| With the development of urbanization,the discharge of municipal wastewater has increased rapidly with each passing year.At present,aerobic treatment is widely used in municipal wastewater treatment.Good removal efficiency can be achieved in the aerobic system,but it has many disadvantages,such as large space requirements,high construction and operating costs and so on.Anaerobic treatment is an attractive technology because of its small layout aerea,low sludge production,low operational cost,and production of methane.The application of anaerobic treatment of municipal wastewater has not yet been fully promoted,so further research and development are still needed.Synthetic municipal wastewater was treated using a strengthen circulation anaerobic reactor(SCAR)with anaerobic granule sludge.The effect of temperature and Alkalinity on the pollutant removal efficiency and characteristics of granular sludge were systematically investigated in this work.The distribution characteristics and evolution of microbial community were analyzed by high throughput sequencing.The main conclusions were as follows.The results of the experiment demonstrated that temperature changes(40?~14?)did not show obvious influence on the COD removal rate,and the COD removal efficiency was always above 81%.Decreasing the temperature resulted the increment of the proportion of median diameter(0.85 ~ 2mm)granular sludge.With the temperature gradually decreased from 40? to 14?,the dehydrogenase activity and the specific methanogenic activity increased initially and then reduced,while the content of EPS presented an opposite trend,especially the S-EPS and TB-EPS significantly increased at a temperature of 14?.The results showed that COD removal rate remained constant with the decrease of alkalinity,but when alkalinity decreased further,the COD removal rate began to decrease,and effluent VFA accumulated slightly,what's more,massive large granular sludge(?>2.4mm)disintegrated,resulting in more sludge floes in the effluent of the reactor.The SMA and DHA,which were both lower under low temperature conditions,showed a decreasing trend with the decrease of the alkalinity of the influent.The content of EPS increased with the decrease of the alkalinity of the influent,which was mainly caused by the increase of polysaccharide,while the content of the protein did not change significantly.In the analysis of diversity of microorganism,it was found that when the temperature drops from 30°C to 14°C,the diversity of bacteria in the same space of the reactor did not change much,while the diversity of archaeal increased.When at the same temperature,the bacterial diversity in the main reaction zone is greater than that in the enhanced reaction zone.The diversity and abundance analysis of microorganism community showed that,under the different temperature conditions,the predominant bacteria in the phylum distribution of the bacteria were Bacteroidete and Chloroflexi,and maintain a relatively high relative abundance;the predominant archaeal in thegenus distribution of the archaeal were Methanosaeta and Methanobacterium.The decrease of temperature had a significant effect on the distribution characteristics and evolution of microbial community.With the decrease of the temperature,the dominance of Bacteroidete decreased gradually,while the Firmicutes and KSB3_Modulibacteria presented an opposite trend.The abundance of Chloroflexi was decreased gradually in the main reaction zone,while it presented an opposite trend in the enhanced reaction zone.Decreasing the temperature resulted the decrease of the abundance of Methanobacterium,and the dominant archaeal changed to Methanosaeta. |
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