Research On Stochastic Model Of Organic Concentration In Constructed Rapid Infiltration System

Modeling of biological membrane process is an important part of design and operation of wastewater treatment system. In recent years, with the deep understanding of uncertainty, the uncertainty of sewage treatment system gets more and more attention and research.Therefore. in order to provide the practical theoretical basis for operation and management of sewage treatment system, it is necessary for us to use the uncertainty theory of uncertainty in the process of organic matter degradation in wastewater treatment system to carry on the system analysis and cognition, and built corresponding mathematical model. And the Stochastic differential equation is widely applied to solve complex problems about uncertainty.Constructed Rapid Infiltration system (CRI system) is a kind of wastewater land treatment method which is mainly aimed at treating the wastewater from small towns or residents. In this paper, take the CRI system as a research objective, its uncertainties of the process of organic matter degradation were studied. First, elaborates the development of mathematical model of biological membrane, and analyzes the domestic and overseas research status of uncertainties of CRI system, then based on the Biofilm mass transfer theory and material balance, builds the deterministic model of organic concentration.And.on the basis of stochastic theory, adding a random disturbance term of a wiener process to establish a stochastic model of organic concentration of CRI system, the model can be used to simulate and predicate the organic concentration in wastewater treatment process of CRI system. And then, obtains the expectation function and variance function by solving stochastic model of organic concentration. At the same time, the stochastic model is abstractly verified by means of the parameter sensitivity analysis of expectation function and variance function.At last, the model is used to simulate and analyze in an actual project of CRI system. Take a CRI system engineering in Chengdu for example, simulates the deterministic and stochastic model of organic concentration by using computer software, and the sumulation results can be concluded that:for not considering the influence of the uncertainties of CRI system in the process of builting the deterministic model of organic concentration, its simulation result is failed to reflect the disturbance changes of the water quality with height. However, the simulation result of the stochastic model of organic concentration conforms to the actual operating conditions, which can reflect the organic concentration’s random changes. The method and theory of model building are analyzed to do some exploratory work for future reseach, and also provide a new way to build and simulate the model of CRI system.To a certain CRI system, if the needed data and parameters are able to be obtained, we can predict the organic concentration and disturbance changes at different heights by using this stochastic model. And it is valuable to judging the operation conditions of the CRI system through correlation analysis, and a theoretical basis for follow-up operation and control are also provided.