Studies On Feasibility And Technical Project Of Urban Rainwater Utilization In Xi'an

Along with the rapid development of urbanization, many cities around the world encounter lack of water resources and water pollution. Rainwater is not only the most economical way of saving natural water resources but also an important part of water circulation system. Besides, rainwater is playing a crucial role in adjusting and saving limited water resources, as well as maintaining the ecological balance. The use of rainwater is essential to improve urban ecological environment, and is one of main approaches to achieve sustainable water resources.This paper presents the availability and the different technical approaches in using rainwater resources in Xi'an. The project is aiming to build up a strong technical backstopping in terms of further development of rainwater utilization.Based on other research papers from mainland and abroad as well as cases of rainwater application, this paper compared the different types of rainwater utilization technology and explored the way of recycling rainwater. In addition, it suggested the available region in rainwater recycle implementation in Xi'an. This paper also analyzed the water resources, rainfall and further rainwater technology development, and feasibility of rainwater utilization. We had measured the quality of outflow from rain pipe network in various regions, and summarized the pollution status and quality of rainwater runoff.This project thoroughly studied the feasibility in transferring urban rainwater to districts, parks and gardens ,and rainwater storage measures in Xi'an. The main findings of study are as follows: (1). According to the characteristic of rainfall in Xi'an, rainwater utilization can be carried out from May to October yearly. (2). In regards with Xi'an overall plan (2004-2020), it is anticipated that there would be approximately 279 million m3 rainwater resources available from urban construction area. (3). Under the condition of having frequent rainfall, the main pollutants in the rain runoff are SS, COD, oil, ammonia nitrogen, total nitrogen and total phosphorus during the mid-late raining period, which are lower than level of domestic sewage. Besides, COD is close to domestic sewage level. Chromaticity color value is comparatively higher than I and II levels, according to the "Standard Of Sewage Synthesis Drainage". The changes of PH and the ammonia nitrogen level during the runoff process are insignificant In addition, SS, oil level are showing decreasing trend over the period. Furthermore, the range of the pollution index variation from the different samplings is not always the same. (4). The experiment of collection and recycle of rainwater in some communities indicated that the technology adopt the process of initial precipitation - initial filter - MBR filter, and filter purification on the artificial vegetation. The operation costs are lower than the water price in Xi'an. Overall, the method of MBR purification is the best one. (5). If the waterproof area occupies 70% and above of the total area, it is possible to collect and use the rainwater. Therefore, it is suitable to implement the rainwater infiltration in green space of street comer and some square spaces. (6). This study also brings forward the regulation on rainwater storage in Xi'an city.