Partial nitrification-denitrification coupled two-stage autotrophic denitrification advanced nitrogen removal method

Abstract

An advanced nitrogen removal method using partial nitrification-denitrification coupled two-stage autotrophic denitrification. Sewage is introduced into a first pool for partial nitrification-denitrification treatment, and then introduced into a first regulating reservoir. Dissolved oxygen content in the first pool is kept at 0.4-0.6 mg/L. Water is discharged when a molar ratio of nitrite nitrogen to ammonia nitrogen in the first regulating reservoir is 1.0-1.3:1. Effluent in the regulating reservoir is introduced into a second pool for anaerobic ammonia oxidation treatment, and then introduced into a second regulating reservoir. In the second pool, pH is 7.0-7.4, a temperature is 22-28° C. Effluent in the second regulating reservoir and sulfides are introduced into a third pool for denitrification treatment. Water is discharged. In the third pool, pH is 7.5-8.0, a temperature is 28-32° C., a mass ratio of sulfur to nitrogen is 1.9-2.0:1.

Claims

1. A partial nitrification-denitrification coupled two-stage autotrophic denitrification advanced nitrogen removal method, comprising the following steps: S1: introducing sewage into a partial nitrification-denitrification pool to perform partial nitrification-denitrification treatment, then introducing the sewage into a regulating reservoir 1, controlling dissolved oxygen content in the partial nitrification-denitrification pool as 0.4-0.6 mg/L, and discharging water when a molar ratio of nitrite nitrogen to ammonia nitrogen in the regulating reservoir 1 is (1.0-1.3):1; S2: introducing effluent in the regulating reservoir 1 into an anaerobic ammonia oxidation pool to perform anaerobic ammonia oxidation treatment, then introducing the effluent into a regulating reservoir 2, and controlling a pH value in the anaerobic ammonia oxidation pool to be 7.0-7.4, wherein a temperature is 22-28° C.; S3: introducing the effluent in the regulating reservoir 2 and 1.1-1.5 g/L of sulfides into a sulfur autotrophic denitrification pool to perform denitrification treatment, discharging water, and controlling a pH value in the sulfur autotrophic denitrification pool to be 7.5-8.0, wherein a temperature is 28-32° C., and a mass ratio of sulfur to nitrogen is (1.9-2.0):1.

2. The method according to claim 1, wherein the sewage in the S1 is landfill leachate.

3. The method according to claim 1, wherein the dissolved oxygen content in the S1 is 0.5 mg/L.

4. The method according to claim 1, wherein in the S1, after the sewage is subjected to partial nitrification-denitrification treatment, the molar ratio of the nitrite nitrogen to the ammonia nitrogen is (1.0-1.3):1.

5. The method according to claim 1, wherein water is discharged when the molar ratio of the nitrite nitrogen to the ammonia nitrogen in the regulating reservoir 1 is 1.2:1.

6. The method according to claim 1, wherein in the S2, the effluent subjected to anaerobic ammonia oxidation treatment flows back to the regulating reservoir 1, so that a total nitrogen concentration in the regulating reservoir 1 is 500-600 mg/L.

7. The method according to claim 1, wherein in the S3, a mass ratio of sulfur to nitrogen is 2:1.

8. The method according to claim 1, wherein in the S3, effluent in the sulfur autotrophic denitrification pool flows back to the regulating reservoir 2, so that a nitrate nitrogen concentration in the regulating reservoir 2 is 90-120 mg/L.

9. The method according to claim 1, wherein in the S3, the sulfide is sodium sulfide.

10. The method according to claim 9, wherein the sodium sulfide is derived from hydrogen sulfide produced in a waste landfill.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a process flowchart of a partial nitrification-denitrification coupled two-stage autotrophic denitrification advanced nitrogen removal method.

(2) FIG. 2 is a systematic schematic diagram of a partial nitrification-denitrification coupled two-stage autotrophic denitrification advanced nitrogen removal method.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(3) The present invention is further illustrated below in combination with embodiments. These embodiments are merely used for describing the present invention, rather than limiting the scope of the present invention. Experimental methods without specific indicated conditions in embodiments below are generally performed in accordance with conventional conditions in the art or in accordance with conditions suggested by manufacturers. Unless otherwise specified, used raw materials, reagents and the like are all raw materials and reagents obtained from commercial approaches such as conventional markets. Any insubstantial changes and replacements made by those skilled in the art on the basis of the present invention belong to the protection scope of the present invention.

Embodiments 1-3

(4) Landfill leachate of a certain waste landfill serves as a sewage source for treatment. The landfill leachate has COD content of 4000-5000 mg/L, and an ammonia nitrogen concentration of 2500-3000 mg/L. The landfill leachate collected in a storage pond is treated to obtain percolate, and the percolate is delivered into a partial nitrification-denitrification pool to react. Various conditions of the percolate are shown in the following Table 1.

(5) Process flow charts of a partial nitrification-denitrification coupled two-stage autotrophic denitrification advanced nitrogen removal method provided by Embodiments 1-3 are as shown in FIGS. 1 and 2. Specific steps are as follows:

(6) The percolate serving as sewage was introduced (unrestrictive aeration) into the partial nitrification-denitrification pool for 10 min, and stirred for 10 h 50 min (aeration was performed at the same time, and DO was controlled as 0.4-0.6 mg/L); precipitation was performed for 0.5 h; water was discharged for 10 min; standing was performed for 20 min; a cyclic water treatment quantity was 1 L; two cycles were operated every day, that is, a daily water treatment quantity of 2 L served as an operating condition of the partial nitrification-denitrification pool; and the effluent was introduced into a regulating reservoir 1. Meanwhile, water quality fluctuation of the effluent in the partial nitrification-denitrification pool was considered; an external reflux ratio of the pool was set as 3, that is, a total concentration of NH.sub.4.sup.+—N and NO.sub.2.sup.−—N in the regulating reservoir 1 was controlled as about 500-600 mg/L; a pH value of the effluent was 7.0-7.5; and HRT of the pool was equal to 3 h. The effluent was further treated by utilizing an anaerobic ammonia oxidation pool and discharged, and introduced into a regulating reservoir 2. 4 L of effluent in a sulfur autotrophic denitrification pool flowed back to the regulating reservoir, so that the NO.sub.3.sup.−—N concentration was 70-120 mg/L. The adding amount of sodium sulfide was determined according to the NO.sub.3.sup.−—N concentration, so that a mass ratio of sulfur to nitrogen is 1.9-2.0. A pH value was controlled as 7.5±0.1, and a temperature was 30±1° C. Through the sulfur autotrophic denitrification pool, the NO.sub.3.sup.−—N was further removed, and sulfide ions were fully removed. Condition setting and treatment results of various embodiments are as shown in the following Table 1.

References Examples 1-2

(7) The references examples 1-2 provide a partial nitrification-denitrification coupled two-stage autotrophic denitrification advanced nitrogen removal method. In the method provided by reference example 1, dissolved oxygen content in the partial nitrification-denitrification pool is controlled as 0.3 mg/L, and other conditions are consistent with those in Embodiment 1; and in the method provided by reference example 2, a mass ratio of sulfur to nitrogen in the sulfur autotrophic denitrification pool is controlled as 2.5:1, and other conditions are consistent with those in Embodiment 1. Condition setting and treatment results of reference examples 1-2 are as shown in the following Table 1.

(8) TABLE-US-00001 TABLE 1 Condition setting and treatment results of the method provided by embodiments 1-3 and reference examples 1-2 Embodiments Reference Examples Condition/treatment results 1 2 3 1 2 Initial NHC.sub.4.sup.+—N concentration  1338.53  1338.53  1338.53  1338.53  1338.53 (mg/L) InitialNO.sub.2.sup.−N (mg/L)   974.85   974.85   974.85   974.85   974.85 InitialNO.sub.3.sup.−—N concentration   246.88   246.88   246.88   246.88   246.88 (mg/L) InitialCOD concentration  3944.18  3944.18  3944.18  3944.18  3944.18 (mg/L) Initial basicity (mg/L) 4156  4156  4156  4156  4156  Dissolved oxygen content (DO,   0.5   0.4   0.6   0.3   0.5 mg/L) Molar ratio of NH.sub.4.sup.+—N to   1.2   1.3   1.0   1.4   1.2 NO.sub.2.sup.−N in effluent Concentration of NH.sub.4.sup.+—N in   31.88   29.54   32.64   58.75   31.88 effluent (mg/L) Removal rateof NH.sub.4.sup.+—N 87.7% 91.5% 93.2% 75.6% 87.7% Concentration of NO.sub.2.sup.−—N in   14.03   10.96   13.48   35.7   14.03 effluent (mg/L) Removal rateofNO.sub.2.sup.−N 94.9% 96.2% 93.6% 87.3% 94.9% Concentration of NO.sub.3.sup.−N in   221.42   212.51   205.36   265.43   221.42 effluent (mg/L) Regulating Total nitrogen content (mg/L) 550  500  600  550  550  reservoir 1 Anaerobic NH.sub.4.sup.+—N removal rate 98.8% 99.6% 98.6% 84.6% 98.8% ammonia (accumulated) oxidation TN removal rate 90.2% 91.5% 92.5% 81.4% 90.2% pool COD removal rate 45.7% .sup. 51% .sup. 48% .sup. 44% 45.7% Regulating NO.sub.3.sup.−—N concentration 90 70 120 110 90 reservoir 2 Sulfur-nitrogen mass ratio   2.0   1.9    1.95   1.8   2.5 COD removal rate .sup. 51% .sup. 49% .sup. 51% .sup. 47% 46.5% Sulfur Sulfur removal rate  100%  100%  100%  100%  100% autotrophic Ammonia <5 <5 <5 <20  <30  denitrification nitrogenconcentration of pool effluent (mg/L) Nitrate nitrogen concentration <5 <5 <5 <20  <20  of effluent (mg/L) NO.sub.3.sup.−—N removal rate 95.3% 96.1% 95.9% 81.7% 83.5%

(9) It can be seen from Table 1 that, according to the method provided by embodiments 1-3, the removal rate of NO.sub.3.sup.−—N in the effluent of the anaerobic ammonia oxidation pool treated by the sulfur autotrophic denitrification pool is up to 95%; and sulfur removal efficiency is up to 100%. After the landfill leachate is subjected to advanced nitrogen removal by a partial nitrification-denitrification coupled two-stage autotrophic denitrification process, the COD, the ammonia nitrogen and the total nitrogen are further removed. The ammonia nitrogen content in the effluent is decreased to be less than 10 mg/L; the nitrate nitrogen content is decreased to be less than 5 mg/L; and the effluent meets the emission standard of Standard for Pollution Control on the Landfill Site of Municipal Solid Waste (GB16889-2008). However, according to the method provided by reference examples, the concentrations of the ammonia nitrogen and nitrite nitrogen in the effluent and the nitrate nitrogen are higher than those in the embodiments, and the total nitrogen in the effluent is difficult to meet the latest emission requirement. Therefore, compared with the reference examples, the embodiments have excellent operating effects.