Study On The Key Technology And Engineering Demonstration Of Rainwater Collecting System

Zhenjiang, which is located along the Yangtze River, has an abundant water resource. But as the socio-economic development, the demand for water is growing, coupled with environmental pollution, pollution-induced water shortage is gradually emerging, while the urban water is seriously wasted and pipe leakage rate is relatively high, so that there are some hidden dangers of water supply to ensure the long-term sustainable development of Zhenjiang. Rainwater is an important part of water circulatory system, and is the most fundamental, the most straightforward and most economical water, additional, it is also extremely significant to groundwater supplement, ecological environment improving and protecting. Therefore, the utilization of rainwater resource is an important way for sustainable development of water resources.This paper mainly studied the key technologies of rainwater collection and utilization system and established a demonstration project in third people's hospital rely on the actual situation of Zhenjiang, aiming to provide the basis and technical support for urban rainwater utilization of Zhenjiang.The paper analytically induced the utilization path and principle of urban rainwater in the base of many documents from home and abroad and lots of examples, so as to analysis the situation of water resource, runoff pollution, water property as well, and calculated water balance.Based on the above researches, the collected rainwater was purified. Purification process is mainly composed of initial rainwater discarding, cyclone separator and ecological floating bed. Meanwhile the pollutants removal capacity of this purification process is determined. Ultimately, we made a technical and economic analysis on the demonstration project.The main research results and conclusions of thesis are summarized as follows: (1) Rainwater of the demonstration projection through the reasonable allocation is able to fully meet the amount of water reuse required. (2) The initial rainwater of the demonstration area can't be directly used because of its high levels of pollutants, and then it is in need of purification treatment. In the initial runoff contain COD up to 210mg/L, SS up to 288mg/L, NH₄⁺-N up to 20.5mg/L, TP up to 7.1mg/L, TN up to 26.3mg/L and the heavy metal content is relatively low. There was a decreasing trend in each pollutant concentration with rainfall duration and finally tends to flat. So we collect the rainwater after abandoning part of the initial flow of rainwater. (3) There is a certain correlation between SS and COD, turbidity, TP, TN in rainwater runoff. And Hydrocyclone can be used to remove part of COD,N,P, while removel the SS. (4) Studied the scour law of stormwater runoff, and obtained that abandoning 3mm initial flow can remove 50% -70% of the pollutants. (5) Designed a set of discharge device of initial rainwater referenced to the existing literature and patent. The components of this device is simple and without manual control. The experimental test data shows that the device is running well and the effect was significantly. (6) Improved and designed of a cyclone separator. Its maximum turbidity removal late reached 77%, SS up to 70%, TP up to 55%, COD reached 53%, TN up to 32%.(7) Simulation test in a laboratory was done using ecological floating bed with water spinach and canna. The results showed that the highest removal rate of NH₄⁺-N reached 85%, COD up to 40%, TN reached 53%, TP reached 57 %. Ecological floating bed used in the field shows that the water quality standards of treated rainwater is superior to that of reused water. And the ecological floating bed created a good visual effect also. (8) Economic analysis showed that rainwater utilization of demonstration projection is 6000m³ per year and the average revenue of rainfall is 3.46 yuan per cubic meter. So it can receive part of the economic income.