Application Of The Improved Fuzzy Comprehensive Evaluation Method In Water Quality Evaluation

Due to the rapidly developing industrialization and the continuously increasingpopulation, water pollution is becoming more and more serious. So water environmentproblem has seriously affected the sustainable development of economy and society inChina. To protect the rational development and utilization of water resources, waterenvironment must be scientific planning and management, and water quality evaluationis an important means of supervision and management of the water environment.The traditional fuzzy comprehensive evaluation method had five influencingfactors, such as evaluation index, membership function, weight assignment, fuzzyoperation and comprehensive evaluation. Through research and analysis on these factors,we established an improved fuzzy comprehensive evaluation method(FCEM). This methodcombined analytic hierarchy process and entropy weight method in an effective way tocalculate weight assignment, and used the multiplication addition operator and theweighted average principle to evaluate the water quality. Because of the above features,the improved FCEM has been successfully applied to evaluating a reservoir waterquality in Chongqing. The research can not only improve the evaluation method itself,but also provide the basis for the environmental protection department management. Weobtained the following conclusions:1) Through the analysis of the weight assignment, then formated the combinationweighting method, effectively combining the analytic hierarchy process and entropyweight method. This combination weighting method considered the influence of themaximum pollution index on water quality, and the interactions between differentpollution indexes. The weight assignment was more in line with the actual situation ofwater quality.2) In traditional FCEM, the weight assignment only selecting single method whichis one-sided, and maximum membership degree principle which is easy to lose data maylead the evaluation results unreasonable. Then the improved FCEM could overcomethese disadvantages, in which the multiplication addition operator was applied toblurring operation, the weighted average principle was using to comprehensiveevaluation. Quantitative sequence on water quality grade made the result morereasonable.3) Through the application of the improved FCEM, it was concluded that in2013 the water quality of the reservoir, October＞May＞January＞April＞December＞November＞February＞March＞June＞July＞August＞September. Thecomprehensive water quality is Ⅰ~Ⅲ, and the worst water quality time of the reservoirwas September, followed by June, July and August.4) Through the comparison of the improved FCEM and artificial neural networkmodel, the evaluation of the results obtained are in good agreement, compared withtraditional method could better reflect the reservoir water quality standards. And theresults of the evaluation were more reasonable. The application of MATLAB softwaremade the improved FCEM more practical.