In recent years, with the deepening of energy-saving and emission-reduction work in China, the construction of urban sewage treatment facilities has been accelerating. A large number of sewage treatment plants have been established throughout the country, and the sewage treatment capacity has been relatively large. However, the vast majority of these treated effluents have not been effectively used, resulting in a greater waste of water resources, but also caused secondary pollution to the environment. China is a country with poor water resources and serious water pollution. It is particularly important for the reuse of wastewater to alleviate the shortage of water resources in China, promote the optimal allocation of water resources, and reduce the discharge of wastewater.
The potential of renewable water utilization in China is huge
Reclaimed water refers to the water that can be reused after it has been properly treated and reaches a certain water quality indicator, meets certain requirements for use. Reclaimed water, large amount of water, stable water quality, little influence by seasons and climate, is a very precious water resource, and it is an internationally recognized “second city water sourceâ€.
In recent years, China's urban sewage treatment capacity has grown by leaps and bounds. As of the first quarter of 2009, China has built and put into operation 1,590 sewage treatment plants, and the designed daily processing capacity has reached more than 90 million m2. Nearly 70 million m2, the annual sewage treatment volume will reach 25 billion m2, accounting for about 50% of the total urban water supply in China.
However, China's wastewater recycling rate is still quite low. According to the city's wastewater reclamation and utilization plan, by 2010, China's urban wastewater recycling capacity will reach 6.8 million m?/day, which will only account for about 10% of the current sewage treatment volume. According to the level of the developed countries, if the rate of renewable sewage utilization reaches 70%, there will be nearly 15 billion m2 of renewable water resources each year that can be exploited and utilized. The potential is very great.
In recent years, with the development of a water-saving society and the development of pollution control in China, renewable water resources in some water-scarce cities have been rapidly promoted and used, such as Beijing, Tianjin, and Qingdao. Reclaimed water is widely used in agricultural irrigation. , industrial recycling water, and urban landscape. Recently, with the deepening of the pollution control work of the South-to-North Water Transfer Project, the use of reclaimed water along the South-to-North Water Transfer Project in Shandong Province has also achieved rapid development.
As most of the cities in China have just started the use of recycled water, and have not even started yet, there is still a huge space and potential for China's urban renewable water resources to be intensified in development and utilization.
Reclaimed water use abroad
The concept of water use in many developed countries is to minimize the use of clean water, reduce the discharge of sewage, and realize the recycling of water resources. The history of the use of recycled water is also relatively long. As early as the 19th century, legislation on the legal use of recycled water was introduced in cities such as London, Boston and Paris. With the continuous improvement of wastewater recycling technology, reclaimed water has been more and more widely used in industrial, agricultural and municipal life.
Israel is one of the countries with the highest utilization of recycled water in the world. As early as the 1960s, Israel listed all wastewater reuse as a national policy, stipulating that if wastewater is not used up, seawater desalination must not be used; every drop of water in the city should be reused at least once. Almost all households in the country have realized tap water and recycled water, and 100% of domestic sewage and 72% of municipal sewage have been reused. At present, the reclaimed water has become an important part of the country's water resources allocation. The annual utilization exceeds 500 million m2, accounting for about 20% of the total water supply.
In addition, as an important water resource, reclaimed water is also increasingly used in many other developing countries in the world. For example, Mexico, Argentina, Brazil and other countries have started to use recycled water, of which the largest proportion is for agricultural irrigation.
The significance of the use of recycled water in our country
The first is an effective way to alleviate the shortage of water resources in China. Sewage recycling is an important way to solve the shortage of water resources in China, especially the lack of water in the northern regions. China's per capita water resources are only one-fourth of the world's per capita. In normal years, the country's annual water shortage is nearly 40 billion m2. There are more than 400 cities with insufficient water supply, and the average agricultural area is 230 million mu due to droughts and droughts every year.
However, on the one hand, the situation of water shortage is very severe. On the one hand, a large amount of renewable water resources has not been used reasonably and effectively. At present, the amount of wastewater that China handles each year has reached a scale of 25 billion m2, and the amount of renewable water resources that are actually used is less than 10%, and there is ample room for development and utilization. At the same time, the reliable use of recycled water resources is an effective measure to open up new water sources, especially to solve the water shortage problem of agricultural irrigation.
Secondly, it is an important link to realize the recycling of water resources and reduce water pollution. Sewage regeneration and recycling use, on the one hand, reduces the amount of clean water resources used, thus reducing the generation and discharge of sewage; at the same time, through the use of recycled water, the pollutants in the water body are degraded during use, reducing these The amount of pollutants entering natural water bodies is an important measure to reduce water pollution.
At present, China's annual total discharge of wastewater reaches 55 billion m2, of which more than 30 billion m3 of domestic wastewater, and nearly 14 million tons of COD in various waste waters, with an ammonia nitrogen content of more than 1.3 million tons. However, the degree of sewage treatment in China is still not high, and even if it is treated centrally by a sewage treatment plant, about 20% of the pollutants will not be effectively removed. This part of the pollutants will enter the tail water discharge of the sewage treatment plant. Natural water causes secondary pollution. If these tail waters are used reasonably and effectively, especially for agricultural irrigation, the nutrients, nitrogen, phosphorus and other elements in the water body will be effectively removed through plant absorption and the growth of the crops will also be promoted.
Third, it is an important measure to promote urban water pollution control and improve the water ecological environment. Urban water pollution governance is fundamental to governance and the key to use. Only by realizing the reclaimed water resources can we establish downstream monitoring mechanisms for downstream water pollution control and promote water pollution control.
Reclaimed water, as industrial water, farmer's irrigation water and urban landscape water, must meet the corresponding water quality discharge standards. If the water quality is not up to standard, it will directly harm the immediate interests of downstream users. On the one hand, it has aroused the general public's awareness of pollution control and environmental protection, and at the same time strengthened the supervision of the “governance†links of upstream urban sewage treatment plants and point source pollution control, and provided for the long-term effective operation of various pollution control measures. The protection ensures that the ecological environment is effectively improved.
Accelerating the use of renewable water resources in China
Although the use of reclaimed water in some cities in China has developed rapidly, it is still at an initial stage from a national point of view. The scale of construction and operation of wastewater recycling and reuse is extremely inconsistent with the shortage of water resources and severe water pollution in China. It is urgently needed. Accelerate the pace of the use of recycled water, give active support in policies, speed up the construction of supporting facilities, create conditions for the reuse of sewage, and make the use of recycled water play an active role in the allocation of water resources and water environmental governance in China.
First of all, we should give active support to the policy and establish a sound renewable water use market. The state, provinces, cities, districts, and counties shall formulate clear plans and objectives for the development and utilization of recycled water, properly plan the construction of reclaimed water plants and the use of recycled water, actively encourage and guide more users to use recycled water, and create a broad market demand for the use of recycled water. .
At the same time, it will accelerate the process of marketization of sewage recycling and establish investment and financing mechanisms, operation management mechanisms, and price formation mechanisms that are in line with market economic laws. And we must establish a reasonable water price system as soon as possible. It is imperative to accelerate the reform of the water pricing system. Only when the price of reclaimed water is lower than the price of surface water and groundwater by a certain margin, the price leverage of reclaimed water can be brought into play, so as to guide reasonable water consumption and promote the popularization and application of reclaimed water.
Second, rationalize the relationship between departments and achieve unified management of renewable water resources. The implementation of sewage recycling and reuse is a large and complex system engineering involving many units and departments such as urban planning, construction, environmental protection, municipal administration, and water conservancy. However, for a long time, water supply and water supply, and water supply and drainage have existed in many cities. There is no specific institution to coordinate, plan and manage the reclaimed water reuse of the city. It is often the use of water regardless of pollution control and pollution prevention. Together force.
Again, speed up the use of recycled water infrastructure. The serious lag in supporting infrastructure construction is a key reason that restricts the development of renewable water use in China. The reuse of reclaimed water requires the establishment of a complete wastewater collection system, treatment system, and reclaimed water supply system, and its investment is considerable.
In addition, one of the main directions for the reuse of reclaimed water is the use of water for agricultural irrigation and ecological environment, and the seasonality of agricultural irrigation is strong, requiring a large storage space for reclaimed water. In many parts of China, renewable water resources do not have such good storage conditions, and a large amount of reclaimed water can only be lost.
Therefore, we must vigorously accelerate the construction of supporting infrastructure for the use of recycled water. In particular, at present, China still faces a global financial crisis. We urgently need to increase investment and stimulate domestic demand. We recommend that national and local governments increase investment in the use of recycled water, and reasonable Plan for reclaimed water use projects and accelerate the construction of infrastructure for the use of recycled water.