JP2004154700A - Denitrification treatment apparatus and denitrification treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a denitrification treatment apparatus by which nitrate nitrogen in raw water such as underground water can be efficiently subjected to removal treatment while stabilizing the nitrate nitrogen, and a denitrification treatment method. <P>SOLUTION: The denitrification treatment apparatus 1 performs denitrification treatment of nitrate nitrogen contained in the raw water by sulfur denitrifying bacteria and has a reaction tank 2, a raw water introducing device 6 for supplying the raw water into the reaction tank 2 and an elemental sulfur and calcium carbonate feeding device 4 for supplying elemental sulfur and calcium carbonate into the reaction tank 2. Further as a discharge device the denitrification treatment apparatus 1 has a gas discharging circulating device 8 for discharging nitrogen gas produced by denitrification treatment in the reaction tank 2 outside the reaction tank 2 and returning a part of nitrogen gas into the reaction tank 2, a membrane separation device 7 which performs membrane separation treatment of the liquid in the reaction tank 2 to separate treated liquid, a treated water discharging device 10 which discharges liquid subjected to membrane separation treatment by the membrane separation device 7 outside the reaction tank 2, and a liquid circulating device 12 which extracts a part of the liquid in the reaction tank 2, controls pH of the liquid within a prescribed range and returns the liquid into the reaction tank. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a denitrification treatment apparatus and a denitrification treatment method, and more particularly to a denitrification treatment apparatus and a denitrification treatment method for denitrifying nitrate nitrogen contained in raw water for drinking water such as groundwater with sulfur denitrification bacteria.
[0002]
[Prior art]
In raw water such as groundwater, for example, ammonia is oxidized by reduction of soil such as livestock excreta to become nitrate nitrogen and permeates into water. The concentration of nitrate nitrogen contained in these raw waters is usually relatively low, less than 50 ppm. However, in order to use it as a water source, it is necessary to take into account the effects on the human body, etc. The concentration of nitrate nitrogen contained is set to be 10 ppm or less, and a treatment for removing nitrate nitrogen contained in these raw waters (hereinafter referred to as “denitrification treatment”) has been conventionally required.
As the denitrification treatment of raw water, a denitrification treatment apparatus for denitrifying nitrate nitrogen in raw water with sulfur denitrifying bacteria has been conventionally known (for example, see Patent Document 1). As used herein, the term "sulfur denitrifying bacteria" refers to bacteria that metabolize sulfur compounds in some form as a main reaction for growth, accumulate elemental sulfur in cells, and participate in denitrification reactions. Sulfur denitrifying bacteria originally inhabit widely in raw water such as groundwater.
A conventional denitrification apparatus for denitrifying nitrate nitrogen in raw water with the sulfur denitrifying bacteria will be described in detail with reference to FIG.
As shown in FIG. 5, a conventional denitrification treatment apparatus 50 includes a reaction tank 52 having an open top, in which an elemental sulfur powder 54 as a carrier for sulfur denitrifying bacteria is accommodated. I have. Above the reaction tank 52, there is provided a step 52a for suppressing the flow rate of the liquid in the reaction tank 52 in order to enhance the sedimentation of the elemental sulfur powder 54 in the reaction tank 52.
On the other hand, a raw water introduction pipe 56 is connected to a lower part of the reaction tank 52, and raw water containing nitrate nitrogen is introduced into the reaction tank 52 from the raw water introduction pipe 56. When raw water is introduced into the reaction tank 52 from the raw water introduction pipe 56, the elemental sulfur particles 54 in the reaction tank 52 flow. Sulfur denitrifying bacteria and the like, which are originally contained in raw water and participate in the denitrification reaction, adhere to the surface of the elemental sulfur particles 54 and proliferate, forming favorable granules for denitrification. Processing is performed.
[0003]
Further, a gas exhaust pipe 58 and a treated water exhaust pipe 60 are connected to the upper part of the reaction tank 52, respectively. Nitrogen generated by the denitrification treatment in the reaction tank 52 is discharged from a gas vent tube 58. Further, the treated water after the denitrification treatment in the reaction tank 52 is withdrawn from the treated water discharge pipe 60, and a part of the treated water is branched to the treated water branch pipe 60a, and the rest is treated water from the treated water branch pipe 60b. It is designed to be discharged outside the system.
The treated water branched to the treated water branch pipe 60a is sent to the pH controller 62, where an alkali such as NaOH is supplied to the treated water, and a pH adjustment suitable for denitrification is performed. The water whose pH has been adjusted by the pH controller 62 is returned to the raw water introduction pipe 56 again, and is used for denitrification.
[0004]
[Patent Document 1]
JP-A-6-182393 [0005]
[Problems to be solved by the invention]
However, in the conventional denitrification treatment apparatus 50, the more the raw water containing low-concentration nitrate nitrogen is to be denitrified at a higher speed, the more the treated water discharged from the treated water discharge pipe 60 and the inside of the reaction tank 52 The outflow of the elemental sulfur particles 54, sulfur denitrifying bacteria and the like becomes severe. For this reason, there is a problem that stable denitrification treatment is difficult, and there is a limit in increasing denitrification treatment efficiency.
[0006]
In view of the above, the present invention has been made to solve the above-described problems of the related art, and a denitrification treatment apparatus and a denitrification treatment apparatus capable of efficiently removing nitrate nitrogen in raw water such as groundwater while stabilizing the same. It is intended to provide a nitriding treatment method.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a denitrification treatment apparatus for denitrifying nitrate nitrogen contained in raw water with sulfur denitrifying bacteria, and supplies a reaction tank and raw water into the reaction tank. Raw water supply means, elemental sulfur and calcium carbonate supply means for supplying elemental sulfur and calcium carbonate into the reaction tank, nitrogen gas generated by the denitrification treatment in the reaction tank is discharged outside the reaction tank, and nitrogen gas is discharged. Means for returning the part to the inside of the reaction tank, membrane separation processing means for separating the processing liquid by membrane separation of the liquid in the reaction tank, and a reaction tank for separating the processing liquid subjected to membrane separation by the membrane separation processing means Discharging means for discharging the processing liquid to the outside.
[0008]
Further, the present invention preferably further includes a thiosulfate supply means for supplying thiosulfate to raw water supplied into the reaction tank from the raw water supply means.
In the present invention, preferably, the membrane separation processing means has a microfilter or an ultrafiltration membrane as a filter medium.
Further, in the present invention, preferably, the treatment liquid discharging means further supplies chlorine or hypochlorite to supply and mix chlorine or hypochlorite to the treatment liquid subjected to the membrane separation treatment by the membrane separation treatment means. A mixing means, and a chlorine amount detecting means for detecting the chlorine amount in the processing liquid mixed by the chlorine or hypochlorite supply mixing means.
Further, the present invention preferably further comprises a pH control return means for extracting a part of the liquid in the reaction tank, controlling the liquid within a predetermined pH range, and returning the liquid to the reaction tank. Good.
[0009]
Further, the present invention is a denitrification treatment method for denitrifying nitrate nitrogen contained in raw water with sulfur denitrifying bacteria, comprising a raw water supply step of supplying raw water into a reaction tank, and elemental sulfur and sulfur in the reaction tank. A sulfur and calcium carbonate supply step of supplying calcium carbonate, a gas discharge return step of discharging nitrogen gas generated by the denitrification treatment in the reaction tank to the outside and returning a part of the nitrogen gas to the reaction tank, A membrane separation treatment step of separating the treatment liquid by membrane separation of the liquid in the reaction tank, and a treatment liquid discharge step of discharging the treatment liquid subjected to the membrane separation treatment in the membrane separation treatment step to the outside of the reaction tank It is characterized by.
Preferably, the present invention further comprises a thiosulfate supply step of supplying thiosulfate to raw water supplied to the reaction tank in the raw water supply step, and chlorine or A chlorine or hypochlorite supply mixing step of supplying and mixing chlorite, and a chlorine amount detection step of detecting the chlorine amount in the processing liquid mixed in the chlorine or hypochlorite supply mixing step. , Is provided.
Further, the present invention may preferably include a pH control return step of extracting a part of the liquid in the reaction tank, controlling the liquid in a predetermined pH range, and returning the liquid to the reaction tank.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a denitrification treatment apparatus and a denitrification treatment method of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram of a denitrification treatment apparatus according to a first embodiment of the present invention. As shown in FIG. 1, a denitrification treatment apparatus 1 according to a first embodiment of the present invention includes a reaction tank 2. This reaction tank 2 does not include means such as a step 52 for suppressing the flow rate of the liquid in the reaction tank provided in the reaction tank 52 of the conventional denitrification treatment apparatus 50. It does not hinder the shape.
A raw water introduction device 6 is connected to a lower portion of the reaction tank 2, and raw water containing nitrate nitrogen (NO ₃ −N) or the like is introduced into the reaction tank 2 from the raw water introduction device 6. I have. The reaction tank 2 is provided with a device 4 for supplying elemental sulfur and calcium carbonate, and the supply device 4 supplies powdered elemental sulfur (S) and calcium carbonate (CaCO ₃ ) into the reaction tank 2. ing.
When raw water is introduced into the reaction vessel 2 from the raw water introduction device 6 and powdered elemental sulfur and calcium carbonate are supplied into the reaction vessel 2 from the elemental sulfur and calcium carbonate supply device 4, elemental sulfur in the reaction vessel 2 While the particles 5 flow and the liquid in the tank is neutralized, the sulfur denitrifying bacteria originally contained in the raw water adhere to the surface of the elemental sulfur particles 5 and multiply, so that the denitrification treatment is performed. ing.
[0011]
Further, a membrane separation device 7 is provided in the reaction tank 2. The membrane separation device 7 is, for example, a box or tube completely sealed with a microfilter having a pore size of about 1 μm, or a filter medium (not shown) such as an ultrafiltration membrane capable of fractionating in a region having a molecular weight of about 20,000. Including a main body 7a. The main body 7a, which is completely sealed with the filter medium or the like, filters suspended substances in a reaction tank liquid containing elemental sulfur particles 5, denitrifying microorganisms including sulfur denitrifying bacteria, and other pathogenic microorganisms such as Escherichia coli and Christosporium. Then, only the clarified liquid is passed through and separated as treated water.
In addition, a gas discharge circulation device 8, a treated water discharge device 10, and a liquid circulation device 12 are provided above the reaction tank 2.
The gas discharge circulating device 8 branches a part of the nitrogen gas generated by the denitrification process in the reaction tank 2 to the gas circulation path 8a and circulates it to the lower part in the reaction tank 2, and discharges the remainder of the generated nitrogen gas. The water is discharged from the passage 8b to the outside of the reaction tank.
The treated water discharge device 10 discharges treated water obtained by filtering the suspension in the reaction tank 2 with the membrane separation device 7 to the outside of the system.
The liquid circulation device 12 sends the suspension in the reaction tank 2 to the pH control device 14 and adds an alkali such as NaOH to a pH suitable for denitrification, preferably a pH of about 6 to about 8.5. Adjustments are made. The liquid whose pH has been adjusted by the pH controller 14 is returned to the reaction tank 2 again, and is reused in the denitrification treatment.
[0012]
Next, a denitrification treatment method (operation) by the above-described denitrification treatment device 1 of the first embodiment of the present invention will be described. First, is introduced into the reaction vessel 2 raw water containing nitrate nitrogen (NO 3 _-N) and the like from the raw water introduction device 6, powdery elemental sulfur (S) and calcium carbonate (CaCO ₃₎ is elemental sulfur and calcium carbonate It is supplied from the supply device 4 into the reaction tank 2. At this time, the liquid in the reaction tank 2 is in a state in which elemental sulfur particles (S) 5, nitrate ions (NO ₃ ⁻ ) in raw water, denitrifying bacteria, and the like are flowing and suspended. At the same time, the sulfur denitrifying bacteria contained in the raw water adhere to the surface of the elemental sulfur particles 5 and proliferate, and the denitrification reaction proceeds, and as shown in the following reaction formula 1 (simplified formula), nitrogen gas (N ₂ ) Occurs.
Sulfur denitrifying bacteria contained in raw water can be used, but they are aerobically grown by adding a sulfur compound such as elemental sulfur or thiosulfate to activated sludge or soil in advance. When seeded in the reaction tank 2, the denitrification performance can be obtained more quickly.
NO ₃ ⁻ + S + H ₂ O → N ₂ ↑ + SO ₄ ²⁻ + H ⁺ (Reaction formula 1)
As described above, as the denitrification reaction as in the reaction formula 1 proceeds, the liquid in the reaction tank 2 tends to react on the acidic side, but is neutralized by the calcium carbonate supplied by the supply device 4. Due to this effect, when the concentration of nitrate nitrogen in the raw water is sufficiently low, the pH change is small, so that the treatment may be performed without the pH control device 14 or without adding alkali. Calcium carbonate also has an action of neutralizing pH and supplying inorganic carbon, which is a nutrient necessary for the growth of sulfur denitrifying bacteria, and thus has an action of rapidly growing sulfur denitrifying bacteria.
Phosphoric acid is required as another nutrient source, but the amount of phosphorus may be about 1/150 of the nitrate nitrogen in raw water, and may be added if insufficient in raw water. Other necessary trace metal salts are usually sufficiently contained in raw water.
[0013]
In addition, a part of the nitrogen gas generated in the reaction tank 2 is branched to a gas circulation path 8a by the gas discharge circulation device 8 and circulated to the lower part in the reaction tank 2, and the rest is out of the system by the gas discharge path 8b. 8b. The nitrogen gas circulated in the lower part of the reaction tank 2 is used for stirring the suspension in the reaction tank 2 and for cleaning the surface of a filter medium (not shown) of the membrane separation device 7.
Next, a suspension containing elemental sulfur particles 5, denitrifying microorganisms including sulfur denitrifying bacteria, and other pathogenic microorganisms such as Escherichia coli and Christosporium in the reaction tank 2 is subjected to membrane separation by the water pressure in the reaction tank 2. Ultrafiltration or the like is performed by the filter medium of No. 7, and only the filtrate is separated as treated water. This treated water is discharged out of the system by the treated water discharge device 10.
[0014]
Here, in the present embodiment, for the ultrafiltration of the suspension in the reaction tank 2 by the membrane separation device 7, the use of the water pressure in the reaction tank 2 has been described as an example. Instead, the membrane separation device 7 may be provided with a device or the like that applies a pressure so as to actively draw the suspension in the reaction tank 2 into the filter medium of the membrane separation device 7.
Further, in the present embodiment, an example in which the membrane separation device 7 is provided in the reaction tank 2 has been described as an example. However, the present invention is not limited thereto. May be communicated by a communication pipe or the like, and the denitrification treatment in the reaction tank 2 and the membrane separation treatment of the membrane separation device 7 may be individually performed.
[0015]
On the other hand, the suspension in the reaction tank 2 containing the elemental sulfur particles 5 and sulfur denitrifying bacteria, etc., which cannot be passed through the filter medium of the membrane separation device 7 and is left outside the filter medium, is subjected to the pH control device 14 by the liquid circulation device 12. Where an alkali such as NaOH is added to adjust the pH of the liquid to a predetermined pH range suitable for denitrification, preferably to a pH of about 6 to about 8.5. The liquid whose pH has been adjusted by the pH control device 14 is returned to the raw water introduction device 6 again, and is reused in the reaction tank 2 for denitrification.
[0016]
As described above, according to the denitrification treatment apparatus 1 according to the first embodiment of the present invention, during the denitrification treatment in the reaction tank 2, the nitrogen gas generated in the reaction tank 2 is reacted by the gas discharge circulation device 8. The nitrogen gas circulates in the lower part of the tank 2, and this nitrogen gas promotes stirring of the suspension in the reaction tank 2 and cleaning of the surface of the filter medium of the membrane separation device 7. For this reason, the membrane separation device 7 can perform a stable membrane separation process, and since the shape of the reaction tank 2 does not hinder the flow rate in the reaction tank 2, the conventional denitrification treatment device 50 can be used. In comparison, the speed of the denitrification reaction in the reaction tank 2 can be increased, and the reaction tank 2 can be made compact.
[0017]
In addition, the smaller the particle size of the elemental sulfur particles 5 is, the more the denitrification reaction can be promoted and the speed can be increased. However, in the conventional denitrification treatment device 50, the outflow of the elemental sulfur particles 5 and the like is large, In order to maintain 5 or the like, the particle size was limited to 50 μm. However, according to the denitrification treatment apparatus 1 according to the first embodiment of the present invention, even the elemental sulfur particles 5 having a particle diameter of, for example, 5 μm can be prevented from flowing out by the membrane separation apparatus 7, and the elemental sulfur in the reaction tank 2 can be prevented. Solids such as particles and sulfur denitrifying bacteria can be maintained at a high concentration. For this reason, the denitrification treatment can be performed several times faster than the conventional denitrification treatment device 50, and the reaction tank 2 can be made more compact. Further, the membrane separation device 7 filters suspended substances containing pathogenic microorganisms such as Escherichia coli and Christosporium in addition to the elemental sulfur particles 5 and sulfur denitrifying bacteria in the reaction tank 2, and only the clear filtrate is treated water. Because it is separated, it is particularly effective for water treatment.
[0018]
Furthermore, according to the denitrification treatment apparatus 1 according to the present embodiment, the suspension in the reaction tank 2 containing the elemental sulfur particles 5 and sulfur denitrifying bacteria, etc., which cannot pass through the filter medium of the membrane separation device 7 and remain outside the filter medium. The suspension is circulated to the raw water at a pH suitable for denitrification by the liquid circulation device 12 and the pH control device 14 to promote stirring of the suspension in the reaction tank 2. Therefore, the speed of the denitrification reaction in the reaction tank 2 can be increased, and the reaction tank 2 can be downsized.
[0019]
Next, FIG. 2 shows an example of the result of the nitrate nitrogen concentration (hereinafter referred to as “NO ₃ −N concentration”) in the treated water when the denitrification treatment device 1 according to the first embodiment of the present invention is used. It is a graph. As shown in FIG. 2, the concentration of NO ₃ -N in the treated water is always significantly lower than the standard of 10 ppm or less specified in the enforcement regulations of the Water Supply Law, and the denitrification treatment apparatus according to the first embodiment of the present invention. By means of 1, good and stable denitrification treatment can be performed.
[0020]
Next, a second embodiment of the denitrification treatment apparatus and the denitrification treatment method of the present invention will be described with reference to FIGS.
FIG. 3 is an overall configuration diagram of a denitrification processing apparatus according to a second embodiment of the present invention. Here, in FIG. 3, the same parts as those of the denitrification processing apparatus 1 according to the first embodiment of the present invention shown in FIG. 1 described above are denoted by the same reference numerals, and the description thereof will be omitted.
As shown in FIG. 3, the denitrification treatment device 30 according to the second embodiment of the present invention includes a thiosulfate supply device 32, and the thiosulfate supply device 32 is inserted into the reaction tank 2 from the raw water introduction device 6. A thiosulfate such as sodium thiosulfate (Na ₂ S ₂ O ₃ ) is additionally supplied to raw water containing NO ₃ ^{− and the} like before being introduced.
[0021]
Further, the denitrification treatment apparatus 30 according to the second embodiment of the present invention is configured such that, in the treated water discharge apparatus 10, a chlorine or sodium hypochlorite supply apparatus 34, a chlorine or sodium hypochlorite mixing apparatus 36, and a residual chlorine An automatic detection device 38 is provided.
The chlorine or sodium hypochlorite supply device 34 includes a device such as a pump 34a, and supplies chlorine (Cl ₂ ) or sodium hypochlorite (NaClO) into the treated water filtered by the membrane separation device 7. Has become.
The chlorine or sodium hypochlorite mixing device 36 mixes the treated water filtered by the membrane separation device 7 with Cl ₂ or NaClO supplied from the supply device 34.
The residual chlorine automatic detection device 38 continuously and automatically detects the amount of chlorine (Cl ₂ ) remaining in the liquid mixed by the mixing device 36, and mixes the amount from the pump 34a of the supply device 34 based on the detected data. The amount of Cl ₂ or NaClO supplied to the device 36 is controlled.
[0022]
Next, a denitrification treatment method (operation) by the above-described denitrification treatment device 30 of the second embodiment of the present invention will be described.
First, the thiosulfate supply device 32 adds thiosulfate such as Na ₂ S ₂ O _{3 to} raw water containing nitrate nitrogen (NO ₃ ⁻ ) or the like before being introduced into the reaction tank 2 from the raw water introduction device 6. Raw water that is additionally supplied and contains S ₂ O ₃ ^2- is introduced into the reaction tank 2.
In the reaction tank 2, a denitrification reaction as shown in a reaction formula 2 (simplified formula) proceeds by NO ₃ ⁻ , S ₂ O ₃ ^{2− and the} like contained in the raw water, and nitrogen gas (N ₂ ) is generated.
[0023]
2NO ₃ ⁻ + 2S ₂ O ₃ ²⁻ + 4H ₂ O → N ₂ ↑ + 4SO ₄ ²⁻ + 8H ⁺ (Reaction formula 2)
[0024]
Here, for reference, a more strict reaction formula of Reaction Formula 2 is shown in the following Reaction Formula 3 (for example, see References (1) and (2)).
Reference (1) Batchelor B et. al. , Autotropic denitrification using elemental sulfur, JWPCF (1978) p. 1986-2001.
Reference (2) Bisogni J .; J. et. al. Denitrification using thiosulfate and sulfide, J. Am. Env. Eng. Div. (1977-8).
[0025]
^{_{NO 3 - + 0.844S 2 O 3}} 2- + 0.347CO 2 + 0.0865HCO 3 - + 0.0865NH 4 + + 0.434H 2 O = 0.0865C 5 H 7 NO 2 + 0.5N 2 ↑ + 1.689SO 4 2- + 0.697H ⁺ (Reaction formula 3)
[0026]
Further, in the reaction tank 2, the membrane separation device 7 filters the elemental sulfur particles 5 and the denitrifying bacteria contained in the water in the reaction tank 2, as well as pathogenic microorganisms such as Escherichia coli and Christosporium, and filters the treated water. It is sent to the chlorine or sodium hypochlorite mixing device 36 of the discharge device 10.
Regarding the treated water supplied to the mixing device 36, when the S ₂ O ₃ ^2- supplied to the raw water by the thiosulfate supply device 32 on the upstream side of the reaction tank 2 becomes excessive with respect to NO ₃ ⁻ contained in the raw water, S ₂ O ₃ ^2- remains in the treated water. Therefore, the chlorine or sodium hypochlorite supply device 34 supplies Cl ₂ or NaClO to the remaining treated water containing S ₂ O ₃ ^2- and mixes the same, thereby converting S ₂ O ₃ ^2- with chlorine. It is removed by reaction (see reaction formula 4).
[0027]
^{_{4HClO + 2Na + + 2S 2 O}} 3 2- + 6OH -
→ 2Na ⁺ + 2SO ₄ ²⁻ + 4Cl ⁻ + 5H ₂ O (Reaction formula 4)
[0028]
In the treated water from which the S ₂ O ₃ ^2- has been removed in the mixing device 36, chlorine remains, but the residual chlorine automatic detecting device 38 continuously and automatically detects the residual chlorine amount and the like contained in the treated water, and detects it. The data is transferred to the supply device 34, and the supply device 34 controls the amount of Cl ₂ or NaClO supplied to the mixing device 36.
Here, since the content of free residual chlorine in the tap water is specified by the Water Supply Law enforcement regulations to be 0.1 ppm or more, the residual chlorine amount detected by the residual chlorine automatic detection device 38 is 0.1 ppm or more. Thus, the supply device 34 controls the amount of Cl ₂ or NaClO supplied to the mixing device 36.
Here, when the residual chlorine automatic detection device 38 detects the residual chlorine amount as 0.1 ppm or more, the treated water is discharged out of the system as clean water.
On the other hand, when the residual chlorine automatic detection device 38 detects the residual chlorine amount as less than 0.1 ppm, the supply device 34 supplies the mixing device 36 with Cl ₂ or Cl ₂ until the residual chlorine amount of the treated water becomes 0.1 ppm or more. The NaClO amount is readjusted, and the treated water is discharged out of the system after the water treatment is completed.
[0029]
According to the denitrification apparatus 30 according to the second embodiment of the present invention, NO ₃ ^{− in} the raw water fluctuates greatly, and the denitrification reaction caused by elemental sulfur particles or denitrifying bacteria cannot follow the conventional denitrification apparatus 50. Even so, the S ₂ O ₃ ^2- supplied to the raw water by the thiosulfate supply device 32 has solubility and facilitates the denitrification reaction in the reaction tank 2, so that the denitrification treatment can be surely performed. it can.
In addition, regarding S ₂ O ₃ ²⁻ supplied to the raw water by the thiosulfate supply device 32, more appropriate supply of the S ₂ O ₃ ^2- amount is expected in view of the fluctuation of NO ₃ ^{− in} the raw water. NO ₃ ⁻ can be removed, and treated water with less residual S ₂ O ₃ ²⁻ can be obtained.
[0030]
Next, FIG. 4 is a graph showing exemplary results of NO 3 _-N concentration in the treated water in the case of using the denitrification device 30 according to the second embodiment of the present invention. As shown in FIG. 4, NO 3 _-N concentration in the treated water, a criterion of 10ppm or less which is determined with tap Law Enforcement Regulations is always significantly lower than, NO ₃ in the raw water ^- even when large variations in the According to the denitrification treatment apparatus 30 according to the second embodiment of the present invention, good and stable denitrification treatment can be reliably performed.
[0031]
【The invention's effect】
As described above, according to the denitrification treatment apparatus and the denitrification treatment method of the present invention, it is possible to efficiently remove nitrate nitrogen in raw water such as groundwater while stabilizing it.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a denitrification treatment apparatus according to a first embodiment of the present invention.
FIG. 2 is a graph showing an example of a result of a nitrate nitrogen concentration in treated water when the denitrification treatment device according to the first embodiment of the present invention is used.
FIG. 3 is an overall configuration diagram illustrating a denitrification processing apparatus according to a second embodiment of the present invention.
FIG. 4 is a graph showing an example of a result of a nitrate nitrogen concentration in treated water when a denitrification treatment device according to a second embodiment of the present invention is used.
FIG. 5 is an overall configuration diagram showing a conventional denitrification treatment apparatus.
[Explanation of symbols]
1, 30 denitrification treatment device 2 reaction tank 4 elemental sulfur and calcium carbonate supply device 5 elemental sulfur particles 6 raw water introduction device 7 membrane separation device 8 gas discharge circulation device 8a gas circulation passage 8b gas discharge passage 10 treated water discharge device 12 liquid Circulation device 14 pH control device 32 Thiosulfate supply device 34 Chlorine or sodium hypochlorite supply device 36 Chlorine or sodium hypochlorite mixing device 38 Automatic residual chlorine detection device

Claims (8)

A denitrification treatment apparatus for denitrifying nitrate nitrogen contained in raw water with sulfur denitrifying bacteria,
A reaction tank,
Raw water supply means for supplying raw water into the reaction tank,
Element sulfur and calcium carbonate supply means for supplying elemental sulfur and calcium carbonate into the reaction vessel,
Gas discharge and return means for discharging nitrogen gas generated by the denitrification treatment in the reaction tank to the outside of the reaction tank and returning a part of the nitrogen gas to the reaction tank;
Membrane separation treatment means for separating the treatment liquid by membrane separation treatment of the liquid in the reaction tank,
A processing liquid discharging means for discharging the processing liquid subjected to the membrane separation processing by the membrane separation processing means to the outside of the reaction tank,
A denitrification treatment device comprising: 2. The denitrification treatment apparatus according to claim 1, further comprising thiosulfate supply means for supplying thiosulfate to the raw water supplied into the reaction tank from the raw water supply means. The denitrification treatment apparatus according to claim 1 or 2, wherein the membrane separation means has a microfilter or an ultrafiltration membrane as a filter medium. The treatment liquid discharging means further comprises a chlorine or hypochlorite supply mixing means for supplying and mixing chlorine or hypochlorite to the treatment liquid subjected to membrane separation treatment by the membrane separation treatment means, The denitrification treatment apparatus according to any one of claims 1 to 3, further comprising chlorine amount detection means for detecting the chlorine amount in the treatment liquid mixed by the hypochlorite supply mixing means. 5. A pH control return means for extracting a part of the liquid in the reaction tank, controlling the liquid within a predetermined pH range, and returning the liquid to the reaction tank. Item 2. The denitrification treatment device according to item 1. A denitrification treatment method of denitrifying nitrate nitrogen contained in raw water with sulfur denitrifying bacteria,
A raw water supply step of supplying raw water into the reaction tank,
A sulfur and alkali supply step of supplying elemental sulfur and alkali into the reaction vessel,
A gas discharge return step of discharging nitrogen gas generated by the denitrification treatment inside the reaction tank to the outside of the reaction tank and returning a part of the nitrogen gas to the inside of the reaction tank;
A membrane separation treatment step of separating the treatment liquid by membrane separation treatment of the liquid in the reaction tank,
A treatment liquid discharging step of discharging the processing liquid subjected to the membrane separation processing in the membrane separation processing step to the outside of the reaction tank,
A denitrification treatment method comprising: Further, a thiosulfate supply step of supplying thiosulfate to the raw water supplied into the reaction tank in the raw water supply step, and a chlorine or hypochlorite supply to the treatment liquid subjected to membrane separation in the membrane separation step And a chlorine or hypochlorite supply mixing step, and a chlorine amount detection step of detecting the chlorine amount in the treatment liquid mixed in the chlorine or hypochlorite supply mixing step. Item 7. The denitrification treatment method according to Item 6. The denitrification treatment according to claim 6 or 7, further comprising a pH control return step of extracting a part of the liquid in the reaction tank, controlling the pH within a predetermined range, and returning the liquid to the inside of the reaction tank. Method.

Images