JPS59115789A - Activated sludge method using packing material - Google Patents

Abstract

PURPOSE:To perform a cleaning treatment of sewage with simple control without requiring return sludge in the stage of a sewage treatment by circulating and flowing a wire-shaped packing material by the air blown therein in an activated sludge tank thereby sticking the films of living things to the packing material. CONSTITUTION:Sewage 5 is streamed into an activated sludge tank 4 from the upper part and at the same time air is blown through a pipe 1 into the tank 4 from near the bottom thereof. The ascending of air foam 3 and the vertical turning flow in the sewage in the tank 4 are induced by the air blown therein. A wire-shaped packing material 2 made of a plastic is charged at about 5% the volume of the sewage into the sewage in the tank 4. The material 2 turns and circulates together with the sewage to form a fluidized bed and the zoogloea ramigera films stick onto the surfaces thereof and said films together with the oxygen in the air blown into the sewage oxidize and decompose the pollutant, whereafter the sewage enters a sludge settling tank 9. The sludge is scraped by a scraper 13 and is discharged 12. Supernatant water 11 overflows from the tank 9 and is released.

Description

[Detailed Description of the Invention] The present invention relates to a wastewater treatment method in which a filler put into an activated sludge tank is circulated and flowed mainly in the vertical direction in wastewater, and in particular, it has the characteristics of both the activated sludge method and the biofilm method. Concerning wastewater purification methods.

The activated sludge method is a wastewater treatment method that has existed for a long time, and can be said to be the most popular method in Japan.However, it is weak against load fluctuations, tends to cause bulking, and requires return sludge, and there are problems with its maintenance and management. This method has problems such as requiring a considerable amount of effort and skill. It is no exaggeration to say that most of the septic tanks used for floor treatment, especially small septic tanks for homes and apartments, do not function properly because they are not properly maintained. Zooglaia, which is the main bacteria in the activated sludge method, originally lives on stones on riverbeds and purifies rivers, but naturally it does not require maintenance.

Focusing on this, recently the easy-to-maintain biofilm method, especially the immersed bed method, has begun to revive and become popular, especially in small septic tanks.

The immersed bed method is a method in which biofilm is attached to a fixed bed of block-shaped packing immersed in a liquid, and does not require return sludge, making maintenance easier than the conventional activated sludge method.

However, in this method, the BOD concentration in the wastewater is high, and over time, excessive biofilm is generated in the fixed bed, which tends to cause clogging of the fixed block-shaped packing. If a blockage occurs, not only will the wastewater not be purified in that area, but it will also become anaerobic and cause a bad odor. Furthermore, even when no blockage occurs, it is difficult to uniformly flow the first stream into the bed, which tends to cause uneven flow, which also creates an anaerobic region.

In the case of biological treatment, increasing aeration efficiency is important in reducing blower power costs. In this sense, the circulating flow entrains air bubbles compared to the upward flow, so the residence time of the air bubbles is longer and the aeration efficiency can be increased. However, when a fixed bed is placed in a circulating flow, resistance occurs, which impedes the water flow and prevents the entrainment of air bubbles, resulting in a reduction in aeration efficiency.

Furthermore, as a fluidized bed method, there is a conventional method in which powdered activated carbon is added to activated sludge, and microbial blocks are formed using this as a nucleus to prevent bulking. However, in this method, the powdered charcoal is buried in the sludge block and flows out of the system as surplus sludge, making the powdered charcoal disposable.

Therefore, the price of powdered coal leads to an increase in operating costs, and the amount of surplus sludge increases.

In addition, there is also a method of using a polypropylene surface-structured packing material, such as the one disclosed in Japanese Patent Publication No. 47-41225, as a floating bed, but in this case, maintenance such as cleaning of the air diffuser is In addition, anaerobic areas occur due to blockage with biofilm, reducing purification efficiency.Also, in a state where biofilm is not attached, the bed rises above the water surface, causing biofilm to form. If it gets stuck too much, it will start to sink and the floor will become unstable.

The object of the present invention is to provide an advantageous wastewater treatment method that compensates for the drawbacks of conventional methods such as the activated sludge method, the immersed P-bed method, the conventional fluidized bed method, and the floating bed method, and takes advantage of the advantages.

According to the method of the present invention, the biofilm on the surface of the packing is continuously renewed, aerobic treatment and anaerobic treatment are performed in parallel, and the effects of reducing the amount of excess sludge and increasing the processing speed are significant.

Embodiments of the present invention will be described using the drawings.

The drawings are flowcharts illustrating embodiments of the invention. In the figure, raw wastewater 5 is supplied to the activated sludge tank 4 from the top 1, and air is blown into the raw wastewater 5 stored in the activated sludge tank 4 through an air blowing pipe 1, creating a circulating flow that rotates in the vertical direction. bring forth. This air blowing pipe 1 can be selected from any pipe suitable for the purpose of generating a downward rotating flow in the stored raw wastewater. For example, an air diffuser pipe, an air lift pump, an ejector, or a blower is used, and the tip nozzle of the air blowing pipe is provided with a plurality of air blowing ports 7 depending on the shape of the inner wall of the activated sludge tank 4, and is used to blow into the stored waste liquid. The air introduced is blown into the bottom of the activated sludge tank 4. The blown air becomes bubbles and rises in the stored wastewater, and due to the buoyancy of the bubbles, the stored wastewater generates a circulating flow that rotates in the vertical direction as shown by the arrow in the figure. When the filling material 2 is put into the stored wastewater in the activated sludge tank 4 formed in this way and rotating and circulating in the vertical direction, the filling material 2 rides on the circulating flow of the stored water and rotates vertically in the direction of the arrow in the figure. A fluidized bed of moving and circulating packing is formed.

The gist of the present invention is to form a fluidized bed of this packed material, to attach and remove biofilm on the surface of this packed material, and to perform anaerobic and aerobic treatment of wastewater at the same time.

As will be described later, the biofilm adheres to the surface of the packing 2 that forms a fluidized bed in the stored water as it rotates from the bottle upwards and from the top downwards. The state of biofilm adhesion is that an anaerobic film is attached to the surface of the wire rod of the packing (7) This anaerobic film is covered with an aerobic film, and further substances are generated in a stepwise manner, forming a food chain, and excess sludge is removed. The fresh, active biofilm is retained on the surface of the flowing packing while repeating the detachment and attachment of multiple biofilms.The air blown into the stored wastewater causes the filling 2 to flow. At the same time, the stored wastewater is rotated and circulated along with the filling material to supply oxygen to aerobic bacteria.The stored water that has remained in the activated sludge tank 4 for a predetermined time is overflowed with treated water along with a relatively small amount of sludge. The treated water is guided from the lower through a conduit 8 to a well-known settling tank 9. The partition plate 6 of the activated sludge tank 4 has the function of blocking direct mixing of raw wastewater 5 and treated water. The treated water containing sludge is separated by the sludge scraping device 1 which is rotated by the drive device 14, and is taken out from the sludge removal conduit 12 and treated separately.On the other hand, clear water is passed from the effluent overflow port 10 to the effluent conduit. It is released after 11 days.

In the above description, the filling material suitably used in carrying out the present invention is preferably a filling material having a linear structure as typified by Japanese Utility Model Publication No. 44-14682, and particularly a filling material having a structure disclosed in Japanese Patent Application No. 57'-25808. A filling having a longest representative diameter, that is, a maximum horizontal diameter of one filling when left still, is 30 ffm or more, and is preferably made of plastic with a specific gravity between 0.88 and 099. It will be done. As for the amount of filler to be added, the effect will already be seen if 5 parts of the liquid volume is added, and as the amount of filler increases, 20-50% is generally added in consideration of successiveness.

The filling used in the present invention mainly has a linear structure, so if the filling has a maximum representative diameter of 30 mm or less, the gaps in the linear structure will be blocked by biofilm, and the renewal of the biofilm will be inhibited. 5.1 is also unfavorable because a large size impedes normal uniform fluidization and results in insufficient renewal of the biofilm. For these reasons, as an example of the filler used in the present invention, there is a polyprolene linear structure filler with a longest representative diameter of 145 mm, a specific gravity of 0.92, and a turbid cross section of 18 mm.

These linear-structured fillers are made of wires with cross-sectional areas ranging from 1 mA to 60 mm depending on size. The filler used in the present invention is a plastic having a specific gravity of 088 to 99, and these fillers may be used alone or in combination.

This is a condition in which the fluidization of the filling is not inhibited even if the specific gravity of the filling containing solid gold increases somewhat with respect to the stored wastewater due to the attachment of biofilm to the surface of the filling that circulates and flows in the stored wastewater. Suitable plastic materials are mainly polypropylene and polyethylene. Other plastics can also be used by adding appropriate additives and adjusting the specific gravity as described above.

Also, fillers with surface structures other than linear structures, such as
7-41225, it is not impossible to use a packing material in the present invention, but from the viewpoint of fluidity ratio and biofilm attachment and renewal, Id,
・One thing: Zooglea ramigera adheres to the surface of the filling in the stored wastewater that flows in this way, forming a biofilm.

The biofilm is in contact with the constantly renewed fluid and adsorbs dissolved oxygen and BOD substrates in the fluid.

In other words, since the packing material itself retains the biofilm, there is no need for return sludge as in the activated sludge method, and since the sludge is carried by the upper circulation flow, pore surfaces that do not come in contact with the liquid are formed, like in an immersed bed. Never. Activated sludge contains a large amount of senescent bacteria that have already lost their activity, and although they may consume oxygen, they do not adsorb BOD. On the other hand, in a biofilm, aged bacteria naturally fall off, so only young and active bacteria are attached, and even a small amount of filler can be effective.

This is evidenced by the fact that when the dehydratase activities of biofilm-adhering bacteria and surplus sludge bacteria are compared, there is a difference of several times or more. In addition, in the general activated sludge method, protozoa and metazoa have a long generation and flow out of the tank before becoming parents, so the amount of these animals generated is small. However, many zooglaea-eating microorganisms are generated in the biofilm attached to the filler, forming a food chain, and as a result, excess sludge is reduced.

Processing surplus sludge requires a large amount of fuel and power for dehydration, drying, and incineration, so the formation of a food chain can be said to be a phenomenon linked to energy conservation.

Also, in a biofilm, the surface becomes aerobic and the inside becomes anaerobic.
For example, NH3 nitrogen is oxidized to NO2 or NO3 in the aerobic part and reduced to N2 in the anaerobic part, achieving denitrification. Therefore, when a filler is added to a general activated sludge process, the nitrogen removal rate increases.

In addition, when the water temperature drops in winter, dissolved oxygen in the liquid increases, and the activity of the biofilm decreases7, reducing oxygen consumption, so oxygen penetrates deep into the biofilm, and as a result, the aerobic part The thickness increases.

By adding the filler in this way, stable performance can be maintained even in winter. The present invention does not require a frame for fixing the f-materials as is the case with the immersion 41-body method, making it possible to reduce construction costs, shorten construction and delivery times, and facilitate operational management.

In the above explanation, the method of blowing air from one direction of the activated sludge tank 4 to form a fluidized bed of packed material was explained. The circulation flow is not limited to vertical circulation in the direction, for example, a circulation flow that ascends the center of the activated sludge tank 4 obtained by blowing air into the center of the activated sludge tank 4 and descends from the top to the bottom of the inner wall, or On the contrary, air is blown into the activated sludge tank 4 by blowing air into the activated sludge tank 4 to create a circulating flow that rises from below along the bottom inner wall and descends from the center.
It is also possible to flow the filling from the entire bottom surface of the container. In this case, a hard vinyl chloride filler having a specific gravity of about 1.6 to 1.4 can also be used. However, in terms of equipment costs and operational management, the above-mentioned fluidized bed that rotates and circulates up and down is superior for implementing the present invention. Furthermore, the inner wall of the activated sludge tank 4 is preferably a curved surface that provides no resistance to the circulating flow that rotates up and down. Furthermore, mechanical stirring using a stirrer or the like is unsuitable because it crushes the filler.

As described above, the present invention can facilitate maintenance and management by simply adding filler to a conventional activated sludge device, making it maintenance-free, and can increase the BOD removal rate and nitrogen removal rate. Other advantageous effects include reducing the amount of surplus sludge generated and making use of the traditional advantages of biofilms, such as maintaining performance in winter.

[Brief explanation of drawings]

The figure is a flowchart showing one embodiment of the present invention. 1... Air blowing pipe 2... Filling filter... Air bubbles
4 Activated sludge tank 5... Raw wastewater 6
・・Partition plate 7 ・Treatment water overflow port 8 ・Treatment water conduit 9 ・Sedimentation tank 10 ・・Discharge water overflow port 11 ・・
Effluent water conduit 12...Sludge removal conduit 13 Sludge scraping device 14 Drive device patent applicant Nippon Steel Kakoki Co., Ltd. 4

Claims (1)

[Claims] A filler is introduced into the vertically circulating flow of the wastewater generated by pressurizing air into the wastewater to be treated in an activated sludge tank, and a fluidized bed of the filler rotating in the wastewater is formed to form a fluidized bed of the wastewater. Activated sludge method using packed material for treatment.