Determining The Operational Condition Of Muct And A~2O Processes For AO Process Upgrading For Municipal Wastewater Treatment

With the development of agricultural and industrial industry, the pollution in thenatural water body caused by the wastewater is increasingly serious and it is imperative topromote the capability and capacity of sewage plants. The research subject discussed in thisthesis was against this background. In the level of lab experiment, the A~2O and MUCTprocess were selected to modify the present process used in certain municipal wastewatertreatment plant which adopted SDAO process and then to verify their process conditions.A pilot scale study adopted Synchronous domestication method. During initial periodwithout adding carbon source, removal rates of COD and NH4+-N in the effluentreached95%and90%, meanwhile concentration of the effluent could meet thedischarge standard of first class A in GB18918-2002, however, removal rates of TP andTN were worse. Removal rates of TP and TN could reach a steady state, that is, thereactors started successfully after adding carbon source.In the constrast experiment between A~2O process and MUCT process: eachmonitoring index all reached the discharge standard of first class A in GB18918-2002.In the experiment simulating sludge drain, restorability of A~2O process was favourable;after adopting a step-feed on MUCT prcess, removal efficiency of TN and TP improvedobviously, average concentrations of TN and TP in the effluent were （20.3±2.1)mg/Land （0.9±0.4)mg/L.The results from the control experiments were as follows: when the sodium acetatewas taken as the carbon source, the optimal phosphorous release ranged from15mg/L to25mg/L and the TP of effluent can be up to the first class B standard in A~2O process,the TP of effluent can be up to the first class A standard only if the optimal phosphorousrelease between20mg/L and30mg/L in MUCT process. When the glucose was takenas the carbon source, the phosphorous release ranged from8mg/L to20mg/L and theTP of effluent can be partially up to the first class B in A~2O process, while the removalefficiency of MUCT was less effective. The conclusion was achieved that thephosphorous removal effect of the two processes was better when sodium acetate ascarbon source than glucose and that the formation of simple organic substances such asVFA might be the constraint factor in phosphorous removal process.The results of PCR-DGGE experiment showed that the difference of nitrogen andphosphorous removal effect was related to the enrichment degree of preponderantfungus. The filamentous bacteria bands were found in every reaction tank except theaerobic tank in MUCT process, therefore it was possible that filamentous bulkingexisted in these tanks. To improve the effluent effect, the process parameters should beadjusted or some types of packing should be added so as to hold back the preponderantfungus. The quantitative PCR experiments showed that the microorganism in A~2Oprocess was stable, while that in the MUCT process fluctuated dramatically.The results showed: A~2O was better than MUCT significantly. the COD、NH4+-N andTN of the A~2O effluent were all close to standard A of first class in GB18918-2002, and TPcould only conform to standard B of the first class so that the A~2O needed to be assisted byother phosphorous removal devices. The effluent TP conformed to standard A of the firstclass in GB18918-2002when sodium acetate was used as supplementary carbon source,and this type of supplementary carbon source would not have influence on othernutrient removal targets. This research had favorable reference function to the pilotplant experiments.