After signing the Millennium Declaration in 2000, the member states of the United Nations formulated the Millennium Development Goals (MDGs), of which target 7 is to ensure environmental sustainability. During the Millennium Development Goals period, the proportion of the global population with access to improved sanitation facilities increased from 54% to 68%, and more than 2.1 billion people around the world have access to improved sanitation facilities.
The rapid development of global environmental sanitation has also accelerated the progress of the sewage treatment industry: in the past 10 years, China's urban sewage discharge has increased from 32.9 billion tons to about 41.7 billion tons, an increase of more than 30%; The sewage treatment rate has increased rapidly. In the past 2012, China's sewage treatment rate exceeded 85% and is expected to reach 95% in 2020. Nevertheless, with the increasing voice of environmental sustainable development in recent years, the problems existing in the traditional sewage treatment model have gradually been recognized and continuously concerned by all sectors of society. Open a new mode of sewage treatment. For a long time, the role of urban sewage treatment plant has been regarded as reducing the pollution of sewage direct discharge to the local receiving water body. In order to meet the set water quality standards, various technologies and means are superimposed or used in series. The main purpose is to separate and remove pollutants in sewage or convert them into harmless substances, so as to purify water. Therefore, in addition to consuming a large amount of electric energy and chemicals such as flocculants and disinfectants, the sewage treatment plant will also produce a large amount of excess sludge and greenhouse gases.
It is estimated that the annual power consumption of China's sewage treatment industry accounts for 2-3% of China's total power consumption. In addition, the emissions of greenhouse gases such as methane and nitrous oxide produced in the process of sewage treatment account for 4-5% of China's non carbon dioxide emissions. Under the background of global energy crisis, climate change and resource shortage, the traditional mode of sewage treatment is also undergoing great changes. The development of a new mode of sewage treatment with energy-saving, low-carbon and effective recycling and deep reuse of available substances in sewage has attracted extensive attention of the international community. However, how to understand the environmental sustainability potential of sewage treatment mode is lack of scientific and systematic methods.
Net environmental benefit of sewage treatment to solve this problem, researchers from the ecological environment research center of the Chinese Academy of Sciences put forward the concept of net environmental benefit (NEB), that is, to reduce the environmental impact caused by problems such as energy consumption, chemical use and greenhouse gas emission in the sewage treatment process through multiple dimensions such as technology and policy, and maximize the recycling and reuse of useful substances in sewage and sludge. Aiming at this concept, they constructed a multi-objective evaluation framework for sewage treatment focusing on energy conservation, low carbon and deep resource recovery, and developed index weight algorithm and scenario time series prediction tool by using computational simulation and big data methods.