Integration Of Denitrifying Phosphorus Removal With Autotrophic Nitrogen Removal Process For Treating Digested Piggery Wastewater

Anaerobic process is widely used in piggery wastewater pretreatment as its efficient removal of Organics. However, it is very hard to meet the discharge limit using traditional biochemical methods because the C/N of the effluent digested water from anaerobic process is relatively low. Therefore, it is urgent to develop new type of process for digested water to achieve deep nitrogen and phosphorus removal and meet the discharge limit stability. In view of this, the study presented an integration of denitrifying phosphorus removal (DPAO) with autotrophic nitrogen removal process(Sharon-Anammox) for treating digested piggery wastewater. With simulated wastewater, we studied the stability control method of Sharon-Anammox and the application of DPAO in high concentration wastewater. On the basis of simulated wastewater, we studied the practical application of this process in digested wastewater and its stability control strategy. The main results are as follows.(1) For Sharon process, we discussed two kind of method runs for the stability of process. It showed that "low concentration with high flux "operation mode boot process faster, ammonia conversion load (NCR) can be raised to 2.04 kg N/d/m3 after 30 d. q-PCR results confirmed it can maintain higher sludge nitrification activity, conducive to the rapid enrichment of ammonia-oxidizing microorganisms.In the case of moderate alkalinity, DO make little difference on the effluent NO2"-N/NH4+. However, if alkalinity is overdosed, we need to control DO strictly to achieve stable effluent. In conclusion, "low concentration with high flux" operation mode is more portable and DO control is necessary In the case of overdosed alkalinity.(2) We improved the ammonia removal rate (NRR) of Anammox and studied the impact of influent NO2--N/NH4+-N and COD concentration on Anammox stability. The NRR can be raised to 1.31 kg N/d/m3 after 120d. Average substrate removal ratio (NO2 -N removal/NH4+-N removal) is 1.24, nitrate produce ratio (NO3--N/NH4+-N removal) is 0.15. q-PCR results showed that Anammox bacteria is the main microbe, and contains a small amount of nitrification and denitrifying microbe. A higher influent NO2-N/NH4+-N and moderate concentration of COD (lower than the demand for NO3--N denitrification) will not have a significant effect on Anammox system stability, besides, it can even improve TN removal rate through the con-effect of denitrifying microbe and Anammox bacteria.(3) Primary studied the stability of DPAO system and its microbiological mechanisms, based on this, established the stable and efficient combination mode of aerobic and anoxic phosphorus removal. Operation showed that at room temperature, control pH can increase phosphate accumulating organisms (PAO) and significantly reduce glycogen accumulating organisms (GAO), but GAO still presented in the system. When the carbon source was alternatively supplied, GAO rapidly reproduction leads to system deterioration, limited its application in treatment of high concentration wastewater. In view of this, we came up with a combination of aerobic and anoxic phosphorus removal mode to improve biological phosphorus removal ability and stability. It showed that combination pattern of phosphorus removal (aerobic reaction 2 h combined with anoxic reaction 1.5 h) steady removed 50 mg/L PO43"-P and 50 mg/L NO3--N, it's nitrogen and phosphorus removal is the same to ideal DPAO process, but it has better stability and is more suitable for piggery digested water.(4) On the basis of basic research with simulated wastewater, coupled process ability and stability were investigated with actual digested wastewater. Results showed that DO and pH is most important for Sharon docking with the Anammox efficiently. DO control for aerobic phase have significant influence on the removal of PO43"-P 2h aerobic reaction time with DO 6 mg/L is optimum. When the actual digested wastewater influent contains COD 700-2000 mg/L, NH4+-N 500-700 mg/L, PO43"-P 35 mg/L, the"Sharon-Anammox coupled with DPAO" removal process effluent COD 150-200 mg/L, NH4+-N 20-25 mg/L, PO43"-P 6 mg/L, without NO3"-N and NO2"-N. Thus, The coupled process proposed in this study is superior to those of conventional treatment process as it's higher operating load, removal rate and stability. It has potential practical applications ability.