Study On The Technology Of Comprehensive Utilization And Resourcelization For Rainwater In Xi'an City

At present, many cities in Northwest China are facing with the problems of water resource shortage and water environment pollution. Rainwater, as the important ink of the water circulation system in nature, takes key effect on adjustment and replenishment of the regional water resource and ecological environment. The comprehensive utilization of cityscape rainwater is an important composition to improve the urban ecological environment, and is one of major approaches to achieve the water resource sustained growth.This subject aimed at study the feasibility and the technical scheme of the cityscape rainwater utilization in Xi'an, which could provide scientific basis and technical support for the city's rainwater utilization.In this paper, on the basis of analysis of a large number of literature and its application cases both at home and abroad, diverse methods and means of cityscape rainwater utilization were summed up, and then through analyzing the situation of water resources, the pollution of storm runoff and the characteristics of water quality in Xi'an, the feasibility of the cityscape rainwater utilization were researched.Based on the above research, a dynamic test that applied the fluidized pellet bed solid-liquid separation technology to treat rainwater was stated. This process could collect and utilize rainwater, and would be an important approach to make use of rainwater in xi'an. In addition, the utilization of rain permeation was another approach, so a relevant pilot test was conducted. At last, the major approaches and means of rainwater comprehensive utilization for xi'an city were concluded.The major conclusions of this paper are stated as follow: (1) the average rainfall for many years in Xi'an was 583.7 mm, rainfall was rich in resources, nearly 70 percent of the rainfall concentrated in the summer and autumn, which it could provide a very convenient condition for rainwater collection and utilization, (2) In Xi'an runoff, the major pollutants is the SS, COD and like oil, in the early runoff COD_Cr as high as 1230 mg /l, SS of 2288 mg / L, oil up to 161 mg / L. Rainfall is also stable COD_Cr300～400 mg/laround, SS in the 800～1000 mg/L, were higher than those in "Integrated wastewater discharge standard," 1,2-class standards, cause serious pollution, must be fully dealt with before the use of purification, (3) The utilization of rainwater is an important measure to resolve a city's water resources shortage. Applying the high efficiency granulation-type Solid-liquid separation equipment, the patent technology of Xi'an University of Architecture and Technology, the dynamic test of campus rainwater treatment was accomplished, in which the control factors of the coagulant dosage of PAC, the aid coagulant dosage of PAM, the flow velocity and the forced stirring speed were obtained when the treatment load was 2m³/h. the treated water's turbidity could reach 10NTU below, the water quality indexes of the treated water could meet the standard of City Miscellaneous Water Quality Control Indicators (GB/T18920). (4) By the use of green water purification technology has a set programme. green space could have restore water function, and the restored rainwater could be the supply for plant growth by capillary action in un-rainfall time, so it would save numerous irrigation water, (5) many approaches and means of rainwater comprehensive utilization for xi'an city were suggested.