What are the practices that affect the "synergy of pollution reduction and carbon reduction"?

In recent years, many river basins and provinces in China have introduced their own sewage treatment and discharge standards. Among them, many standards put forward quasi-Class IV or even quasi-Class III effluent discharge requirements.

This means that the water quality of the sewage discharged up to the standard is close to the water quality of the general industrial water area and the recreational water area where the human body is not in direct contact, and even close to the water quality of the secondary protection zone of the surface water source of centralized domestic drinking water. Is this necessary? Is it scientific?

The phenomenon of excessive upgrading of the sewage treatment industry has long attracted attention from many parties. In April 2022, the Ministry of Ecology and Environment, the Ministry of Housing and Urban-Rural Development, the National Development and Reform Commission, and the Ministry of Water Resources jointly issued the Implementation Plan for the Deepening of the Battle for the Treatment of Urban Black and Odorous Water Bodies, making arrangements for the relevant work during the 14th Five-Year Plan period. In particular, it mentions that "the effluent standards of sewage treatment plants should not be blindly raised. "This is also the first official response from the national policy level to the problem of excessive upgrading of the sewage treatment industry.

Not long ago, the National Development and Reform Commission, the Ministry of Housing and Urban-Rural Development, and the Ministry of Ecology and Environment jointly issued the "Implementation Opinions on Promoting the Synergy of Sewage Treatment, Pollution Reduction and Carbon Reduction" (hereinafter referred to as the "Implementation Opinions"), which once again emphasized that all localities should "formulate local standards for sewage discharge in a scientific and reasonable manner and according to local conditions".

In addition to the changing policy orientation, there has also been a long-term discussion on this issue by those in the field of water environment, calling for no emphasis on excessive effluent standards. However, the reporter noticed that the previous discussion focused more on the actual effects of sewage treatment costs, processes and high operation and maintenance costs, which led to some facilities "basking in the sun". In the context of the "dual carbon" strategy, there is a new angle on how to look at this issue.

"Excessive upgrading" is a significant problem of uncoordinated pollution reduction and carbon reduction in the current field of sewage collection and treatment

Hao Xiaoguang, an expert member of the Shanxi Provincial Urban Drainage Professional Committee, told reporters: "The "Implementation Opinions" put forward the concept of 'synergy of pollution reduction and carbon reduction' in sewage treatment, which is the focus and highlight of the entire document. It makes it clear that pollution reduction and carbon reduction must go hand in hand. Sewage treatment plants have always been energy-intensive industries with high energy consumption and high investment in the traditional sense, and the "synergy of pollution reduction and carbon reduction" is proposed, which elevates sewage treatment from a single role in promoting the improvement of the water environment to the role of promoting the improvement of the overall environment from the level of "big environmental protection", giving the sewage treatment a broader connotation. ”

In China, the carbon emissions of the sewage treatment industry account for about 1% of the total emissions of the whole society, accounting for the largest proportion in the environmental protection industry. In the context of the "dual carbon" strategy, it is of new significance to discuss the problem of "excessive upgrading" of sewage treatment.

Peng Yongzhen, an academician of the Chinese Academy of Engineering and an expert in sewage treatment, once analyzed that some cities are in a hurry to control water environmental pollution and blindly raise urban sewage discharge standards, resulting in an increase in treatment costs by more than several times.

Wang Jiazhuo, deputy chief engineer of the China Academy of Urban Planning and Design, president of the Ecological Municipal Institute of the Chinese Academy of Planning and Design (Beijing) Planning and Design Co., Ltd., and a professor-level senior engineer, told reporters: "Compared with the relevant foreign standards, China's first-class A emission standards are originally very high. However, in recent years, various localities have issued their own local emission standards and river basin emission standards. Most of these standards are implemented in accordance with quasi-Category IV, and even quasi-Category III emission standards have appeared recently. The research results of some domestic scholars show that excessive upgrading and transformation of sewage treatment plants not only has a poor input-output ratio from an economic point of view, but also significantly increases carbon emissions. This is the most significant problem of uncoordinated pollution reduction and carbon reduction in the field of sewage collection and treatment, although the pollutant discharge has been reduced, but the carbon emission has increased significantly. In the context of synergy in pollution reduction and carbon reduction, the excessive improvement of sewage treatment plant discharge standards is one of the most important issues that should be paid attention to at present. ”

In order to play a leading role in pollution reduction and carbon reduction, China will build 100 green and low-carbon benchmark plants for sewage treatment with efficient recycling of energy resources in 2025.

In this regard, Hao Xiaoguang believes: "To clarify the scientific and reasonable measurement standards of 100 green and low-carbon benchmark factories, first of all, there must be reasonable environmental emission standards at the local level. In order to cope with the high local requirements for effluent quality, some sewage treatment plants use methods such as over-aeration, over-control of sludge concentration, and over-dosing. This is contrary to the concept of green and low-carbon, and should reverse the high-carbon operation situation caused by unreasonable excessive upgrading in some regions. ”

Is it "over-raised" and how is it measured?

Although it is necessary to rationally look at the problem of high carbon emissions caused by excessive upgrading of sewage treatment plants, it should be noted that not all upgrading standards are "excessive", and they cannot be generalized.

A senior expert in the field of water environment believes that it depends on what water bodies the effluent of the sewage treatment plant is discharged to? What are the functions of these water bodies, and what requirements should be met? If the downstream of the sewage treatment plant is close to the state-controlled section, the transboundary section, or close to other high-function water bodies, the discharge standard can also be appropriately raised for specific pollutants after economic and technological comparison; but assuming that it is discharged into a water body with lower function, the water environment capacity of these water bodies is also guaranteed, then it is sufficient to discharge according to the standard of Class A . Therefore, on the one hand, it is necessary to ensure the quality of the water environment, and on the other hand, it is necessary to respond to the requirements of the state for pollution reduction and carbon reduction. The situation varies greatly from place to place, and it is necessary to take it into account comprehensively.

Peng Yongzhen believes that China has a vast territory, and the environment, climate and living habits of the east, west, north and south regions are very different, and the water quality, quantity and environmental capacity of the receiving water bodies are not the same, so the actual situation should be considered when formulating and implementing sewage discharge standards, and it is not necessary to be "uniform".

Wang Jiazhuo said: "The documents of the three ministries and commissions clearly put forward that sewage discharge standards should be formulated scientifically and rationally and according to local conditions. Obviously, the reason for this is that the current emission standards in some places are unscientific and unreasonable, and they do not adapt measures to local conditions, and they demand that the standards continue to be raised across the board. The requirements of the document on the scientific and reasonable formulation of sewage discharge standards according to local conditions have pointed out the direction for how to spend limited funds on the cutting edge to achieve the maximum input-output ratio and the synergy of pollution reduction and carbon reduction under the current situation of local financial constraints. Moreover, the document clarifies the factors that need to be considered in the formulation of sewage treatment discharge standards, including problem orientation, economic and social development, water environment capacity, sewage water quality, energy consumption and drug consumption, etc., which have been improved and refined compared with the previous formulation, which is of great significance for promoting the high-quality development of urban sewage treatment and promoting the synergy of pollution reduction and carbon reduction. ”