The Application Research On The Uncertainty Theories And Methods In The Optimal Design Of Municipal Wastewater Treatment Plant

There are all kinds of uncertainty during the optimal design of the municipal wastewater treatment plant (MWTP). Since little emphasis on uncertainty is paid to optimal design, that alternative designs generated using classic optimal design model may not be optimal for the real design system. So it is significantly important how to take uncertainty into account validly during the optimal design of MWTP, and establish low-sensitive system to enhance the applicability in practice.In this paper, the research achievements obtained by researchers home and abroad were summarized, and the main problems and uncertainty existed during the design and operation of optimal design of MWTP have been given a concrete analysis and estimation. Firstly, concerning the objective random and uncertainty in process alternative choice for MWTP, multilevel fuzzy-grey coupling model was established by combining analytic hierarchy process, which can provide an assistant tool for decision-making for correlative sections and superiors. Secondly, for highly-nonlinear interval parameter optimal design. model of MWTP, classic optimization techniques are not only laborious in calculation, but also the global optimum isn't searched effectively. So genetic algorithm combined with typical step-search method was introduced to improve the searching efficiency. And the validity of the algorithm was verified by a practical application of the improved algorithm in optimal design of some MWTP. Thirdly, the typical Lawrence-McCarty mode, that is design method based on sludge retention time, was applied to the optimal design of activated sludge system. And at the optimal point, sensitivities of optimal design to selected values of uncertain parameters such as influent load, dynamic parameters, performance parameters of diffusers and thickening constants of final clarifier were evaluated. Finally, based on the sensitivity analysis, the robust design in quality control engineering was introduced into the optimal design of activated sludge system, and its mathematics framework and solution approach were recommended.