Environmental problem is one of the most important problems in the development of national economy, which is affecting people's social life comprehensively and profoundly. Environmental deterioration has become the main factor leading to human diseases and deaths, so 2 1 century will be the century of decisive battle between human beings and environmental pollution and ecological destruction. Among many environmental problems, water pollution and water shortage will be one of the most serious problems in the world for a long time to come. For example, two-thirds of lakes in China are polluted by eutrophication to varying degrees, and 63% of the seven major water systems have lost their drinking water function due to different degrees of pollution. Water pollution is developing from east to west, from tributaries to main streams, from cities to rural areas, from surface to underground, and from regions to river basins. According to the disclosure of the State Environmental Protection Bureau, the serious problems faced by seven river basins in China are water pollution and water resources shortage, organic pollution in major rivers is widespread, and eutrophication in major lakes is serious. The pollution levels of the seven major water systems are: Haihe River, Liaohe River, Yellow River, Huaihe River, Songhua River, Yangtze River and Pearl River. More than 70% of the four rivers in Liao, Huai, Huang and Hai are polluted. Water pollution and the lack of surface water resources have accelerated the predatory development of groundwater, which not only led to the formation of several regional groundwater "falling funnels" in China, but also the high-intensity surface water leakage and land-based pollution, which made the groundwater quality worse and worse, and the well water in many places was inedible. Although China is rich in fresh water resources and the total surface water resources rank sixth in the world, due to its large population, the per capita water resources are far below the world average, which is 1 10 and less than the world average 1/4. China is listed as one of the 13 countries with per capita water shortage in the world. Coupled with uneven distribution of water resources and serious pollution, it will aggravate the shortage of water resources. In recent 20 years, the shortage and unreasonable utilization of water resources have become increasingly prominent, which has become a restrictive factor for social and economic development. It can be said that the water pollution in China has broken through the last line of defense. If water pollution is not cured, the Chinese nation will have no tomorrow. Industrial pollution is one of the main reasons for the deterioration of water environment. Because the domestic industrial technology level is generally low and the industrial structure is unreasonable, the growth mode of extensive economic has not been fundamentally changed, and the emissions of various pollutants from enterprises above the county level are still increasing. It often happens that an enterprise pollutes a river and a whole sky. In addition, domestic sewage is another major source of water pollution. With the improvement of living standards, the daily sewage discharge is increasing, accounting for more than 0/3 of all wastewater discharge. Water pollution has caused serious social and economic problems, which is manifested as threatening the drinking water safety of urban and rural residents; Sewage irrigation causes land pollution, which leads to the accumulation of toxic substances in the produced grain; The incidence of intestinal diseases, cancers and congenital malformations of infants in polluted areas is relatively high. Finally, China is a developing country, with backward urban infrastructure and less investment in environmental protection than western developed countries, so the urban sewage treatment rate is low, resulting in different degrees of water pollution. Based on the current situation of water pollution and water shortage in China, how to reduce the pollution in China?