JPS6228688B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is an organic sewage treatment method that includes a biological treatment process to remove malodorous gases generated from organic sewage (human waste, human waste septic tank sludge, sewage, wastewater, trash leached sewage, livestock discharge sewage, etc.). This relates to a method of deodorizing using a treatment facility. [Prior art] Generally, the foul-smelling gas emitted from organic wastewater is
It generates an intolerable odor and deteriorates the living environment over a fairly wide area. Therefore, it is necessary to remove the emitted odor components by some means. Conventionally, methods for removing these malodorous components include cleaning methods using acids and alkaline agents (chemical absorption method), physicochemical adsorption methods using activated carbon, etc.
Chemical oxidation method using ozone, hypochlorous acid, etc.
There are ion exchange methods, combustion decomposition methods, and biological decomposition methods. [Problems to be Solved by the Invention] However, when these deodorizing methods are comprehensively evaluated, they have the following serious deficiencies, and there is a strong demand for technical improvement. Requires large amounts of chemicals such as absorbents, adsorbents, and oxidizing agents. Requires large amounts of water as absorbent carrier.
Deodorization methods based on physical adsorption and chemical fixation use adsorbents,
Not only does it cost a lot of money to reactivate the fixative, but it also becomes a problem to dispose of the desorbed malodorous substances. Furthermore, the biodegradation method is still at the proposal stage and there is room for technical improvement. To summarize the above, it must be said that conventional deodorizing techniques are not resource-saving or energy-saving, and that biodegradation methods are not systemically complete as a deodorizing technique. [Objective of the Invention] The present invention aims to solve the problems of the above-mentioned conventional methods and to provide a method that can extremely rationally deodorize malodorous gases generated from organic sewage using the organic sewage treatment system. This is the purpose. [Means for Solving the Problems] That is, the present invention provides a method for bringing malodorous gas generated from an organic sewage treatment facility into contact with foam formed on the water surface of an aeration tank for aerobic biological treatment of organic sewage. , a method for deodorizing malodorous gas, characterized in that the foam is broken and liquefied by mechanical impact, and is guided to a gas-liquid contact tower to be brought into contact with the malodorous gas, and at the same time, the malodorous gas absorption liquid is returned to the aeration tank. It is. Hereinafter, each embodiment of the present invention will be explained with reference to the drawings. In Figure 1, organic wastewater 1 such as human waste is
The activated sludge flows into the aeration tank 2 of the activated sludge treatment process, and after BOD components are removed by microbial activity, the activated sludge is separated in the solid-liquid separation process 3 using a sedimentation tank, centrifuge, etc., and the treated water 4 and thickened sludge 5, a part of which is returned to the aeration tank 2 as return sludge 6, and the other part is disposed of as surplus sludge 7. Above the water surface 8 of the aeration tank 2, foaming occurs as a result of the aeration operation by the aeration device 10, and a foam layer 9 is formed. This bubbling phenomenon becomes more severe when human waste is treated with activated sludge without dilution (meaning not diluted with river water, groundwater, etc.) or with low dilution ratio, and when the amount of aerated air in the aeration tank 2 is large. . Biological treatment of high-concentration organic wastewater, such as human waste with a BOD of 10,000 to 15,000 mg, naturally requires a large amount of aerated air, which causes intense foaming. If this foaming is left untreated, the foam will overflow outside the aeration tank 2 and cause serious problems such as being blown away by the wind or activated sludge adhering to the foam escaping outside the aeration tank 2 together with the foam. They had to inject drugs or dilute human waste in large quantities. Therefore, in the present invention, the foam 9' of the foam layer 9 is suctioned from the suction pipe 20 by the self-priming supply pump 19, and the height of the foam layer 9 is maintained below a certain value, and the suctioned foam 9 is ' is liquefied by mechanical impact in the supply pump 19, and this liquid is supplied to the upper part of the absorption pipe (packed tower, tray tower, etc.) 21, while the malodorous gas supplied from the fan 23 is 11 (Human waste input tank of organic sewage treatment facility,
(generated from the storage tank, sludge dewatering chamber, and drying and incineration process of the dehydrated cake) in a countercurrent manner. Through experiments conducted by the present inventor, it has been found that when the liquefied foam 9' is brought into gas-liquid contact with the malodorous gas 11, deodorization is carried out very effectively. It is presumed that this is due to the action of the surface-active substances and microorganisms concentrated in the foam layer 9. Therefore, if the malodorous component absorption liquid 22 is recycled to the aeration tank 2 and retained in the aeration tank 2,
The malodorous components are fully assimilated and decomposed by the action of the malodorous component decomposing bacteria present in the activated sludge. Note that aeration can be performed by causing the absorption liquid 22 to fall naturally into the aeration tank 2 from a position higher than the water surface 8, or by forcibly discharging and dropping it with a pump, using a waterfall effect at the water surface 8. I can do it. Furthermore, in this example, the supply pump 19 does not suck only the foam 9', but also sucks both the foam 9' and the activated sludge below the water surface 8 and supplies it to the suction tower 21, thereby removing the bad odor. Ingredients can be absorbed more effectively. In FIG. 1, 11' is a processing gas, 12 is an aeration blower, and 12' is air. On the other hand, the example in Figure 2 is similar to the example in Figure 1,
This is a case where biological nitrification and denitrification method is applied as a biological treatment process. That is, the organic wastewater 1 flows through the first denitrification tank 13, the nitrification tank 14, the second denitrification tank 15 in this order, and
The effluent from the denitrification tank 15 flows into a solid-liquid separation process 3 such as a centrifuge, where it is separated into treated water 4 and thickened sludge 5, and most of the thickened sludge 5 is sent to the first denitrification tank as return sludge 6. 13, and a portion is transferred as surplus sludge 7 to a dewatering process (not shown). Note that 17 is an exhaust pipe for N ₂ gas. Next, the functions and effects of each of the above embodiments will be described. (1) Actions and effects common to the example in Figure 1 and the example in Figure 2 In conventional methods, when organic wastewater is biologically treated,
There was a problem in which severe foaming occurred during the biological treatment process, making stable treatment impossible unless antifoaming agents or diluting water were added. Since the bubbles are removed by suction, the foaming problem can be solved without the need to add antifoaming agents or diluting water, and the suctioned and removed foam and foam liquid (foam that has broken and become liquid) can be removed as a foul-smelling gas. The novel idea of using it to absorb water can solve both the foaming problem and the bad odor problem at once. The liquid (absorbing liquid) that has absorbed malodorous components in the absorption tower is supplied to the aeration tank in the organic sewage treatment process, so the microorganisms in the aeration tank and the long residence time in the aeration tank are used to remove malodorous components. can be broken down scientifically. In other words, since the organic sewage treatment process can be effectively used to treat the malodorous component-absorbing liquid generated from the deodorizing process, there is no need to provide a separate treatment process for the malodorous component-absorbing liquid. Furthermore, since oxygen gas in the malodorous gas is also absorbed into the absorption liquid at the same time, combined with the waterfall effect described above, the amount of air from the blower to the aeration tank and, therefore, the required power can be reduced. (2) Actions and effects according to the example shown in Figure 2 Since the microbial slurry containing nitrifying bacteria and denitrifying bacteria is used as an absorption medium for malodorous components, the gas containing nitrogen-based malodorous components is very effectively deodorized. [Example] Human waste having the water quality shown in Table 1 was processed without dilution through the biological nitrification and denitrification process shown in Figure 2.
It was treated at 10Kl/day.

[Table] The operating conditions for the biological nitrification and denitrification process were set as follows. 1 Volume of the 1st denitrification tank......30m ³ 2 Volume of the nitrification tank...60m ³ 3 Volume of the 2nd denitrification tank...30m ³ 4 MLVSS...18000-2000mg/ 5 Solid-liquid separation method...Using a centrifuge During treatment, foaming occurred violently in the nitrification tank, but as a result of installing a suction pipe of a self-priming pump (Side Piper, manufactured by Wallenrap Co., Ltd.) on the foam layer and suctioning out the foam, the height of the foam layer from the water surface of the nitrification tank was reduced. was able to be kept within 50 cm and did not overflow outside the tank. When the foam from the nitrification tank is passed through the self-priming pump, the foam breaks down and becomes liquid. A flow rate of this liquid equivalent to 100 m ³ /day is sucked from the foam layer on the water surface of the nitrification tank, Method, height 2m, diameter 1
m) and brought into gas-liquid contact with the malodorous gas in a countercurrent manner. Note that the foam liquid was supplied from the upper part of the absorption tower. The odor concentration of the malodorous gas (gas mixed with malodorous gas discharged from the human waste storage tank, dehydrator room, and dehydrated cake dryer) is 30,000 to 50,000, and the air flow rate to the absorption tower is 8Nm ³ /min. The absorption tower effluent was recycled to the nitrification tank or the first denitrification tank. As a result of operation under the above conditions, deodorization and prevention of abnormal foaming were carried out extremely effectively, and the odor concentration of the exhaust gas from the absorption tower was 300 to 450. For reference, the water quality of biologically nitrified and denitrified water is shown in Table 2, and the ammonia and amines contained in the foul-smelling gas are biologically nitrified and denitrified. was excellent.

〔Effect of the invention〕

As described above, the present invention rationally integrates the biological treatment process for human waste and the deodorization process for malodorous gas, so the process configuration is simplified and special deodorization equipment is not required. As a result, the construction cost of the entire treatment equipment can be significantly reduced, and there is no need for deodorizing chemicals (acid, alkaline solution, activated carbon, ozone, sodium hypochlorite, etc.) or fuel such as heavy oil, which were required in the past. This method offers many benefits, such as resource-saving and energy-saving deodorizing treatment, and easy maintenance and management of the device.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are system explanatory diagrams showing embodiments of the present invention. 1... Organic sewage, 2... Aeration tank, 3... Solid-liquid separation process, 4... Treated water, 5... Thickened sludge, 6...
...Return sludge, 7... Surplus sludge, 8... Water surface, 9...
...foam layer, 9'... foam, 10... air diffuser, 1
1...Odor gas, 11'...Processing gas, 12...
Blower, 12'... Air, 13... First denitrification tank, 14... Nitrification tank, 15... Second denitrification tank, 1
7... Exhaust pipe, 19... Supply pump, 20... Suction pipe, 21... Absorption tower, 22... Absorption liquid, 23...
…Juan.

Claims (1)

[Claims] 1. When bringing malodorous gas generated from an organic sewage treatment facility into contact with foam formed on the water surface of an aeration tank for aerobic biological treatment of organic sewage, the foam is removed by mechanical impact. 1. A method for deodorizing malodorous gas, which comprises breaking the foam, liquefying it, guiding it to a gas-liquid contact tower, bringing it into contact with the malodorous gas, and returning the malodorous gas absorption liquid to the aeration tank. 2. The method according to claim 1, wherein the malodorous gas absorbing liquid is allowed to fall onto the water surface of the aeration tank.