| Contaminant gross control of water pollutants is an urgent and arduous task in pollution prevention work, the final demand form of whose three classifications is capacity gross control. One key problem of water environment capacity research is reasonable calculation and optimal allocation. Those researches based on control unit division can supply an effective connection between the minimum space vehicle of basin environment management and water quality targets of the study basin, which makes one of the important management methods in water environment capacity gross control.There are national control unit, provincial control unit, county control unit, town control unit and so on according to the size of administration area. Given cumulative effect and avoiding repetition,1000km2is the suitable space limit of town control unit. Division of control units is completed by quantitative, automatical method and then artificial auxiliary modification from angle of water quality to land pollution sources, through certain principles and different indicators. Water environment capacity is formed by three types of self-purification capacity, dilute capacity and delivery capacity. Designed parameter and model based on presetinvestigation is key to water environment capacity calculation. Such multiple dimensions in current models are zero, one, two and even three-dimensional. Comprehensively proportion distribution, multi-objective optimization allocation model, analytic hierarchy processes (AHP), gini coefficient are the four most widely used allocacation methods in water environment capacity research field.As study area of the paper, Changzhou city in Jiangsu province was divided into13town control unit and serisd from101to113based on water ecological function zone, water system map, town administrative division, pollution source distribution and contol section position. Monomial water quality index evaluation was carried out to monitor two common pollutants (CODcr and NH3-N) of plentiful, flat, dry such three water period and59control section in13town control units. Results chosen CODcr as the main pollutants of research area. Chosing different models for rivers and lakes, water environment capacity of13control units could be got by addition of calculation results. Ge Lake wasn’t included in subsequent research as113control unit individually because it didn’t have land source. Comparing CODcr calculation results of water environment capacity with total emission amount of actual land pollution sources in only101to112units,103,107,109,111were chosen as four priority units for their overweight rate higher than30percent. Among the four,111-Wunan River Unit had the largest overweight rate up to36.1percent. Within the priority control unit111, this study constructed a three layer distribution system of "pollution type-pollution detailed type-sewage individual", selected a more-than-one-level index system of such aspects as economic, sociecity and environment every class of every layer, then calculated synthesis weight based on the index system, and finally distributed environment capacity from control unit to sewage individual according to the integrated weight. CODcr capacity allocation results of three layer structure conformed to emission status, abatement level and cut potential in Wunan River control unit. The results also provided guidance for COD cut of key pollution sources and input distribution in future, which could make certain senses in basin environment management. |
