城市污水经处理设施深度净化处理后的水(包括污水处理厂经二级处理再进行深化处理后的水和大型建筑物、生活社区的洗浴水、洗菜水等集中经处理后的水)统称“中水”。因其水质介于自来水(上水)与排入管道内污水(下水)之间,故称为“中水”。中水利用也称为污水回用。近年来,随着人口增长和社会经济的迅速发展。水资源短缺已成为世界性的普遍问题。我国是水资源匮乏的国家,水资源总量为2.8×104亿 m~3,居世界第6位,而实际可利用的水资源量为1.1×104亿m~3。世界人均占有量约为1.29万 m~3,我国人均占有量仅为0.22～0.27万 m~3,列第88位。据预测,2030年前后,我国人口增至16亿时,将出现用水高峰,人均水资源量降到1760m~3。按国际上承认标准,人均资源量少于1700m~3即为用水紧张国家,到2030年我国水资源需求量已接近可利用水量的极限。由于我国水资源在地区上分布很不均衡,长江以北水资源量仅为全国的五分之一,是水资源供求矛盾最突出的地区。在全国现有城市中,有近一半城市缺水,其中100座城市严重缺水,面对如此严重的形势,在城市中有效地处理城市废水,进行中水利用是缓解城市水荒极其重要的途径。中水是城市水资源之一。它水量大而稳定,就地可取,用水成本较低。今年北方地区遭受百年不遇的大旱,使许多水库、河流出现从 Urban sewage treatment facilities after the depth of the purified water (including the sewage treatment plant after the secondary treatment and then deepen the treatment of water and large buildings, living communities, bathing water, washing water and other centralized treatment of water) collectively “Water”. Because of its water quality between tap water (Sheung Shui) and discharged into the pipe between the sewage (water), it is called “water ”. Water use is also known as wastewater reuse. In recent years, with the rapid population growth and rapid socio-economic development. Water scarcity has become a universal problem worldwide. China is a water-scarce country with total water resources of 2.8 × 104 billion m 3, ranking sixth in the world, while the actual available water resources are 1.1 × 104 billion m 3. The world average per capita is about 12900 m ~ 3, China’s per capita share is only 0.22 ~ 0.27 million m ~ 3, ranked 88th. It is predicted that by the year 2030, when the population in our country increases to 1.6 billion, the water peak will occur and the water resources per capita will drop to 1,760 m3. According to the internationally accepted standards, the per capita resources of less than 1700m ~ 3 are water-stressed countries, and by 2030 China’s water demand is close to the limit of available water. Due to the uneven distribution of water resources in the region, the water resources in the north of the Yangtze River is only one fifth of the national total, which is the most prominent contradiction between water supply and demand. Nearly half of the existing cities in the country are short of water, of which 100 are seriously water-scarce. In the face of such grave situation, it is extremely important to effectively treat urban wastewater in urban areas and to use water reclaimed from the water in urban areas . Water is one of the city’s water resources. It is large and stable water, it is desirable on the spot, the cost of water is lower. This year the northern region suffered a severe drought once in a century, causing many reservoirs and rivers to emerge