Study On Biological Phosphorus And Nitrogen Removal From Piggery Anaerobic Digestion Effluent By Two-stage SBR Process

Nitrogen and phosphorus are the main pollutants in piggery anaerobic digestion effluent.However,the current research on biological phosphorus and nitrogen removal of piggery anaerobic digestion effluent mainly focuses on the traditional biological phosphorus and nitrogen removal process.This study learns from the existing biological nitrogen removal technology and creates two-stage sequencing batch reactor(SBR)process which aim at the processing of the anaerobic digestion effluent.Through artificial wastewater which simulating piggery anaerobic digestion effluent,the study determines the optimum operating conditions of SBR and carbon source dosing method and the influence of the proportion of main pollutant removal efficiency,which later applied to the practical processing of piggery anaerobic digestion effluent.Biological phosphorus removal SBR was started by gradually shortening solid retention time(SRT).The removal efficiency of SBR for main pollutants under different drainage ratios and the ratio between chemical oxygen demand and phosphorus of inflow(C/P)was investigated.Later the microbial community structure in SBR was characterized.The results show that shortening SRT can improve the phosphorus removal rate of SBR,but an over-shorten SRT will cause sludge loss.Then we got a conclusion that the optimal SRT is 10 days.After considering the effluent quality and treatment efficiency,the drainage ratio should be controlled to30%.When C/P reaches more than 30,adding carbon source does little effect on phosphorus removal.Biological phosphorus removal SBR could effectively enrich microorganisms with phosphorus removal effect,and the proportion of Flavobacterium reached 4.13%.The biological denitrification SBR was activated by gradually reducing the drainage ratio.The effects of different ratio between chemical oxygen demand and nitrogen of inflow(C/N)and external carbon sources on the removal efficiency of main pollutants in SBR were investigated.Later the community structure of microorganisms in SBR was characterized.The results show that the effluent water quality cannot be significantly improved by further reducing the drainage ratio under the condition of 10% drainage ratio,and the optimal drainage ratio is 10%.When C/N is less than 4,at least 50.06 mg/L of nitrate nitrogen in the reactor cannot be denitrified,and the effluent is difficult to reach the standard.Addition of carbon source at the anoxic stage is very effective to reduce the total nitrogen of effluent.Adding 400 mg/L carbon source can reduce the total nitrogen of effluent by 64.24mg/L.Biological denitrification SBR could effectively enrich microorganisms with denitrification effect,in which denitrifying bacteria Thauera and nitrifying bacteria Alcaligenes accounted for 68.08% and 5.85%,respectively.The two-stage SBR process was used to treat the actual piggery wastewater anaerobic digestion effluent.The results show that the phosphorus removal rate can be increased by 29.27% by adding 600 mg/L of carbon source in the influent,and the total nitrogen of effluent can be reduced by 66.52 mg/L by adding 400 mg/L of carbon source at the anoxic stage.Under the condition of adding carbon sources by two times,the removal rates of COD,TP,ammonia nitrogen,total nitrogen by two-stage SBR process are 85.08%,56.89%,97.48%,96.36%,respectively.However,the effluent COD and TP cannot meet the relevant standards,which mainly due to that the effluent COD is refractory organics.At the same time,the requirement of TP was hard to reach for single biological treatment.The pH in the reactor is stable and the residual basicity is enough.In the situation of high-ammonia-nitrogen inflow,the reactor can still maintain most processing capacity except COD index.