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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.
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.
The basic principle of sewage prevention and control is the combination of prevention, treatment and management.
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.
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.
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.
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.
Earthworms, commonly known as earthworms, also known as Eel, are the representative animals of Oligochaeta in annelida. Earthworms are saprophytic living animals. They live in humid environment and feed on corrupt organic matter. They are full of a large number of microorganisms but seldom get sick. This is related to the unique number of antimicrobial immune systems in these earthworms.
In scientific classification, they belong to unidirectional earthworms. The body is cylindrical (distinct from the cylindrical shape of linear animals), symmetrical on both sides and segmented: it consists of more than 100 segments. After the Eleventh segment, there is a dorsal foramen in the middle of the back of each segment; there is no skeleton, it belongs to invertebrates, with bare body surface and no cuticle. Except for the first two segments of the body, all the other segments have bristles. Hermaphroditism, allogeneic fertilization, reproduction by the ring to produce cocoons, reproduction of the next generation. There are more than 2500 known earthworms. Darwin pointed out in 1881 that earthworms are the most important animal group in the world’s evolutionary history.
Body wall and secondary body cavity
The body wall of earthworms consists of cuticle, epithelium, circular muscular layer, longitudinal muscular layer and coelomic epithelium. The outermost layer is a single layer of columnar epithelial cells whose secretions form cuticle. The membrane is very thin, consisting of collagen fibers and non-fibrous layers with small holes. Cylindrical epithelial cells were mixed with fine glands cells, divided into mucous cells and protein cells, can secrete mucus and make the body surface moist. Earthworms encounter intense stimulation. Mucous cells secrete a large amount of mucus to wrap the body into a mucous membrane, which has a protective effect. Epithelial cells have short basal cells at the base, and some people think that they can develop into columnar epithelial cells. Sensory cells aggregate to form sensory organs and disperse between epithelial cells. The nerve fibers of a thin layer of nerve tissue under the epithelium are connected at the base. In addition, there are photoreceptor cells, the base of epithelium, also connected with the nerve fibers below it.
The muscles of earthworms belong to the twill muscles, which generally account for about 40% of the body volume. They are well-developed and flexible. When the longitudinal muscular layer of some segments of the earthworm contracts and the circular muscular layer relaxes, the segment becomes thicker and shorter, and the retracted bristles born on the body wall obliquely extend into the surrounding soil; at this time, the circular muscular layer of the former segment contracts, the longitudinal muscular layer relaxes, the segment becomes thinner and longer, and the bristles retract, thus breaking away from the surrounding soil. The bristle support of the latter segment pushes the body forward. In this way, the contraction wave of muscles gradually passes forward and backward along the longitudinal axis of the body.
The coelomic compartment is separated by the septum according to the body segment, and each compartment is connected with a small hole. Each body chamber is formed by the development of left and right two body sacs. The medial part of the sac formed visceral membranes, while the dorsal and ventral parts formed dorsal and peritoneal mesenteries. In earthworms, the mesentery of the abdomen degenerates, only part between the intestine and the abdominal vessels exists, while the mesentery of the back disappears. The part between the anterior and posterior coelomic sacs is closely together, forming a septum. Some species have no septum in the esophagus.
The digestive tract runs longitudinally in the central part of the body cavity and passes through the septum. The muscular layer of the wall of the digestive tract is well developed, which can improve peristalsis and digestive function. The digestive tract is differentiated into mouth, mouth, throat, esophagus, sand sac, stomach, intestine and anus. The mouth can be turned out from the mouth to ingest food. The pharyngeal muscles are well developed, the muscles contract, and the pharyngeal cavity enlarges to support feeding. There is a single-cell pharyngeal gland outside the pharynx, which secretes mucus and proteinase, moisturizes food and has a preliminary digestive effect. After pharynx, there is a short and thin esophagus with esophageal glands on its wall. It can secrete calcium and neutralize acidic substances. The back of the esophagus is a muscular sand sac (gizzard), lined with a thick cutin membrane, which can grind food. From mouth to sand sac, the ectoderm is formed and belongs to foregut. The digestive tract behind the sand sac is rich in microvessels and glands, which is called stomach. There is a circle of gastric glands in front of the stomach, which functions like pharyngeal glands. The digestive tract enlarges to form the intestine, and its dorsal central fovea enters into a blind canal (typhlosole), which enlarges the area of digestion and absorption. Digestion and absorption are mainly performed in the intestine. The outermost visceral membranes of the intestinal wall specialize into yellow cells. Since the 26th body segment, a pair of conical cecum (caeca) extending forward from both sides of the intestine can secrete a variety of enzymes, which are important digestive glands. The stomach and intestine originate from the endoderm and belong to the midgut. The posterior intestine is relatively short, accounting for about 20 body segments in the posterior end of the digestive tract. It has no blind passage and no digestive function. Open to the body through the anus. The digestive system of earthworms consists of more developed digestive ducts and glands. The digestive ducts are composed of oral cavity, pharynx, esophagus, crop sac, sand sac, stomach, small intestine, cecum, rectum and anus.
Earthworms are very special. Like their body segments without obvious merger, their hearts are also divided into several segments in the front of the body, generally 4-5, which are circular, like enlarged blood vessels, so they are also called circular blood vessels. The dorsal side of the annular heart is connected with the dorsal blood vessel from the back to the front, and the ventral side is connected with the abdominal blood vessel from the front to the back. The abdominal blood vessel and its branches are connected with the inferior nerve blood vessel from the front to the back. The annular heart has thicker muscular walls than blood vessels and pulsates. There are also valves that open unilaterally to ensure blood flow from the dorsal to the abdominal vessels. Generally speaking, the blood flow is powered by the pulsation of these independent annular hearts. The direction of blood flow is from back to front (in the dorsal vessels), from back to abdomen (in the annular heart), and from front to back (abdominal vessels and subnervous vessels).
Respiration and Excretion
The excretory organs of earthworms are posterior renal tubules. In general, each segment has a pair of typical posterior renal tubules.