METHOD FOR RETAINING AMMONIA NITROGEN AND REMOVING ANTIBIOTICS IN BIOLOGICAL TREATMENT OF LIVESTOCK WASTEWATER

Abstract

A method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater is provided. A nitrification inhibitor is added into an aerobic bioreactor with a sludge age greater than or equal to 30 days to inhibit the activity of nitrifying bacteria. The nitrification inhibitor is preferably 2-chloro-6-(trichloromethyl)pyridine or allylthiourea. By adding a chemical agent capable of inhibiting the activity of nitrifying bacteria into the aerobic biological treatment unit for treating livestock and poultry farming wastewater, the occurrence of ammonia nitrogen nitrification is inhibited without sacrificing the degradation of COD and antibiotics by heterotrophic bacteria, so that the aims of retaining ammonia nitrogen while removing antibiotics are realized.

Claims

1. A method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater, wherein a nitrification inhibitor is added into an aerobic bioreactor with a sludge age greater than or equal to 30 days to inhibit the activity of nitrifying bacteria.

2. The method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater as claimed in claim 1, wherein said nitrification inhibitor is 2-chloro-6-(trichloromethyl)pyridine, allylthiourea, 3,4-dimethylpyrazole phosphate, or dicyanamide.

3. The method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater as claimed in claim 2, wherein the dosage of 2-chloro-6-(trichloromethyl)pyridine in the aerobic bioreactors is in a range from 1.5 to 5.0 mg/g VSS.Math.d.

4. The method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater as claimed in claim 2, wherein the dosage of allylthiourea in the aerobic bioreactors is in a range from 10 to 30 mg/g VSS.Math.d.

5. The method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater as claimed in claim 1, wherein an anaerobic biological treatment is employed before an aerobic biological treatment performed by said aerobic bioreactor to remove COD.

6. The method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater as claimed in claim 5, wherein said anaerobic biological treatment is performed by a conventional UASB reactor with a hydraulic residence time of 2 to 10 days, a sludge concentration of 10 to 40 g/L, and a pH value of 7.0 to 8.5.

7. The method for retaining ammonia nitrogen and removing antibiotics in biological treatment of livestock wastewater as claimed in claim 1, wherein an aerobic biological treatment is performed by said aerobic biological treatment with a hydraulic residence time of 3 to 6 days, a sludge concentration of 3000 to 6000 mg/L, a pH value of 6.5 to 8.5, and a dissolved oxygen concentration of 1.0 to 6.0 mg/L.

Description

DESCRIPTION OF DRAWINGS

[0018] The FIGURE is a diagram of the anaerobic-aerobic biochemical treatment process of the livestock wastewater in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0019] The present invention is further illustrated combining with specific implements below. The experimental methods used in the following implements are conventional methods unless otherwise specified. The materials, reagents and the like used in the following implements are commercially available unless otherwise specified. It shall be understood that the implements are used only to illustrate the present invention but not to limit its scope.

Example 1

[0020] Wastewater from a pig farm in Jinshan District, Shanghai is treated by the anaerobic-aerobic biochemical treatment process of the present invention, which is shown in the FIGURE.

[0021] In the FIGURE, operation conditions of the UASB reactor, the aerobic tank A and the aerobic tank B are listed.

[0022] (1) UASB Reactor

Hydraulic residence time (HRT): 3 days;
Sludge concentration (MLSS): 151 g/L; and,
pH value: 7.50.5.

[0023] (2) Aerobic Tank A

Hydraulic residence time (HRT): 3 days;
Sludge residence time (SRT): 40 days;
Sludge concentration (MLSS): 4500500 mg/L;
pH value: 8.00.5; and,
Dissolved oxygen concentration (DO): 3.00.5 mg/L.

[0024] (3) Aerobic Tank B

Hydraulic residence time (HRT): 3 days;
Sludge residence time (SRT): 40 days;
Sludge concentration (MLSS): 4500500 mg/L;
pH value: 8.00.5;
Dissolved oxygen concentration (DO): 3.00.5 mg/L; and,
Dosage of 2-chloro-6-(trichloromethyl)pyridine: 3.0 mg/g VSS.Math.d.

[0025] The average COD concentration of the influent is 5610 mg/L and the average ammonia nitrogen concentration of the influent is 835 mg/L. After the operation of the anaerobicaerobic biochemical treatment system shown in the FIGURE is stable, the effluent of the secondary sedimentation tank A has an average COD concentration of 247 mg/L and an average ammonia nitrogen concentration of 7.3 mg/L. As a consequence, in a case that no 2-chloro-6-(trichloromethyl)pyridine is added into the aeration tank, the removal rate of COD is about 95.6% in average, and the removal (or nitrification) rate of ammonia nitrogen is about 99.1% in average. Meanwhile, the effluent of the secondary sedimentation tank B has an average COD concentration of 355 mg/L and an average ammonia nitrogen concentration of 731 mg/L. As a consequence, in a case that 2-chloro-6-(trichloromethyl)pyridine is added into the aeration tank, the removal rate of COD is about 93.7% in average, and the removal (or nitrification) rate of ammonia nitrogen is about 12.5% in average.

[0026] It comes to a conclusion that adding an appropriate amount of 2-chloro-6-(trichloromethyl)pyridine into the aeration tank can effectively inhibit the nitrification of ammonia nitrogen without sacrificing the degradation of COD, so that the COD concentration of the effluent meets the requirements of reusing to field.

[0027] Moreover, after the operation of the anaerobic-aerobic biochemical treatment system shown in the FIGURE is stable, the concentrations of two main antibiotics, sulfonamides and -lactams, in the influent, the effluents of the secondary sedimentation tank A and secondary sedimentation tank B are respectively determined by HPLC-MS/MS, so as to calculate the total concentration and total removal rate of these two major antibiotics. The result shows that the total concentration of these two major antibiotics of the influent is 323.1 g/L in average, the total concentration of these two major antibiotics of the effluent of the secondary sedimentation tank A is 23.6 g/L in average, and the total concentration of these two major antibiotics of the effluent of the secondary sedimentation tank B is 31.0 g/L in average.

[0028] As a consequence, the removal rate of antibiotics is about 92.7% in average in a case that no 2-chloro-6-(trichloromethyl)pyridine is added into the aeration tank, while the removal rate of antibiotics is about 90.4% in average in the case of adding 2-chloro-6-(trichloromethyl)pyridine into the aeration tank. The removal rates in these two cases are not much different.

[0029] It comes to a conclusion that adding an appropriate amount of 2-chloro-6-(trichloromethyl)pyridine into the aeration tank may has little effect on removing antibiotics from the anaerobic-aerobic biochemical treatment system.

[0030] In conclusion, the occurrence of ammonia nitrogen nitrification is inhibited by adding 2-chloro-6-(trichloromethyl)pyridine capable of inhibiting the activity of nitrifying bacteria into the aeration tank, without sacrificing the degradation of COD and antibiotics.

Example 2

[0031] The wastewater source, treatment process and operating conditions in this Example are the same as those in Example 1. The only difference is that the 2-chloro-6-(trichloromethyl)pyridine added into the aeration Tank B in Example 1 is replaced by allylthiourea, which is added at 15 mg/g VSS d.

[0032] The average COD concentration of the influent is 5382 mg/L and the average ammonia nitrogen concentration of the influent is 792 mg/L. After the operation of the anaerobicaerobic biochemical treatment system shown in the FIGURE is stable, the effluent of the secondary sedimentation tank A has an average COD concentration of 286 mg/L and an average ammonia nitrogen concentration of 10.3 mg/L. As a consequence, in a case that no allylthiourea is added into the aeration tank, the removal rate of COD is about 94.6% in average, and the removal rate of ammonia nitrogen is about 98.7% in average. Meanwhile, the effluent of the secondary sedimentation tank B has an average COD concentration of 430 mg/L and an average ammonia nitrogen concentration of 652 mg/L. As a consequence, in a case that allylthiourea is added into the aeration tank, the removal rate of COD is about 92.0% in average, and the removal (or nitrification) rate of ammonia nitrogen is about 17.7% in average.

[0033] It comes to a conclusion that adding an appropriate amount of allylthiourea into the aeration tank can effectively inhibit the nitrification of ammonia nitrogen without sacrificing the degradation of COD, so that the COD concentration of the effluent meets the requirements of reusing to field.

[0034] Moreover, after the operation of the anaerobic-aerobic biochemical treatment system shown in the FIGURE is stable, the concentrations of two main antibiotics, sulfonamides and -lactams, in the influent, the effluents of the secondary sedimentation tank A and secondary sedimentation tank B are respectively determined by HPLC-MS/MS, so as to calculate the total concentration and total removal rate of these two major antibiotics. The result shows that the total concentration of these two major antibiotics of the influent is 284.5 g/L in average, the total concentration of these two major antibiotics of the effluent of the secondary sedimentation tank A is 23.2 g/L in average, and the total concentration of these two major antibiotics of the effluent of the secondary sedimentation tank B is 34.5 g/L in average.

[0035] As a consequence, the removal rate of antibiotics is about 91.8% in average in a case that no allylthiourea is added into the aeration tank, while the removal rate of antibiotics is about 87.8% in average in the case of adding allylthiourea into the aeration tank. The removal rates in these two cases are not much different.

[0036] It comes to a conclusion that adding an appropriate amount of allylthiourea into the aeration tank may has little effect on removing antibiotics from the anaerobic-aerobic biochemical treatment system.

[0037] In conclusion, the occurrence of ammonia nitrogen nitrification is inhibited by adding allylthiourea capable of inhibiting the activity of nitrifying bacteria into the aeration tank, without sacrificing the degradation of COD and antibiotics.

[0038] The above descriptions are only the preferred schemes of the present invention, and it should be noted that for ordinary technicians in the technical field, without departing from the principles of the present invention, some improvements and polishing can also be made, and these improvements and polishing should also be considered as the scope of protection of the present invention.