Study On Water Quality Of Roof Rainwater And Experimental Sand Filter Test In Jinan City

With the rapid economic development and increasingly rapid pace of urbanization, the area of impervious zone increases year by year, on the one hand, it not only reduced the amount of groundwater recharge, but also resulted in waste of water resources; on the other hand, it led to environmental degradation and flood disasters. In addition, the urban rainwater drainage system will be under enormous pressure.Faced with these numerous problems, urban rainwater utilization attracted the attention of domestic and foreign scholars, urban rainwater utilization is becoming an important measure to alleviate urban water crisis and improve the urban water environment during the process of urbanization in China, and the study of groundwater recharge with rainwater as one of the important measures to resolve the water shortage is paid much attention from international and domestic academic scholars. Substantial experimental studies about groundwater recharge are being under study, and got some research results. The study on roof rainwater quality and the treatment methods are significant to slove the water short and improve the city environment in Jinan.The average annual rainfall in Jinan city is 664mm, and the rainfall concentrated in flood season; as housing area of the urban area occupies 67-70%, which provides a natural place to collect rainwater, and the roof rainwater quality is relatively good compared with road runoff and vegetation runoff; in addition, with large permeability coefficient of fracture-karst aquifer, the aquifer will provide a good condition for infiltration, all of these factors are conducive to the implementation of groundwater recharge. Therefore, studying on the water quality characteristics of roof runoff in Jinan City and exploring a simple and feasible measure to deal with roof runoff before implementation of groundwater recharge will provide important and basic data for the next step. Specific studies are as follows:1. Summerize the water quality characteristics of urban roof runoff and analyse the feasible scheme for groundwater with roof rainwater; Roof runoff has obvious characteristics, that is to say, first flush effects with high concentrations of pollutants, complex components, lots of influence factors and runoff rainwater quality regionally; and the roof runoff water quality is relatively good and easy to collect compared with green and road, therefore, groundwater recharge can be achieved after the treatment of roof runoff.2. Combined with precipitation condition of Jinan City, including the annual precipitation from 1951 to 2006, summer precipitation and daily maximum rainfall, etc. By analysis of rainfall monitoring and roof rain water quality testing, summed up the water quality of rainwater temporally and spatially and the characteristics of the roof rainwater quality and its changes in law; roof rainwater in Jinan belongs to micro-polluted water, and the major pollutants in roof runoff in flood season conclude SS, turbidity, color, NH3-N, NO2-N and volatile phenol, and there are minor metal ions in roof rainwater. Sources were analyzed based on the pollutants in the roof runoff, and it indicated that the air pollution in Jinan is serious, and the pollutants originated from cumulative dust, fossil fuel combustion and vehicle exhaust.3. Calculate the available quantity of roof rainwater in Jinan, and water quality index method was applied to evaluate the roof rainwater quality, and the evaluation results confirmed the poor water quality in spring and relative good quality in flood season, and it also provided a basis for the feasibility of groundwater recharge with roof rainwater;4. By measuring the permeability coefficient and porosity of sand layers with different sizes, an appropriate sand filter system was designed to remove the pollutants in roof rainwater. From the experiment results, the sand column was effective to remove turbidity, color, volatile phenol, and metal ions and so on. However, it had a bad effect on removing ammonia nitrogen, nitrite nitrogen and volatile phenol. In addition, the removal of most pollutants such as turbidity, color and suspended solids mainly occurred at the upper layer, and at last the improvements of test scheme in next step were proposed.