c: Extension portion 22d: Opening 23: Space 30: Sewage treatment system 31: Solid-liquid separation device 32: Biological treatment device 33: Dilution tank 100: Biological treatment device 102: Receiving tank 102w: Wall 103: Filter bed tank 104: Carrier 105: Circulation pump 106: Stand 108: Circulation line 109: Container 109a: Storage section 109h: Suspension section 110: Sprinkler 112: Hook 200: Biological treatment device 202: Raw water pump 204: Inflow line 206: Raw water tank 207: Outflow line 208: Treated water tank 210: Chemical storage tank 212: Chemical injection line 214: Chemical injection pump 216 : Raw water line 310 : Container 311 : Storage section 312 : Hanging section 313 : Input port 315 : Hook section 320 : Container 321 : Storage section 322 : Hanging section 323 : Input port 324 : Lid 325 : Hook section

Claims (3)

A water tank for storing organic wastewater;
A biofilm for biologically treating organic wastewater;
means for supplying to the organic wastewater in the receiving tank an insect growth regulator for inhibiting the growth of fly larvae;
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;
Equipped with
A non-aeration type biological treatment device, wherein the means for supplying the insect growth regulator is a water-permeable container for containing the insect growth regulator in tablet form and for immersing it in the organic wastewater in the receiving tank. The non-aeration type biological treatment device according to claim 1 , wherein the container is hung on a wall on the inlet side of the water receiving tank. 3. The non-aeration type treatment device according to claim 1 or 2 , wherein the organic wastewater is human waste.