JP3845515B2 - System and method for removing nitrogen and phosphorus in waste water - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, sewage, can be from domestic wastewater or industrial wastewater containing nitrogen and phosphorus compounds, such as human waste of removing nitrogen and phosphorus simultaneously, relates to nitrogen and removal system and method for removing phosphorus in the waste water, in particular its long It relates to stable operation.
[0002]
[Prior art]
Often the problem of eutrophication in closed waters has been raised, with nitrogen and phosphorus being the main causative agents. Conventionally, biological denitrification has been used to remove nitrogen and chemical agglomeration has been used to remove phosphorus. However, the chemical agglomeration method has a disadvantage that a large amount of sludge is generated by using a large amount of chemicals. Recently, an anaerobic-aerobic activated sludge method is a biological nitrogen and phosphorus removal method. As it came to be noted.
[0003]
In the biological denitrification method, organic nitrogen derived from protein and urea is ammoniated, nitrified, and denitrified using nitrifying bacteria and denitrifying bacteria, and released and removed as nitrogen gas. On the other hand, in the biological dephosphorization method, since phosphorus is involved in the form of phosphoric acid and does not gasify, it utilizes the fact that phosphorus-accumulating bacteria in sludge ingest phosphorus at high concentrations. In other words, phosphorus-accumulating bacteria preferentially ingest sludge organic matter in an absolute anaerobic zone where there is no dissolved oxygen or bound oxygen such as nitrate nitrogen by experiencing both anaerobic and aerobic atmospheres. In the subsequent aerobic zone, phosphorus is released, and the ingested bacterial organic matter is metabolized and proliferated, and excess phosphorus is ingested than the released phosphorus. In the biological dephosphorization method, sludge containing excessive phosphorus is taken out of the system as excess sludge, and phosphorus is removed.
[0004]
FIG. 2 shows a typical example of the anaerobic-anoxic (absolute anaerobic) -aerobic activated sludge method using the biological denitrification method and the biological dephosphorization method. In the following description, the anaerobic zone is a region in which molecular oxygen is not dissolved but bound oxygen such as NOx is present, which is a so-called facultative anaerobic region. An absolute anaerobic region where no bound oxygen is present. The biological nitrification denitrification method is described as a mechanism in which bacterial groups having different properties between aerobic nitrification bacteria and facultative anaerobic denitrification bacteria work sequentially.
[0005]
2 is an anaerobic biological treatment zone 22 which is a phosphorus release step, an anaerobic biological treatment zone 23 which is a denitrification step, and air is blown from an air pipe 25 to nitrify and excessive intake of phosphorus. An aerobic biological treatment zone 24 in which a part of the treatment liquid (nitrification liquid) containing nitrate nitrogen generated by nitrification is returned to the anoxic biological treatment zone 23, and a solid for separating sludge It consists of a liquid separator 27 and a separated sludge return system 28. The treated water is taken out of the system from the separated water discharge pipe 29. 21 is a drainage supply pipe, and 30 is a sludge discharge pipe. However, the nitrification liquid returned by this method has reached 1 to 3 times the wastewater to be treated. Further, for example, in sewage treatment, treatment of 14 to 18 hours is required, which is about twice as long as that of the standard activated sludge method. The release of phosphorus in the anaerobic biological treatment zone 22 that is indispensable for phosphorus removal may be inhibited by bound oxygen in nitrate nitrogen contained in the return sludge and dissolved oxygen contained in waste water. .
[0006]
As a conventional method, for example, Japanese Examined Patent Publication No. 61-33638 discloses a means for simultaneously removing nitrogen and phosphorus from organic waste water containing nitrogen and phosphate, that is, an anaerobic biological treatment zone is placed at the head, followed by aerobic. A method is described in which a plurality of biological treatment zones and anoxic biological treatment zones are arranged as one unit, and wastewater is stepped and supplied to each anaerobic biological treatment zone except the final one. However, as described above, in the first anaerobic biological treatment zone, there is a possibility that dissolved oxygen is contained in the waste water and nitrate nitrogen is contained in the returned sludge, so that sufficient phosphorus is not released.
[0007]
[Problems to be solved by the invention]
Environmental measures are increasingly demanding. The conventional anaerobic-anoxic-aerobic activated sludge method requires a large-capacity treatment tank as compared with the standard activated sludge method, the amount of circulating nitrating liquid is large, and the release of phosphorus is easily inhibited. Such issues were raised. Even if the anaerobic-anoxic-aerobic activated sludge method is used using existing sewage treatment plant equipment to improve the nitrogen and phosphorus removal function, the amount of wastewater treatment is greatly reduced, making it easy. Cannot be implemented. Therefore, the present invention is capable of maintaining efficient nitrogen and phosphorus removal performance stably for a long period of time, and suppresses a reduction in treatment capacity when using existing wastewater treatment plant equipment. The present invention has been completed with the object of providing a biological nitrogen and phosphorus removal system for waste water and a removal method that do not require circulation of the nitrification solution.
[0008]
[Means for Solving the Problems]
FIG. 1 shows a flow sheet according to an embodiment of the present invention, and the present invention, which is a means for solving the problems, will be specifically described with reference to the flow sheet. In the present invention, an anaerobic biological treatment zone 4a is provided at the head, followed by an anaerobic biological treatment zone 5, and a plurality of aerobic biological treatment zones 6a and 6b and at least one anaerobic biological treatment zone 4b are provided. The treatment apparatus 1 which is alternately arranged in the direction of the wastewater flow and uses the last treatment zone 6b as the aerobic zone, and the wastewater to be treated are disposed at the first anaerobic biological treatment zone 4a, and the above-described further anaerobic Drainage supply pipe 3 for supplying a step to a part or all of the sex biological treatment zone 4b, a solid-liquid separation device 2 for separating sludge in the effluent flowing out from the treatment device 1, and the separated sludge for oxygen-free treatment a sludge return pipe system 7 to return to the sex biological treatment zone 4a, in any of anoxic biological treatment zone 4, the oxidation-reduction potential meter 10 for measuring the redox potential of the biological reaction in the zone, the A wastewater characterized by comprising a system 14 for circulating a treatment liquid containing dissolved oxygen or bound oxygen to an anaerobic zone excluding the head when the oxidation-reduction potential indicates a reduction region and causes the possibility of phosphorus release. A nitrogen and phosphorus removal system is provided. In the above removal system, the capacity of the anaerobic biological treatment zone 5 provided at the head is at least 1.5 hours of the average residence time of the liquid to be treated , and the anaerobic biological matter in the treatment apparatus 1 It is desirable that the total volume of the aerobic biological treatment zones 6a and 6b be 1 to 2 with respect to the total volume 1 of the treatment zones 4a and 4b. The aerobic biological treatment zone 6 is provided with air blowing means 8, and the anaerobic biological treatment zone 4, the anaerobic biological treatment zone 5 and the aerobic biological treatment zone 6 are provided with positive stirring means 9. Good.
[0009]
Furthermore, the present invention starts with the anaerobic biological treatment zone 4a and the anaerobic biological treatment zone 5, and further flows through a plurality of aerobic biological treatment zones 6a and 6b and at least one anaerobic biological treatment zone 4b. Using the treatment apparatus 1 arranged alternately in the direction and making the last treatment zone 6b aerobic, the first anaerobic biological treatment zone 4a and a part of the further arranged anaerobic biological treatment zone 4b or After all the wastewater to be treated is step-fed and sequentially flowed through the downstream zone, the effluent is led to the solid-liquid separation device 2 to separate sludge, and the separated sludge is introduced to the top anaerobic biological treatment zone 4a. danger of sends back, either by measuring the redox potential of the biological reaction in the zone with a redox potential meter in anoxic biological treatment zone, the value indicates a reduction zone phosphorus released into If, to provide a treatment solution containing dissolved oxygen or binding oxygen removal method of nitrogen and phosphorus in the waste water, which comprises circulating the top anoxic zone excluding. In this removal method, the oxidation-reduction potential of the biological reaction solution in the zone is measured using the oxidation-reduction potentiometer 10 in any anoxic biological treatment zone 4b, and the value indicates a reduction region, which may cause phosphorus release. In some cases, i.e., generally -200 mV or less, preferably -150 mV or less, it is desirable to circulate the treatment liquid containing dissolved oxygen or bound oxygen to the anaerobic zone 4b except the head.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described more specifically with reference to the drawings and embodiments. In addition, in order to make drawing and description easy to understand, a zone having a small number of zones is illustrated. In the system for removing nitrogen and phosphorus in wastewater of the present invention, in order to carry out biological treatment of wastewater, an oxygen-free biological treatment zone 4a for reducing and consuming oxygen in the wastewater and sludge at the head is continued. The anaerobic biological treatment zone 5 for causing the release of phosphorus is further arranged in succession by alternately arranging a plurality of aerobic biological treatment zones 6a and 6b and at least one anaerobic biological treatment zone 4b in the flow direction. Is provided with an aerobic biological treatment treatment zone 6b. The processing apparatus 1 is normally comprised by 1 tank, and the inside is divided | segmented into the some processing zone 4a, 5, 6a, 4b, 6b by the partition plate 11 of the up-down direction. The waste water and sludge supplied to the top anaerobic biological treatment zone 4a pass through the lower end of the partition plate 11a, then overflow the upper end of the partition plate 11b, and sequentially flow from upstream to downstream by repeating these steps.
[0011]
The capacity of the anaerobic biological treatment zone 5 provided at the head is at least 1.5 hours, preferably 2 hours or more of the average residence time of the liquid to be treated . If it is too short, phosphorus in the sludge may not be released sufficiently. Air is blown into the aerobic biological treatment zones 6a and 6b through the air supply pipe 8 in order to supply a required amount of oxygen. The volume ratio of the total anaerobic biological treatment zone 4 and the total aerobic biological treatment zone 6 is generally set so that the former 1 is preferably 1 to 2. This is because the digestion reaction, which is an aerobic biological treatment, is slower than the denitrification reaction, which is an anaerobic biological treatment.
[0012]
Wastewater containing nitrogen and phosphorus is treated by anaerobic biological treatment zone 4a, a part of which is provided at the head of the treatment apparatus 1 by the drainage supply pipe 3, and the remaining wastewater is provided downstream. Step fed to zone 4b. Wastewater containing sludge that has been processed by passing through the treatment device 1, that is, treated water, flows out from the outlet side of the treatment device 1 to the solid-liquid separation tank 2, and a part of the separated sludge (usually slurry) is returned to the return pipe. The system 7 returns to the top anaerobic biological treatment zone 4a, and the remaining sludge is taken out of the system through the sludge discharge pipe 12. The separated water is also taken out of the system through the separated water discharge pipe 13.
Now, in the first anaerobic biological treatment zone 4a, consumption of dissolved oxygen contained in some of the supplied wastewater and sludge and reduction of combined oxygen proceed, and return using organic matter contained in the wastewater. Denitrification of nitrate nitrogen in sludge is performed.
[0013]
The wastewater in a state where the combined oxygen and dissolved oxygen are released flows into the anaerobic biological treatment zone 5. In the anaerobic biological treatment zone 5, phosphorus in sludge is released under absolutely anaerobic conditions and flows into the next aerobic biological treatment zone 6a. In the aerobic zone 6a, nitrification of ammonia nitrogen contained in the waste water from the stay in the anaerobic biological treatment zone 4a and excessive intake of phosphorus are performed. In the next anaerobic biological treatment zone 4b, nitrate nitrogen generated in the previous aerobic zone 6a is denitrified using the organic matter in the wastewater supplied in steps. Further, in the next aerobic zone 6b, nitrification of ammonia nitrogen contained in the inflow water from the anaerobic zone 4b and excessive intake of phosphorus are performed. In the same manner, the waste water is alternately processed in the anaerobic zone and the aerobic zone, and flows downstream through repeated denitrification of organic nitrogen compounds, nitrification, and excessive intake of phosphorus. In order to effectively distribute and supply the organic matter necessary for denitrification and to uniformize the processing load in each zone, the wastewater supplied stepwise to the oxygen-free zone 4b in the middle of the flow direction is treated in the same manner.
[0014]
In this embodiment, for the sake of simplicity, the case where there are two anaerobic zones 4a and 4b and two aerobic zones 6a and 6b has been described, but the number of zones can be further increased depending on the processing conditions. By configuring the entire processing apparatus 1 with one tank, cost and occupied area can be saved. However, it can also be configured by a continuous multi-tank apparatus in which each zone is an independent tank, or can be configured by a tank row grouped into one tank for each of the zones. Moreover, the partition plate 11 is for making the flow of waste water approach the piston flow, and not all partition plates necessarily divide the zone. One or more partition plates may be provided in one zone. A partition plate may be provided in the horizontal direction to divide each zone into horizontal zigzags.
[0015]
When the addition was reduced redox potential of either anoxic biological treatment zone, anoxic zone except the first using the circulation pipe 14 a portion of the treated water containing nitrate nitrogen (effluent water) Cycle to 4b. This can also be expected to improve nitrate nitrogen removal performance. The effluent water containing nitrate nitrogen that has flowed out of the processing apparatus 1 is sent to the solid-liquid separator 2 and separated into separated water and sludge. Part of the separated sludge containing excessive phosphorus is discharged out of the system as excess sludge. The remaining sludge is returned to the top anoxic zone 4a by the sludge return piping system 7 as return sludge. For the solid-liquid separator 2, a precipitation method such as a precipitation basin is usually used, but is not limited to the precipitation method.
[0016]
[Reference example]
Next , the process will be specifically described based on a reference example . In order to confirm the effect of the present invention, the first subsidence effluent of the combined sewage treatment plant was treated using the present invention. First, a processing tank having a capacity of 6.7 m 3 is partitioned from the upstream side at a volume ratio of 1: 2: 4: 1.5: 1 in the same manner as the apparatus shown in FIG. Then, one anaerobic biological treatment zone followed by two anaerobic biological treatment zones were provided with one anaerobic biological treatment zone in between. The total volume of the aerobic zone was about 2 versus the total volume 1 of the two anaerobic biotreatment zones. Then, the above-mentioned overflow water of 16m3 / day is supplied to the two oxygen-free zones in a step ratio of 1: 1, and the return sludge of 8m3 / day is returned to the first oxygen-free zone, and it is continuously operated for about 3 months. It was. Meanwhile, the total nitrogen concentration and total phosphorus concentration of the measured overflow water (drainage) and the total nitrogen concentration and total phosphorus concentration in the separated water flowing out from the solid-liquid separator are shown in FIG.
[0017]
【The invention's effect】
In the present invention, by providing an anaerobic biological treatment zone and an anaerobic biological treatment zone at the head, it becomes possible to release phosphorus with high efficiency in a stable and sufficient deoxygenated state. The phosphorus in it can be removed. As for nitrogen, an anaerobic biological treatment zone and an aerobic zone are provided alternately to perform biological nitrification and denitrification, and by supplying raw water in steps, organic substances necessary for denitrification are effectively distributed and supplied. can do. In addition, due to the step inflow, the load of processing nitrogen in each zone is reduced, and an efficient processing apparatus can be designed.
[0018]
Therefore, if the nitrogen and phosphorus removal method of the present invention is used, the capacity of the treatment tank will not greatly exceed the capacity of the standard activated sludge process, and a large amount of wastewater treatment will not be significantly reduced. Efficiently high removal performance can be stably maintained for a long time without circulating the nitrification solution. Use of the present invention makes it possible to use high-capacity equipment that conforms to the standard activated sludge process, and to stably maintain high removal performance for a long period of time without greatly reducing the amount of existing wastewater treatment and without circulating a large amount of nitrification liquid. Can be maintained.
[Brief description of the drawings]
1 is a flow sheet of an embodiment of the present invention. FIG. 2 is a flow sheet of a conventional anaerobic-anoxic-aerobic activated sludge process. FIG. 3 is a passage of nitrogen and phosphorus in raw water and treated water of the embodiment. Concentration fluctuation 【Explanation of symbols】
1: Treatment device 2: Solid-liquid separation device 3: Drain supply pipe 4: Anoxic biological treatment zone (a: head)
5: Anaerobic biological treatment zone 6: Aerobic biological treatment zone (b: End)
7: Sludge return piping system 8: Air blowing means (air blowing pipe)
9: Active stirring means 10: Redox potential measuring device 11: Partition plate 12: Sludge discharge pipe 13: Separation water discharge pipe 14: Circulation pipe

Claims (4)

An anaerobic biological treatment zone is provided at the beginning, followed by an anaerobic biological treatment zone, and a plurality of aerobic biological treatment zones and at least one anaerobic biological treatment zone are alternately arranged in the direction of the drainage flow. , Using a treatment device having the last treatment zone as an aerobic zone, and supplying wastewater to be treated to a part or all of the first anaerobic biological treatment zone and the further arranged anaerobic biological treatment zone. After the downstream zone is circulated in order, the effluent is led to a solid-liquid separator to separate sludge, and the separated sludge is returned to the anaerobic biological treatment zone at the head of the treatment device, and either In the anaerobic biological treatment zone, the redox potential of the biological reaction solution in the zone is measured using a redox potentiometer. Nitrogen and method for removing phosphorus in the waste water, characterized in that the treatment liquid containing bound oxygen, circulates top anoxic zone excluding. When the oxidation-reduction potential of the biological reaction liquid in the zone measured with a redox potentiometer in any anoxic biological treatment zone becomes −200 mV or less, a treatment liquid containing dissolved oxygen or bound oxygen is used. The method for removing nitrogen and phosphorus in waste water according to claim 1, wherein the method circulates in an anaerobic zone excluding the head. An anaerobic biological treatment zone is provided at the beginning, followed by an anaerobic biological treatment zone, and a plurality of aerobic biological treatment zones and at least one anaerobic biological treatment zone are alternately arranged in the direction of the drainage flow. A processing device having an aerobic zone as the last processing zone;
Drainage supply piping for stepping the wastewater to be treated to the top anaerobic biological treatment zone and part or all of the further arranged anaerobic biological treatment zones;
A solid-liquid separation device for separating sludge in the effluent flowing out of the treatment device;
A sludge return piping system for returning the separated sludge to the anaerobic biological treatment zone at the top of the treatment device;
In any anoxic biological treatment zone, a redox potentiometer that measures the redox potential of the biological reaction solution in the zone;
And a system that circulates a treatment liquid containing dissolved oxygen or bound oxygen to an anaerobic zone excluding the head when the oxidation-reduction potential indicates a reduction region and may cause phosphorus release. Nitrogen and phosphorus removal system in waste water. The capacity of the anaerobic biological treatment zone provided at the head is at least 1.5 hours of the average residence time of the liquid to be treated , and the total capacity 1 of the anaerobic biological treatment zone in the processing apparatus including the head is 1 On the other hand, the system for removing nitrogen and phosphorus in waste water according to claim 3 , wherein the total volume of the aerobic biological treatment zone is 1 to 2.

Images