| The shortage of water resources has become a major problem which influences the development of modern economic society. Wastewater Land Reuse could recycle the wastewater effectively with cheap cost, so it is the optimized strategy of China and the world to solve this problem.However, as far as Wastewater Land Reuse is concerned, two issues are still worth our further study. One is the selection of hydraulic loading of the accepting land, and the other is the evaluation of the impact of pollutants on groundwater. For the first issue, the traditional solution is as follows: use water balance formula or conducting (conduct) laboratory simulation tests first to determine the largest hydraulic loading of subsurface infiltration system, and then select the appropriate hydraulic loading. The drawback of these methods is that the real situation and the complex situation of the near area can not be put into good consideration. As regards the second issue, the traditional approach is emplacing wells around the field to monitor the water quality conditions of groundwater. The disadvantage of this method is that human and financial resources are badly cost. This paper attempts to study the two issues by mathematical simulation methods on the basis of previous studies.Choosing Ying dong Wastewater Land Reuse system in Chongming County of Shanghai as object, the three-dimensional model of groundwater flow and water quality about this land was established by use of Visual MODFLOW software developed by Water-loo hydrogeological software company as platform. The main parameters of the model were measured and the boundary condition was provided by the real data. The model was calibrated through the hydrological and water quality data measured from September 2006 to April 2007. The calibrated model could well reflect the situation of the hydrology and water quality of the groundwater in the field.Then, taking Donghai village as a sample, the paper demonstrates how to use calibrated model to provide technical support for possible Wastewater Land Reuse system.Firstly, the maximum allowable hydraulic loading of possible Wastewater Land Reuse system was identified by the model: other conditions being unchanged, the following hydraulic loading conditions were simulated: 4,000 mm/yr, 3000mm/yr, 2500mm/yr and 2000 mm/yr. The result shows that backwater appeared when the hydraulic loading was greater than 2500 mm /yr and that it disappeared when the hydraulic loading was 2000 mm/yr. Then the situation that the hydraulic loading was 2200 mm /yr and 2300 mm/yr respectively was simulated. In the end, the maximum allowable hydraulic loading of the system was constrained between 2200 mm/yr and 2300mm/yr.Then, the impact of this possible Wastewater Land Reuse system on the groundwater was evaluated by the model. The pollutants of subsurface infiltration system were simulated for 10 years under the hydraulic loading of 2200 mm/yr. The results showed that the pollutants will immediately transfer adown, and spread around at a certain depth. The natural transfer of pollutants is not obvious, with the fact that the pollutants transferred only 35 meters in the horizontal direction and 15 meters in the vertical direction within 10 years.Finally, the interaction between Wastewater Land Reuse system and pumping well nearby was also simulated. The results showed that the transfer of pollutants in the horizontal direction changed a lot. Pollutants mainly moved to the direction of pumping well at a certain depth. After 10 years, the pollutants have moved 220 meters towards the pumping well.
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