Operation Characteristics Of Double Sludge Process With Post Aeration Membrane

The urban domestic sewage in south China has the characteristics of low COD/P water quality,and it is difficult to reach the standard of nitrogen and phosphorus in the traditional process of treating low COD/P wastewater.Denitrifying phosphorus removal process has good effect of simultaneous nitrogen and phosphorus removal,at the same time,it can save carbon source and reduce sludge yield.a new modified double sludge denitrification and phosphorus removal process?A₂NO-MBR?is proposed on the basis of the existing A₂N double sludge process with this paper aims at the low COD/P urban sewage;The paper mainly researches on operating characteristics and variation characteristics of community structure with the process for treating simulated domestic wastewater and actual domestic wastewater.?1?A₂NO-MBR process was used to treat simulated domestic wastewater,the effluent COD was all lower than 30mg/L,the effluent ammonia were 1mg/L,2.5mg/L,7.3mg/L,6.92mg/L and 5.59mg/L and effluent TN were 16.96mg/L,11.4mg/L,14.5mg/L,9.92mg/L and 8.94mg/L with the COD/P ratios for 20,30,40,50 and 60,respectively,the effluent TP was 0.73mg/L which was much higher than that 0.1mg/L of other COD/P ratios systems when the influent COD/P ratio for 20;The online monitoring of p H and ORP could be used to reflect the process of anaerobic phosphorus release and denitrifying phosphorus removal process,ORP could also indicate the degree of anaerobic phosphorus release;DO and p H could be combined to indicate the nitration reaction end point,so p H and ORP could be combined to indicate the A₂NO-MBR process characteristics of anaerobic phosphorus release and anoxic phosphorus uptake.?2?A₂NO-MBR process was used to treat the simulated domestic wastewater,and the activity of sludge decreased with the COD/P ratio decreasing;Releasing phosphorus rate and sludge phosphorus content changed maximum at the early stage of anaerobic with the COD/P ratio for 60,followed by the ratio of COD/P for 50,40and 30,respectively,the ratio of COD/P for 20 change minimum in the system,and the change of COD concentration in anaerobic phase was linear relationship with the amount of phosphorus released from the sludge;The ratio of denitrifying phosphorus removal rate and aerobic phosphorus removal rate continuous decreased with the increasing of influent COD/P ratio,and the highest reached 96.4%;The PHB of the sludge storage in the body was used as electron donor by phosphorus removal microorganism for denitrifying phosphorus removal and aerobic phosphorus removal in anoxic phase and post aeration phase.?3?Microbiological analysis results show seed and sludge samples from different systems all took Proteobacteria as the leading at the phylum level,and the proportion of Proteobacteria,Bacteroidetes,Chloroflexi and Chlorobi in sludge samples from A₂OSBR systems of simulated domestic wastewater COD/P ratio for 50,simulated domestic wastewater ratio for 20 and the actual domestic wastewater were all higher than 90%,followed by Seed,and it was least in the sludge sample of N-MBR systems.In the genus level,the proportion of Candidatus Accumulibacter and Dechloromonas related with PAOs in the sludge from A₂OSBR systems of simulated domestic wastewater COD/P ratio for 50,simulated domestic wastewater ratio for 20and the actual domestic wastewater accounted for a larger proportion,which were20.9%,10.89%and 13.5%,respectively,but the proportion of Candidatus Competibacter with the relevant GAOs were 9.44%,10.94%and 15.07%,respectively;Nitrospira and Nitrosomonas in the N-MBR significantly got enrichment.?4?The results showed that A₂NO-MBR process was used to treat actual domestic wastewater,the influent COD,ammonia,TN and TP were 100³20mg/L,50⁵7mg/L,52⁵9mg/L and 4mg/L,respectively,the effluent TN were 22.5mg/L,15.56mg/L and 13.48mg/L with the COD/P ratio for 27,52 and 75,respectively,effluentCODwasalllessthan30mg/L,ammoniaofeffluentwas8.53mg/L⁹.63mg/L,and effluent TP was all less than 0.5mg/L;The removal of COD mainly occurred in the anaerobic phase and the utilization rate of the COD increased with the increasing of COD/P ratio during anaerobic period;The COD and TP concentrations in the high COD/P ratio systems were much higher than that in the low COD/P ratio systems at the end of anaerobic,and the removal rate of COD and the phosphorus release rate were positively correlated with the influent COD/P ratio;The TN removal rate of system and the removal rate of TN during anoxic period increased with the increasing of influent COD/P ratio,NH₄⁺-N removal changed little under different COD/P ratios condition and the low COD/P ratio systems showed obvious nitrate accumulation at the end of anoxic;The removal rate of TP was positively correlated with the removal rate of TN and NO₃^--N during anoxic period.