Study On The Technical Scheme Of The First Sewage Treatment In Gaoming District Of Foshan City

With the sustainable development of cities,our country pays more and more attention to the problem of environmental pollution,the national emission standards of Sewage Treatment have been gradually upgraded from Grade B to Grade A in GBl8918-2002,which put forward higher requirements on the selection of process and operation management of Sewage Treatment.Therefore,most cities are facing the problem of improving standards in Sewage Treatment.Based on the current operation of sewage treatment,this paper takes a upgrading and reconstruction project of a Sewage Treatment in Foshan as an example to design the upgrading and reconstructiong process according to the corresponding standards.The actual treatment scale of the Sewage Treatment is 78.4 million m³/d,and the effluent quality is the Grade B standard.From the analysis of the influent water quality,the BOD₅/TN is 4.06,BOD₅/TP is 28.63,BOD₅/COD is 0.42～0.77,which indicates that the carbon source of the influent water quality is sufficient,no additional carbon source is needed,and the biodegradability is very good.The standard rate of COD,BOD₅,NH₄⁺-N,TN,TP,SS is100%,100%,41.67%,25%,16.67%,25%respectively.Therefore,the key point of the improvement is to further strengthen the removal of ammonia nitrogen,TN,TP and SS.In order to select the upgrading and reconstruction scheme pertinently and to maximize the Sewage Treatment efficiency,the comprehensive evaluation system of the upgrading and reconstruction scheme of a Foshan Sewage Treatment with four levels and 16 Index-3schemes was established by using AHP method,Scheme 1（MBBR）,Scheme 2（BAF）and Scheme 3（multi-grade AO）were analyzed respectively from four aspects:technical performance benefit,environmental impact level,economic benefit and social impact,the weight of each index in the comprehensive evaluation system of a Sewage Treatment upgrading and reconstruction program in Foshan was obtained.Finally,the three alternative programs were evaluated by the expert scoring method.The total scores were 8.1358,7.8856and 7.6315,respectively,the optimal process of MBBR was determined,and the second stage biological treatment process was A/A/O micro-exposure oxidation ditch process,so the nitrogen and phosphorus removal of the second stage biological treatment process should be brought into full play,it is not only beneficial to fully excavate the existing process capacity,but also can reduce the investment cost of the upgrading and reconstruction project to the greatest extent.Therefore,adding fillers to MBBR process can increase the biomass of the current biological pond,reduce the load of the biological pond,achieve efficient nitrogen and phosphorus removal,and improve the quality of the effluent water.Finally,the rationality and accuracy of the evaluation system are verified by analyzing the effluent quality of the Sewage Treatment.The results showed that the concentration of NH₄⁺-N,TN,TP and SS were 1.26mg/L,7.37 mg/L,0.26 mg/L and 4.83 mg/L respectively,which were 32.99%,20.26%,16.34%and 5.59%higher than the original process,it can reach Grade A emission standard stably and has good environmental and social benefits.