| With China’s increasingly serious problem of surface water pollution, standardsof sewage treatment continue to improve. Shanxi Province issued "The three yearsaction plan on Weihe pollution control". And the Xi’an Municipal Government issueda document "Urban sewage treatment plant pollutant discharge standard"(GB18918-2002) in2013which required the urban sewage treatment plant shouldmeet an A standard, and those can not meet the emission standards wastewatertreatment plant must be upgrading. Based on the background, this thesis is aboutstudying the A2/O process of Xi’an sewage treatment plant, resolving the long termproblem of water quality, and proposed the corresponding upgrade program. Theimprovement of Weihe River water quality in Xi’an has important social andeconomic benefits.After running research and analysis to the sewage treatment plant process and theindicators of water, COD, BOD5, SS, ammonia can reach a stable level A standards,but exceeded TN and TP indexes are the main limiting factors which caused thewater can’t meet the A standard. The results of analysis showed that the cite sewagetreatment plant has problems such as: carbon shortage, poor anoxic denitrification andhigh level of anaerobic nitrate of phosphorus, and so on.For the above problems, the rehabilitation is below: transfer the inverted A2/Oprocess into traditional A2/O process, increasing the residence time in order tostrengthen anoxic denitrification, disable some early sedimentation tank to increase the carbon source. Through these upgrades, the nitrate content of anaerobic tankdecreased from an average of3.67mg/L to0.17mg/L, the dissolved carbon ofanaerobic tank increased from25.69mg/L to31.77mg/L, the dissolved carbon ofanoxic tank increased from25.35mg/L to27.14mg/L after transformation, the effectof denitrification and dephosphorization was significantly improved, and all theindexes of water can reach a stable A standard. |
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