Discussion on environmental quality standards for surface water

- Aug 11, 2020-

"Surface Water Environmental Quality Standard" (GB 3838-2002) since its implementation in 2002, has become an important tool for my country's surface water environmental quality evaluation and assessment, and has played an important role in my country's surface water environmental management. For more than ten years, with the change of the surface water environmental protection situation in my country, the improvement of surface water environmental quality and the continuous development of scientific research in the field of water environment at home and abroad, the need to revise the "Surface Water Environmental Quality Standard" has become increasingly urgent.

The Necessity of Revision of "Surface Water Environmental Quality Standard"

The object of surface water environmental protection needs to be further clarified to maintain a good water environment quality. It is an important part of China's comprehensive construction of a well-off society and an ecological civilization. It is an important measure to implement the scientific development concept and promote the sustainable development of the economy and society to protect the people's health Basic conditions for health The "Water Pollution Prevention and Control Law of the People's Republic of China" was revised in 2008 to further clarify the purpose of water environmental protection, that is, prevent water pollution, protect and improve the environment, ensure drinking water safety, and promote comprehensive economic and social coordination. Continuous development, while further clarifying the legal status of surface water environmental quality standards, and adding special chapters for the protection of drinking water sources and other special water bodies. In addition, the 18th National Congress of the Communist Party of China proposed to vigorously promote the construction of ecological civilization and build a beautiful China, which also contains higher requirements for the quality of the water environment. The water ecosystem is an important component of the surface water environment. Its health status is closely related to the quality of surface water, and the quality of surface water affects the realization of the use of water bodies and human health. Therefore, protecting the surface water environment is to maintain the surface water ecology System health, protect human health, and meet the basic requirements of water quality for different use functions. The above goals need to be further reflected and strengthened in the "Surface Water Environmental Quality 

The determination of chemical oxygen demand will cause secondary pollution, and the replacement of chemical oxygen demand by total organic carbon is an international requirement.

  Total Organic Carbon (TOC.) is the total amount of carbon contained in organic matter in water, which can fully reflect the pollution level of organic matter to water bodies. It is a comprehensive indicator of organic pollutants in water together with chemical oxygen demand (COD) and biological oxygen demand (BOD), and the organic pollutants in water reflected by TOC are more comprehensive and reasonable.

Theoretically, COD is the consumption of oxygen (02) to represent oxygen consumption, TOC is to use carbon (C) to represent oxygen consumption, the ratio of the two is O2/C=32/12=2.67, due to different regions and different Differences in water quality, etc. The concentration values of COD and TOC will be different; for water samples of different regions and different water quality, COD and TOC are measured separately, and the least squares method is used to perform regression analysis on the measurement results to obtain the linear correlation mathematics model. The International Organization for Standardization issued ISO8245-1987 "Guidelines for the Determination of Total Organic Carbon (TOC) in Water Quality" in 1987 and 1SO8245-1999 "Determination of Total Organic Carbon (TOC) and Soluble Organic Carbon (DOC) in Water Quality" in 199. The "Guidelines" replaces IS082451987, adds a method for determining soluble organic carbon (DOC.), and regulates the storage conditions of samples and reagents. At present, the United States mainly uses TOC to characterize the organic matter content in water bodies. Japan also began to include T0C in the Japanese Industrial Standard (JISK0102) in the early 1970s, and has now developed to use the TOC method to replace the traditional BOD/COD ratio method to test the biodegradability of organic matter. The United States, Japan, the United Kingdom, and some countries in the European Union began to use TOC and total oxygen demand (TOD) as comprehensive monitoring indicators for organic pollutants since the late 1980s and to control them.

   my country's surface water pollution characteristics have changed

Since the implementation of the current "Surface Water Environmental Quality Standards", the water environmental quality of the main river systems in my country has improved significantly. According to the data released by the China Environmental Quality Bulletin, in 2002, the seven major water systems were polluted in different ways.The proportion of sections meeting Grade III water quality was 29.1%, and the proportion of sections with poor Grade V water quality was 40.9%: In 2012, the total national surface water control sections nationwide For light pollution, the proportion of sections meeting Grade III water quality among the ten major river basins under national control reached 68.9%, and the proportion of sections with poor Grade V water quality was 10.2%. The main pollution indicators have also changed. In 2002, the main pollution indicators were petroleum, chemical oxygen demand, ammonia nitrogen, permanganate index, volatile phenol and mercury, which were characterized by the mixture of industrial pollution sources and domestic pollution sources. The main pollution indicators are chemical oxygen demand, five-day biochemical oxygen demand, permanganate index, ammonia and total phosphorus characterized by a mixture of domestic pollution sources and livestock and poultry breeding pollution sources. At the same time, monitoring data for many years shows that some indicators in the current "Surface Water Environmental Quality Standards" have never been detected in surface water bodies in my country for many years. The above phenomena indicate that the monitoring and management objectives of the surface water environment in my country need to be adjusted accordingly. At the same time, new persistent pollutants (POPs) represented by perfluorinated compounds, personal care products and pharmaceuticals have been widely detected in the water environment, and some countries have formulated corresponding management standards. Therefore, my country should consider the revision of "Surface Water Environmental Quality Standards" in a timely manner based on the characteristics of surface water pollution and changes in water environmental management needs.

   my country's water quality analysis capabilities have been greatly improved

With the continuous development of water quality analysis instruments and water quality analysis methods, China's water quality analysis technology has been greatly improved in recent years. Convenient, efficient, and environmentally friendly water quality analysis methods have been continuously applied to actual water quality monitoring work. Water quality analysis methods More diversification, the detection limit of pollutants is also continuously reduced. Restricted by the analysis level at that time, about 50% of the current "Surface Water Environmental Quality Standards" used the national standard method before 2001, and a considerable part of it was the national standard method in the 1980s; another 50% adopted the national standard method. It is a temporary analysis method. Since 2003, the Ministry of Ecology and Environment has revised or promulgated nearly a hundred standards for water pollutant analysis methods. Therefore, it is urgent to revise the analysis method part of "Surface Water Environmental Quality Standard" to meet the urgent needs of current water environment monitoring and analysis.

Concluding remarks

   According to the "13th Five-Year Development Plan for National Environmental Protection Standards (Draft for Comment)" issued by the Ministry of Ecology and Environment, the revision of "Surface Water Environmental Quality Standards" (GB 3838-2002) has been included in the agenda. With the advancement of analytical technology and the development of new methods, GC-MS, LC-MS, ICP-OES, ICP-MS and other technologies will gradually replace traditional GC, LC, AAS and other time-consuming and laborious detection methods. At the same time, as people's requirements for the living environment continue to increase, the corresponding emission restrictions will gradually become stricter, and higher requirements will be placed on testing instruments. I believe that with the release of the new version of the standard, the field of water quality testing will usher in new development opportunities.