Research On Water Quality Analysis And Treatment Experiment Of Roofing Rainwater Of Yangzhou

With the development of urbanization, water resource has become increasingly tense. So exploiting resource and reducing expenditure become very important. As renewable resource, rainwater is utilized not only to alleviate the water crisis but also to improve the urban water environment. Compared with other underlying surfaces which collect rainwater, roof rainwater is easier to be collected and lighter polluted, so recycling of roof rainwater is more feasible.Because of geographic location and climate condition, the weather of spring and winter in Yangzhou city is dry and rainless, but summer and autumn is rainy. Asymmetrical rainfall distribution in time and space gives rise to flood disaster and brings menace to people’s life and property security. If the natural water resources are recycled, it can not only save the water resource, but also alleviate the pressure of municipal drainage system.On the basis of monitoring rainfall of Yangzhou for a year, this paper firstly analyzes the characteristic of rainfall and the change rule of water quality of roof rainfall runoff, then analyzes the treatment effect through rainwater treatment experiment, the conclusions as follows:(1) Roof rainwater of Yangzhou belong to light pollution source, whose main pollutants are COD, SS, Turbidity. But the total nitrogen and total phosphorus are low. Total nitrogen and PH of rainwater accord with the quality standard of non-drinking water, even achieve the water standard of class Ⅲ,Ⅳ surface water. The total phosphorus is low, however, still higher than the quality standard of non-drinking water, so the roof rainwater must be further treated.(2) The water quality of Roof rain associated with the roof type, season, rainfall intensity, rainfall duration:the rainwater quality on the new green magnesium aluminum manganese alloy is better than which on the concrete flat roof; compared with the dry season, the water quality in the rainy season is better; along with the rainfall intensity increasing, roofing is scoured powerfully, then the rainwater quality faster tends to lower and stable value; as the extension of rainfall, the pollution index of runoff water quality as a whole have a downward trend, and gradually stabilize.(3) For all rainwater, roof runoff pollution is more serious in the early15min, then the rainfall quality is better and stabilized gradually, so take the early15min of duration of rainfall as initial abandon-flow time. Through roof runoff water quality and water quantity evaluation, roof runoff of Yangzhou during the year is plentiful, after the initial abandon-flow of the early rain water, the remaining can be treated to be used as natural water reuse.(4) Through Quartz sand filter column, removal efficiency of turbidity, SS and COD good. Through direct filtration, the average remove rate of SS was over80%, and the averag remove rate of turbidity was62.5%, and for the COD, the average remove rate was over50%however, for the TN and TP, removal efficiency was worse. By coagulating and precipitatin after dosing coagulant, then filtering, the effluent water quality is superior. And the remove ra of SS, turbidity and COD respectively achieve90%,99%,80%.Overall, roof runoff water quality of Yangzhou is good. We can use it as non-drinking wate and landscape water after collecting and processing.