Water quality standards refer to the standards for water use or discharge specified by the state, department or regionPhysics、Chemistry、biologyRequirements to be met in terms of nature.It is a mandatory decree with legal effect based on water quality standards, a yardstick for judging whether water quality is applicable, a goal of water quality planning and a technical basis for water quality management. For water quality for different purposes, there are different requirements, so that different water quality standards can be formulated according to the natural environment, technical conditions, economic level, profit and loss analysis.China has formulated and promulgated a series of water quality standards, such as "sanitary standards for drinking water", "sanitary standards for industrial enterprise design", "water quality standards for farmland irrigation", "water quality standards for fishery"“Sea water quality standard”, "surface water environmental quality standards", "technical principles and methods for formulating local water pollutant discharge standards", "water pollution discharge standards", etc., which provide a legal basis for water quality management.[1]
The sanitary standard of drinking water is a legal hygienic standard issued in a certain form with the approval of relevant national departments, which stipulates the quantity of various factors (physical, chemical and biological) of drinking water and human health, as well as the relevant code of conduct for the realization of the quantity, in order to protect the health of the population and ensure the quality of human life.At the end of 2006, the Ministry of Health, together with relevant departments, completed the revision of the 1985 version of the Sanitary Standards for Drinking Water, and officially promulgated the new version《Hygienic standard for drinking water》(GB5749-2006).[2]
Hygienic standards for the design of industrial enterprises
The standard is in GBZ1-2002《Hygienic standards for the design of industrial enterprises》The standard is mandatory except for individual sentences which are clearly indicated as reference clauses.The Hygienic Standard for the Design of Industrial Enterprises GBZ1-2010 was officially implemented on August 1, 2010.The standard includes air, water and soil quality protection.[3]
Water quality standard for farmland irrigation
For implementation《Environmental Protection Law of the People's Republic of China》This standard is formulated to prevent pollution of soil, groundwater and agricultural products, protect human health, maintain the ecological environment and promote economic development.This standard specifies all aspects of farmland irrigation water quality, implementation of standards and sampling monitoring methods.This standard is applicable to farmland irrigation water with surface water, groundwater, treated urban sewage and industrial wastewater of similar quality to urban sewage as water sources nationwide.This standard is not applicable to medicine, biological productsChemical Reagents, pesticide, petroleum refining, coking and organic chemical wastewater for irrigation.Since October 1, 1992, the Water Quality Standard for Farmland Irrigation (GB 5084-92) has been implemented.[4]
Class II: mainly applicable to centralizedDrinking WaterThe first level protection area of surface water source, habitat for rare aquatic organisms, spawning ground for fish and shrimp, feeding ground for young and juvenile fish, etc;
Class III: mainly applicable to centralized domestic drinking water, secondary protection areas of surface water sources, wintering and migration channels of fish and shrimp, aquaculture areas and other fishery waters and swimming areas;
Class IV: mainly applicable to general industrial water areas and entertainment water areas not directly contacted by human body;
Class V: mainly applicable to agricultural water areas and waters with general landscape requirements.
Provisions for various water uses:
Class I water quality: good water quality.Groundwater only needs disinfection treatment, and surface water can be used for drinking after simple purification treatment (such as filtration) and disinfection;
Class II water quality: slightly polluted.Regular purification treatment (such asflocculation, sedimentation, filtration, disinfection, etc.), whose water quality can be used for drinking;
Class III water quality: applicable to the secondary protection area of centralized domestic and drinking water source, general fish protection area and swimming area;
Class IV water quality: applicable to general industrial protection areas and entertainment water areas not directly contacted by human body;
Class V water quality: applicable to agricultural water areas and waters with general landscape requirements.The water body exceeding the five water quality standards has basically no use function.[7]
Technical principles and methods of local water pollutant discharge standards
In accordance with the provisions of Article 11 of the Environmental Protection Law of the People's Republic of China (for trial implementation), "Protect rivers, lakes, seas, reservoirs and other waters and maintain good water quality", the Technical Principles and Methods of Local Water Pollutant Discharge Standards are hereby formulated to unify the guiding ideology, technical regulations, basic procedures and methods for formulating local water pollutant discharge standards nationwide.This standard is the national basic environmental standard, which is applicable to the formulation of pollution discharge standards for surface water discharged into rivers, lakes, reservoirs, etc.Local water pollutant discharge standards shall be formulated by all regions. In addition to the provisions of this standard, national guidelines, policies and regulations on environmental protection shall also be implemented.[8]
Total solids(TotalSolids): the total amount of solid matter left after the water sample is evaporated and dried at 103-105 ℃, also known as evaporation residue.
two
Suspended solids and dissolved solids: the amount of residual solids after filtering the water sample and evaporating the filtrate intercepts is called suspended solids, and the amount of residual solids after evaporating the filtrate is called suspended solids.
three
Volatile solidsVolatileSolids and Fixed Solids: the weight lost by burning the solid in the water sample after evaporation and drying at a certain temperature (600 ℃).It can be used to indicate the organic content.The weight of residue after burning is called fixed solid.
four
conductivityConductivity refers to the conductivity of a certain volume of solution, that is, the conductivity of the solution between two flat electrodes with an area of 1 square centimeter and a distance of 1 cm at 25 ℃.
Chemical index
one
Non specific indicators:conductivity、PH value, hardness, alkalinity, inorganic acidity, etc;
Non specific organic indicators: total oxygen consumption, chemical oxygen consumption, biochemical oxygen consumption, total organic carbon, potassium permanganate index, phenols, etc;
Some indicators are single indicators, such as temperaturePH value、dissolved oxygenEtc;Some indicators refer to the water quality conditions formed under the action of multiple factors according to the common characteristics of a certain type of substances, which are called comprehensive indicators, such asBiochemical oxygen demand(BOD) refers to the pollution status of organic matter in the water that can be biodegradable, and the total hardness refers to the amount of inorganic salts such as calcium and magnesium in the water.[10]
Difference of water quality standards between China and foreign countries
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China's water quality standards mainly focus on hydrochemical and physical indicators, and the system needs to be improvedWater environment qualityEfforts are still needed to conduct a comprehensive evaluation.The current water quality standards are formulated according to different waters and their use functions. Some water quality standards differ from WHO water quality standards and US water quality standards or reference limits not only in terms of indicator items, but also in terms of indicator limits.
For some priority pollutants, China's water quality standard value ratioworld health organizationorU.S. Environmental Protection AgencyThe given standards or reference limits are more stringent, and China's current standards add more pollutant items that do not give recommended values in foreign benchmark tables, such as the priority control pollutant metal silver, non priority control pollutant metal aluminum,Organic pesticideClass I pollutants include parathionmalathionAnd phosphorus absorption, and disinfection by-product chloride.The reasons why the World Health Organization has not given their recommended values are as follows: 1. Not enough information on the human health toxicity of silver and aluminum has been obtained;2. For the above pesticide pollutants,WHO believes that these pesticides have been banned in developed countries, and the concentration that may exist in drinking water is far lower than the concentration that has toxic effects on human body;3. For chlorides,WHO believes that the residual chloride concentration in drinking water after treatment is not enough to have an impact on health.Therefore, the basis for the establishment of these pollutant limits in Chinese standards needs further discussion and research.[11]
data statistics
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The Statistical Bulletin of National Economic and Social Development of the People's Republic of China in 2022 shows that in 2022, 81.9% of the coastal waters in the whole year will meet the national Class I and Class II sea water quality standards, 4.1% of the Class III sea water, and 4.1% of the Class IV sea waterFour types of seawater account for 14.0%.[12]
