KR20080019038A - Nitrogen-rich wastewater treatment method and struvite formation method using bone - Google Patents

Abstract

A method for treating nitrogen-rich wastewater and forming struvite using bone is provided to prepare a large amount of struvite economically while removing nitrogen from nitrogen-rich wastewater economically by supplying, at a low cost, a liquid in which calcium ions and phosphate ions are dissolved. A method for treating nitrogen-rich wastewater and forming struvite using bone comprises: (a) a calcium/phosphorous dissolution step of dissolving calcium ions and phosphate ions while contacting bone with acid for at least 5 minutes to prepare a calcium/phosphorous solution; (b) an anaerobic treatment step of injecting the calcium/phosphorous dissolved solution into an anaerobic reaction tank together with nitrogen-rich wastewater that is wastewater to be treated, thereby treating the wastewater using anaerobic microorganisms to discharge anaerobic effluent; and (c) a struvite forming step of forming struvite from the anaerobic effluent. The acid of the step(a) is selected from the group consisting of waste acid generated at industrial sites, low grade acid, purchasable acid, and fermented acid having a pH range of 1.5 to 5.5 generated by subjecting food waste to acidification.

Description

Nitrogen-rich wastewater treatment method and struvite formation method using bone}

The present invention relates to a method for producing a large amount of struvite economically while economically removing nitrogen from waste nitrogen-containing wastewater by inexpensively supplying a solution in which calcium ions and phosphate ions are dissolved.

There are many biological and physicochemical methods for the treatment of excess nitrogen containing wastewater, but it is difficult or expensive to maintain the removal efficiency. Recently, a method for removing phosphate and nitrogen at the same time by preparing a MAP salt of magnesium ammonium phosphate (MgNH ₄ PO ₄ 6H ₂ O) crystal in which magnesium ions, ammonium ions and phosphate ions are formed in a molar ratio of 1: 1: 1. The research is active and the reaction is as follows.

_{^{Mg 2 + + NH 4 + +}} PO 4 3 - + 6H 2 O → MgNH 4 PO 4 6H 2 O

In addition, MAP salt formation instead of Mg ^{2 +} ions, and generate analogs (Analog) such as calcium ions are replaced Calcium Ammonium Phosphate in, it referred to through a homologue of MAP and MAP host referred rubayi Trad. Phosphorus and nitrogen in the wastewater are removed by struvite efficiently, and struvite can be sold as a slow-release fertilizer. Sustained fertilizer refers to a fertilizer that is nontoxic to plants and that does not oxidize for a long time with one use and continues to be effective.

 Struvite manufacturing technology includes foreign technologies such as Japanese Patent No. 11-267665 of Tsunekawa et al. And US Patent No. 4,389,317 of Trentelman, and Korean Patent Publication Nos. 10-2002-0005521, 10-2000-0019613, 10-2004-0070408, While domestic technologies such as 10-2007-0135309 exist, the concentration of nitrogen is high, while the concentration of Mg, calcium and phosphate is high when the Mg, calcium and phosphate are supplied to the chemical during wastewater treatment with a low concentration of Mg, calcium and phosphate. There is no technique prepared to compensate for the disadvantage that the amount of struvite formation is limited and a large amount of ammonia nitrogen remains. In other words, there is no patent or technology for providing an inexpensive supply of Mg, calcium and phosphate to further remove nitrogen from the nitrogen-rich wastewater and economically increase the yield of struvite.

An object of the present invention is to provide a method for producing a large amount of struvite economically while economically removing nitrogen from waste nitrogen-containing waste water by inexpensively supplying a solution in which calcium ions and phosphate ions are dissolved.

The configuration of the present invention for achieving the above object,

(a) a calcium / phosphorus dissolving step (10) of preparing calcium / phosphorus dissolving solution by dissolving calcium ions and phosphate ions while contacting a bone with an acid;

(b) the anaerobic treatment step 20 of treating the anaerobic microorganisms by adding the calcium / phosphorus lysate with the wastewater to be treated to an anaerobic reactor;

(C) is formed by a struvite manufacturing step 30 to form a struvite from the anaerobic effluent flowing out from step (b).

Referring to the configuration of the present invention in more detail, step (a) is a step of contacting the bone (acid) with the acid (acid), depending on the type of acid dissolved in a significant amount of calcium and phosphate in only 5 minutes of contact It confirmed that it became / phosphorus solution. Acids that can be used include all acids that can be purchased, such as waste acid and low rate acid, which are produced at industrial sites, and acid fermentation solutions with a pH of 1.5 to 5.5 by acidifying food wastes. (fermented acid) may be used.

 In addition, it is also possible to proceed with the acid fermentation and calcium / phosphorus dissolution step by additionally adding bone together with the organic matter in the acid fermentation tank, which is a process for producing an acid fermentation solution, in this case, acid fermentation and calcium / Dissolution of phosphorus proceeds simultaneously. That is, acid fermentation produced during acid fermentation of food waste and livestock manure reacts with bone to dissolve calcium and phosphate, thereby reducing the purchase cost and transportation cost of waste acid.

When dissolving and supplying additional calcium ions is necessary, the shell cover is put together with the bone to supply as much calcium as desired while contacting the acid, or a separate calcium dissolving tank is provided to separate the shell of the shell by acid. Supply methods are also available.

Since the pH of the calcium / phosphate solution prepared in step (a) is low, a large amount of alkaline agent is required to create the proper conditions (pH 9-9.2) for the preparation of struvite. It is not economical to use it for true byte production.

Therefore, in step (b), the calcium / phosphate solution prepared in step (a) is added to the anaerobic reactor with waste nitrogen-containing wastewater to be treated, and the organic matter is decomposed into anaerobic microorganisms, converted into methane gas and carbon dioxide, and a considerable amount of organic nitrogen is converted. Converting to ammoniacal nitrogen.

The nitrogen-containing wastewater refers to all kinds of wastewater containing more nitrogen than Mg, calcium and phosphate, such as sewage, livestock wastewater, industrial wastewater, food waste, food waste stripping liquid, sewage sludge, and the like.

 Because of the pH adjustment in the anaerobic reactor due to the dissolution of carbon dioxide from the anaerobic treatment, the pH of the anaerobic effluent is maintained between 6.8 and 8.2 regardless of the influent properties. Therefore, the anaerobic treatment process has the advantage of minimizing the input of alkaline agent to make conditions suitable for struvite formation (pH 9.0-9.2).

Anaerobic reactors that can be used include digesters, anaerobic contact processes, fluidized bed reactors using fluidized microorganisms, anaerobic filters using microorganisms attached to carriers, and attachments. And UASB series such as hybrid anaerobic reactors using floating microorganisms, upflow anaerobic sludge blankets (UGASB), extended granule sludge beds (EGSB), and internal circulation (IC) using granules formed of microorganisms. All anaerobic reactors currently in operation, including reactors, can be used.

Step (c) is a step for forming the struvite, and various methods and patent methods for struvite formation may be used.

Compared with the current struvite manufacturing method using step (b) after step (b) without step (a), the present invention improves the nitrogen removal efficiency and consequently decreases the effluent nitrogen concentration, and the struvite yield It has the advantage of being economically increased.

According to the present invention, a calcium / phosphorate solution prepared by dissolving bone in an acid at low cost is anaerobicly treated with an excess of nitrogen containing wastewater and a struvite is produced from the treated water, thereby efficiently removing a large amount of nitrogen while removing nitrogen economically. True bytes can be produced economically.

Hereinafter, the structure of the present invention will be more clearly understood by the following examples, and the effects thereof will be demonstrated.

<Example 1>

Total effective capacity of 1m ^3, and a height of 3m is equipped with an up-flow equipment and aeration that supplies NaOH and Mg ions equipment for livestock waste water to remove impurities in the anaerobic reactor to the back end anaerobic reactor is operated while flowing into the 150L / d's true The treated water was analyzed while a bite manufacturing facility was installed to form struvite. The amount of magnesium-containing compound was injected to increase the concentration of Mg ions to 972 mg / L (40 mmole / L), and to run for one month while injecting an alkaline agent to maintain the effluent pH of the struvite manufacturing equipment at 8.8 to 9.0. The average values of the analysis results are summarized in the table below. The characteristics of livestock wastewater from which contaminants have been removed are expressed before anaerobic treatment, the effluent from the anaerobic wastewater treatment stage after the anaerobic treatment, and the effluent from the struvite manufacturing equipment after crystal separation. .

During the experiment, 5 kg of pork bone and 4 kg of oyster shell were dissolved in 40 L of waste acid having a pH of 2.2 for 7 days, and a calcium / phosphate solution was prepared every week. The solution was operated with 5 L / d of raw water in an anaerobic reactor. One month after the start of the analysis, the results are expressed as the calcium / phosphate solution in the table below.

TABLE 1 mg / L

Item Before anaerobic treatment Before supplying calcium / phosphate solution After supplying calcium / phosphate solution After anaerobic treatment After crystal separation After anaerobic treatment After crystal separation CODcr 31,000 11,000 9,250 11,200 9,099 T-N 3,800 2,150 1,962 2,159 1,472 NH ₄ -N 1,250 1,480 1,305 1,490 888 PO ₄ -P 550 580 12 1,986 4.2

In the current production method of strubi without the supply of calcium / phosphorus solution, the phosphate phosphorus 18.3 mmol / L (97.9%) is ammonia when 40 mmole / L Mg ion is supplied to the struvite manufacturing facility after the anaerobic reactor. Nitrogen was removed from 12.47 mmol / L (11.8%), Mg, ammonium and phosphate ions were removed at a molar ratio of 3.21: 1: 1.47, and the concentration of ammonia nitrogen flowed out at 1,305 mg / L.

However, after supplying the calcium / phosphorus solution, 63.3 mmol / L (99.8%) of phosphate and 42.29 mmol / L (40.0%) of ammonia nitrogen were removed without additional supply of Mg ions. The concentration was reduced to 888 mg / L.

Additional Mg, Ca, PO ₄ The addition of calcium and phosphorus solution prepared from bone and shellfish without anaerobic treatment before anaerobic treatment and the addition of alkali to the anaerobic treated water for a slight increase in pH result in the additional removal of nitrogen and additional production of struvite. It is an advantage of this patented process.

<Example 2>

After completing the above experiment, the amount of calcium / phosphate solution prepared in the same manner was increased from 5 L / d to 10 L / d, and one month after the same experiment was started, the results are shown in the table below. Expressed before stopping supply. After this experiment was completed, the oyster shell was discontinued for the additional supply of Ca ions, and the same experiment was conducted while maintaining the supply amount of calcium / phosphate dissolving solution made only of bone at 10 L / d. The analysis results were expressed as after shellfish supply was stopped.

Table 2 [mg / L]

Item Before anaerobic treatment Before stopping shellfish supply After stopping shellfish supply After anaerobic treatment After crystal separation After anaerobic treatment After crystal separation CODcr 31,000 11,200 9,086 11,200 9,099 T-N 3,800 2,159 972 2,159 972 NH ₄ -N 1,250 1,490 299 1,490 658 PO ₄ -P 550 2,886 4.4 1,412 42.6

Before stopping the shellfish supply and increasing the supply of calcium / phosphate solution from 5L / d to 10L / d, phosphate 92.96mmole / L (99.85%) and ammonium nitrogen 84.6mmole / L (80.0%) It was found that the concentration of ammonia nitrogen was greatly improved to 299 mg / L. After stopping the feeding of shellfish, 44.2 mmole / L (97.0%) of phosphate and 58.7 mmole / L (55.5%) of ammonia nitrogen were removed to maintain 658 mg / L of ammonia nitrogen in the effluent. 42.6 mg / L remained. The livestock wastewater used in the experiment should be used with calcium / phosphate solution prepared from bone and shellfish to keep the remaining phosphate phosphorus low. Therefore, it is considered appropriate to use calcium / phosphate solution prepared from bone and shellfish. When the flow was stopped, it was confirmed that insufficient calcium phosphate was insufficient to remove phosphate.

<Example 3>

Sludge from the high temperature digester treating liquor wastewater was collected and filled into 100L digester and supplied with 5L / d of liquor wastewater to supply NaOH and Mg ions to the rear of the medium temperature anaerobic digester operated and struvite equipped with aeration equipment. The treated water was analyzed while the manufacturing equipment was installed to form struvite. The amount of magnesium-containing compound was injected to increase the concentration of Mg ion to 486 mg / L (20 mmole / L), and an alkaline agent was injected for one month while maintaining the effluent pH of the struvite manufacturing equipment at 8.8 to 9.0. The average value of the analysis results is summarized in the table below, and the characteristics of alcoholic wastewater were treated before anaerobic treatment, the effluent from anaerobic wastewater treatment stage after anaerobic treatment, and the effluent from struvite manufacturing equipment after crystal separation.

During the experiment, 0.5 kg of pork bone was dissolved in 3 L of waste acid having a pH of 2.2 for 7 days, and a calcium / phosphate solution was prepared every week. The solution was started with 0.1 L / d of raw water and introduced into an anaerobic reactor. The results of the analysis for one month after the month are expressed as the calcium / phosphate solution in the table below.

Table 3 [mg / L]

Item Before anaerobic treatment Before supplying calcium / phosphate solution After supplying calcium / phosphate solution After anaerobic treatment After crystal separation After anaerobic treatment After crystal separation CODcr 51,000 14,000 12,250 14,200 12,350 T-N 1,800 1,450 1,210 1,460 710 NH ₄ -N 250 890 808 890 423 PO ₄ -P 340 250 2.1 1,486 2.5

The current method for producing struvite without supplying calcium / phosphorus solution.Phosphate phosphorus is 8.00mmole / L (94.8%) ammonia nitrogen is 5.86mmole / L (9.2%) was removed and the concentration of ammonia nitrogen leaked to 808 mg / L.

However, after supplying 0.1 L / d of calcium / phosphorus dissolved in bone, 47.9 mmol / L (99.8%) of phosphate phosphorus and 33.4 mmol / L (52.5%) of ammonia nitrogen were removed without supplying Mg ion. The concentration of ammonia nitrogen in the effluent was reduced to 423 mg / L.

Additional Mg, Ca, PO ₄ Anaerobic treatment of calcium / phosphorus dissolving solution with bone alone without alcohol supply, along with alcoholic wastewater, further removal of nitrogen from alcoholic wastewater and increase of struvite by only adding alkaline agent to increase pH slightly in anaerobic treated water. lost. The reason for the high removal rate of phosphate phosphorus by dissolving bones without shellfish is that the concentration of magnesium and calcium ions in the drinking liquor was exceptionally high.

1 is a flowchart showing the configuration of the present invention.

* Explanation of Signs of Major Parts of Drawings *

       10: calcium dissolving device

20: anaerobic wastewater treatment step 30: struvite formation step

Claims (5)

(a) a calcium / phosphor dissolution step of dissolving calcium ions and phosphate ions while contacting an acid with an acid for at least 5 minutes to produce a calcium / phosphor dissolution solution; (b) an anaerobic treatment step of discharging anaerobic effluent by inputting the calcium / phosphate solution into an anaerobic reactor with an excess of nitrogen-containing wastewater to be treated; (c) nitrogen excess wastewater treatment and struvite manufacturing method comprising a struvite manufacturing step of forming struvite from the anaerobic effluent The method of claim 1, wherein the acid of step (a) is produced by acidification of waste acid, low rate acid, commercially available acid, and food waste generated in an industrial site. Nitrogen excess wastewater treatment and struvite production method selected from the group consisting of fermented acid with a pH of 1.5 ~ 5.5 According to claim 1, wherein the calcium / phosphorus dissolving step of step (a) using the acid fermentation solution produced in the acid fermentation tank as the acid and the bone is added to the acid fermentation tank acid and fermentation of calcium / phosphorus dissolution step Nitrogen-excess wastewater treatment and struvite production process simultaneously in fermenter According to claim 1 or claim 2 or claim 3, if additional calcium supply is required to further dissolve calcium by adding a shell cover (shell cover) to the calcium / phosphorus dissolution step of step (a), Nitrogen-excess wastewater treatment and struvite manufacturing method for separately supplying calcium dissolving solution which separately installs a calcium dissolving tank for reacting shellfish with acid to calcium / phosphorus dissolving step of step (a)     The waste nitrogen-containing wastewater according to claim 1 or 2 or 3 or 4 is selected from the group consisting of sewage, livestock wastewater, industrial wastewater, food waste, food waste stripping liquid and sewage sludge. And waste nitrogen containing wastewater treatment and struvite manufacturing method, which is more wastewater containing nitrogen than phosphorus phosphate

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