The Application Of BOD-DO Water Quality Model On The Determination Of The Sewage Closure Factor

Sewage closure is important measure for municipal water environmental quality control. Rather more factors such as economic, environment and hydrology should be taken into account to confirm sewage closure multiplication factor and can hardly be quantitative analyzed. Generally, the bigger the closure factor is, the more the investment will be, and the more environmental benefit will be; the less the closure factor is, the less the investment will be, but the more back effect will be. So the environment standard should be the constraint condition for water quality model and determine the reasonable sewage closure factor.All real systems are of three dimensions as water quality model concerned. But water quality model can often be simply regard as zero, one or two dimensions water model. One dimensioned water quality model can be effective on river water quality planning. One dimensioned BOD-DO model for river is a well studied and mature water quality model; it is adaptive and can reflect the reality. So the one dimensioned BOD-DO model for river is employed to plan the Anqing New River District water environment.Aiming at the speciality of the task, the paper formed relationship models among water quality and quantity of rainwater, polluted water and river water, and together flux and multiplication factor of combined system. Explicit difference method is employed to solve the one-dimensioned model, on-site testing and picktest to decide COD, BOD and DO of the water and its variety. Gradient method is employed to confirm main water quality model parameters on the ground of relationships among indexes.One-dimensioned BOD-DO model is employed to solve water environment capacity and reasonable sewage closure factor, thus new ways are put up for sewage closure factor of old city zone combined drainage system which will help to confirm the scale of drainage system and waste water treat plant.