Research On High-performance Nitrogen Removal Of Piggery Biogas Effluent By Microbial Bio-augmentation

Piggery biogas effluent is aquaculture wastewater with high concentration of ammonia nitrogen(NH4⁺-N) and chemical oxygen demand（COD） after anaerobic fermentation. It’s difficult to be used by microorganism because of its low COD/N. It becomes a technical problem that the effluent nitrogen and phosphorus can not reach standards. The strains of ammonia removal, process conditions and the nitrogen removal of enhanced sequencing batch bioreactor（SBR） by bio-augmentation under laboratory conditions were studied.The results are as follows:（1） Ammonia oxidizing bacteria（AOB, Nitrosomonas europaea） AT7 and nitrite-oxidizing bacteria（NOB, Nitrobacter winogradskyi） Y3-2 for biogas effluent treatment were selected out. The NH4⁺-N was approximately removed 71.1% by AT7 after 3 days when the initial ammonia concentration was 200 mg/L-250 mg/L. The accumulation of nitrite was reduced 41.7% by Y3-2 after 4 days.（2）The removal rate of NH4⁺-N was 77.8% when the inoculum concentration of AT7 and Y3-2 was 105 CFU/m L with shaking speed was 200 r/min and adding 0.3 g straw powder per 100 m L.When NH4⁺-N concentration reduced to 60 mg/L or less, with methanol as the carbon source which was added once per 2 days, removal rate of NH4⁺-N was 80.36% after 3 days.（3）In the SBR system, alternate aeration for 6 h and standing for 2 h respectively. Inoculated AT7 and Y3-2 105 CFU/m L in SBR system respectively, NH4⁺-N removal rate was 89.3% after 3 days, the production of nitrate(NO3^--N) increased 39.7%.（4）Adjusted COD/N to 11:1 with methanol, adding nitrifying bacteria and denitrifying bacteria, removal rates of NH4⁺-N, TN, COD and TP were 98.7±0.4%, 83.7±0.8%, 97.4±0.2%, 70.6±5.0%. Fructo-oligosaccharides wastewater can replace methanol as carbon source and reduce cost. Removal rates of NH4⁺-N, TN, COD and TP were 98.9±0.3%, 95.1±1.5%, 97.1±0.3%, 73.9±3.9%.（5）The piggery biogas effluent with high concentration of NH4⁺-N（771 mg/L） could be treated by the way of diluting to reduce concentration of NH4⁺-N to 200 mg/L-250 mg/L with disposed effluent from SBR. The SBR ran stably after 21 days, removal rates of NH4⁺-N, TN, COD and TP were 98.2±0.2%, 77.8±0.5%, 94.1±0.6%, 77.1±1.6%.（6）In outdoor simulation experiment, the average temperature was between 9℃-20℃, removal rates of NH4⁺-N, TN, COD and TP reached 97.9±0.2%,73.8±0.9%,92.1±0.9%,80.4±1.9%. It showed that in a certain temperature range, temperature change do not have much effect on the operation of SBR system.