Study On Sewage Recycling And Utilization In Shenzhen

Currently, the whole world is facing new crises - water crises. The condition in China is no optimistic. As China has a large population, the per capita water resources are only 2300 m3 - a quarter of world average. And meanwhile, the pollution in the river, lake and other water bodies are becoming increasingly serious. We are confronting a severe test of water shortage in terms of water resources and quality. Particularly, on one hand, Shenzhen is in such a critical shortage of water resources that 80% of the total water consumption in the city is imported from other regions through water works, and water shortage is still a frequent phenomenon. On the other hand, the sewage in the city is polluting the environment. Clear rivers in the past have become dikes of foul water. As a result, not only the security of water consumption is affected, but also the garden-like landscape of the city is ruined. How to deal with water issue appropriately has become extremely stringent and important.This paper has studied many cases of water recycling in China and other countries. For example, U.S.A. saw its first case of water recycling in 1920. They used the in-depth recycled water in industry, agriculture and public utility projects. Up to now, they have obtained prominent results in that water is in sound recycle in the macro-circulation in the society. The total water consumption in cities is increasing by year, however, the total consumption of new water is decreasing year after year. Dalian, China, a coastal city, is lack of water. In 1992, it finished the model project of sewage recycling. Dalian has seen the actual good results. It is proved by facts that urban sewage recycling can effectively solve the conflict between shortage and pollution of water of water resources, which has utmost practical meanings to Shenzhen that is short of water. From the sources of recycled sewage, the paper has made a detailed analysis on the industrial structure, city function, living habit, etc. in Shenzhen, and determined the main potential uses of the recycled sewage in the city, i.e., industrial area, public utilities, green areas, and ecological water in water bodies and rivers in the city. Furthermore, based on field investigation and statistic data, the paper has calculated the recycled water consumption in the short and long term. Up to 2010, it will be 1.15 million m3/d. Under this circumstance, with consideration of the distribution and processing capacity of the existing sewage plants in Shenzhen, it is suggested that the centralized recycling method should be adopted, and the plan of the recycled system isdetermined. At the same time, the paper has made comprehensive analysis on water quality requirements of different recycled water. For example, as the water used in the green area often contacts children and pedestrian, it should be odorless, insipid, and transparent. The overall coliform group should be less than 500; and to protect flowers and grasses, the residual chlorine should not be too high. It is recommended that national water standards of GHZB1 - 1999 IV water body should be adopted for the recycled water in the city. Based on the study of mature water treatment technologies in China and abroad, as well as the actual conditions including the scale and quality requirements of recycled water, we hold that it is appropriate to implement "bio-membrane process" because the advantages of this process include no sedimentation tank, small floor space, low capital investment, no drug consumption, low running cost, convenient administration, and good output water quality.In the last part of the paper, after technical economic analysis, the author proved that sewage recycling in Shenzhen, on one hand, is economical because water utility fee of RMB 327 million per year would be saved comparing with the tap water; on the other hand, it is reliable. For Shenzhen, water recycling can relieve the pressure on water supply, improve and restore the water environment, and bring prominent social and environmental benefits. However...