JP2007185598A - Microorganism immobilized gel carrier type wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment apparatus which has a low construction cost and running cost, and is easy of operation control. <P>SOLUTION: In a wastewater treatment apparatus using a microorganism immobilized gel carrier, an immersed membrane filtration type sludge separation system and a settling tank type sludge separation system are both installed. Wastewater is denitrified and/or nitrified in a gel tank 3 having a raw water feed pump 1 and an aeration device 4, and then fed to a total oxidation tank 8 containing gel carriers through a separating cylinder 5 to be oxidized by an aeration device 10. After separating the gel carriers by a membrane system 9, sludge is separated by a settling tank 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wastewater treatment apparatus of a microorganism-immobilized gel carrier system. More particularly, the present invention relates to a wastewater treatment apparatus using a microorganism-immobilized gel carrier, which is provided with both a sludge separation facility using a submerged membrane filtration method and a sludge separation facility using a sedimentation tank method. According to the wastewater treatment apparatus provided with both the sludge separation facility by the submerged membrane filtration method and the sludge separation facility by the settling tank of the present invention, not only the facility construction cost and running cost can be reduced, but also the operation management becomes easy.

  Conventionally, organic wastewater such as household wastewater, urban sewage, and various industrial wastewater has been treated by the activated sludge method. Recently, in order to make the wastewater treatment equipment compact, a microorganism-immobilized gel carrier (hereinafter, microorganism-immobilized) is used. Many methods and apparatuses have been proposed that use a gel carrier as a gel carrier, and a method for treating waste water using the gel carrier. The characteristics of the gel carrier system are that the BOD treatment capacity is large and that sludge volume reduction is efficiently realized in the total oxidation tank, and sludge separation is usually carried out in a sedimentation tank.

  The gel carrier system has a feature that the sludge particle shape increases in the complete oxidation tank (total oxidation tank) for self-oxidation of sludge and the sludge separation is easy. Since the size of the sedimentation tank is determined by the above, the characteristic of the gel carrier system that the sludge particle shape can be enlarged is not fully utilized.

Recently, a sludge separation system using a membrane has been proposed in many cases (for example, Patent Document 1), but the sludge separation system using a membrane has an advantage that the filtrate water can be reused as intermediate water. Yes, this method is expected to grow in the future. However, in the general activated sludge method, since the sludge particle shape is small, it is necessary to make the pores of the membrane small. As a result, the water permeability deteriorates, the membrane equipment becomes large, and the membrane price is high. There is also a problem that operation troubles frequently occur due to sludge leaks and clogging of the membrane, and further improvement is necessary.
Japanese Patent Laid-Open No. 11-42497

  As a countermeasure against such a problem, in a general activated sludge method, operation is performed with a large margin in the amount of membrane installed, for example, a large margin in the amount of membrane installed. Membrane equipment has been installed outside the aeration tank and has been developed by the sludge circulation method. This is not only high in membrane cost, but also requires a lot of power to operate the circulation pump. It has become increasingly clear that wastewater treatment equipment using membranes is not necessarily industrially advantageous.

  Recently, the development of a sludge separation method using a submerged membrane that installs a membrane inside the aeration tank has been focused and focused on the fact that the amount of electricity used is reduced, but the submerged membrane method is much more advanced than conventional membranes. Since it is necessary to use an expensive membrane, it is disadvantageous in terms of cost, and improvement of membrane cost and system development are urgently needed.

  The problem to be solved by the present invention is not to improve the membrane cost, but to provide a wastewater treatment device with a low construction cost and a low running cost from the system side, and also a wastewater treatment device with easy operation management. Is to provide.

  When installing wastewater treatment facilities, in general, in order to avoid excessive investment, it is usual to adopt either the sedimentation tank method or the membrane method, which is more advantageous. In order to take advantage of the advantages, it is rather advantageous to use both in combination, and as a result of repeated studies on sludge separation, according to both the immersion membrane method and the precipitation tank method, the characteristics of the gel carrier method As a result, the present inventors have found that the above-mentioned problems can be achieved. That is, the present invention is a wastewater treatment apparatus using a gel carrier, wherein both a sludge separation facility using a submerged membrane filtration system and a sludge separation facility using a sedimentation tank system are provided side by side.

  ADVANTAGE OF THE INVENTION By this invention, the waste water treatment equipment which provided both the sludge separation equipment by a submerged membrane filtration system and the sludge separation equipment by a sedimentation tank system can be provided. According to the wastewater treatment apparatus of the present invention, wastewater treatment can be carried out industrially advantageously, equipment construction costs and running costs can be reduced, and operation management can be facilitated.

  The wastewater treatment facility of the present invention is applicable to general activated sludge facilities, but exhibits a great effect particularly when a gel carrier system capable of downsizing the facilities is employed. As a gel carrier to be introduced into an aeration tank such as a gel tank, a polymer hydrous gel is preferable in terms of BOD removal ability, nitrification ability, and denitrification ability when bacteria are attached. When the hydrogel is used, the hydrogel is brought into contact with the membrane surface by flowing in the treatment tank, and the effect of cleaning the membrane surface is great. Among them, the polyvinyl alcohol (PVA) hydrogel has a network structure on the surface and inside of the carrier, so that microorganisms are liable to inhabit it, and it has excellent organic compound scavenging properties, as well as excellent mechanical strength. Therefore, it is preferable.

  The higher the average degree of polymerization and / or saponification degree of PVA, the lower the concentration of PVA, so that the moisture content of the gel can be increased. From this point, the average degree of polymerization of PVA is preferably 1000 or more, and more preferably 1500 or more. The degree of saponification of PVA is preferably 95 mol% or more, more preferably 98 mol% or more.

  In order to prevent the elution and deterioration of PVA, it is desirable to acetalize PVA. If the degree of acetalization is too low, the water resistance will be low, and if it is too high, it will be hydrophobized and the microorganisms will not live well, so it is preferably 10 to 60 mol%, more preferably 20 to 55 mol%. Specific examples of the PVA water-containing gel include Kuraray's trade name Klagale.

  The immersion membrane used in the wastewater treatment apparatus of the present invention may be durable, for example, polysulfone, polyacrylonitrile, polyolefin, cellulose, polyamide, polyester, PVA, poly (meth) acrylate Resins such as those based on polyimide, polyimide and polyvinylidene can be mentioned. These membranes can be used in any shape such as hollow fibers and flat membranes, but those having a hollow fiber shape are preferable in terms of handleability and compactness, for example, those having an inner diameter of about 200 to 2500 μm are preferable. used. Of these, polyvinylidene fluoride (PVDF) is preferable.

  The processing capacity of the immersion film to be installed usually has a considerable margin. For example, a design philosophy of periodically replacing half of the installed units may have a capacity margin of up to twice. However, in the wastewater treatment apparatus of the present invention, since the sedimentation tank is provided after the membrane facility, in principle, it is not necessary to have a margin for the capability of the membrane facility, and a large cost reduction can be achieved.

  In general, there is no leak in the membrane equipment, and its operation management is strictly required. In other words, even if sludge leaks, it is not allowed to exceed the regulation value. Therefore, it is necessary to always monitor and take action if sludge leaks. That is, when a leak occurs, it is necessary to immediately switch the membrane equipment, reduce the drainage load, or raise the drainage to the primary shelf, but if there is a settling tank as in the present invention, some sludge leaks Since it is allowed, the mental burden on operation management is reduced.

  When the wastewater treatment apparatus using the gel carrier has a total oxidation tank, the sludge particle shape can be increased, so that the pore diameter of the membrane can be preferably increased to 0.1 μm or more. In other words, the water permeability can be increased by increasing the pore diameter. In addition, the number of membrane equipment can be reduced, and the installation cost of the membrane equipment can be further reduced.

  In the present invention, the case where the aeration tank is composed of a gel tank and a total oxidation tank will be specifically described. In this case, the total oxidation tank is the final aeration tank. In the wastewater treatment apparatus of the present invention, it is preferable that both the outflow water from the final aeration tank and the filtered water from the immersion membrane installed in the final aeration tank flow into the precipitation tank. In addition, when installing a submerged membrane in the final aeration tank, install it separately and configure each membrane equipment to be opened and closed so that the filtered water from each submerged membrane can individually flow into the sedimentation tank It is preferable to do this. In the wastewater treatment apparatus of the present invention, the final aeration tank is preferably a total oxidation tank.

  Since the role of the sedimentation tank in the wastewater treatment apparatus of the present invention is, in principle, the treatment of sludge leakage from the membrane, or assistance during membrane maintenance, it has a margin to cope with large fluctuations in the amount of treated water and load. It is not necessary, and the amount of sludge generated in the sedimentation tank is very small, so that the equipment for the sludge retention part and sludge extraction part of the sedimentation tank can be made small.

  The wastewater treatment equipment that uses the gel carrier is much smaller than the general activated sludge equipment in the aeration tank, and construction costs are reduced. Therefore, even if an expensive submerged membrane equipment is used for the sludge separation part, the total construction cost Then, it can be made smaller than the construction cost of the conventional activated sludge equipment. The sedimentation tank facility construction is the most expensive part in the wastewater treatment facility, but the height of the sedimentation tank can be lowered by using a membrane together, that is, the sedimentation tank facility can be made small, so the entire apparatus It is much smaller than general activated sludge equipment and can be made inexpensive.

  The wastewater treatment apparatus in which two sludge separation methods are combined with the gel carrier system of the present invention is not limited to any purpose such as BOD removal, denitrification treatment, advanced treatment, sludge reduction, and adopts a gel carrier. It can be used for any purpose of wastewater treatment. Hereinafter, the waste water treatment apparatus of the present invention will be specifically described with reference to the drawings and examples.

  FIG. 1 is a schematic flow diagram showing an example of the waste water treatment apparatus of the present invention. FIG. 1 specifically illustrates an example of a wastewater treatment apparatus including a gel tank and a total oxidation tank, and a final aeration tank is a total oxidation tank, and these and a precipitation tank. Reference numeral 1 denotes a raw water supply pump for supplying raw water, and the raw water is supplied from the raw water supply line 2 to the gel tank. The supplied raw water is introduced into the gel tank 3. In the gel tank, 4 is an aeration device for aeration, 5 is a separation cylinder made of a wire mesh or the like for filtering treated water, and 6 is a blower for aeration. In the figure, F, T, and P are a flow meter, a thermometer, and a pressure gauge, respectively, provided as necessary. Valves are appropriately displayed in each equipment, but these are provided as needed. The description is omitted because it is not an essential part.

  The gel tank is a tank for performing denitrification and / or nitrification, and FIG. 1 is an example of BOD treatment in which the gel tank is an aeration tank such as a nitrification tank. About%. The gel carrier is fluidized by a diffuser and the waste water is treated under aerobic conditions. The treated water filtered by the separation cylinder is introduced into the total oxidation tank 8 through the gel treatment line 7. Providing an anaerobic filtration device or an initial sedimentation tank for anaerobic treatment in front of the gel tank is more effective because suspended matter in the waste water is removed.

  Membrane equipment 9 is immersed in the total oxidation tank, and the same gel carrier is flowed by the air diffuser 10 so that the waste water is completely oxidized. The membrane equipment is sucked by the suction pump 11, and the membrane-filtered treated water is introduced into the inner cylinder 13 of the settling tank 12 from the discharge side of the suction pump. The treated water treated in the total oxidation tank is introduced from the total oxidation treatment line 14 into the inner cylinder 13 of the precipitation tank 12. A flocculant may be added to the entire oxidation treatment line as necessary in order to reduce sludge extraction.

  The treated wastewater introduced into the settling tank inner cylinder rises from the bottom of the inner cylinder while allowing sludge to settle, and is discharged out of the system as supernatant water 15. Sludge is returned and circulated by the sludge return / circulation pump 16 through the sludge return line 17 to the entire oxidation tank. The supernatant water may be discharged as it is, or may be used as recovered water after appropriate sterilization.

Example 1
Gel aeration tank volume 1.25 m ^3, the complete oxidation tank, and waste water treatment apparatus comprising a membrane facility 2 group from the precipitation tank immersed volume 1.25 m ³ having a membrane area of 25 m ² volume 2.5 m ³ new When the raw water containing 100 ppm of BOD was installed and treated at 25 m ³ / day, the BOD of the treated water was stable at 20 ppm, and the amount of generated sludge was hardly recognized.

Example 2
A new 200m ³ standard activated sludge facility consisting of a 500m ³ aeration tank with a sludge conversion rate of 100% (sludge of almost the same amount as the treated BOD amount) and 600m ³ is inadequate. The waste water treatment apparatus of the present invention is constructed by diverting the existing aeration tank to a total oxidation tank and immersing four membrane facilities having a membrane area of 25 m ^{2 in} the total oxidation tank. When the raw water containing was treated at 400 m ³ / day, the BOD of the treated water was stable at 30 ppm, and the amount of generated sludge was 150 kg / day in dry weight.

It is the flow schematic at the time of using the waste water treatment equipment of the present invention for BOD processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water supply pump 2 Raw water supply line 3 Gel tank 4 Aeration apparatus 5 Separation cylinder 6 Blower 7 Gel processing line 8 Total oxidation tank 9 Membrane equipment 10 Aeration apparatus 11 Suction pump 12 Settling tank 13 Inner cylinder 14 Total oxidation processing line 15 Sewage water 16 Sludge return / circulation pump 17 Sludge return line

Claims (8)

A wastewater treatment apparatus using a microorganism-immobilized gel carrier, wherein both a sludge separation facility using a submerged membrane filtration system and a sludge separation facility using a settling tank are provided side by side. The wastewater treatment apparatus according to claim 1, wherein the microorganism-immobilized gel carrier is a polyvinyl alcohol-based hydrogel. The wastewater treatment apparatus according to claim 2, wherein the polyvinyl alcohol-based hydrogel is an acetalized polyvinyl alcohol-based hydrogel. The waste water treatment apparatus according to any one of claims 1 to 3, wherein the resin constituting the immersion film is polyvinylidene fluoride. The waste water treatment apparatus according to any one of claims 1 to 4, wherein the pore diameter of the immersion membrane is larger than 0.1 µm. The effluent from the final aeration tank constituting the waste water treatment apparatus and the filtered water from the submerged membrane installed in the final aeration tank are configured to flow into the sedimentation tank. Wastewater treatment equipment. The waste water treatment apparatus according to claim 6, wherein the immersion membrane is divided and installed in a final aeration tank so that filtered water from each immersion membrane individually flows into the precipitation tank. The waste water treatment apparatus according to claim 6 or 7, wherein the final aeration tank is a total oxidation tank.

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