Study Of Nitrogen And Phosphorus Removal And Microbial Character On The Combination Of Simultaneous Nitrification/Denitrification And Denitrifying Phosphorus Removal

Because of the existed problem that insufficient carbon source in wastewater and high aeration energy consumption for biological nitrogen and phosphorus removal in domestic wastewater,a novel process based on SBR was proposed with seven stages:feeding-anaerobic stage-low oxygen aeration stage-anoxic stage-aerobic stage-sedimentation-drainage.Phosphorus release conducted in anaerobic stage,simultaneous nitrification and denitrification(SND)in low oxygen aeration stage,denitrifying dephosphatation in anoxic stage,nitrification and phosphorus uptaken in aerobic stage,the combination of SND and denitrifying phosphorus removal was achieved in the single sludge system.The effluent concentrations of COD,NH4+-N,NO3--N,NO2--N and TN in SND reactor after the domestication process finished were 9 mg/L,3.77 mg/L,7.46 mg/L,0.17 mg/L and 12.83 mg/L;DPR was developed in three stages,and the final effluent COD,NO3--N and TP concentrations were 11 mg/L,5.03 mg/L and 0.2 mg/L.SND sludge and denitrifying phosphorus sludge were mixed and further domesticated after the sludge acclimation finished.The combination of SND and denitrifying dephosphatation was achieved when the effluent concentrations of COD,NH4+-N,TN and TP were stable around 13mg/L,2.52mg/L,9.73mg/L and 0.24mg/L,respectively,which met the A atandard of the Discharge Standard GB18918-2002.The microbie shape in SND reactor was globular mainly,and Alcaligenes faecalis,Paracoccus denitrificans,Hyphomicrobium sp.,Dechloromonas sp.may exist in the system for denitrification,while Aurantimonas sp.,Nitrobacter winogradskyi,Nitrosomonas sp.mammonia oxidizing bacteria served as nitrification and ammonia oxidation.The microbe shape in DPR reactor was globular and short rod,and there may have Acinetobacter sp.with phosphorus accumulating effect and Rhodocyclus sp.,Streptococcus sp.,Arthrobacter sp.with the function of denitrifying phosphorus accumulating.In the coupling SBR system,many bacillus brevis,spherical bacteria and few filamentous bacteria were observed by SEM?PCR-DGGE and High Seq sequencing technology were applied for the study of microbial community composition.It presented that Nitrobacter winogradskyi,Aurantimonas sp.for nitrification,Paracoccus denitrificans,Hyphomicrobium sp.and Dechloromonas sp.functioned as denitrification,while Streptococcus sp.,Arthrobacter sp.,Enterobacter sp.and Pseudomonas sp.were the dominant bacteria for phosphorus accumulation.In the initial coupling system,the number of OTU of was larger atfirst,and the OTU value was smaller after trained for 93 days and 101 days,indicating that the microbial diversity was smaller and the domestication effect was better.CSmay CSJun and CSJul sample have higher Shannon index,indicating that the system has a higher diversity of microorganisms during the domestication period from 25 to 93 days.Chao index of CSJun CSJul and CSAug is relatively low after domestication for a period of time,indicating that the microbial species abundance reduced in the reactor,and the specific species selection and enrichment was achieved.In the early microorganism domesticated stage of the coupling system,only small similarity in community structure.The similar degree of microbial community in the sludge increased after the domestication proceeded until the microbial structure was stabilized.The dominate strains in the coupling system were Proteobacteria(26.65%),Bacteroidetes(1.82%),and Nitrospirae(0.997%).The initial pH in the coupling SBR system affects the activity of different functional coenzyme.DHA was more active in the anaerobic and SND section,and began to gradually decline from anoxic to aerobic period.More,DHA activity increased with the increase of pH value;PPK and ADK activity changed little during one whole cycle,while PPK activity decreases with the increase of pH,with the optimum pH 7.6;ADK activity changes less than 2.5%and ADK activity increases with the increase of pH.HAO enzyme activity increased with the increased of pH.NAR and NIR enzyme activity declined both with pH increasing.When pH increased from 7.2 to 8.0 in the coupling system,the NAR and NIR enzyme activity decreased from 11.83 mU/mg protein to 3.53 mU/mg protein,and from 4.79 mU/mg protein to 0.729 mU/mg protein.In the SND system,the number of AOB,NOB,GAO and Denitrifier was alike,and the bacteria related to nitrification and denitrification were dominant in the reactor.A large number of PAOs were concentrated in the DPR reactor,which was the dominant strain in the system.In the coupling SBR system,quite large number of AOB,NOB,PAOs and Denitrifier served as the dominant strain after stable operation,and the condition in the system can surport the growth of these functional bacteria.The relative abundance of PAO,AOB,NOB,and denitrifier existed in the combined-SBR system was stabilized at 41±11%,10±4%,13±9%and 16±12%,respectively.The coupling SBR system enhanced the efficiency of nitrogen and phosphorus removal by applying SND and denitrifying phosphorus removal technology.It can enrich and maintain nutrient removal related microorganisms,can determine the variation of microbial population category and community structure,and the influence of external factors(pH value).The process,which relieved the carbon source competition between denitrification and anaerobic phosphorus release,is suitable for the treatment of domestic wastewater with low C/N ratio.