| With the urban expansion, population growth and the improvements of residents’ living standards, bring new challenges to integrated management of solid waste (SW). The Waste Collection and Transportation System (WCTS) is an important component of Integrated Municipal Solid Waste Management System (ISWMS), as well as a key issue of urban sanitary services. Therefore, optimization of WCTS is an important support to the urban ecosystem and sustainable development of WCTS.Based on the present research, the systematic optimization of WCTS, is extended in urban geographical space. The dissertation can be divided into five parts as follows:Firstly, the background and significance of the original research are introduced. The aim is to investigate the locations of the nodes and related combinatorial optimization problems, and involve the allocation and cost-effective optimization of WCTS.Secondly, the paper has reviewed domestic and foreign literatures that comparing or summarizing respectively from perspectives of integrated solid waste management (ISWM), system planning and operational optimization, includes the following aspects of collection/transportation modes and technical methods, recycle and separated collection, technical and economic analysis and evaluation, planning layout and facility location, capacity configuration, and network analysis. In addition, the application of geographic information system in WCTS is also reviewed.Thirdly, the concepts, constitution, function and modes of urban WCTS are well discussed. Three collection and transfer modes, namely direct mode, level-one transfer mode, and level-two (multi-level) transfer mode, are thoroughly analyzed. Moreover, according to the correlation of WCTS and spatial geometry, the system of geographical units related to WCTS is advanced.Fourthly, the optimization model of WCTS based on geographical units is established, by linking geographical units with waste collection areas correspondingly in Geographic Information System (GIS), which aim to solve the location problem of facility nodes and extract the geographical units. And then, the global optimization model, namely a mixed integer nonlinear programming model (MINLP) with single objective is presented, which is meant to minimize the total cost of the collection and transport system. The model covers selective indexes of facilities scale, routing selection, vehicle allocation, personnel assignment, which abstracted as the related0-1decision variables. Main constraints, such as the effective operation time of the system, vehicle configuration that allowed to the node facilities, has been setup in order to achieve the completion of waste collection and transportation operations. Besides, quantitative regulations from current industry standards about waste collection and transportation is set as constraints or parameters in this model, in order to achieve generic significance while considering the actual situation.Fifthly, in case study, by solving the MINLP model, there are14nodes facilities and its corresponding collection and transportation geographical units. Results show that, the total generated amount of SW by prediction is540.7t/d, and total cost of WCTS is40271.6yuan per day; that is to say, the average shipping cost of solid waste per tonne is74.55yuan/t. The number of node facilities of type-Ⅰ, type-Ⅱ, type-Ⅲ of collecting stations is1,5,1, and for type-Ⅳ, type-Ⅴ of transfer stations, the number is5,2respectively. The total area of entire collection geographic units is69.24km2, which accounting for about3.68%of the total land area of the urban domain. The results also indicated that, for small cities or towns with its relatively independent collection geographical areas, it’s reasonable to adopt the direct mode and supplementary level-one transfer mode.To sum up, the dissertation has researched the based on a combination optimization of WCTS based on geographical units at theoretical level, and its conclusions also has reference value in solving relevant practical problems. |
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