Study On Comprehensive Model Of Rural Wastewater Treatment Technologies Alternative Selection

The lagging of the construction of the sewerage network in small towns in China and the scarcity of wastewater treatment facilities have resulted in low wastewater treatment rates and serious pollution of the surrounding water bodies.Although there are many wastewater treatment technologies in small towns,there is a lack of wastewater treatment technologies optimization for different types of small towns.The wastewater treatment process selection model for small towns is convenient for decision makers to determine the optimal process from a large number of wastewater treatment processes,shorten the time for decision making.The optimization of wastewater treatment process in small cities and towns is a multi-objective decision-making problem.At present,single-objective optimization decision-making methods,such as cost-benefit analysis,are still widely used.Those methods do not fully consider the impact of various factors and are therefore biased.This dissertation adopts a fuzzy comprehensive evaluation method to establish a three-level fuzzy comprehensive evaluation system that includes three indicators of economy,technology,and management,including eight indicators and fifteen wastewater treatment technologies.The types of the small towns in each province were divided into four aspects which are the degree of economic development of small towns,the amount of water resources,and the control Temperature and typical topography,the two-by-two comparison method in the analytic hierarchy process was studied in the determination of the weight of the indicator.Therefore,a small town wastewater treatment process optimization model was established through the modified fuzzy comprehensive evaluation method.The main research contents of this dissertation are as follows:The 15 most widely used technologies in the 935 small town wastewater treatment plants investigated were A/A/O,CAS,oxidation ditch,A/O,constructed wetland,contact oxidation,MBR,A/O+ constructed wetland,and A/A/O + advanced treatment.The 15 wastewater treatment technologies were selected as the assessment technologies.In this dissertation,the grey relational analysis method is used as the verification method of the fuzzy comprehensive evaluation method.Taking wastewater treatment technologies optimization in Chongqing as an example to establish a comparative analysis of the grey correlation analysis model and the fuzzy comprehensive evaluation decision model.In the Fuzzy Comprehensive Evaluation Model The degrees of constructed wetlands,A/O+ constructed wetlands,SBR,oxidation ditch,A/A/O,CASS,FMBR,MBR,contact oxidation processes,A/A/O+ advanced treatment,A/O,A/A/O +BAF,BAF,contact oxidation +constructed wetland,A/A/O+MBR were 0.73,0.70,0.68,0.62,0.59,0.59,0.58,0.57,0.56,0.51,0.51,0.43,0.40,0.36,0.32;The gray correlation analysis of the above technologies in the grey correlation analysis model is respectively 0.77,0.62,0.62,0.57,0.55,0.55,0.55,0.58,0.53,0.52,0.52,0.49,0.47,0.45,0.46.That is,the constructed wetlands,A/O+ constructed wetlands,and SBR processes are the best in the wastewater treatment process in small towns in Chongqing,followed by oxidation ditch,A/A/O,CASS,FMBR,MBR,and contact oxidation processes and A/A/O+ advanced treatment,A/O,A/A/O +BAF,BAF,contact oxidation +constructed wetland,A/A/O+MBR are the least applicable.The evaluation results of the two methods are the same,so the reliability and accuracy of the fuzzy comprehensive evaluation model established in this paper is high.The fuzzy comprehensive evaluation model was used to optimize the wastewater treatment technologies in small towns in 31 provinces across the country.The optimization results were: The optimization results in Shanxi,Heilongjiang,Anhui,Jiangxi,Hubei,Hunan,Guangxi,Hainan,Chongqing,Sichuan,Guizhou,Yunnan,Shaanxi,Gansu,Qinghai and Xinjiang were consistent,that is,the constructed wetlands,A/O+ constructed wetlands,SBR,and oxidation ditch are the best,followed by A/A/O,CASS,contact oxidation,MBR,FMBR,and A/A/O+ advanced treatment processes.A/O,A/A/O +BAF,BAF,contact oxidation +constructed wetland,A/A/O+MBR are the least applicable;The optimization results for Beijing,Tianjin,Shanghai,Jiangsu,Shandong showed that MBR,A/O+ artificial wetland,FMBR,CASS are the best technologies,followed by A/A/O + advanced treatment,A/A/O +BAF,SBR,A/A/O,A/A/O +MBR,oxidation ditch.The least suitable processes are A/O contact oxidation,BAF,contact oxidation +constructed wetland,constructed wetland;The results for Tibet,Hebei,Inner Mongolia,Liaoning,Jilin,Zhejiang,Fujian,Henan,Guangdong and Ningxia showed that the A/O+ constructed wetlands,MBR,CASS,and SBR are the best,followed by FMBR,oxidation ditch,A/A/O,A/A/O + Advanced treatment,A/O,constructed wetland.The least suitable processes include contact oxidation,A/A/O +BAF,A/A/O +MBR,BAF,contact oxidation + constructed wetlands.