JP2013202423A - Waste water treatment system by amorphous calcium silicate hydrate, and method for utilizing the recovered substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treatment system developing decoloration and disinfection effect and further denitrification effect along with an excellent dephosphorization effect with respect to waste water obtained by treating organic sewage such as barn sewage, and a method for utilizing a recovered substance.SOLUTION: A waste water treatment system includes a treatment tank into which a slurry of CSH and raw water are introduced, a neutralization and denitrification tank into which the liquid drawn out of the treatment tank is introduced, and a solid-liquid separation tank into which the slurry drawn out of the treatment tank is introduced. A precipitate taking in phosphorus or phosphorus and a coloring component is formed in the treatment tank and the slurry containing the precipitate is drawn out of the treatment tank to be guided to the solid-liquid separation tank while a precipitate-containing solid component (used CSH) is recovered in the solid-liquid separation tank and the nitrate nitrogen contained in the liquid is removed as nitrogen gas in the solid-liquid separation tank and the liquid is neutralized by carbon dioxide.

Description

The present invention relates to a treatment system for livestock sewage and the like using amorphous calcium silicate hydrate (referred to as CSH) and a method of using the recovered material, and more specifically, a treatment tank using CSH and a neutralization denitrification tank. It is related with the wastewater treatment system which combined, and the utilization method of the collection thing.
The wastewater treatment system of the present invention has excellent effects in phosphorus removal / recovery, nitrogen removal, decolorization, and disinfection of harmful microorganisms in livestock wastewater treatment.

Organic sewage containing manure (referred to as sewage) is discharged from the barn. This livestock sewage contains a large amount of organic matter, has a high COD (chemical oxygen demand) and BOD (biochemical oxygen demand), and it can cause water pollution if discharged untreated. A purification method for reducing COD and BOD using a sludge method or the like has been known (Patent Document 1: Japanese Patent Laid-Open No. 10-174991).

However, the conventional treatment method using the activated sludge method has a problem that phosphorus contained in sewage can not be sufficiently removed. For this reason, the coagulation sedimentation method using an inorganic type coagulant is utilized, and the processing method of aeration of livestock sewage to insolubilize and remove soluble phosphorus in the sewage is also known (Patent Document 2: JP 2001-179267 A). Slaked lime is also used as a kind of inorganic flocculant. It is known that slaked lime also has a disinfecting effect.

Furthermore, a dephosphorizing agent mainly composed of calcium silicate is conventionally known as a dephosphorizing means for drainage. For example, Japanese Patent Application Laid-Open No. 61-263636 (Patent Document 3) describes a water treatment agent mainly composed of calcium silicate hydrate having a CaO / SiO ₂ molar ratio of 1.5 to 5. Japanese Patent Publication No. 02-20315 (Patent Document 4) describes a dephosphorization material made of calcium silicate hydrate having closed cells with a porosity of 50 to 90%. Furthermore, Japanese Patent Laid-Open No. 10-235344 (Patent Document 5) describes a dephosphorization material formed into a spherical or hollow shape having a diameter of about several millimeters and containing calcium silicate hydrate as a main component. JP-A-2000-135493 (Patent Document 6) proposes a dephosphorization method using wollastonite.

In the treatment of sewage sewage, there is no restriction on the color of the wastewater after treatment, but since the dark wastewater is misunderstood as untreated, it causes complaints, so decolorization is one of the important issues in sewage treatment. Incidentally, as a general method for decolorizing waste water, there are known methods of using activated carbon adsorption method, ozone oxidation method, and granular material composed of porous calcium silicate hydrate such as ALC powder as a decolorizing agent ( Patent Document 7: Japanese Patent Laid-Open No. 08-131822).

Japanese Patent Laid-Open No. 10-174991 JP 2001-179267 A JP-A 61-263636 Japanese Examined Patent Publication No. 02-020315 JP-A-10-235344 JP 2000-135493 A Japanese Patent Laid-Open No. 08-131822

The processing method of Patent Document 1 has a low effect of removing phosphorus, and the processing method of Patent Document 2 has little effect on decolorization. Furthermore, the calcium silicate hydrate used in the treatment methods of Patent Documents 3 to 5 is mostly crystalline, such as ALC, and adsorbs and removes phosphorus in porous voids. Similar to the processing method of Document 6, there is a problem that it takes a long processing time. Moreover, there is no decoloring effect. Moreover, although the processing method of patent document 7 describes decoloring a coloring liquid using calcium silicate hydrates, such as ALC, since ALC is a crystalline substance mainly having tobermorite, it originates in sewage sewage Even if ALC powder is added to the waste water, sufficient decoloring effect cannot be obtained and the dephosphorization effect is low.

In addition, removal and recovery of phosphorus from wastewater is important from the viewpoint of eliminating water pollution and playing a part in the recycling of phosphorus, a depleting resource. As for nitrogen, at present, the drainage standard for nitrate nitrogen in livestock agricultural wastewater is tentatively 900 mg / L, but regulations may be strengthened in a few years, and further reduction will become important in the future. There is no color drainage regulation, but there is a strong demand for decolorization.

As for the disinfection of wastewater, chlorine disinfection is currently used because it is only necessary to comply with the regulation of 3,000 / ml or less coliform of wastewater. Chlorine disinfection is not necessary if the amount of Escherichia coli in the wastewater is 3000 / mL or less in normal biological treatment, but in the unlikely event that harmful microorganisms such as foot-and-mouth disease virus are mixed, only such conventional measures are taken. However, there is a possibility that it will be insufficient, and in the future, effective disinfection technology with a view to foot-and-mouth disease will be required.

The present invention solves the above-mentioned problems in the conventional treatment method, and exhibits excellent dephosphorization effect, decolorization and disinfection effect, and denitrification effect for wastewater treated with organic sewage such as livestock sewage. A wastewater treatment system and a method for using the collected material are provided.

ADVANTAGE OF THE INVENTION According to this invention, the wastewater treatment system by the amorphous calcium silicate hydrate which consists of the following structures and the utilization method of the collection | recovery are provided.
[1] A treatment tank into which a slurry of amorphous calcium silicate hydrate (referred to as CSH) and raw water are introduced, a neutralization denitrification tank into which a liquid extracted from the treatment tank is introduced, and an extraction from the treatment tank A solid-liquid separation tank into which the slurry is introduced,
In the treatment tank, a precipitate containing phosphorus or phosphorus and coloring components contained in the raw water is produced under alkaline liquidity, and the slurry containing the precipitate is extracted from the treatment tank and led to a solid-liquid separation tank, and the solid-liquid separation tank And collecting used CSH containing the above precipitate,
On the other hand, the neutralization denitrification tank is filled with porous inorganic particulates carrying denitrification bacteria, and the liquid extracted from the treatment tank is introduced into the neutralization denitrification tank, and the neutralization denitrification tank is introduced. Sodium thiosulfate and carbon dioxide gas are introduced into the nitrogen tank, and nitrate nitrogen contained in the liquid is reduced to nitrogen gas in the neutralization denitrification tank, and the liquid is neutralized with carbon dioxide gas. Wastewater treatment system.
[2] The wastewater treatment system according to the above [1], wherein the raw water is discharged from a barn or organic industrial wastewater.
[3] The inside of the treatment tank is adjusted to pH 8 or more to produce a precipitate incorporating phosphorus, or the pH is adjusted to 11 or more to produce a precipitate incorporating a coloring component together with phosphorus and disinfecting. The wastewater treatment system according to [2].
[4] A diaphragm valve operated by gas pressure is provided in a pipe line for injecting CSH into the treatment tank, and the diaphragm valve is connected to a cylinder of carbon dioxide gas introduced into the neutralization denitrification tank by a pipe line. When the pressure of the cylinder is reduced, the valve opens, the suction side pipe line of the CSH injection pump is opened to the atmosphere, and the injection of the CSH into the treatment tank is stopped. Any of the above [1] to [3] The wastewater treatment system described in
[5] The wastewater treatment system according to any one of [1] to [4], wherein the used CSH recovered by solid-liquid separation is used as a by-product phosphate fertilizer.
[6] The wastewater treatment system according to any one of [1] to [5] above, wherein used CSH recovered by solid-liquid separation is used as an adsorbent for free cesium and free strontium.
[7] A by-product phosphate fertilizer or an adsorbent of free cesium and free strontium comprising a solid content recovered from the solid-liquid separation tank of the wastewater treatment system according to [1].

The wastewater treatment system of the present invention is excellent in dephosphorization effect and denitrification effect for wastewater discharged from livestock barn or raw water of organic industry, and further, decolorization effect by treating the inside of the treatment tank at pH 11 or more. And can enhance the disinfection effect.

The precipitate produced in the treatment tank of the wastewater treatment system of the present invention has good dehydration properties, can be easily separated into solid and liquid, and solids with high bulk density (used CSH) can be recovered. Moreover, since the solid content containing about 20% of soluble phosphoric acid can be recovered, this solid content can be used as a by-product phosphate fertilizer. By using it as a by-product phosphate fertilizer, it can contribute to the construction of resource-recycling agriculture.
Furthermore, since the used CSH has a property of adsorbing free cesium and free strontium, it can be used as an adsorbent for free cesium and free strontium.

Conceptual diagram of the wastewater treatment system of the present invention Graph showing CSH addition and phosphorus removal rate Graph showing CSH addition and phosphorus concentration Graph showing CSH addition amount and chromaticity removal rate Graph showing the amount of CSH added and the removal rate of coliforms Graph showing CSH addition amount and E. coli removal rate Graph showing pH change of neutralization denitrification tank Graph showing the denitrification effect of the neutralization denitrification tank Graph showing cesium and strontium adsorption effect of unused CSH Graph showing cesium and strontium adsorption effect of used CSH

Hereinafter, the present invention will be specifically described based on embodiments.
The wastewater treatment system of the present invention comprises a treatment tank into which a slurry of amorphous calcium silicate hydrate (referred to as CSH) and raw water are introduced, a neutralization denitrification tank into which a liquid extracted from the treatment tank is introduced, and A solid-liquid separation tank into which the slurry extracted from the treatment tank is introduced, and in the treatment tank, a precipitate containing phosphorus or phosphorus and coloring components contained in the raw water is generated under alkaline liquidity, and the precipitate is The contained slurry is extracted from the treatment tank and guided to a solid-liquid separation tank, and used CSH containing the precipitate is collected in the solid-liquid separation tank, while the neutralized denitrification tank is a porous inorganic supporting denitrifying bacteria. In the neutralization denitrification tank, sodium thiosulfate and carbon dioxide gas are introduced into the neutralization denitrification tank, and the liquid extracted from the treatment tank is introduced into the neutralization denitrification tank. Included in the liquid That liquid by carbon dioxide with nitrate nitrogen is removed as by reduction of nitrogen gas is waste water treatment system characterized in that it is neutralized.

An example of the waste water treatment system of the present invention is shown in FIG.
The waste water treatment system of the present invention includes a treatment tank 10 into which CSH slurry and raw water are introduced, a neutralization / denitrification tank 11 into which a liquid extracted from the treatment tank 10 is introduced, and a slurry extracted from the treatment tank 10. A solid-liquid separation tank 12 to be introduced is provided. The processing tank 10 is a cylindrical tank that is long in the vertical direction. The neutralization denitrification tank 11 is also a cylindrical sealed tank that is long in the vertical direction, and a discharge pipe line 40 is connected to the top. The neutralized denitrification tank 11 is filled with granular activated carbon 41 carrying denitrifying bacteria. In addition to activated carbon, various porous inorganic particulates can be used for supporting denitrifying bacteria.

A CSH slurry storage tank 13 and raw water storage tank 14 are connected to the processing tank 10 by a pipe line 15. The pipe line 15 is introduced into the processing tank 10 and extends toward the bottom. The CSH slurry storage tank 13 is connected to a pipe line 15 by a pipe line 16, and a pump 17 for feeding the CSH slurry is provided in the pipe line 16. A pipe line 42 branches off on the suction side pipe line of the pump 17, and a gas pressure type diaphragm valve 18 is provided in the pipe line 42. The diaphragm valve 18 is connected to a carbon dioxide cylinder 19.

The raw water storage tank 14 is connected to a pipe line 15 by a pipe line 20, and a pump 21 for feeding the raw water is provided in the pipe line 20. The storage tank 14 can be an existing activated sludge treatment water tank or the like.

The CSH slurry is introduced into the pipeline 15 through the pipeline 16, and the raw water is introduced into the pipeline 15 through the pipeline 20. The CSH slurry and raw water mixed in the pipe line are introduced into the tank through the pipe line 15 from the bottom of the treatment tank 10. The injected CSH forms a layer 25 in the treatment tank, and the raw water passes through this layer 25 in an upward flow, flows out from the top of the treatment tank 10, and the CSH accumulated above a certain level is the highest in the layer 25. It is pulled out from the upper part and sent to the solid-liquid separation tank 12. In order to prevent the formation of water supply in the CSH layer 25, the CSH layer 25 is disturbed by supplying compressed air from the bottom of the CSH layer 25 for about 0.1 to 3 minutes a day, and then again It is also effective to perform an operation for forming 25.

The treatment tank 10 is connected to the neutralization denitrification tank 11 through a pipe line 26. The liquid that has flowed out from the top of the treatment tank 10 is introduced into the tank from the bottom of the neutralization denitrification tank 11 through the pipe 26. A storage tank 27 for denitrification sodium thiosulfate is connected to the pipe line 26 via an injection pump 28. Further, a carbon dioxide cylinder 19 is connected to the pipe line 26 by a pipe line 29, and a flow meter 30 for measuring the carbon dioxide gas flow rate is provided in the pipe line 29. A static mixer 31 that mixes sodium thiosulfate and carbon dioxide gas with a liquid supplied from the pipeline 26 is provided in the pipe line 26 near the bottom of the neutralization denitrification tank 11, and the carbon dioxide gas and sodium thiosulfate are contained in the tank. It is mixed immediately before it flows into. Further, the carbon dioxide gas cylinder 19 is connected through a pipe line 32 to a diaphragm valve 18 provided in the pipe line 16 of the CSH slurry storage tank 13.

The solid-liquid separation tank 12 is connected to the processing tank 10 through a pipe line 33. The pipe 33 is provided with a pump 34 for extracting sludge containing CSH slurry. The solid-liquid separation tank 12 is formed of, for example, a polyester cylindrical woven fabric suspended vertically with the lower end portion closed by a binding band, and the recovered slurry is introduced from the open upper end portion, and the liquid component is separated by gravity. The remaining solid content may be air-dried as it is for a required time, and then the structure is such that the binding band at the lower end is cut and the solid content is dropped and recovered.

The CSH used in the wastewater treatment system of the present invention is a porous coagulation composed of amorphous calcium silicate hydrate produced by reacting amorphous silicic acid with lime and free lime [Ca (OH) 2]. It is a collection. The amount of free lime in CSH is preferably 2.5 to 90 wt%. Since this CSH is amorphous, it has a better dephosphorization effect than crystalline calcium silicate hydrate. Moreover, the decoloring effect is also good by containing free lime.

The mixed CSH slurry and raw water are introduced into the tank from the bottom of the processing tank 10 through the pipe 15. The inside of the tank becomes alkaline by CSH. The injected CSH forms a layer 25 in the treatment tank, and the raw water passes through the layer 25 in an upward flow and flows out from the uppermost part of the treatment tank 10. While the raw water passes through the CSH layer 25 under an alkaline solution having a pH of 8 or higher, the phosphorus contained in the raw water is taken into the CSH and precipitates. The amount of CSH introduced can be increased to increase the pH in the tank to 11 or higher, and the removal of colored components by CSH can be promoted by this increase in pH, and disinfection of E. coli and foot-and-mouth disease viruses, etc. Can do.

The liquid extracted from the treatment tank 10 is introduced into the neutralization denitrification tank 11 and neutralized by aeration of carbon dioxide. A simple and stable neutralization treatment can be performed by aeration of carbon dioxide gas. In order to prevent the alkaline treated water from being discharged when the carbon dioxide cylinder is emptied unintentionally, a pipe 42 is branched into the suction side pipe of the CSH injection pump 17, and the pipe 42 is provided with a gas pressure type diaphragm valve 18. When the pressure of the cylinder 19 is lowered, the valve 18 is opened and the pipe line 42 is opened to the atmosphere. Therefore, the injection of the CSH slurry into the treatment tank 10 is stopped. The alkalinization of the neutralization denitrification tank 11 is prevented.

Since the neutralized denitrification tank 11 is filled with granular activated carbon 41 carrying denitrification bacteria, when an appropriate amount of sodium thiosulfate is introduced through the conduit 43, the denitrification bacteria grow in the tank. Denitrification of nitric acid proceeds. The grown denitrifying bacteria die under high alkaline conditions, but when the carbon dioxide gas injection stops unintentionally and the neutralization function is lost, the CSH injection to the treatment tank 10 is also stopped. The nitriding tank 11 is not alkalinized and the denitrifying bacteria are prevented from being killed.

The used CSH is extracted from the treatment tank 10 and introduced into the solid-liquid separation tank 12. Here, for example, it flows into a polyester woven fabric made of polyester, and the separation of the liquid by gravity proceeds, and the solid matter (used CSH) remaining in the cylinder is recovered by air drying as it is.

As shown in Table 1, the solid-liquid separation performance of the CSH slurry by the polyester tubular woven fabric is 99.5% of the suspended solids recovery rate, indicating a high value, and good solid-liquid separation is possible. It is. In addition, as shown in Table 2, the collected used CSH contains about 20 wt% of soluble phosphoric acid, which is a by-product phosphate fertilizer (a type of ordinary fertilizer with a soluble phosphoric acid concentration). The standard may be registered as 15 wt% or more). Moreover, since this collection | recovery also contains lime, it is suitable as a neutralization fertilizer of acidified soil, Furthermore, since soluble silicic acid is also included, when it applies to rice cultivation, the fertilizer application amount of siliceous fertilizer can also be reduced.

Furthermore, the collected used CSH has the property of adsorbing cesium ions and strontium ions. By applying it to agricultural land contaminated with radioactive cesium and radioactive strontium, the fertilizer effect of phosphoric acid, lime and silicic acid can be improved. In addition, there is an effect of adsorbing and holding free cesium and free strontium.

[Example 1]
In the wastewater treatment system shown in FIG. 1, after CSH is added to livestock sewage in a slurry state with a solid content of 5 to 10 dry weight / liquid volume (DW / V)% and retained in the treatment tank for 2 to 5 hours, The liquid was extracted from the treatment tank and introduced into the neutralization denitrification tank, and sodium thiosulfate solution (concentration of 0.6 to 1.0%) was added to this liquid amount of 5.9 to 6.3 L / min. The solution was extracted after 5 to 1.1 mL / min and carbon dioxide gas were introduced into the neutralization denitrification tank at a rate of 3.6 to 8.9 mL / min and allowed to stay for 18 to 20 hours. Under these conditions, the removal rate of phosphorus, chromaticity, coliform group, and E. coli by treatment was examined. The results are shown in FIGS. The addition amount (DW / V%) is the added mass part of CSH with respect to 100 parts by volume of raw water.

FIG. 2 shows the removal rate of raw water phosphorus with respect to the amount of CSH added to livestock sewage with a raw water phosphate concentration of about 25 mg / L. The case where slaked lime is used is shown in comparison. In the CSH treatment of the present invention, phosphorus is removed 100% at a CSH addition amount of about 0.15 DW / V%. On the other hand, slaked lime has an addition amount of about 0.15 DW / V% and a phosphorus removal rate of about 90%.

FIG. 3 shows the effect of the CSH treatment on the raw water having a phosphate phosphorus concentration of about 100 to 120 mg / L (a solution obtained by adding sodium phosphate to the purification treatment water of livestock sewage). As shown in the figure, the phosphorus removal rate is about 50% when the CSH addition amount is 0.055 DW / V%, but the phosphorus can be removed almost 100% when the addition amount is 0.07 DW / V% or more.

The chromaticity reduction effect of the barn sewage is shown in FIG. The chromaticity was determined by measuring the absorbance at 390 nm after removing the suspension with a filter, and obtaining the chromaticity from a calibration curve prepared using a chromaticity standard solution. In the CSH treatment of the present invention, the removal rate of chromaticity is close to about 90% at a CSH addition amount of 0.3 DW / V%, but when slaked lime is used, the removal rate of chromaticity is about 70% at the same addition amount. Degree.

FIG. 5 shows the effect of removing the coliforms of the sewage sewage. Furthermore, the removal effect of E. coli is shown in FIG. In the CSH treatment of the present invention, the removal rate of coliform bacteria and E. coli is about 100% at a CSH addition amount of 0.15 DW / V%, but when using slaked lime, the removal rate of coliform bacteria at the same addition amount. Is about 90%, and the removal rate of E. coli is about 70%.

FIG. 7 shows the effect of neutralization treatment by carbon dioxide injection in the treatment system. As shown in the drawing, in the treatment system of the present invention, the pH of the liquid is stably maintained in the vicinity of 6 by the injection of carbon dioxide gas.

About the CSH containing slurry collect | recovered by the said CSH process, and the filtrate which filtered this slurry with the polyester-made cylindrical woven fabric, the floating substance density | concentration was measured and the recovery rate of solid content was investigated. The results are shown in Table 1. It was confirmed that the solid content (used CSH) was almost completely recovered. In addition, the content of the collected solid content was examined. The results are shown in Table 2. Highly soluble phosphoric acid was a high concentration of about 20 wt%, while harmful metals were below the standard value for ordinary fertilizers.

The denitrification effect of the neutralization denitrification tank is shown in FIG. In addition, this effect examination is about inflow NOx-N concentration of about 450 mg / L, hydraulic residence time (per tank empty volume) 2.6 to 4.8 days, water temperature 16.9 to 25.3 ° C., inflow NOx The ratio of thiosulfate sulfur concentration to sulfur concentration (sulfur / nitrogen) was 9.2. By introducing sodium thiosulfate into the neutralization denitrification tank, denitrification bacteria grow in the tank and denitrification proceeds, and the removal rate of nitrate and nitrite nitrogen (NOx-N) is 30-75%.

[Example 2]
CSH was added to the livestock sewage in a slurry state having a solid content of 5 to 10 DW / V% at 0.1 to 0.15 DW / V%, and was retained in the tank for a certain time, and then extracted from the treatment tank. The extracted slurry was put into a polyester filter cloth in a solid-liquid separation tank, and after separating the liquid, it was air-dried. Furthermore, after drying at 105 degreeC for 1 day, it was made into fine powder with the mortar. Similarly, unused materials were air-dried and then dried at 105 ° C. and then pulverized. These powders were added to 25 mL sample solutions (prepared by dissolving non-radioactive cesium chloride and strontium chloride in distilled water) in beakers with the addition amount of 1, 2, 4, 8, 16, 32 DW / V%, respectively. Added. After the addition, the beaker was left in a water bath state in an ultrasonic cleaner (Branson, Model 5510) and sonicated for 30 minutes to promote dispersion of the powder in the solution. After sonication, the dispersion was filtered with a filter (Millipore Millex-LH: manufactured by hydrophobic PTFE), and the cesium and strontium concentrations in the filtrate were quantified. As a quantification method, in the case of unused CSH, an ion chromatography device (Dionex DX-120 type, CS-12A column, eluent 20 mmol / L methanesulfonic acid) is used. In the case of used CSH, an ICP-MS analyzer is used. It was. The results are shown in FIGS.

As a result, no adsorption ability was observed in the unused CSH (FIG. 9), whereas the adsorption ability of both components was confirmed in the used CSH (FIG. 10). In particular, for strontium, a high adsorption rate reaching 82% was obtained even with a low spent CSH addition amount of 1 DW / V%.

10-treatment tank, 11-neutralization denitrification tank, 12-solid-liquid separation tank, 13-storage tank, 14-storage tank, 15-pipe. 16-line, 17-pump, 18-diaphragm valve, 19-carbon dioxide cylinder, 20-line, 21-pump, 25-CSH layer, 26-line, 27-reservoir, 28-pump, 29-line 30-flow meter, 31-static mixer, 32-pipe, 33-pipe, 34-pump, 40-pipe, 41-activated carbon, 42-pipe, 43-pipe

Claims (7)

A processing tank into which a slurry of amorphous calcium silicate hydrate (referred to as CSH) and raw water are introduced, a neutralization denitrification tank into which a liquid extracted from the processing tank is introduced, and a slurry extracted from the processing tank A solid-liquid separation tank to be introduced,
In the treatment tank, a precipitate containing phosphorus or phosphorus and coloring components contained in the raw water is produced under alkaline liquidity, and the slurry containing the precipitate is extracted from the treatment tank and led to a solid-liquid separation tank, and the solid-liquid separation tank And collecting used CSH containing the above precipitate,
On the other hand, the neutralization denitrification tank is filled with porous inorganic particulates carrying denitrification bacteria, and the liquid extracted from the treatment tank is introduced into the neutralization denitrification tank, and the neutralization denitrification tank is introduced. Sodium thiosulfate and carbon dioxide gas are introduced into the nitrogen tank, and nitrate nitrogen contained in the liquid is reduced and removed to nitrogen gas in the neutralization denitrification tank, and the liquid is neutralized with carbon dioxide gas. Wastewater treatment system.
The wastewater treatment system according to claim 1, wherein the raw water is wastewater discharged from a barn or organic industrial wastewater.
The inside of the treatment tank is adjusted to pH 8 or more to produce a precipitate incorporating phosphorus, or the pH is adjusted to 11 or more to produce a precipitate incorporating a coloring component together with phosphorus and sterilization is performed. Wastewater treatment system.
A diaphragm valve operated by gas pressure is interposed in a pipe line for injecting CSH into the treatment tank, and carbon dioxide gas is introduced into the diaphragm valve from a cylinder of carbon dioxide gas introduced into the neutralization denitrification tank. The wastewater treatment system according to any one of claims 1 to 3, wherein injection of CSH into the treatment tank is stopped by a pressure drop of the cylinder.
The wastewater treatment system according to any one of claims 1 to 4, wherein the solid content recovered by solid-liquid separation is used as a by-product phosphate fertilizer.
The wastewater treatment system according to any one of claims 1 to 5, wherein a solid content recovered by solid-liquid separation is used as an adsorbent for free cesium and free strontium.
A by-product phosphate fertilizer or an adsorbent for free cesium and free strontium comprising a solid content (used CSH) recovered from the solid-liquid separation tank of the wastewater treatment system according to claim 1.

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