JP2005095758A - Method and apparatus for treating water containing inorganic-state nitrogen or phosphorus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a method and an apparatus for treating the water containing inorganic-state nitrogen or phosphorus, in each of which nitrate nitrogen and nitrite nitrogen are removed/reduced by sulfur denitrification being a biological reaction, phosphoric acid and ammonia nitrogen are also reduced easily at the same time by the action of magnesium hydroxide and recovered for fertilizer etc. and the magnesium hydroxide is washed with citric acid so that the effect of magnesium hydroxide can be exhibited surely over a long period of time. <P>SOLUTION: The water containing inorganic-state nitrogen and phosphorus is made to pass through a single reaction tank 1 packed with a material 2 consisting of sulfur, calcium carbonate, magnesium hydroxide and, if necessary, a vermiculite-purified stone so that the inorganic-state nitrogen is removed/reduced and the phosphorus is recovered as magnesium ammonium phosphate or calcium phosphate. A magnesium hydroxide reaction tank is arranged for exhibiting the effect of the magnesium hydroxide surely over a long period of time so that the magnesium hydroxide is washed with citric acid in the magnesium hydroxide reaction tank. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to reduction of removal of nitrate nitrogen and nitrite nitrogen mainly by sulfur-oxidizing bacteria from livestock sewage treatment water, septic tank treatment water, sewage treatment water, aquaculture fishery wastewater, food processing wastewater treatment water, etc. In addition to the reaction of magnesium, phosphoric acid and ammonium, the treatment method of inorganic nitrogen / phosphorus containing water used for the purification of water by reducing the recovery of phosphoric acid and ammonia nitrogen by the reaction of calcium and phosphoric acid and the recycling of wastewater components And the apparatus.

  Heterotrophic denitrification in which organic carbon source is denitrified as an electron donor is complicated to manage due to the large amount of bacterial sludge treatment associated with the introduction / maintenance and operation of dedicated facilities. In addition, heterotrophic denitrification with solid substrates such as biodegradable plastics and fatty acids, which are considered to be relatively easy to manage, has problems in terms of cost and long-term stability.

  On the other hand, denitrification technology using sulfur-oxidizing bacteria, which are autotrophic bacteria, has been put to practical use because it shows relatively high denitrification efficiency under conditions with a low BOD / N ratio and is easy to manage. In recent years, it has been studied in various fields. This is a study on denitrification treatment of steel material nitric acid cleaning wastewater with sulfur-oxidizing bacteria (Non-Patent Document 1).

  In addition, there is concern about the release of nitrous oxide, a global warming gas, in the broad sense of denitrification. For example, sulfur denitrification and pH adjustment should be performed in paddy soil and upland soil where nitrous oxide generation has been pointed out. However, there is also a report that the possibility of the generation of nitrous oxide being suppressed compared to the case where an organic substance is the only electron donor (Non-patent Document 2).

  Further, in denitrification using sulfur-oxidizing bacteria, the substance applied as a denitrification substrate is basically only sulfur as a solid. This is a by-product that is currently obtained in large quantities during petroleum refining, and does not require both energy and chemical synthesis like methanol, solid fatty acids, and biodegradable plastics used for heterotrophic denitrification.

  However, in denitrification using sulfur-oxidizing bacteria, since the bacteria absorb oxygen from nitric acid and oxidize sulfur, sulfuric acid is generated. Therefore, neutralization of treated water is essential, and denitrification is also pH 7 Since it is suitably performed in the vicinity, the pH in the denitrification tank needs to be kept almost neutral. If sulfuric acid is completely neutralized, it does not conflict with Japanese environmental standards.

  For this reason, various alkaline substances are applied for neutralization, but the application of calcium carbonate is the cheapest because of the neutral neutralization effect required for the growth of sulfur-oxidizing bacteria and the mild neutralization effect. And practical.

  Therefore, one of the inventors of the present invention has developed and proposed a composition for imparting microbial activity and a method for producing the same, in which a required amount of calcium carbonate is homogeneously dispersed in a sulfur matrix (Patent Document 1). This is an epoch-making method in which efficient denitrification and neutralization can be easily realized with one material.

  By the way, so-called livestock wastewater treated water may contain not only nitrate nitrogen and nitrite nitrogen but also ammonia nitrogen and phosphoric acid at a relatively high concentration, and these ions are removed or reduced in advanced treatment. Is desired.

  Among them, as a method for removing and recovering phosphoric acid and ammonia nitrogen, a method of forming magnesium ammonium phosphate has been proposed (Patent Document 2). This requires application of a device with many management items to which a necessary amount of magnesium hydroxide is continuously added, and is not suitable for simple combined use with an existing livestock wastewater treatment device or the like.

  Various methods for removing nitrogen and phosphorus simultaneously have been proposed (Patent Documents 3 to 5). These are all complex devices with many additions of magnesium salts and many other management items, and are difficult in terms of diffusion to livestock operators, for example. In addition, the method by ion exchange or adsorption has a short life of the removal material, and is not practical because it requires frequent exchange (Patent Document 6).

As methods for removing nitrogen and phosphorus simultaneously, methods other than those described above have also been proposed (Patent Documents 7 to 9). However, these methods are not intended to recover and reuse phosphorus.
The 35th Annual Meeting of the Japan Society on Water Environment, March 2001, p. 196 Proceedings of the 33rd Annual Meeting of Japan Society on Water Environment, March 1999, p. 368 JP-A-11-285377 JP 2003-126877 A JP-A-8-141582 JP-A-8-155485, JP-A-8-318293 JP-A-11-239785 JP-A-6-23390 Japanese Patent Laid-Open No. 7-241484 Japanese Patent Laid-Open No. 10-249385

  The present invention removes nitrate nitrogen and nitrite nitrogen by sulfur denitrification, which is a biological reaction, and simultaneously and easily reduces phosphoric acid and ammonia nitrogen by the action of magnesium hydroxide, recovered for fertilizers, etc. An object of the present invention is to provide a method and apparatus for treating inorganic nitrogen / phosphorus-containing water that can be used and that the effect of magnesium hydroxide can be reliably exhibited over a long period of time by washing with citric acid.

  In the method for treating inorganic nitrogen / phosphorus-containing water according to claim 1 of the present invention, a material comprising inorganic nitrogen / phosphorus-containing water, sulfur, calcium carbonate and magnesium hydroxide, and vermiculite refined stone as required. It is characterized in that water is passed through a single reaction tank filled with, and removal of inorganic nitrogen is reduced and phosphorus is recovered and reduced as magnesium ammonium phosphate and calcium phosphate.

  In the method for treating inorganic nitrogen / phosphorus-containing water according to claim 2 of the present invention, a material comprising vermiculite fine stone to which inorganic nitrogen / phosphorus-containing water is added, sulfur, calcium carbonate and magnesium hydroxide as required. The water is passed through a single reaction tank filled with water, and the removal of inorganic nitrogen is reduced and phosphorus is recovered and reduced as magnesium ammonium phosphate and calcium phosphate within the range of treatment pH 8-9.

  In the method for treating inorganic nitrogen / phosphorus-containing water according to claim 3 of the present invention, the inorganic nitrogen / phosphorus-containing water is passed through a denitrification reaction tank mainly composed of sulfur and calcium carbonate, nitric acid and nitrous acid. After denitrifying nitrogen, the ammonia nitrogen and phosphorus are recovered and reduced as magnesium ammonium phosphate and calcium phosphate in a lump or granular magnesium hydroxide tank.

  In the method for treating inorganic nitrogen / phosphorus-containing water according to claim 4 of the present invention, the inorganic nitrogen / phosphorus-containing water is passed through a denitrification reaction tank mainly composed of sulfur and calcium carbonate, and nitric acid and nitrous acid. After denitrifying and reducing nitrogenous nitrogen, it is possible to recover and reduce ammonia nitrogen and phosphorus as magnesium ammonium phosphate and calcium phosphate by setting the treatment pH to 8 to 9 in a bulk or granular magnesium hydroxide tank And

  In the method for treating inorganic nitrogen / phosphorus-containing water according to claim 5 of the present invention, the single reaction tank according to claim 1 or 2, or the denitrification reaction tank and the magnesium hydroxide tank are provided by an air diffuser or the like. It is characterized by maintaining the reaction such as denitrification, preventing clogging in the tank, and easily collecting magnesium ammonium phosphate and calcium phosphate by backwashing appropriately.

  In the method for treating inorganic nitrogen / phosphorus-containing water according to claim 6 of the present invention, it is difficult to remove by physical washing such as back washing, which is generated on the surface of massive magnesium hydroxide in a magnesium hydroxide tank. By appropriately washing the deposits with citric acid, the treatment pH in the magnesium hydroxide tank is maintained at 8-9, and the recovery and reduction of ammonium nitrogen and phosphorus as magnesium ammonium phosphate and calcium phosphate can be easily continued. Features.

  In the inorganic nitrogen / phosphorus-containing water treatment apparatus according to claim 7 of the present invention, the inorganic nitrogen / phosphorus-containing water is supplied to the single reaction tank according to claim 1 or 2 to The removal of nitrate nitrogen and nitrite nitrogen is reduced by sulfur denitrification, which is a reaction, and precipitation of phosphoric acid and ammonia nitrogen is reduced as magnesium ammonium phosphate by magnesium hydroxide contained in the filling material. Magnesium hydroxide has a high pH in the tank, which promotes the formation of calcium phosphate, maintains the reaction by appropriate backwashing, and facilitates recovery of the produced magnesium ammonium phosphate and calcium phosphate. It is characterized by.

  In the inorganic nitrogen / phosphorus-containing water treatment apparatus according to claim 8 of the present invention, the biological reaction is achieved by supplying the inorganic nitrogen / phosphorus-containing water to a denitrification reaction tank mainly composed of sulfur and calcium carbonate. Sulfur denitrification reduces the removal of nitrate nitrogen and nitrite nitrogen, and subsequently reduces the precipitation of phosphoric acid and ammonia nitrogen as magnesium ammonium phosphate by bulk or granular magnesium hydroxide in the magnesium hydroxide tank. At the same time, the formation of calcium phosphate is also promoted by the magnesium hydroxide having a high pH, and the reaction is maintained by appropriate backwashing for both tanks and appropriate citric acid washing for the magnesium hydroxide tank. In addition, it is easy to recover the produced magnesium ammonium phosphate and calcium phosphate. .

  According to the method and apparatus for treating inorganic nitrogen / phosphorus-containing water according to the present invention, nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, phosphorous such as swine sewage and other livestock wastewater treated water and septic tank treated water It not only excels in effective purification of water to be treated where simultaneous removal of acid is desired, but also contributes to reduction in chromaticity.

  The method for treating inorganic nitrogen / phosphorus-containing water according to the present invention is a method of filling inorganic nitrogen / phosphorus-containing water with a material composed of sulfur, calcium carbonate and magnesium hydroxide, and vermiculite refined stone as required. Basically, the water is passed through the reaction tank, and the removal and reduction of inorganic nitrogen are reduced and phosphorus is recovered and reduced as magnesium ammonium phosphate and calcium phosphate.

  However, if it is intended to recover and reduce phosphorus more reliably, inorganic nitrogen and phosphorus-containing water are passed through a denitrification reaction tank centered on sulfur and calcium carbonate to remove nitric acid and nitrite nitrogen. After the nitrogen reduction, ammonia nitrogen and phosphorus can be recovered and reduced as magnesium ammonium phosphate and calcium phosphate in a massive or granular magnesium hydroxide tank. Moreover, in order to maintain a favorable process, the single reaction tank, a denitrification reaction tank, and a magnesium hydroxide tank can be appropriately backwashed or washed with citric acid.

  In this method, as a material consisting of sulfur, calcium carbonate and magnesium hydroxide, and vermiculite fine stone added as necessary, it is possible to use each powder, fine grain, and lump regardless of natural product or synthetic product. it can. Preferably, sulfur is a combustible material, and magnesium hydroxide and vermiculite concentrate are also flame retardant materials. Therefore, a mixture formed by applying a nitrate nitrogen denitrification substrate developed by one of the present inventors (JP-A 2000-343097) may be used.

  In addition, the denitrification reactor mainly composed of sulfur and calcium carbonate is mainly composed of the above-mentioned nitrate nitrogen denitrification substrate or a mixture composed of sulfur, calcium carbonate and magnesium hydroxide, and sulfur and calcium carbonate. Although it is desirable to use a mixture (see Patent Document 1), it is also possible to use individual powders, fine particles, and lumps.

  Further, in the massive or granular magnesium hydroxide tank, massive or granular magnesium hydroxide, rocks containing magnesium hydroxide, or crushed materials such as brucite can be used.

  As a single reaction tank, an apparatus (Example 1) as shown in FIG. 1 can be used. In FIG. 1, reference numeral 1 is a reaction tank, 2 is a material composed of sulfur, calcium carbonate and magnesium hydroxide, 3 is a backwash blower, 4 is a diffuser, and 5 is a siphon breaker. However, it is not limited to this embodiment, and the processing direction may be an upward flow.

  Furthermore, as a denitrification reaction tank mainly composed of sulfur and calcium carbonate and a massive or granular magnesium hydroxide tank, an apparatus as shown in FIG. 2 (Example 2) can be used. In FIG. 2, reference numeral 1 is a denitrification reaction tank, 2 is a material composed of sulfur, calcium carbonate and magnesium hydroxide, 3 is a backwash blower, 4 is an air diffuser, 5 is a siphon breaker, and 6 is a magnesium hydroxide tank. 7 is a lump or granular magnesium hydroxide, 8 is a citric acid feeding pump for washing, and 9 is a treated water discharge valve. However, this embodiment is not limited to the form, and the processing direction may be an upward flow.

  In the apparatus, the valve 9 is provided so that phosphoric acid can be easily reduced and recovered by changing the open position with the treated water pH. That is, if satisfactory processing performance cannot be obtained even if the low-position valve is opened, the higher-position valve is opened, so that phosphoric acid and ammonia nitrogen can be reduced and recovered.

  Thus, the treatment method and apparatus for inorganic nitrogen / phosphorus-containing water according to the present invention is not only efficient reduction and removal of nitrate nitrogen and nitrite nitrogen, but also magnesium phosphate, phosphoric acid as calcium phosphate, As it contributes to the reduction and recovery of ammonia nitrogen, it is suitable for purification of wastewater containing them. In addition, magnesium ammonium phosphate and calcium phosphate are discharged into the drainage during backwashing and are easy to recover, contributing to the recycling of these resources for agriculture and horticulture.

  In order to confirm the effectiveness of the above-described inorganic nitrogen / phosphorus-containing water treatment, the apparatus of FIG. 1 (Example 1) and the apparatus of FIG. 2 (Example 2) are prepared as the present invention, and anaerobic treatment (UASB method). ) And aerobic treatment (water sprinkling filter method), the pig house sewage (raw water) after the two-stage treatment was tested and tested.

  In both Examples 1 and 2, the reaction vessel 1 was equipped with a volume of 6 liters. In Example 1, as a material 2, 3 liters of a material having a particle diameter of 5 to 20 mm composed of calcium carbonate: 35%, sulfur: 35%, magnesium hydroxide: 20%, vermiculite fine stone: 10% is applied. The raw water having the water quality shown in No. 1 was passed through in 36 hours by HRT (per material volume, the same applies hereinafter).

  In Example 2, as a material 2, 3 liters of a material having a particle diameter of 5 to 20 mm composed of calcium carbonate: 45%, sulfur: 35%, magnesium hydroxide: 20% was filled in the reaction tank 1 and passed for 36 hours in HRT. When water was continued and phosphoric acid removal performance deteriorated, the use of tank 6 filled with Brusite crushed material 7: 0.33 L having a particle size of 5 to 10 mm was started, and the effluent from tank 1 was discharged for 3 to 4 hours in HRT. The water was passed through. The water quality of the liquid passed through the tank 6 is as shown in Table 2.

  After the phosphate phosphorus removal rate of the brucite coarsely packed column decreased, the material 7 was appropriately immersed in a 2% citric acid solution for half a day to recover the phosphate removal performance. Table 3 shows the water quality of the liquid that was passed after the citric acid washing was started appropriately. In both Examples 1 and 2, backwashing with the blower 3 was appropriately performed.

  As a comparative example, magnesium hydroxide is not contained, a material having a particle size of 5 to 20 mm and containing 54.5% calcium carbonate and 45.5% sulfur: 3 liters is packed in a 6 liter column, and HRT20 to The same treatment as in Example 1 was performed at 33 hours. The water quality of the liquid passed is as shown in Table 4.

  The test results were as shown in FIGS. FIG. 3 shows changes in the removal rate of phosphate phosphorus and oxidized nitrogen in Example 1. FIG. 4 shows changes in the phosphate phosphorus removal rate by the Brusite crushed material packed column of Example 2. FIG. 5 shows performance recovery when a Brusite Crude Packed column with reduced phosphoric acid removal performance was washed with 2% citric acid. FIG. 5 shows ammonia nitrogen removal performance at the same time. FIG. 6 shows the phosphate phosphorus removal performance in the comparative example.

  In the comparative example, a phosphoric acid removal rate of 40 to 60% was obtained until the 10th day after the start of water flow, but thereafter, the phosphoric acid removal rate decreased to 20% or less (see FIG. 6). In contrast, Example 1 was stable at a high removal rate of 90% or more until about the 40th day, and was clearly superior to the comparative example (see FIG. 3).

  In Example 1, the pH of the treated water was as high as 8.3 to 8.7 until about 40th day when the phosphate removal rate of 90% or more was maintained, but denitrification was suppressed. Thus, the removal rate of oxide nitrogen of 95% or more was maintained (see FIG. 3). If the pH of the treated water is less than 8.0, the phosphoric acid removing effect is lowered, so the pH of the treated water is preferably in the range of about 8-9.

  In Example 2, the Brucite crude product packed column maintained a phosphate phosphorus removal rate of around 80% until the 37th day (see FIG. 4).

  When the Brusite crushed packed column with reduced phosphate phosphorus removal performance is washed with 2% citric acid solution (implemented on the 2nd and 22nd days), the phosphate phosphorus removal performance may be recovered. It was confirmed (see FIG. 5).

  Washing waste liquid containing citric acid can be treated by ordinary biological treatment such as activated sludge method. It was confirmed that ammonia nitrogen was also removed by a maximum of about 25%. Moreover, since the fluctuation | variation of the removal rate of ammonia nitrogen corresponds with the change pattern of a phosphate phosphorus removal rate, it is estimated that ammonia nitrogen is removed as magnesium ammonium phosphate.

  Moreover, although it is a visual comparison, the color tone was improved in both the Examples and Comparative Examples compared to the raw water.

  In order to adjust the pH of the treated water while maintaining the above-described ability to remove phosphoric acid, for example, aluminum sulfate or dihydrate gypsum may be mixed.

  In addition, this invention is not limited to the form of the implementation (Example 1, 2) mentioned above.

It is explanatory drawing which shows the processing apparatus of inorganic nitrogen and phosphorus containing water which concerns on Example 1 of this invention. It is explanatory drawing which shows the processing apparatus of the inorganic nitrogen and phosphorus containing water which concerns on Example 2 of this invention. It is a graph which shows the change of the removal rate of oxidized nitrogen and phosphate phosphorus in Example 1 of this invention. It is a graph which shows the change of the removal rate of phosphate phosphorus by the brucite crushed material packed column of Example 2 of this invention. It is a graph which shows the performance recovery | restoration situation and the removal performance of ammonia nitrogen at the time of wash | cleaning the Brusite crushed material packed column with which the removal performance of phosphate phosphorus fell with 2% citric acid. It is a graph which shows the removal performance of the phosphorous phosphorus in a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Material which consists of sulfur, calcium carbonate, and magnesium hydroxide 3 Backwash blower 4 Air diffuser 5 Siphon breaker 6 Magnesium hydroxide tank 7 Lumped or granular magnesium hydroxide 8 Washing citric acid liquid feed pump 9 Treated water Discharge valve

Claims (8)

  Water containing inorganic nitrogen and phosphorus is passed through a single reaction tank filled with materials composed of sulfur, calcium carbonate and magnesium hydroxide, and vermiculite fine stone added as necessary, to reduce inorganic nitrogen and reduce phosphorus. A method for treating inorganic nitrogen / phosphorus-containing water, characterized in that phosphorus is recovered and reduced as magnesium ammonium phosphate and calcium phosphate.   Water containing inorganic nitrogen / phosphorus is passed through a single reaction tank filled with materials composed of vermiculite fine stone added with sulfur, calcium carbonate and magnesium hydroxide, if necessary, and treated with a pH of 8-9. A method for treating inorganic nitrogen / phosphorus-containing water, characterized in that removal of reduced nitrogen and recovery / reduction of phosphorus as magnesium ammonium phosphate and calcium phosphate are performed.   Inorganic nitrogen / phosphorus-containing water is passed through a denitrification reactor centered on sulfur and calcium carbonate to reduce denitrification of nitric acid and nitrite nitrogen, and then phosphoric acid is used in a massive or granular magnesium hydroxide tank. A method for treating inorganic nitrogen / phosphorus-containing water, characterized by recovering and reducing ammonia nitrogen and phosphorus as magnesium ammonium and calcium phosphate.   Inorganic nitrogen / phosphorus-containing water is passed through a denitrification reactor mainly composed of sulfur and calcium carbonate to reduce denitrification of nitric acid and nitrite nitrogen, and then treated in a bulk or granular magnesium hydroxide tank. 8 to 9, a method for treating inorganic nitrogen / phosphorus-containing water, characterized by recovering and reducing ammonia nitrogen and phosphorus as magnesium ammonium phosphate and calcium phosphate.   The single reaction tank according to claim 1, or the denitrification reaction tank and the magnesium hydroxide tank are appropriately backwashed with an air diffuser or the like to maintain the reaction such as denitrification, prevent clogging in the tank, and phosphorus The method for treating inorganic nitrogen / phosphorus-containing water according to any one of claims 1 to 4, wherein magnesium ammonium phosphate and calcium phosphate are easily recovered.   The treated pH in the magnesium hydroxide tank is appropriately washed with citric acid to remove deposits that are difficult to remove by physical washing such as backwashing, which are produced on the surface of the magnesium hydroxide tank. 5. The method for treating inorganic nitrogen / phosphorus-containing water according to claim 3, wherein the ammonia nitrogen and phosphorus can be easily and continuously recovered and reduced as magnesium ammonium phosphate and calcium phosphate. .   By supplying the inorganic nitrogen / phosphorus-containing water to the single reaction tank according to claim 1 or 2, removal of nitrate nitrogen and nitrite nitrogen is reduced by sulfur denitrification which is a biological reaction. At the same time, the magnesium hydroxide contained in the filling material reduces the precipitation of phosphoric acid and ammoniacal nitrogen as magnesium ammonium phosphate, and at the same time, the magnesium hydroxide has a high pH in the tank, which promotes the formation of calcium phosphate. An inorganic nitrogen / phosphorus-containing water treatment apparatus characterized in that those reactions are maintained by appropriate backwashing and that the produced magnesium ammonium phosphate and calcium phosphate can be easily recovered. By supplying inorganic nitrogen / phosphorus-containing water to a denitrification reaction tank centered on sulfur and calcium carbonate, removal of nitrate nitrogen and nitrite nitrogen has been reduced by sulfur denitrification, which is a biological reaction. In addition, precipitation of phosphoric acid and ammonia nitrogen as magnesium ammonium phosphate is reduced by bulk or granular magnesium hydroxide in the magnesium hydroxide tank, and at the same time, the inside of the tank becomes high pH by magnesium hydroxide, so that calcium phosphate is also generated. The reaction is maintained by appropriate backwashing for both tanks and appropriate citric acid washing for the magnesium hydroxide tank, and recovery of the produced magnesium ammonium phosphate and calcium phosphate is facilitated. To treat water containing inorganic nitrogen and phosphorus.

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