Study On Water Quality Standards For Storm Water Infiltration Based On Risk Assessment In Pinggu Basin Of Beijing

With the reduction in the amount of surface water resources and the deterioration of water quality, there is growing reliance on groundwater resources development and utilization. However, the rapid decline of groundwater table as well as a series of environmental problems, forced the restoration of groundwater to be an important measure which can improve the shortage of water resources and maintain ecological environment balance in the region. The climate of study area is a typical monsoon climate of the north, a large number of floods runoff in summer and shortage of water resources become a pair of sharp contradictions in reality. It is necessary to fully exploit all available water resources in order to effectively alleviate regional water scarcity problems and improve the regional ecological environment. Under these conditions, the sufficient storm water in summer can be recharged into underground storage space not only ease the pressure of water shortages to some extent of the study area, but also improve the regional environment.During the process of storm water recharge into groundwater, the quality of recharged water is one of the key issues which affects the health of groundwater environment. The poor quality of recharged water will cause the clogging of aquifer or recharge equipment, groundwater contaminated after the water enter the aquifer, and even harm to human health if the people use the groundwater. Therefore, make a proper quality standards of recharge water is on-going root of the problem. This work can keep the ecological environment from damage, the protection of health as well as ensure the safety of artificial recharge.The regional storm water quality is better than the reused water by comparing the quality characteristics. Furthermore, the groundwater in study area is used for drinking, it is not proper to adopt the reused water quality standards for artificial recharge directly. The existing water quality standards of domestic and international area for recharging are all based on different conditions which are limited to use. There is a common issue in the existing artifical recharge water quality standards, that is, the lack of controlling of clogging indicators which would bring about the of hidden dangers to high-performance and continued operation engineering.The indicators of storm water quality are selected according to different categories of storm runoff in the study area. The principles of water quality determination are set that is protecting environment, keeping human health and preventing clogging during recharging as well as borrowing ideas from the existing artificial recharge of water quality standards. The paper proposed storm water quality standards based on the risk of groundwater pollution, human health and clogging. The storm water quality standards are determined though three methods: groundwater pollution risk assessment, human health risk model and the standards of clogging for recharging water in Netherlands.The tests and analysis of the samples gave the results of storm water quality characteristics in study area. The main kinds of pollutants in storm water were organic pollutants, nutrients, heavy metals and suspended solids. These pollutants will affect the use of the potential of storm water. By analyzing the different types of storm water quality in the study area, it is can be seen that the water quality of cellar, reservoirs and a part of rivers in the upper reaches are better, comparing to the quality of storm water in river downstream, roofs, roads and ponds, which are subject to serious pollution of the water quality. Therefore, the study area has a greater potential for storm water to use. At the mean while, the cleaner water is also to ensure the safety of the recharge relatively.The study area can be divided into five subareas that each one has its own water resource for recharging into ground. The process can be achieved according to different utilization patterns of storm water. After analysis, the suitable water resources for recharging are mainly storm water in reservoirs of the study area. The paper adopted the risk assessment model called Consim to assess the risk of groundwater pollution. The model simulated the transport process of typical contaminants of recharged water in every subarea to make sure if the study area has pollution risk. Evaluation results show that the hydro-geological conditions in the study area, the groundwater pollution risk of some pollutants exist varying degrees in study area.This paper brought forward the principles of storm water pre-treatment based on its uncertainty and water quality characteristics. The storm water pretreatment should make full use of the existing conditions, make great efforts to develop ecological treatment technologise, take into account the efficient and long-term project-based and give attention to the economic development. The practices such as storm water retention ponds, bio-channels, constructed wetlands and sand filters were determined as the main pretreatment of storm water recharge by analyzing the various types of storm water quality characteristics. According to the actual condition, the integrated suggestions plan of the study area can be proposed based on understand the mechanism of removal of pollutants and effective of the practices.