| Aerobic granular sludge has significant advantages in water treatment,which made it a research focus rapidly in the current field of water treatment.Biological activity of granular sludge mainly depends on the structure and function of microbial communities.The aerobic granular sludge has perfect function due to its structural characteristics.The formation of the aerobic zone,anoxic zone and anaerobic zone from outside to inside the granular makes microbial communities richer.Therefore,the study of aerobic granular sludge microbial communities can provide a theoretical basis for the optimization of aerobic granular sludge treatment process,with great value.In this study,sludge was cultured firstly and the change of each index in the cultivation process was detected.And then we investigated the characteristics and microbial morphology during the formation of granular sludge.In addition,the microbial communities in aerobic granular sludge were analyzed,the specific contents were as follows:The aerobic granular sludge was cultivated with synthetic wastewater.The influent and effluent Chemical Oxygen Demand(COD),ammonia,orthophosphate and other indicators were detected under low dissolved oxygen(0.5?1 mg/L)conditions.The results showed that mature aerobic granular sludge could effectively remove COD,ammonia nitrogen and phosphorus to.The effluent COD was less than 50 mg/L,and the removal efficiency was more than 90%.The effluent ammonia nitrogen was lower than 1 mg/L and the removal efficiency was more than 99%.Simultaneous nitrification and denitrification was achieved due to the coexistence of nitrifying bacteria and denitrifying bacteria in aerobic granular sludge.The average concentration of the effluent phosphate was 0.89 mg/L and the removal rate was 67.40%with the action of phosphons-accumulating bacteria releasing phosphorus in anaerobic conditions and uptaking phosphorus in aerobic conditions.Sludge properties and microbial morphology in different periods were observed during the the formation of aerobic granular sludge.The results showed that the sludge concentration gradually increased during the cultivation,with a final concentration of 4200 mg/L.Sludge settling properties improved gradually in this process.SVI value was reduced from 71.43 mL/g to 26.65 mL/g.In the morphology,sludge became oval or round micro-particles with smooth surface and a clear outline whose surface was rough and irregular at the beginning of the cultivation.The diameter was about 0.5 mm.The microbial diversity was richer and microbial activity was higher.The microbial community structure and dynamic change of the sludge under low dissolved oxygen(0.5?1 mg/L)were analyzed by PCR-DGGE technique.We can draw that sludge microbial community structure existed some differences in which populations became more abundant and biodiversity increased obviously in different periods during the formation of granular sludge.The microbial flora great difference between granular sludge and flocculent sludge indicated that the microbial populations occurred succession in the process of sludge granulation,characterized by the disappearance of some species and enrichment of other bacteria.Micro-aerobic granular sludge was cultivated successfully after the reactor running 140 d.The microorganisms had a wide variety.There were mainly bell insects,epistylis,rotifers and nematodes whose presence increased the length of the food chain and can contribute to the removal of the pollutant.The sequencing results of dominant bacterial community showed that the dominant bacterial community in granular sludge showed high homology(more than 95%)to Caldilinea aerophila,Acidovorax temperans,Curvibacter delicatus,Pleomorphomonas oryzae,Microbacterium ginsengisoli,Pseudomonas psychrophila and Thauera aminoaromatica,which played an important role in various stages of SBR processing respectively. |
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