Study On The Alternate Anaerobic/Anoxic-Aerobic Membrane Denitrifying Phosphorus Removal Process

The municipal wastewater in south C hina is characterized as low carbon to nitrogen ratio(C/N) and carbon to phosphorus ratio(C/P), the effluent nitrogen and phosphorus of traditional processes are often hardly meet the standard for the low C/N 、C/P wastewater treatment. Denitrifying phosphorus removal process exhibits effcient treatment of simultaneous nitrogen and phosphorus, and has the advantages of carbon requirement reducing and lower sludge production. In this study, aiming at low C/N 、C/P wastewater treatment, we created an innovative double sludge denitrifying phosphorus removal processes based on the existing A2 N, called alternate anaerobic/anoxic–aerobic membrane denitrifying phosphorus removal process(A2N-MBR). We started-up the A2N-MBR process with acetate as the sole carbon source, along with the A2N-MBR long-term continuous running,the treatment efficiency of biological nutrient had been investegated.Then the effect of different carbon sources(acetate、propionate、acetate and propionate mixed(1:1)、glucose) on nitrogen and phosphorus removal perfermance and community structure when the A2N-MBR was operated steadily.(1)Anaerobic/anoxic SBR of the system was inoculated with the activated sludge from the reactor that had been successfully enriched with DPB.Then we started-up the reacter with acetate、propionate、acetate and propionate mixed(1:1)、glucose as the carbon sources, respectively. When the carbon sources were acetate、propionate、acetate and propionate mixed(1:1),the total phosphorus concentration(TP)of influent was 6.6-6.8mg/L, the influent N/P ratio were 8.8、6.1、6.8, respectively,the A2N-MBR process achieved the best removal efficiency, the whole total phosphorus effluent were about 0.5mg/L, the phosphorus removal efficiency was above 92%, the whole total nitrogen effluent were under 12.5 mg/L, the nitrogen removal efficiency was above 77%, CO D 、 NH3-N and TN met the first grade A standards of GB 18918-2002.When the system took glucose as carbon source, COD、NH3-N、TN removal efficiency were respectively about 91%、94%、73% in the system, the effluent concentration of COD、NH3-N and TN were respectively 20mg/L、2.4mg/L、11.4mg/L, but the phosphorus removal efficiency was relatively poor, the average removal efficiency was 58.6%, the effluent concentration of phosphorus was 2.6mg/L.(2)There was a positive correlation between p H 、 ORP curve and COD consumption curve、P-release curve in the system with acetate as carbon source. p H and O RP could be used as the control parameters for phosphate release, ORP also could be used to indicate the end point of the phosphate uptake in anoxic phase.(3) There was linear relationship between phosphorus uptake and nitrate consumption with with acetate and propionate as carbon sources, the phosphorus uptake/NO3--N reduction ratios were respectively 1.21、1.04. To the electron acceptors of nitrite, the phosphorus uptake/NO2--N reduction ratios was1.0(the nitrite concentration was 20 mg/L in initial test) in the system with acetate as carbon source. When the nitrite concentration was as high as 20mg/L, there was an inhibitory effect on denitrifying phosphorus removal in the system with propionate as carbon source.(4) The phosphorus removal efficiency in the systems with four kinds of carbon sources(acetate、propionate、acetate and propionate mixed(1:1)、glucose) were analysed, the concentration of anaerobic phosphorus release in the system with acetate as carbon source was the highest, but which was the least in the system with glucose as carbon source. It took the least time to anaerobic phosphorus release and anoxic phosphorus uptake in the system with propionate as carbon source, the anaerobic phosphorus release efficiency of sludges with four kinds of carbon sources were averaged at 4.60 mg P/g MLSS·h 、 2.75 mg P/g MLSS·h 、 2.59 mg P/g MLSS·h 、0.78 mg P/g MLSS·h, respectively,organic substrate utlization efficiencies(P/C) in anaerobic phase were respectively 0.17、0.12、0.13、0.03, the anoxic phosphorus efficiency of four systems were averaged at 7.3 mg P/g MLSS·h、6.45 mg P/g MLSS·h、6.02 mg P/g MLSS·h、2.54 mg P/g MLSS·h.(5) The sludge community structure of the A2N-MBR was analyzed,the anaerobic and aoxic seed sludges had the richest microbial diversity. Secondly was the sludge fed with acetate. Sludge fed with acetate was more similar with the seed sludges than others, they had the common proportion of 35.8%. At the phylum level, Proteobacteria was the most abundant phylum for the seeds and system sludge samples with four kinds of carbon sources. The abundance of Proteobacteria、Chloroflexi and Bacteroidetes reached above 90% in system sludges with differents carbon sources. At the genus level, The abundances of Candidatus Accumulibacter and Dechloromonas(PAO-like) were rather high. The relative abundances of Candidatus Accumulibacter in four systems with propionate、acetate and propionate mixed(1:1)、glucose as carbon sources were respectively 38.7%、20.7%、34.4%、21.5%, whereas,the abundances of Candidatus Accumulibacter(GAO-like) were more and more higher in four system sludges, there were 1.3% 、 1.5% 、 2.0% 、3.8%,respectively.