JP3407342B2 - Biological denitrification / phosphorus removal equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological denitrification / dephosphorization treatment apparatus, and in particular, it is possible to reduce the size of the apparatus, reduce the cost, and improve the treatment efficiency. The present invention relates to a fixed-bed biological denitrification / phosphorus removal apparatus. [0002] Hitherto, as a biological dephosphorization / denitrification treatment apparatus using a floating system (activated sludge method), a combination of an anaerobic tank, a denitrification tank and an aerobic tank has been known. The feature of the floating method is that the homogeneous sludge flows down to the subsequent tank sequentially with the water flow. [0003] On the other hand, the fixed-bed system, in which microorganisms are retained in a filler (filter material) or the like for biological treatment, requires a higher load on raw water (water to be treated) than the floating system to increase treatment efficiency. On the other hand, there is an advantage that the cost can be increased, but there is a disadvantage that the equipment cost is generally high. Conventionally, as a method of performing a dephosphorization treatment by a fixed bed method, raw water is sequentially passed through a plurality of treatment tanks, first treated in an anaerobic treatment tank, and then treated in an aerobic treatment tank. After performing the treatment for a predetermined period, at least one of the anaerobic treatment tanks is in an aerobic state,
There has been proposed a method of changing the flow direction of raw water so that the raw water flows from the anaerobic processing tank to the aerobic processing tank. In other words, for biological dephosphorization, it is necessary to switch the anaerobic treatment tank to the aerobic state after performing the treatment for a predetermined period of time. At the same time, the direction of flow of raw water has been changed. [0006] However, in order to make the anaerobic treatment tank aerobic after a predetermined period of time, a mechanism for bringing all the treatment tanks into which raw water flows into an aerobic state, For example, it is necessary to provide a diffuser, a member for preventing the fixed bed filter medium from flowing out due to the diffuser, and the like, so that the equipment is complicated and the equipment cost is high. As described above, since the fixed floor method itself has a high equipment cost, the necessity of an air diffuser or the like for each processing tank in this way leads to a further increase in the equipment cost. Is not preferred. In the case where nitrogen components are present in the raw water, the biological dephosphorization reaction does not proceed unless the nitrate nitrogen generated in the aerobic treatment tank is removed. Need to be removed. Therefore, in order to simultaneously perform biological dephosphorization and denitrification in a fixed bed system, it is necessary to use another treatment system. The present invention has been made in view of the above-mentioned conventional circumstances, and provides a fixed-bed type biological denitrification / dephosphorization treatment apparatus capable of reducing the size, cost, and improving the treatment efficiency of the apparatus. The purpose is to do. [0010] The biological denitrification / phosphorus removal treatment apparatus of the present invention comprises an anaerobic treatment tank and an aerobic treatment tank, and each treatment tank is provided with a fixed biological bed. In a biological denitrification and dephosphorization treatment apparatus, raw water is sequentially passed through a first anaerobic treatment section, a second anaerobic treatment section, and an aerobic treatment tank, and a part of the effluent of the aerobic treatment tank. Is introduced into the second anaerobic treatment section, the first flow path selection for discharging the remaining part of the effluent of the aerobic treatment tank out of the system as treated water, and the raw water as the second anaerobic treatment section, Water is sequentially passed through the anaerobic treatment section and the aerobic treatment tank, and a part of the effluent of the aerobic treatment tank is introduced into the first anaerobic treatment section, and the remaining part of the effluent of the aerobic treatment tank is treated as treated water. The present invention is characterized by comprising a flow path switching means for selectively selecting the second flow path to be discharged to the outside. In, the filler constituting the fixed bed of each processing tank is not particularly limited, but anthracite, sand,
Plastic, foamed plastic, sponge, or the like can be used. When biological dephosphorization and denitrification are performed in an anaerobic tank, a denitrification tank, and a nitrification tank, raw water is first introduced into the anaerobic tank to remove organic substances, and then denitrification is performed in the denitrification tank. (And dephosphorization). In this case, the amount of organic matter absorbed in the anaerobic tank is limited. On the other hand, the amount of denitrification in the denitrification tank is also limited because the denitrification reaction does not proceed if the absorbed organic matter is consumed. There is. Therefore, in order to carry out biological dephosphorization and denitrification in a fixed-bed system, the anaerobic tank and the denitrification tank are periodically switched, that is, the anaerobic process and the denitrification are performed in one anaerobic treatment section. It is necessary to alternately perform the nitrification step and alternately perform the denitrification step and the anaerobic step in the other anaerobic treatment section. By this switching, absorption of organic substances and release of phosphorus, and denitrification and Reactions of phosphorus absorption proceed continuously and efficiently. [0013] In the biological denitrification / phosphorus removal apparatus of the present invention, when the first flow path is selected, the first anaerobic treatment section is used as the anaerobic section and the second anaerobic treatment section is used. Functions as a denitrification unit, and the aerobic treatment tank functions as a nitrification tank, while
When the second flow path selection is selected, the second anaerobic processing section functions as an anaerobic section, the first anaerobic processing section functions as a denitrification section, and the aerobic processing tank functions as a nitrification tank. Then, by alternately selecting the first and second flow paths, the first anaerobic treatment section and the second anaerobic treatment section alternately perform the anaerobic step or the denitrification step. In the anaerobic step, the release of phosphorus accumulated in the biofilm in the denitrification step at the time of the previous flow channel selection, while in the denitrification step, the phosphorus is absorbed by the biofilm in the previous anaerobic step The denitrification and phosphorus absorption are performed at the same time using the organic matter thus obtained. That is, first, raw water flows into an anaerobic tank (one of a first anaerobic processing section and a second anaerobic processing section), and organic matter in the raw water is converted into a biofilm (fixed-bed microorganisms). And, along with this absorption, the phosphorus accumulated in the biofilm in the previous channel selection is released. The effluent from the anaerobic tank flows into the denitrification tank (either the first anaerobic processing section or the second anaerobic processing section) and is returned from the nitrification tank (aerobic processing tank) at the subsequent stage. Denitrification of nitrate nitrogen (N ₂ gasification) contained in a part of water and absorption of phosphorus by a biofilm are simultaneously performed. In the denitrification and dephosphorization, the organic matter absorbed in the biofilm in the previous flow path selection is used. As a result, water from which phosphorus and nitrate nitrogen have been removed flows out of the denitrification tank. The effluent from the denitrification tank then flows into a nitrification tank (aerobic treatment tank). In the nitrification tank, the entire fixed bed is aerobic, and the ammonia nitrogen in the influent is nitrified into nitrate nitrogen. As described above, a part of the effluent from the nitrification tank is returned to the denitrification tank, and the nitrate nitrogen contained therein is denitrified. As described above, in the present invention, the aerobic treatment tank provided with facilities such as a diffuser for aerobic and a member for preventing the outflow of the filter medium as a nitrification tank is fixed, Since the anaerobic section and the denitrification section are switched by selecting a route, the number of aerobic treatment tanks requiring an air diffuser or the like can be reduced, and the size and cost of the equipment can be reduced. Since the nitrification tank is fixed as an aerobic treatment tank and the nitrification tank is not placed in an anaerobic state, the concentration of nitrifying bacteria can be increased. Organic matter has already been removed from the nitrification tank inflow water, and a favorable environment for nitrifying bacteria in the nitrification tank is maintained. In addition, the nitrification capacity in the nitrification tank is significantly improved as compared with the conventional floating method. Under such an excellent effect, biological dephosphorization and denitrification by a fixed bed method can be performed. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a system diagram showing one embodiment of a biological denitrification / phosphorus removal apparatus according to the present invention, and FIG. 2 shows a biological denitrification / phosphorus removal apparatus according to another embodiment. It is a system diagram. The biological denitrification / phosphorus removal apparatus shown in FIG. 1 has a first anaerobic treatment section 1 and a second anaerobic treatment section 5 as an anaerobic treatment tank 5.
Aerobic treatment tank 3 having anaerobic treatment section 2 and diffuser 4
It is mainly composed of Reference numerals 1A, 2A, and 3A denote biological fixed beds formed in each treatment tank. In FIG. 1, 11A, 11
B, 12A. 12B, 13A, 13B. 14, 15A,
15B shows piping. In the biological denitrification and dephosphorization treatment apparatus of this embodiment, in the first flow path selection, as shown in FIG. 1A, raw water is supplied to a pipe 11A, a first anaerobic treatment section 1, Water is sequentially passed through the pipe 12A, the second anaerobic treatment section 2, the pipe 13A and the aerobic treatment tank 3, and a part of the effluent of the aerobic treatment tank 3 is passed through the pipe 15A from the second anaerobic treatment section 2. And the remaining part is discharged from the pipe 14 outside the system as treated water. In this first flow path selection, the first anaerobic processing section 1 functions as an anaerobic section, the second anaerobic processing section 2 functions as a denitrification section, and the aerobic processing tank 3 functions as a nitrification tank. However, as described above, the absorption of organic matter and the release of phosphorus in the first anaerobic treatment section 1 and the second anaerobic treatment section 2
In the above, the denitrification of nitrate nitrogen and the absorption of phosphorus are performed, and the nitrification of ammoniacal nitrogen is performed in the aerobic treatment tank 3, and a part of the effluent containing nitrate nitrogen from the aerobic treatment tank 3 is removed. It is returned to the second anaerobic treatment section 2 which is a nitrification tank, and is denitrified. After such processing is continued for a predetermined period,
As shown in FIG. 1B, the flow is switched to the second flow path selection, and the raw water is supplied to the pipe 11B, the second anaerobic treatment section 2, the pipe 12B,
First anaerobic treatment section 1, pipe 13B and aerobic treatment tank 3
And a part of the effluent of the aerobic treatment tank 3 is introduced into the first anaerobic treatment section 1 through a pipe 15B, and the remaining part is discharged out of the system through a pipe 14 as treated water. In the selection of the second flow path, the first anaerobic treatment section 1 functions as a denitrification section, the second anaerobic treatment section 2 functions as an anaerobic section, and the aerobic treatment tank 3 functions as a nitrification tank. However, as described above, the absorption of organic matter and the release of phosphorus in the second anaerobic treatment section 2 and the first anaerobic treatment section 1
In the above, the denitrification of nitrate nitrogen and the absorption of phosphorus are performed, and the nitrification of ammoniacal nitrogen is performed in the aerobic treatment tank 3, and a part of the effluent containing nitrate nitrogen from the aerobic treatment tank 3 is removed. It is returned to the first anaerobic treatment section 1 which is a nitrification tank and denitrified. The biological denitrification / phosphorus removal apparatus shown in FIG. 2 is mainly composed of a single anaerobic treatment tank 5 and an aerobic treatment tank 3 having a diffuser 4. Reference numerals 5A, 5B, and 3A denote biological fixed beds formed in each treatment tank. In FIG.
21A, 21B, 22A, 22B, 23, and 24 show piping. In this biological denitrification and dephosphorization treatment apparatus, the biological fixed bed of the anaerobic treatment tank 5 is vertically divided into two to form two biological fixed beds 5A and 5B. A pipe 24 is connected between 5A and 5B. In the biological denitrification / phosphorus removal apparatus of the present embodiment, in the first flow path selection, as shown in FIG. 2A, raw water is introduced into the upper part of the anaerobic treatment tank 5 from the pipe 21A. Then, the effluent of the anaerobic treatment tank 5 is extracted from the lower part of the anaerobic treatment tank 5 and flows through the pipe 22A to the aerobic treatment tank 3, and a part of the effluent of the aerobic treatment tank 3 is connected to the pipe 24.
It is introduced into the anaerobic treatment tank 5 and the remaining part is discharged out of the system from the pipe 23 as treated water. In this first flow path selection, the biological fixed bed 5A of the anaerobic treatment tank 5 is used as an anaerobic part and the biological fixed bed 5B
Represents a denitrification unit, and the aerobic treatment tank 3 functions as a nitrification tank, and absorbs organic substances and releases phosphorus in the fixed biological bed 5A, and denitrifies nitrate nitrogen and removes phosphorus in the fixed biological bed 5B. Absorption and nitrification of ammonia nitrogen are further performed in the aerobic treatment tank 3, and a part of the effluent containing nitrate nitrogen from the aerobic treatment tank 3 is introduced into the biological fixed bed 5B which is a denitrification part. To be denitrified. After such processing is continued for a predetermined period,
As shown in FIG. 2B, the flow is switched to the second flow path selection, raw water is introduced into the lower part of the anaerobic treatment tank 5 from the pipe 21B, and the effluent of the anaerobic treatment tank 5 is transferred to the upper part of the anaerobic treatment tank 5. The effluent from the aerobic treatment tank 3 is introduced from the pipe 24 into the anaerobic treatment tank 5 through the pipe 24, and the remainder is treated as the treated water from the pipe 23. Discharge outside the system. In the selection of the second flow path, the biological fixed bed 5B of the anaerobic treatment tank 5 is used as an anaerobic part and the biological fixed bed 5A
The aerobic treatment tank 3 functions as a nitrification tank, and the aerobic treatment tank 3 functions as a nitrification tank. Absorption of organic substances and release of phosphorus are performed in the fixed biological bed 5B, and denitrification of nitrate nitrogen and phosphorus are prevented in the fixed biological bed 5A. Is absorbed, and nitrification of ammonia nitrogen is further performed in the aerobic treatment tank 3.
A part of the effluent containing nitrate nitrogen from the wastewater is returned to the biological fixed bed 5A, which is a denitrification tank, to be denitrified. As described above, according to the biological denitrification / phosphorus removal apparatus of the present invention, the aerobic treatment tank as the nitrification tank is fixed, and the anaerobic part and the denitrification part are connected by switching the flow path of the anaerobic treatment tank. Can be switched alternately to perform efficient fixed-bed biological dephosphorization and denitrification. The illustrated biological denitrification / phosphorus removal apparatus is one embodiment of the present invention, and the present invention is not limited to the illustrated one. For example, the number of anaerobic treatment tanks (the first anaerobic treatment section / the second anaerobic treatment section) and the number of aerobic treatment tanks are not limited to one, and two or more tanks may be provided. Although the flow path switching means is not shown in FIGS. 1 and 2, by appropriate valve switching,
The illustrated flow path can be easily selected. In the present invention, the treatment conditions in each treatment tank are not particularly limited, but the aerobic treatment tank as a nitrification tank has a dissolved oxygen concentration of 1.5 to 2.0 to promote a good nitrification reaction. It is preferable to keep the aerobic state of about 0 mg / l. Hereinafter, the present invention will be described in more detail with reference to specific examples. Example 1 The biological denitrification / denitrification treatment is performed by the biological denitrification / dephosphorization treatment apparatus of the present invention shown in FIG. Was. Raw water quality BOD: 130 mg / l TN: 25 mg / l TP: 3 mg / l Anthracite was used as a filler for the fixed bed of each treatment tank, and the residence time was set at 2 hours for each treatment tank. Was. Water introduced from the aerobic treatment tank to the denitrification tank of the first or second anaerobic treatment section is equivalent to twice the amount of raw water,
The selection of the first flow path and the selection of the second flow path were performed every two hours. As a result, the TP of the treated water was 0.1 mg /
0.8 mg / l in the range of 1 mg or less to 2.5 mg / l
/ L, and the average value of TN was 10 mg / l or less, and a remarkably good treatment result was obtained. As described in detail above, according to the biological denitrification / dephosphorization treatment apparatus of the present invention, it is a biological dephosphorization / denitrification treatment apparatus using a fixed bed system, Provided is a biological denitrification / phosphorus removal apparatus which can be reduced in size and cost and can achieve good treatment efficiency. In particular,
If an anaerobic tank is used to perform anaerobic and denitrification in a single tank, the number of required processing tanks is small, and the size of the equipment can be further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram showing one embodiment of a biological denitrification / phosphorus removal treatment apparatus of the present invention. FIG. 2 is a system diagram showing another embodiment of the biological denitrification / phosphorus removal apparatus of the present invention. [Description of Signs] 1 First anaerobic processing section 2 Second anaerobic processing section 3 Aerobic processing tank 4 Air diffuser 5 Anaerobic processing tank

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C02F 3/28-3/34 C02F 3/02-3/10

Claims (1)

(57) [Claims] [Claim 1] An anaerobic treatment tank and an aerobic treatment tank are provided,
In a biological denitrification and dephosphorization treatment apparatus in which a biological fixed bed is provided in each treatment tank, raw water is sequentially passed through a first anaerobic treatment section, a second anaerobic treatment section, and an aerobic treatment tank. At the same time, a first flow path for introducing a part of the effluent of the aerobic treatment tank into the second anaerobic treatment section and discharging the remaining part of the effluent of the aerobic treatment tank outside the system as treated water; The second anaerobic treatment section, the first anaerobic treatment section and the aerobic treatment tank are successively passed through water, and a part of the effluent of the aerobic treatment tank is introduced into the first anaerobic treatment section to form an aerobic treatment. Biological denitrification / phosphorus removal, characterized by comprising flow path switching means for selectively selecting a second flow path for discharging the remaining part of the treatment tank effluent as treated water to the outside of the system. Processing equipment.