Two-echelon Decision-making Research On The Separated Msw Transportation And Treatment System Based On "2+n" Mode

An effective measure to improve the municipal solid waste(MSW)management levels and the quality of sanitation is to conduct source separation,separated collection and transportation,and separated treatment,instead of just burning or burying it.Therefore,the separated MSW transportation and treatment system is becoming a priority for the administrators of many cities in China.Decision-making on the separated MSW transportation and treatment system scientifically and rationally is a complex project,involving multiple parts including source separation,separated collection,separated transportation and separated treatment.At present,most researches on MSW source separation and building the separated MSW transportation and treatment system have two problems:1)the rational and effective indicator used to evaluate the effect of source separation is lacking;2)the global consideration of the different categories of waste streams in the separated MSW transportation and treatment system is lacking and the possible interrelations between these waste streams that may be built by intermediate sorting are ignored.To address these needs,this work conducts a two-echelon decision-making research on the separated MSW transportation and treatment system.The thesis introduces the "2+n" mode of MSW separation to help study two main points including "source separation of MSW" and "transportation and treatment system".The core of the mode is to give priority to the two-category methods at source separation node and in the initial stage,and to further elaborate it at different sources or with the development of source separation.This mode includes two meanings,namely "first the easy,then the difficult;first the rough,then the fine" and "rough separation at source,fine sorting at intermediate node".A two-echelon decision-making system of the separated MSW transportation and treatment system is built based on this mode.First,taking the optimal "effect" of source separation as the point of penetration,this research proposes an effect evaluation indicator(namely effect coefficient ?)combined with the characteristics of classifier problem and consistency check problem.The indicator can be used as a tool to evaluate and compare the effects of different source separation methods,and the first-echelon decision-making can be accomplished by selecting the optimal one.Secondly,taking the optimal "benefit" of the separated MSW transportation and treatment system as the point of penetration,the operational research tool is used to build a global programming model for the separated MSW transportation and treatment system with the decision-making of intermediate sorting on the basis of in-depth analysis of system structure.The model takes the result of first-echelon decision-making as one of the inputs,and the outputs include the routing of different waste streams,the categories of waste sorted in the intermediate nodes,the sites,numbers and capacities of the transportation and treatment facilities,etc.Then the second-echelon decision-making can be accomplished.Based on the results of two-echelon decision-making,the integrated separated MSW transportation and treatment system can be built.The proposed two-echelon decision-making system is applied in a case study in Yuelu District of Changsha.First,a site experiment of source separation was conducted in a community of Yuelu District.Based on the experiment results,the confusion matrixes of the effects of source separation are formed.Combined with the cost matrix,the effect coefficients ? of four different separation methods are calculated.The results show that,the effect coefficients of two-category(food waste and other waste,F&O)separation method,two-category(recyclables and other waste,R&O)separation method,three-category separation method and four-category separation method are 0.609,0.448,0.417 and 0.392 respectively,and their descriptions are "good","fair","fair" and "poor"respectively.The results of first-echelon decision-making indicate that the two-category(F&O)separation method should be applied in the generation sources of Yuelu District.On the basis of the results,the genetic algorithm is used to solve the proposed global programming model for the separated MSW transportation and treatment system with the decision-making of intermediate sorting.The results of second-echelon decision-making indicate that the total cost of the system is 35.54e+04 yuan per day,and the average cost of MSW per tonne is 200.6 yuan/t.Shipping cost takes up the highest proportion in the total cost,which accounting for 70.07%,and the whole transportation part(including transfer station cost)accounts for 76.96%.The system include 2 transfer stations with sorting function,1 food waste treatment plant and 1 recyclables treatment center.Food waste and recyclables should be sorted for further treatment in both of the transfer stations with sorting function.Compared with the mixed transportation and treatment system,the separated MSW transportation and treatment system saves 15.9 yuan/t and 7.34%regarding the average cost of MSW per tonne.The advantage of the system is that,the pollution from the MSW which is effectively separated is easier to control,thus part of the separated MSW can be treated by relevant facilities in the planning area,which avoids long distance transportation.Lastly,the two-echelon decision-making research is accomplished by making relevant suggestions on planning and management of the system through sensitivity analysis.The research results suggest that,the proposed effect evaluation indicator has good applicability,which can help decision makers determine the optimal source separation method with good effect;the proposed two-echelon decision-making system can provide some references for the planning and construction of separated MSW transportation and treatment system in our country.