Optimization On The Post-treatment Process For A Closed Unlined Landfill Via Aerobic Bioreactor Technology

In recent years, there are a large number of closed landfills in china. With the rapid expansion of urbanization, many landfills, which used to be in the suburbs, are located in densely populated areas, become potential pollution sources of cities. The landfills, which may cause fire and explosion, not only are occupying a large number of urban lands, but also have a huge influence on the urban environment. Therefore, how to conduct a fast treatment and ecological restoration on closed landfills is an urgent and important problem. Compared with other treatment technologies, aerobic bioreactor technology can be effectively applied in situ treatment for closed landfill due to its shorter cycle of treatment, less emission of methane, lower pollution of leachate and less cost of post-maintains.The technology of aerobic bioreactor has been applied in America, Germany, Italy and Canada, but the research on its process design is still at an early stage. Most researches on this technology are about the effect of a single parameter through experiments or simulation, in which the influence of process structure and multiparameters are ignored. So the influence of all related parameters on process designs and project investment should be considered together in the process of aerobic bioreactor design. Based on a project of the post-treatment process for a closed unlined landfill via aerobic bioreactor technology in china, its process design is analyzed to establish a mathematic model to optimize project investment in this paper. The main contents in this paper are as follows:1. A mixed-integer nonlinear programming (MINLP) model is established for the post-treatment process of a closed landfill via aerobic bioreactor technology. To optimize the project investment, the minimization of total project investment is set as the objective function and the design specifications, the material balance and the equipment parameters are considered as constraints.2. In order to get better optimization result, the genetic operator for the optimization of aerobic bioreactor process design are specified: population size N=100, maximum generation Maxgen=1000, crossover probability Pc=0.8and mutation probability Pm=0.003.3. The proposed model is employed to optimize the investment of the post-treatment process for a closed unlined landfill via aerobic bioreactor technology in China. Compared with the conventional design, the total investment is reduced by22.7%based on proposed model.