JP2018015744A - Circulation type nitrification and denitrification system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circulation type nitrification and denitrification system having high nitrification performance even in a cold season.SOLUTION: This circulation type nitrification and denitrification system 1 includes a trickling filter apparatus 2 for nitrifying waste water W and an anoxic filter apparatus 3 for denitrifying the waste water W. The trickling filter apparatus 2 is equipped with a trickling filter 22 formed by filling a cylindrical trickling filter cylinder 21 with many filter materials 22a, and a heating water pipe 26 in which water warmer than air flows, for heating the trickling filter 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a circulation type nitrification denitrification system provided with a trickling filter.

  As a method for treating wastewater such as sewage and factory wastewater, a biological wastewater treatment method for treating wastewater by microorganisms is widely used. As biological wastewater treatment methods, an activated sludge method, a watering filter method, a circulating nitrification denitrification method and the like are known. Among them, the circulation nitrification denitrification method is, for example, as shown in Patent Document 1, in addition to decomposition treatment of organic matter in wastewater, nitrification treatment that oxidizes (nitrifies) ammonia in wastewater to nitrate ions by aerobic microorganisms. Then, the nitrogen ions, which are one of the eutrophication-causing substances, can be removed through a denitrification process in which nitrate ions are reduced (denitrified) to nitrogen molecules by anaerobic microorganisms.

  In the circulatory nitrification denitrification method, a large amount of air is required to oxidize ammonia to nitrate ions in the nitrification treatment, and aeration is required. In the nitrification treatment, a larger amount of air than that required for oxidative decomposition of organic matter is required. For example, 1 mg of oxygen is required to oxidatively decompose 1 mg of biochemical oxygen demand (BOD), which is an indicator of organic matter, but 4.6 mg of oxygen is required for oxidation of 1 mg-N of ammonia to nitrate ions. Because it is needed. Therefore, when supplying a large amount of air required by the aeration apparatus, a large amount of electric power energy is consumed. For this reason, as disclosed in Non-Patent Document 1, the inventors of the present application have been researching and developing a circulation type nitrification / denitrification system that realizes nitrification using a sprinkling filter that does not require a special aeration device.

  In the sprinkling filter bed apparatus of the circulation type nitrification denitrification system disclosed in Non-Patent Document 1, drainage is sprinkled from the upper side of the sprinkling filter bed formed by a large number of filter media, and the drainage dripping the surface of the filter media. The organic matter in the wastewater is decomposed by the action of the aerobic microorganism film that proliferated on the surface of the filter medium, and ammonia is oxidized to nitrate ions. The supply of oxygen to the membrane of aerobic microorganisms depends on the diffusion movement or dissolution of oxygen in the air existing in the gaps between a large number of filter media, thus eliminating the need for an aeration apparatus.

JP-A-11-333494

Naoyuki Kishimoto, 3 others, “Roughness and temperature effects on the filter media of a trickling filter for nitrification”, Environmental Technology, 2014, Vol. 35, No. 12, p. 1549-1555

  However, since the filter medium of the sprinkling filter bed of the circulation type nitrification denitrification system disclosed in Non-Patent Document 1 has a structure that is exposed to the outside air, it is easily affected by the air temperature, and in particular, the nitrification capacity is lowered in the cold season. Is remarkable, and can be a major obstacle to operation in regions with cold seasons like Japan.

  This invention is made | formed in view of the reason which concerns, The objective is to provide the circulation type nitrification denitrification system which has high nitrification capability also in a cold season.

  In order to achieve the above-mentioned object, the circulation type nitrification denitrification system according to claim 1 is a circulation type having a sprinkling filter apparatus for performing nitrification treatment of waste water and an oxygen-free filter bed apparatus for performing denitrification treatment of waste water. In the nitrification denitrification system, the sprinkling filter bed apparatus has a sprinkling filter bed formed by filling a large number of filter media inside a cylindrical sprinkling filter bed outer cylinder, and a temperature higher than the air temperature. And a warm water pipe for warm water flowing and warming the sprinkling filter bed.

  The circulatory nitrification denitrification system according to claim 2 is the circulatory nitrification denitrification system according to claim 1, wherein the water trickling filter device is configured such that the heated water pipe is a side wall of the water trickling filter outer cylinder. It is arrange | positioned on the outer peripheral surface of this side wall so that the said trickling filter bed may be heated.

  The circulation type nitrification denitrification system according to claim 3 is the circulation type nitrification denitrification system according to claim 1, wherein the warming water pipe heats the watering filter bed from the inside of the watering filter bed. It is arranged inside the watering filter bed.

  The circulating nitrification denitrification system according to claim 4 is the circulation nitrification denitrification system according to any one of claims 1 to 3, wherein the warm water is warm water adjusted by waste heat. Features.

  The circulation type nitrification denitrification system according to claim 5 is the circulation type nitrification denitrification system according to any one of claims 1 to 4, wherein the warm water is warm water generated from the waste water. And

  According to the circulation type nitrification denitrification system of the present invention, it is possible to have a high nitrification capacity even in the cold season.

It is the schematic which shows the circulation type nitrification denitrification system which concerns on embodiment of this invention. The watering filter apparatus of a circulation type nitrification denitrification system same as the above is shown, (a) is front sectional drawing, (b) is a top view. It is an external view which expands and shows the example of the filter medium of the sprinkling filter bed apparatus of a circulation type nitrification denitrification system same as the above, (a) is a front view, (b) is a side view. The modification of the sprinkling filter bed apparatus of a circulation type nitrification denitrification system same as the above is shown, Comprising: (a) is front view sectional drawing, (b) is a top view. It is the schematic which shows the modification of the circulation type nitrification denitrification system same as the above. The oxygen-free filter bed apparatus used with a circulation type nitrification denitrification system with the sprinkling filter bed apparatus same as the above is shown, (a) is a plan view and (b) is a cross-sectional view taken along the line AA. It is. It is a graph which shows the time-dependent change of the temperature inside the two sprinkling filter beds in the experiment 1 of the circulation type nitrification denitrification system same as the above, and an air temperature. It is a graph which shows the relationship between the average value of the temperature difference inside two sprinkling filter beds in the experiment 1 of a circulation type nitrification denitrification system same as the above, and the amount of circulating water. It is a graph which shows the time-dependent change of the air temperature in the experiment 2 of the circulation type nitrification denitrification system same as the above. It is a graph which shows a time-dependent change of each state nitrogen concentration in the waste_water | drain which flows into the circulation type nitrification denitrification system in Experiment 2 of a circulation type nitrification denitrification system same as the above. It is a graph which shows a time-dependent change of each state nitrogen concentration in the treated water in Experiment 2 of a circulation type nitrification denitrification system same as the above, Comprising: It is a thing about the circulation type nitrification denitrification system which installed the heating water pipe. It is a graph which shows a time-dependent change of each state nitrogen concentration in the treated water in Experiment 2 of a circulation type nitrification denitrification system same as the above, Comprising: It is a thing about the circulation type nitrification denitrification system which does not install a heating water pipe. It is a graph which shows a time-dependent change of the nitrification rate in the experiment 2 of the circulation type nitrification denitrification system same as the above, Comprising: The circulation type nitrification denitrification system which installed the heating water pipe, and the circulation type nitrification denitrification which does not install the heating water pipe Shows the system. It is a graph which shows a time-dependent change of CODCr (chemical oxygen demand by potassium dichromate) in the experiment of a sprinkling filter apparatus same as the above, Comprising the treated water of the circulation type nitrification denitrification system which installed the heating water pipe, It shows the treated water of the circulatory nitrification denitrification system that does not have a hot water pipe and the wastewater that flows into the circulatory nitrification denitrification system. It is a graph which shows a time-dependent change of BOD (biochemical oxygen demand) in the experiment of a sprinkling filter apparatus same as the above, Comprising the treated water of a circulation type nitrification denitrification system which installed the heating water pipe, and a heating water pipe It shows the treated water of the circulation type nitrification denitrification system that is not installed and the wastewater that flows into the circulation type nitrification denitrification system. It is a graph which shows a time-dependent change of SS (floating matter amount) in the experiment of a sprinkling filter apparatus same as the above, Comprising the treated water of the circulation type nitrification denitrification system which installed the warming water pipe, the circulation which does not install the heating water pipe This shows the treated water of the nitrification denitrification system and the wastewater flowing into the circulation nitrification denitrification system. It is a graph which shows the time-dependent change of pH in the experiment of a sprinkling filter apparatus same as the above, Comprising the treated water of the circulation type nitrification denitrification system which installed the warming water pipe, The circulation type nitrification denitrification system which does not install the heating water pipe The treated water and the wastewater flowing into the circulating nitrification denitrification system are shown. It is a graph which shows the time-dependent change of the temperature inside the two sprinkling filter beds in the experiment 3 of the circulation type nitrification denitrification system same as the above, and air temperature. It is a graph which shows the relationship between the average value of the temperature difference of the inside of two sprinkling filter beds, and the flow volume of warm water in Experiment 3 of a circulation type nitrification denitrification system same as the above.

  Hereinafter, modes for carrying out the present invention will be described. As shown in FIG. 1, a circulation type nitrification / denitrification system 1 according to an embodiment of the present invention includes a sprinkling filter apparatus 2 that performs nitrification treatment of the waste water W, and an oxygen-free filter bed apparatus that performs denitrification treatment of the waste water W. 3.

  The trickling filter apparatus 2 performs a nitrification treatment in which ammonia in the waste water W is oxidized (nitrified) into nitrate ions by an aerobic microorganism. Moreover, the trickling filter apparatus 2 contributes also to decomposition | disassembly of the organic substance in the waste_water | drain W by an aerobic microorganism. As shown in FIGS. 2 (a) and 2 (b), the trickling filter apparatus 2 is formed by filling a large number of filter media (carriers) 22 a inside the tubular trickling filter outer cylinder 21. A sprinkling filter bed 22 is accommodated. The filter medium 22a captures sludge (sediment sludge), and aerobic microorganisms that can nitrify ammonia in the waste water W grow on the surface of the filter medium 22a. The upper and lower surfaces of the sprinkling filter bed 22 are exposed to the outside air and supplied with air, and oxygen in the air diffuses and moves through the gaps between the many filter media 22a. In addition, oxygen in the air diffuses and moves even when dissolved in the waste water W supplied from the upper surface of the trickling filter 22. In this way, oxygen is supplied to the membrane of the aerobic microorganism.

  The filter medium 22a can be a molded product made of plastic (for example, made of high-density polyethylene). Further, the filter medium 22a can have various shapes. For example, as shown in FIG. 3, the filter medium 22a can have a cylindrical shape. A large number of filter media 22a having a space inside such as a cylindrical one can appropriately transmit heat and easily maintain the temperature by the air layer in the space.

  The sprinkling filter floor outer cylinder 21 can be attached with a thin plate-like support 23 having a large number of meshes so as to close the bottom of the hollow portion. The mesh-like support body 23 supports a large number of filter media 22 a of the water trickling filter bed 22 accommodated in the water trickling filter outer cylinder 21. Therefore, the mesh size of the support 23 is smaller than that of the filter medium 22a.

  In addition, the sprinkler filter outer cylinder 21 can be provided with a pipe fitting 24 below the sprinkler filter outer cylinder 21. The pipe fitting 24 has an internal space, and a hollow portion of a lower discharge pipe 25 described later communicates with the internal space. The tube fitting 24 can be substantially conical as shown. Further, the sprinkling filter outer cylinder 21 and the pipe fitting 24 have flanges 21a and 24a, respectively, and are fixed to each other with fixing tools (bolts, nuts, etc.) at the flanges 21a and 24a. The internal space of the pipe fitting 24 can be located immediately below. Moreover, the support body 23 can be attached by inserting | pinching between the sprinkling filter floor outer cylinder 21 and the pipe attachment 24. FIG.

  The trickling filter apparatus 2 includes a lower discharge pipe 25 through which treated water P nitrified by the trickling filter 22 is discharged to an oxygen-free filter bed 3 to be described later. Specifically, the lower discharge pipe 25 can be attached to the pipe fitting 24.

  In such a sprinkling filter apparatus 2, drainage W is sprinkled from above the sprinkling filter bed 22, and the drainage W slowly flows downward inside the sprinkling filter floor 22 and dripping the surface of the filter medium 22 a. Then, the ammonia in the waste water W is nitrified by the aerobic microorganisms by the action of the aerobic microorganism film proliferating on the surface of the filter medium 22a. The treated water P from the trickling filter apparatus 2 is discharged to the oxygen-free filter bed apparatus 3 through the lower discharge pipe 25.

  Next, the warming water pipe 26 further provided in the sprinkling filter apparatus 2 will be described. The warming water pipe 26 warms the watering filter bed 22 through which warm water having a temperature higher than the temperature flows.

  The warming water pipe 26 can be disposed in contact with the outer peripheral surface of the side wall of the sprinkling filter outer cylinder 21 (see FIGS. 2A and 2B). Thereby, the trickling filter 22 is heated through the side wall of the trickling filter outer cylinder 21. The warming water pipe 26 can be easily disposed by winding the sprinkling filter floor outer cylinder 21 in a coil shape.

  Moreover, the warming water pipe 26 can also be arrange | positioned inside the sprinkling filter bed 22, as shown to Fig.4 (a), (b). The sprinkling filter bed 22 is heated from the inside by a heating water pipe 26. In this case, the heating of the trickling filter 22 is efficient. The warming water pipe 26 can be wound in a coil shape and disposed inside the sprinkling filter bed 22. In addition, in FIG.4 (b), the heating water pipe 26 is taken out outside by providing a hole in the sprinkling filter floor outer cylinder 21.

  The sprinkling filter bed 22 heated by the warming water pipe 26 can keep the temperature higher than the air temperature as a whole because a large number of close filter media 22a transmit heat to each other. Thereby, in the cold season (for example, the time when the temperature falls below 15 ° C.), it is possible to suppress a decrease in the nitrification ability of the aerobic microorganisms that have prospered on the surface of the filter medium 22a.

  As the warm water in the warming water pipe 26, warm water adjusted in temperature (for example, adjusted to 20 ° C. or higher) can be used. Therefore, the hot water may be a relatively low temperature hot water, so that energy saving can be achieved. Temperature control is performed in the hot water tank 27 and can be used even with relatively low-temperature waste heat, which is difficult to use in normal cases. For example, waste heat such as waste heat from sludge incineration facilities can be used. It is. In FIG. 1, reference numeral 27 </ b> A denotes a pump that sends hot water from the hot water tank 27 to the warming water pipe 26.

  The hot water can be generated from various water (for example, drainage W, cooling drainage such as boiler). When the waste water W is used, the amount of heat of the waste water W itself can be used for the organic matter contained therein. The drainage W can be temperature-controlled and used for warm water. Alternatively, the drainage W can be used for warm water without adjusting the temperature when the cold season is not so long or the temperature of the cold season does not drop so much. Thereby, addition of additional energy for heating can be suppressed or made unnecessary. When the temperature is not adjusted, the warming water pipe 26 is connected to a later-described drainage inflow pipe 34 of the oxygen-free filter bed device 3, and the drainage W is passed through the warming water pipe 26 as shown in FIG. It can flow into the oxygen-free filter bed device 3.

  In addition, when the temperature is extremely lowered (for example, lowered to 8 ° C. or lower), the flow rate of the hot water is increased by increasing the flow rate of the hot water (see FIGS. 8 and 17 described later) or by increasing the temperature of the hot water. This can be dealt with by increasing the amount of heat supplied to the floor 22 (heat supply flux) to enhance the heating effect.

  The anoxic filter bed device 3 performs a denitrification treatment that reduces (denitrifies) nitrate ions in the waste water W to nitrogen molecules by anaerobic denitrification microorganisms. Moreover, the oxygen-free filter bed device 3 can also perform an organic substance decomposition process in the waste water W by anaerobic microorganisms. As shown in FIG. 6, the anoxic filter bed device 3 is provided in an anoxic filter bed tank 31 with a filter bed 32 formed of a filter medium (carrier) overgrown with anaerobic microorganisms, and a filter bed 32. A plurality of partition plates 33. The oxygen-free filter bed device 3 includes a drainage inflow pipe 34, a drainage outflow pipe 35, and a treated water outflow pipe 36. Further, the oxygen-free filter bed device 3 includes an isolation plate 37 that isolates the waste water W and the treated water P. The drainage W that has flowed in from the drainage inflow pipe 34 is denitrified (and decomposes organic matter) through the filter bed 32 while vertically diverting between the plurality of partition plates 33. The drainage W that has passed through the filter bed 32 flows out from the drainage outflow pipe 35 and is sent to the sprinkling filter bed apparatus 1 by the pump 3A (see FIG. 1). Further, the treated water P discharged from the sprinkling filter bed apparatus 1 flows from above, a part of the treated water P flows out from the treated water outflow pipe 36 as the final treated water P, and the rest is filtered again. It passes through the floor 32 and circulates to the sprinkling filter apparatus 1.

  The circulation nitrification denitrification system 1 can further include a precipitation device 4 as a pretreatment device for the waste water W. The precipitation device 4 precipitates and separates a large solid S in the waste water W. The waste water W from which the solid S has been separated and removed is sent to the oxygen-free filter bed device 3 by the pump 4A. The solid material S is discharged by a predetermined mechanism.

  Next, the experiment of the circulation type nitrification / denitrification system 1 conducted by the present inventor will be described below.

  The sprinkling filter outer cylinder 21 of the sprinkling filter apparatus 2 has a cylindrical shape made of transparent acrylic and has a height of 1000 mm and an inner diameter of 80 mm. As the filter medium 22a, a cylindrical high-density polyethylene molded product (specific gravity 0.98) having a diameter of 15 mm and a length of 15 mm (Ramer tube LT-15 manufactured by Dainippon Plastics Co., Ltd.) was used. About 540 g (bulk volume: 4.5 L, filling height: about 900 mm) was filled in the sprinkling filter bed outer cylinder 21 with these filter media 22 a to form the sprinkling filter bed 22. A mesh-like support body 23 is attached to the bottom of the sprinkling filter floor outer cylinder 21. The support 23 is provided with a lower discharge pipe 25.

  The oxygen-free filter bed device 3 is a tank type having a width of 70 mm, a height of 125 mm, and a depth of 320 mm, and an effective volume is 2.15 L, and a string-like contact material in the tank (Creocode KC-30 manufactured by Dainippon Plastics Co., Ltd.) Was filled 180 cm. The flow rate of the waste water W flowing from the drainage inflow pipe 34 is set to 8 L / d (the daily flow rate is 8 L), and the wastewater W flowing out from the drainage outflow pipe 35 is 3.5 of the drainage W flowing into the drainage inflow pipe 34. Double flow rate was set.

  For the experiment, two circulation nitrification denitrification systems 1 (circulation nitrification denitrification systems 1A and 1B) were prepared. Three types of experiments (Experiments 1 to 3) were performed. In each experiment, the conditions of the warming water pipe 26 of the circulation type nitrification denitrification system 1A and the circulation type nitrification denitrification system 1B were varied according to the purpose of each experiment.

  Experiment 1 is an external heating experiment using warm water that has been conditioned. In the circulation type nitrification denitrification system 1A, a water tube 26 is wound around a sprinkling filter outer cylinder 21 in a coil shape to form a warming water pipe 26, and hot water adjusted to 20 ° C. in a warm water tank 27 is circulated to the warming water pipe 26. I passed water. Circulation type nitrification denitrification system 1B did not perform circulation water flow. The amount of circulating water in the circulatory nitrification denitrification system 1A is changed stepwise, and period A (December 17 to December 19, 2015) is 16 L / d, period B (December 20 to December 23) Is 32 L / d, period C (December 24 to December 29) is 64 L / d, period D (December 30, 2015 to January 4, 2016) is 128 L / d, The temperature change inside 22 was measured.

  The result of Experiment 1 is as follows. The curve a in FIG. 7 is the temperature inside the watering filter bed 22 of the circulating nitrification denitrification system 1A, the curve b is the temperature inside the watering filter bed 22 of the circulation nitrification denitrification system 1B, and the curve c is the temperature over time. It is a measurement result which shows a change. From curve c, the temperature was generally 10 ° C. or lower during the experiment. From the curve b, the temperature inside the sprinkling filter bed 22 of the circulation type nitrification denitrification system 1B was changed in accordance with the temperature change in a state slightly lower by 1 ° C. than the temperature. On the other hand, from the curve a, the temperature inside the sprinkling filter bed 22 of the circulating nitrification denitrification system 1A was maintained higher than the temperature and the circulation nitrification denitrification system 1B. In addition, the temporary rapid temperature rise in the circulating nitrification denitrification system 1A on December 29 is caused by the fact that the circulating water from the denitrification tank did not flow due to a pump trouble.

  FIG. 8 shows the relationship between the average value of the difference between the temperature inside the trickling filter 22 of the circulating nitrification denitrification system 1A and the temperature inside the trickling filter 22 of the circulating nitrification denitrification system 1B and the circulating water flow rate. Is. The data in the circulation type nitrification / denitrification system 1A on December 29 is excluded. It can be seen from FIG. 8 that the heating effect of the water trickling filter 22 is enhanced when the amount of circulating hot water is increased.

  Experiment 2 is an internal heating experiment using waste water W that is not adjusted to warm water. The circulation type nitrification denitrification system 1A embeds a coiled warming water pipe 26 (outer diameter 6 mm, inner diameter 4 mm, total length 6.0 m) made of fluororesin (PFA) inside the sprinkling filter bed 22 at the university campus. The generated waste water W (temperature 20.5 ± 1.9 ° C.) was passed through the warm water pipe 26 (the amount of water passed was 8 L / d) and then flowed into the oxygen-free filter bed device 3. The circulation type nitrification denitrification system 1 </ b> B did not install the warming water pipe 26, and directly caused the waste water W to flow into the anoxic filter bed device 3. And each state nitrogen concentration in the treated water P, CODCr (chemical oxygen demand by potassium dichromate), BOD (biochemical oxygen demand), SS (floating matter amount), and changes in pH were measured. .

  The result of Experiment 2 is as follows. FIG. 9 shows a change in temperature over time during the period of Experiment 2. Air temperature is 15 ° C or higher (15.0 to 25.3 ° C) in period 1 (October 6, 2015 to November 26, 2015), period 2 (November 27, 2015 to January 25, 2016) The temperature is less than 15 ° C. (4.6 to 14.9 ° C.), and the period 2 corresponds to a cold period in which the temperature influence on the nitrification reaction is concerned.

  FIG. 10A to FIG. 10C show changes with time in the nitrogen concentration of each state. FIG. 10A shows the change over time in the concentration of nitrogen in the waste water W flowing into the circulatory nitrification denitrification system 1A or 1B, and FIG. 10B shows the nitrogen in the treated water P in the circulatory nitrification denitrification system 1A. FIG. 10C shows changes over time in the concentration of each nitrogen in the treated water P in the circulating nitrification denitrification system 1B. 10B and 10C indicate the concentration of nitrite ions. 10B and 10C indicate the concentration of nitrate ions. The part of the symbol d in FIG. 10A and the part of the symbol i in FIGS. 10B and 10C indicate the concentration of ammonia ions. The part of the symbol e in FIG. 10A and the part of the symbol j in FIGS. 10B and 10C show other modes. Moreover, the curve f of FIG. 10B and FIG. 10C shows the nitrogen concentration (each state nitrogen concentration) in the treated water P from the nitrogen concentration (total of each state nitrogen concentration) of the waste water W which flows into the circulation type nitrification denitrification system 1A or 1B. This is the nitrogen removal efficiency obtained by subtracting

  10A to 10C, over the period 1 and period 2, most of the nitrogen in the waste water W flowing into the circulating nitrification denitrification system 1A or 1B is ammonia ions, and nitrate ions and nitrite ions are hardly recognized. . On the other hand, over the period 1 and the period 2, nitrate ions and nitrite ions are detected from the treated water P in the circulating nitrification denitrification system 1A or 1B, and it is understood that nitrogen removal is in progress. In the period 2, the concentration of ammonia ions in the treated water P in the circulating nitrification denitrification system 1B is relatively high, which is considered to be adversely affected by the low temperature. In period 2, the nitrogen removal efficiency was 71.2 ± 11.6% in the circulating nitrification / denitrification system 1A, whereas in the circulation nitrification / denitrification system 1B, it was 51.8 ± 15.1. The nitrogen removal efficiency is significantly reduced in the circulatory nitrification denitrification system 1B.

  The curve k in FIG. 11 shows the change over time of the nitrification rate in the trickling filter 22 of the circulating nitrification denitrification system 1A, and the curve l shows the change over time of the nitrification rate in the trickling filter 22 of the circulation nitrification denitrification system 1B. There was no significant difference in the nitrification rate of the circulating nitrification denitrification systems 1A and 1B until just before entering period 2 (cold season), but the difference in nitrification rate was more pronounced than before and after the transition to period 2. . The decrease in the nitrification rate in the circulatory nitrification denitrification system 1B is considered to be caused by the nitrification ability of the watering filter bed 22 being reduced due to the low temperature. On the other hand, in the circulatory nitrification denitrification system 1A, no decrease in the nitrification rate over the entire period 2 as seen in the circulation nitrification denitrification system 1B is observed. However, in the circulatory nitrification denitrification system 1A, it can be seen that the nitrification rate gradually decreases when the temperature in the latter half of January falls below 8 ° C. Since the temperature drop is remarkable at this time, it is considered that the heating is insufficient only with the amount of heat of the drainage W. This will be described in detail later in Experiment 3.

FIGS. 12 to 15 show changes in COD _Cr , BOD, SS, and pH with time, curve m is for treated water P discharged from cyclic nitrification denitrification system 1A, and curve n is circulation nitrification. The curve for the treated water P discharged from the denitrification system 1B and the curve o for the waste water W flowing into the circulating nitrification denitrification system 1A or 1B. As can be seen from FIG. 12 to FIG. 15, the concentrations of COD _Cr , BOD, and SS are all kept low in the treated water P in both the period 1 and the period 2 and are significant between the circulating nitrification denitrification systems 1A and 1B. No difference was observed, and as long as COD _Cr , BOD, and SS were used as indicators, no adverse effects due to temperature decrease were observed in any of the circulating nitrification denitrification systems 1A and 1B.

  Experiment 3 is an internal warming experiment with warmed water. In Experiment 2, the temperature inside the trickling filter 22 was not measured, but in Experiment 3, the temperature inside the trickling filter 22 was measured. The circulation type nitrification / denitrification system 1A of Experiment 3 has basically the same configuration as that of Experiment 2, except that the heated water pipe 26 and the oxygen-free filter bed 3 embedded in the watering filter bed 22 are used. The drainage inflow pipe 34 is disconnected, and warm water adjusted to 20 ° C. in the warm water tank 27 is circulated through the warming water pipe 26 into the warming water pipe 26, and the waste water W flows directly into the oxygen-free filter bed 3. I let you. In the circulatory nitrification denitrification system 1B of Experiment 3, as in Experiment 2, the heated water pipe 26 was not installed, but the waste water W was directly flowed into the oxygen-free filter bed 3. In circulation type nitrification denitrification systems 1A and 1B, temperature sensors were incorporated at three positions (250 mm, 500 mm, and 750 mm from the top of the trickling filter bed 22) inside the trickling filter bed 22. The temperature inside the trickling filter 22 was the average of these three temperatures. The amount of water flow is fluctuating. Period E (March 1, 2016 to March 5, 2016) is 17.8 L / d, Period F (March 6 to March 13) is 15 L / d, Period G (March 14 to March 22) is 25 L / d, and period H (March 23 to April 1) is 8 L / d.

  In FIG. 16, the curve p is the temperature inside the watering filter bed 22 of the circulating nitrification denitrification system 1A, the curve q is the temperature inside the watering filter bed 22 of the circulation nitrification denitrification system 1B, and the curve r is the temperature over time. It is a measurement result which shows a change. From the curve r, the temperature during the experiment fluctuated in the range of 8 to 13 ° C. From the curve q, the temperature inside the sprinkling filter bed 22 in the circulating nitrification denitrification system 1B in which warm water was not passed was about +1 to 2 ° C. From the curve p, in the circulating nitrification denitrification system 1A through which warm water was passed, the temperature inside the sprinkling filter bed 22 was further increased by about +1 to 2 ° C.

  FIG. 17 shows the relationship between the average value of the difference between the temperature inside the trickling filter 22 of the circulating nitrification denitrification system 1A and the temperature inside the trickling filter 22 of the circulating nitrification denitrification system 1B and the flow rate of hot water. . The error line in FIG. 17 indicates the sample standard deviation. From FIG. 17, it can be seen that the temperature inside the sprinkling filter bed 22 increases as the flow rate of hot water increases.

  Further, judging from FIG. 17, in Experiment 2, the waste water W having a water temperature of about 20 ° C. was passed through the warming water pipe 26 at a flow rate of 8 L / d, so that the sprinkling filter bed 22 of the circulating nitrification denitrification system 1A. It is presumed that the temperature inside was maintained at about 1.3 ° C. higher than the circulating nitrification denitrification system 1B and about 2-3 ° C. higher than the temperature. Therefore, the decrease in the nitrification rate of the circulatory nitrification / denitrification system 1A observed at the time when the temperature falls below 8 ° C in Experiment 2 indicates that the temperature inside the sprinkling filter bed 22 is 10 to 11 ° C under the condition of the temperature of 8 ° C or less. It is estimated that

  As mentioned above, although the circulation type nitrification denitrification system which concerns on embodiment of this invention was demonstrated, this invention is not restricted to what was described in the above-mentioned embodiment, and within the range of the matter described in the claim. Various design changes are possible.

DESCRIPTION OF SYMBOLS 1 Circulation type nitrification denitrification system 2 Sprinkling filter bed equipment 21 Sprinkling filter bed outer cylinder 22 Sprinkling filter bed 22a Filter medium 23 Support body 24 Pipe fitting 25 Lower discharge pipe 26 Heating water pipe 3 Anoxic filter bed equipment 4 Sedimentation equipment ( Pretreatment device)
W Wastewater P Treated water

Claims (5)

A circulating nitrification and denitrification system having a sprinkling filter bed device for nitrifying wastewater and an oxygen-free filter bed device for denitrifying wastewater,
The sprinkling filter bed device
A sprinkling filter bed formed by filling a large number of filter media inside the cylindrical sprinkling filter bed outer cylinder,
A heated water pipe through which warm water having a temperature higher than the temperature flows and warms the sprinkling filter bed;
A circulatory nitrification denitrification system characterized by comprising: In the circulation type nitrification denitrification system according to claim 1,
The sprinkling filter bed device
The circulating nitrification denitrification system, wherein the warming water pipe is disposed on an outer peripheral surface of the side wall so as to heat the watering filter bed through a side wall of the watering filter bed outer cylinder. In the circulation type nitrification denitrification system according to claim 1,
The circulating nitrification denitrification system, wherein the warming water pipe is disposed inside the water trickling filter so as to heat the water trickling filter from the inside of the trickling filter. In the circulation type nitrification denitrification system according to any one of claims 1 to 3,
The circulating nitrification denitrification system, wherein the warm water is warm water adjusted by waste heat. In the circulation type nitrification denitrification system according to any one of claims 1 to 4,
The circulating nitrification denitrification system, wherein the warm water is warm water generated from the waste water.

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