Category: Water


Comprehensive Prevention and Control of Water Pollution


Taking the water system as a whole, according to the geographical distribution of towns and industrial and mining enterprises along the coast of the water system, as well as the self-purification capacity, pollution capacity and pollution status of the water system, comprehensive prevention and control measures are taken to prevent and control water pollution. It includes various engineering technology means and management measures, which have the characteristics of integrity, comprehensiveness and regionality.
Comprehensive prevention and control of water pollution is a comprehensive application of various measures to prevent and control water pollution. Prevention and control measures involve two types of engineering and non-engineering, mainly:
(1) Reducing the discharge of wastewater and pollutants, including saving production wastewater, stipulating water quota, improving production technology and management system, increasing the reuse rate of wastewater, adopting new technology without pollution or less pollution, and formulating material quota, etc. For water-deficient cities and industrial and mining areas, regional recycling water and wastewater reuse systems should be developed.
(2) Developing regional water pollution prevention and control systems, including formulating urban water pollution prevention and control plans, river basin water pollution prevention and control management plans, implementing the total amount control system of water pollutant discharge, developing sewage after proper manual treatment for irrigation farmland and reuse for industry, establishing sewage reservoirs without polluting groundwater, and low water. Periodic storage of sewage reduces sewage discharge load and conducts controlled dilution during flood period.
(3) Develop wastewater treatment technologies with high efficiency and low energy consumption to treat wastewater.

Meaning

Comprehensive prevention and control of pollution refers to the comprehensive use of various measures to prevent and control water environmental pollution from the whole point of view. It is very necessary to implement comprehensive prevention and control of water pollution, because China is a country with relatively scarce water resources, and there are two manifestations: one is resource-based water shortage, the other is water-quality-based water shortage. For a long time, the purification treatment of sewage outlet based on point source control can not effectively solve the problem of water pollution. Comprehensive prevention and control of water pollution must be carried out from the overall point of view of the region and water system in order to fundamentally control water pollution and solve the problem of water shortage caused by water quality.

Why do this

The necessity and urgency of comprehensive prevention and control of water pollution are embodied in two aspects: first, the contradiction between water resources shortage and unbalanced supply and demand is prominent, and the serious pollution of water environment makes this contradiction more prominent and urgently needs to be solved;

Why is it so urgent?

Secondly, the purification treatment of sewage outlets based on point source control can not effectively solve the problem of water pollution. Comprehensive prevention and control of water pollution must be carried out from the whole region or water system, and the tail control of point source control should be transferred to the source control in order to control water pollution fundamentally.

Principle

The basic principle of sewage prevention and control is the combination of prevention, treatment and management.

Prevention

Through effective control and preventive measures, the amount of pollutants discharged by pollution sources can be reduced to the minimum.
(1) For industrial pollution sources, the most effective control method is to promote cleaner production. Cleaner production refers to the advanced production technology with the smallest utilization of resources and energy and the least pollution emission. The main technical routes adopted in cleaner production include: reforming raw material selection and product design, replacing toxic and harmful raw materials and products with non-toxic and harmless raw materials and products; reforming production process to reduce consumption of raw materials, water and energy; adopting recycling water system to reduce wastewater discharge; and recycling the usefulness of wastewater. Composition, reduce the concentration of wastewater, etc. Cleaner production advocates life cycle analysis and management of products rather than end-treatment.
(2) For domestic pollution sources, effective measures can be taken to reduce their emissions. Such as promoting the use of water-saving appliances, improving people’s awareness of water-saving, reducing water consumption, thereby reducing domestic sewage discharge.
(3) For agricultural pollution sources, in order to effectively control non-point pollution sources, we must start from “prevention”. Promoting scientific fertilization and rational use of pesticides in farmland can greatly reduce the residual fertilizers and pesticides in farmland, thereby reducing the amount of nitrogen, phosphorus and pesticides contained in farmland runoff.

Governance

Through various measures to control pollution sources and polluted water bodies, the pollution sources can achieve “standard discharge” and the water environment can achieve the corresponding water quality function.
It is very difficult or almost impossible for pollution sources to achieve zero discharge. Therefore, it is necessary to properly treat polluted (waste) water to ensure that the discharge standards set by the state or local authorities are met before it is discharged into the water body. Great attention should be paid to the relationship between industrial wastewater treatment and municipal wastewater treatment. For industrial wastewater containing acid, alkali, toxic and harmful substances, heavy metals or other special pollutants, local treatment should be carried out in the plant to meet the discharge standards to the water body or the water quality standards to the urban sewer. Those industrial wastewater similar in nature to municipal domestic sewage can be treated together with municipal sewage as a priority. It is not only unnecessary but also uneconomical to set up sewage treatment facilities separately. The design of urban sewage collection system and treatment plant should not only consider the need of water pollution prevention, but also the need to alleviate the contradiction of water resources. In areas where water resources are scarce, the treated municipal wastewater can be reused for agriculture, industry or municipal administration and become stable water resources. In order to meet the needs of wastewater reuse, its collection system and treatment plant should not be too centralized, but should be close to the reuse target.
In addition, according to the characteristics of water pollution, we should actively take physical, chemical, biological engineering and other means to control pollution, so that the deteriorated aquatic ecosystem can be gradually restored.

Management

Strengthen the supervision and management of pollution sources, water bodies and water treatment facilities in order to promote treatment. Pipe also plays an important role in water pollution control. Scientific management includes regular monitoring and inspection of pollution sources, water treatment facilities and sewage treatment plants, and regular monitoring of water environmental quality to provide basis and information for environmental management.

Main methods

Functional zoning of water environment is the basis for comprehensive prevention and control of water pollution
According to the current functions of water environment and the needs of economic and social development, the functional zoning of water environment is based on surface water environmental quality standards, which is the basis of water source protection and water pollution control. For example, the surface water environmental quality standard divides the water area control functions into five categories: Class I is mainly applicable to source water and national nature reserves; Class II is mainly applicable to primary protection areas of centralized drinking water sources, precious fish protection areas, fish and shrimp spawning grounds; Class III is mainly applicable to centralized drinking water sources II. Class IV is mainly suitable for general industrial water use and recreational water areas where human body does not contact directly; Class V is mainly suitable for agricultural water use areas and waters where general landscape requires.

Principles and methods

The principles of division are as follows: priority protection of centralized drinking water source areas; water body should not reduce its current use function, taking into account planning function; water areas with multiple functions should be classified according to the highest function; professional water standard requirements should be considered as a whole; consideration should be given to each other between upstream and downstream areas, with due consideration to potential functional requirements; and rational use of water body itself. Net capacity and environmental capacity; Consider the combination of land industrial rational layout; Consider the impact on underground drinking water sources; Practical and feasible, easy to manage.

Functional zoning method: according to the principle of adapting measures to local conditions and seeking truth from facts, according to actual measurement, empirical analysis and administrative decision-making.
Controlling pollution and protecting water sources according to functional areas.

(i) The level of protection shall be defined according to the functions of the waters and the requirements for water pollution control shall be put forward. For example, special protected waters refer to the first and second categories of national Surface Water Environmental Quality Standards (GB3838-2002). No new sewage outlets shall be built for such waters. Existing sewage discharge units shall be strictly controlled by local environmental departments in order to ensure that the water quality of accepted waters meets the water quality standards for specified purposes; and key protected waters shall be protected. It refers to the third class waters stipulated by GB3838-2002, and the first class discharge standards stipulated in the Comprehensive Sewage Discharge Standard (GB8978-1996) are applied to the sewage discharged into the waters.
(ii) The total amount control shall be implemented according to the functional areas. The so-called total amount control refers to the maximum allowable emission of some kind of pollution in order to maintain the environmental target value of an environmental functional area. Therefore, water environmental functional zoning is the basis for implementing total water pollution control.
Formulating comprehensive prevention and control plan of water pollution

Main contents and working steps

(i) Based on the investigation and evaluation of water environment, the main problems of water environment are analyzed and determined.
(ii) Division of water pollution control units. According to the analysis conclusion of water environment problems, considering the administrative division, water area characteristics and pollution source distribution characteristics, the source area and receiving water area are divided into water pollution control units.
(iii) Put forward environmental objectives and demonstrate accessibility. At the Fourth Session of the National People’s Congress, the strategic goal of environmental protection across the century was clearly put forward, which is the basis for the goal of comprehensive prevention and control of water pollution. Environmental objectives should include the total amount control objectives of major pollutants and the specific objectives of various sub-items of comprehensive water environment improvement. It is necessary to demonstrate the accessibility of environmental objectives.
(iv) Determine the amount of major pollutant reduction and the proportion of reduction allocation.
(v) To formulate a comprehensive water pollution prevention and control plan and implementation plan.
(vi) Support and guarantee for the implementation of the plan. Including: analysis of sources of funds, formulation of annual plans, implementation of pollutant discharge declaration and registration and pollutant discharge permit system proposals, as well as the necessary technical support.
Several principles that must be adhered to in formulating comprehensive water pollution prevention and control plan
(i) Focusing on economic construction is conducive to the coordinated development of economy and environment.
(ii) Take rational development and utilization of water resources as the core, focusing on the whole process control. By changing the mode of economic growth and promoting cleaner production, pollution can be eliminated in the process of economic reproduction.
(iii) Overall planning, highlighting key points, adapting measures to local conditions and stressing practical results.
(iv) adhering to the principle of comprehensive improvement. Systematic analysis of the planning scheme is needed to achieve overall optimization.

Emission permit system, transition from concentration control to total quantity control

Practice has proved that in carrying out this system, we must follow the following five requirements in the light of China’s current technological level and management system.
(1) Determine the total amount control target from the actual point of view. When it is difficult to determine the environmental capacity of the receiving water body for discharging pollutants, according to the principle of the total amount control plan put forward by the State Environmental Protection Administration in December 1995, the total amount of discharged major water pollutants in 1995 can be regarded as the target total amount, and the proportion of reduction can be determined according to the actual technical and economic level of the region, and allocated to the main body. Pollution sources.
(2) Choose the target of issuing certificates. The main target of issuing permits is the large polluters in the region. A city can catch more than a dozen or dozens of households. It is necessary to select the key control points through investigation and evaluation of pollution sources. For example, Anyang City put forward that we should do a good job of 2, 5 and 8, and control 8 and 9, that is, we should catch 20, 50 and 80 large polluters in batches, and control 70%, 80% and 90% of the city’s water pollution load.

  • Control the total amount of sewage. Measure according to local conditions and control the total amount of sewage.
  • Strengthen environmental supervision and management after issuance of certificates.
  • Pay attention to practical experience and constantly improve the level. In order to implement the sewage discharge permit system, we should first carry out pilot projects, sum up experience and gradually popularize it.
  • But we should also pay attention to the new problems in the process of implementation, such as the paid transfer of pollutant discharge indicators and the trading of pollutant discharge rights.
  • Comprehensive Prevention and Control of Water Pollution in Township Enterprises
  • The discharge of industrial wastewater from township enterprises was only 3.9 billion tons in 1997.
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Greenhouse Gases


Not every gas in the atmosphere absorbs intensely long-wave radiation from the ground. The greenhouse gases in the earth’s atmosphere are called greenhouse gases, mainly carbon dioxide (CO2), methane, ozone, nitrous oxide, freon and water vapor. They absorb almost all the long-wave radiation emitted from the ground, and only a very narrow region absorbs very little, so they are called “window region”. It is through this window that the earth returns 70% of the heat from the sun to the space in the form of long-wave radiation, thus maintaining the ground temperature unchanged. The greenhouse effect is mainly due to the increase in the number and variety of greenhouse gases by human activities, which makes the 70% value decrease and the remaining heat makes the earth warm.

What is greenhouse gas?

However, although CO2 and other greenhouse gases have a strong ability to absorb long-wave radiation from the ground, their amount in the atmosphere is very small. If the atmospheric state of pressure as a atmospheric pressure and temperature of 0 C is called the standard state, then the whole atmosphere of the earth is compressed to this standard state, its thickness is 8000 meters. At present, the content of CO 2 in the atmosphere is 355 ppm, or 355 parts per million. Converting it to the standard state, it will be 2.8 meters thick. This is 2.8 meters thick in the atmosphere of 8,000 meters thick. Methane content is 1.7 ppm, corresponding to 1.4 cm thick. The ozone concentration is 400 ppb (ppb is one thousandth of ppm), which is only 3 mm thick after conversion. Nitrous oxide is 310 ppb, 2.5 mm thick. There are many kinds of freon, but the most abundant Freon 12 in the atmosphere is only 400 ppt (ppt is one thousandth of ppb), converted to the standard state of only 3 microns. This shows that there are few greenhouse gases in the atmosphere. It is also for this reason that human release without restrictions can easily lead to rapid global warming.

History of development

As early as 1938, British meteorologist Carlinda pointed out that CO2 concentration had risen by 6% since the beginning of the century after analyzing sporadic CO2 observations around the world at the end of the 19th century. He also found that there was a warming tendency in the world from the end of last century to the middle of this century, which caused great repercussions in the world. To this end, Kellin of Scripps Oceanographic Research Institute established an observatory in 1958 at an altitude of 3,400 meters in the Maunaroya Mountains of Hawaii, and began the precise observation of atmospheric CO2 content. Because Hawaii is located in the middle of the North Pacific Ocean. Therefore, it can be considered that it is not affected by terrestrial air pollution and the observation results are reliable.

From April 1958 to June 1991, the atmospheric CO2 concentration in the Maunaroya Mountains was observed. It was found that the atmospheric CO2 content in 1958 was only about 315 ppm, which reached 355 ppm in 1991. The seriousness of the problem also lies in the fact that only about half of the 5.5 billion tons of fossil fuels (about 4 tons of CO2 per ton) that humans burn annually (1996) enter the atmosphere and the rest are mainly absorbed by marine and terrestrial plants. Once the ocean is saturated with CO2, the atmospheric CO2 content will increase exponentially. In addition, they also found seasonal variations in CO2 content, with a difference of 6 ppm between winter and summer. This is mainly due to the winter drought and summer glory of vegetation on the vast continents of the Northern Hemisphere, that is, plants absorb CO2 in summer, which makes the atmospheric CO2 concentration relatively lower.

Includings

According to the determination of CO2 concentration in the air of sealed bubbles in the Antarctic and Greenland continental ice sheets, the CO2 content in the atmosphere has been relatively stable for a long time in the past, about 280 ppm. Only from the mid-18th century, before and after the Industrial Revolution began to rise steadily. That is to say, it took 240 years for human beings to increase the atmospheric CO2 concentration from 280 ppm to 355 ppm.

Methane is the second most important greenhouse gas after CO2. Although its concentration in the atmosphere is much lower than CO2, its growth rate is much higher. According to the Second Climate Change Assessment Report issued by the Intergovernmental Panel on Climate Change (IPCC) in 1996, CO2 increased by 30% in 240 years from 1750 to 1990, while methane increased by 145% in the same period. Methane, also known as biogas, is produced when organic matter decays under anoxic conditions. For example, paddy fields, compost and animal manure all produce biogas. Nitrogen monoxide is also known as laughing gas, because inhaling a certain concentration of this gas can cause facial muscle spasm, which looks like laughing. It is mainly produced by burning fossil fuels and organisms using chemical fertilizers. Although the ozone content in the atmosphere decreases in the stratosphere, it increases in the troposphere, which will be discussed later. Freon gases are compounds of chlorine, fluorine and carbon; they do not exist in nature and are entirely human-made. Because of its low melting point and boiling point, non-flammable, non-explosive, odorless, harmless and excellent stability, it is widely used in the manufacture of refrigerants, foaming agents and cleaners. Although the highest concentrations of Freon 12 and 11 in the earth’s atmosphere are very few, their growth rates have been very high in the past, both of which are 5% per year. Because of its severe destruction of the ozone layer in the atmosphere, its concentration in the atmosphere is expected to decrease gradually from the beginning of the 21st century according to the 1987 International Montreal Protocol.

It should be noted that although the atmospheric concentration of greenhouse gases other than CO2 is much lower than that of CO2, some of them are several orders of magnitude smaller, their greenhouse effect is much stronger than that of CO2. Therefore, their contribution to atmospheric greenhouse effect, according to the second IPCC Report, is only one order of magnitude lower than that of CO2. If their total contribution to the greenhouse effect of the Earth’s atmosphere is small compared with CO2 before 1960, it is not negligible that in the near future they will go hand in hand with CO2 and even exceed CO2.
April 2, 2018, DOE Labor

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