The environmental protection work during the 11th Five-Year Plan period has made positive progress. While the national economy is developing rapidly, chemical oxygen demand (COD) is effectively controlled, and the surface water environment quality has generally improved. "Fifteen" late effects of ammonia on water quality and permanganate index was essentially flat, "Eleventh Five-Year" two years ago has become the primary indicator of ammonia affect surface water quality, as well as various types of harmful nitrogen in a form most influential . During the “Twelfth Five-Year Plan†period, while continuing to promote COD pollution reduction, taking into account environmental quality characteristics, stage priorities, existing foundations and technical and economic factors, it is necessary to incorporate ammonia nitrogen into the country’s major water pollutant discharge control. indicators, and by upgrading sewage treatment plants synergies, improve the living source of ammonia nitrogen removal efficiency, seize chemical, paper, food processing, textiles, black metallurgy, petrochemical and other key industries, supplemented by agriculture source pollution control, can effectively control The total amount of ammonia nitrogen emissions will greatly improve the current water quality ammonia nitrogen exceeding the standard and reduce the load of ammonia nitrogen and total nitrogen in the lake.
Why should we carry out ammonia nitrogen pollution prevention and control?
Ammonia nitrogen pollutants have a greater impact on the water environment
Ammonia nitrogen in a water body refers to a compound ammonia in the form of ammonia (NH 3 ) or ammonium (NH 4+ ) ions. Ammonia nitrogen is one of the most harmful forms of nitrogen in various types, and it is a sign that water is polluted. Its harm to aquatic environment is manifested in many aspects. Like COD, ammonia nitrogen is also the main oxygen-consuming pollutant in water. Oxidation and decomposition of ammonia nitrogen consumes dissolved oxygen in water, making the water body black and smelly. Non-ionic ammonia in ammonia nitrogen is the main factor causing toxicity of aquatic organisms, and it is highly toxic to aquatic organisms, and its toxicity is several times larger than that of ammonium salts. In the case of sufficient oxygen, ammonia nitrogen can be oxidized by microorganisms to nitrite nitrogen, which is decomposed into nitrate nitrogen. Nitrite nitrogen combines with protein to form nitrosamine, which is carcinogenic and teratogenic. At the same time, ammonia nitrogen is a nutrient in water, which can provide a nutrient source for algae growth and increase the chance of eutrophication.
Ammonia nitrogen is one of the forms of total nitrogen in natural water. Controlling ammonia nitrogen is beneficial to reduce the load of ammonia nitrogen and total nitrogen in the lake. Although ammonia nitrogen degradation in sewage treatment only converts ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, total nitrogen removal cannot be achieved. However, by controlling the total amount of ammonia nitrogen, the amount of ammonia nitrogen generated at the source can be reduced, and the ammonia nitrogen pollution load entering the water body can be reduced, thereby directly reducing the total nitrogen content of the water body, which is beneficial to alleviating the eutrophication of the lake reservoir.
The emission of ammonia nitrogen pollutants is large, and the pollution load far exceeds the environmental capacity of water bodies.
During the 10th Five-Year Plan period, the total amount of ammonia nitrogen emissions showed a trend of increasing year by year. During the "11th Five-Year Plan" period, the total amount of emissions began to decline, but it still has not reached the level of the early 10th Five-Year Plan. China's ammonia nitrogen emissions far exceed the environmental capacity of the receiving water body and the pressure of the pollution load is the most important cause of the current surface water body ammonia nitrogen exceeding the standard. According to preliminary estimates, the total amount of ammonia nitrogen emissions in 2007 is about four times the environmental capacity. In the future, China's economy will still be in the "double fast" development stage of industrialization and urbanization. The incremental pressure of pollutant discharge is huge, and the contradiction between large ammonia nitrogen emissions and relatively insufficient environmental capacity is still difficult to be fundamentally alleviated.
Ammonia nitrogen has become the main pollution factor affecting China's water quality at this stage
Ammonia nitrogen is the main over-standard pollutant in the seven major water systems. The frequency of ammonia nitrogen pollution is a national pollution problem. In 2007, ammonia nitrogen was the primary pollutant of the Yangtze River, the Yellow River, the Haihe River and the Liaohe River, and it was also the main pollutant of the Pearl River and the Huaihe River. The results of the special plan for water pollution prevention and control in key river basins in 2008 showed that the ammonia nitrogen pollution in key river basins was serious. The ammonia nitrogen in most sections of the Haihe River, Liaohe River, the Three Gorges reservoir area and its upstream, the middle and upper reaches of the Yellow River exceeded the standard, and the ammonia nitrogen in the basins of Taihu Lake, Chaohu Lake and Dianchi Lake was up to standard. The rate is also low. In 2008, the national surface of the national surface water river was 19.2%, and the average concentration of ammonia nitrogen in all sections was 1.9mg/l, which only reached the standard level of V.
According to the "State of the Environment", from 2003 to 2005, the proportion of permanganate index exceeding the standard in the seven major river basins in China was 30.0%, 25.2%, and 38.7%, respectively, and the proportion of ammonia nitrogen exceeding the standard was 37.8%, 31.8%, and 33.3%, respectively. The effect of ammonia nitrogen on water quality is basically the same as that of permanganate index. In 2008, the proportion of the permanganate index of the key watershed exceeding the standard value of V was 10.5% and 7.3%, and the proportion of the section of ammonia nitrogen exceeding the standard value of V was 18.9% and 22.1%. The ammonia nitrogen has exceeded the COD and affected the surface water. The primary indicator of environmental quality. Whether ammonia nitrogen is included in the pollution emission reduction binding index directly affects the environmental quality performance of COD pollution reduction work.
Is there a condition for implementing ammonia nitrogen reduction?
China's ammonia nitrogen removal efficiency has a large space for improvement, and the technical economy is basically controllable and reasonable.
Limited by the development level of the industry, the ammonia nitrogen emission limit of some industry standards in China still has considerable room for tightening compared with similar foreign standards. Some industries lack industry emission standards and are replaced by general emission standards. Some enterprise governance facilities are rudimentary, lack of deep governance facilities, operational management is not in place, and it is impossible to stabilize the discharge of standards. The phenomenon of smuggling and leakage is still present within a certain range. Early construction of urban sewage treatment plants do not have the function of nitrogen and phosphorus in addition, need to be mentioned standard transformation; a lot of sewage treatment plant sewage pipe network do not match, the sewage load is low; in addition, low levels of sewage treatment plant operation, sewage treatment Insufficient fees and inadequate supervision also affect the actual treatment effect, which makes China's current ammonia nitrogen removal efficiency generally low.
The ammonia nitrogen reduction process is mainly divided into two methods: physical and chemical. The physicochemical method has high investment cost and high operating cost, which is easy to cause secondary pollution. Biochemical method has many advantages such as mild conditions, low processing cost and less secondary pollution. The research and development of new technologies for ammonia nitrogen wastewater treatment at home and abroad are mainly concentrated in the field of biological treatment. The traditional biological nitrogen removal process has the characteristics of good organic matter and nitrogen removal. After improvement and optimization, it has a large proportion in the current denitrification process, including A/O process (anaerobic-aerobic method), multi-stage A/ O-denitrogenation process (multiple alternate use of nitrification and denitrification tanks), A/A/O process (anaerobic-anoxic-aerobic process), SBR process (sequence batch reactor), aerated biofilter ( In the process of submerged aerated biological filter), the ammonia nitrogen removal efficiency can reach 70% to 80%, and some of the processes are above 90%. There are no technical constraints on ammonia nitrogen control. Choosing the right biochemical process, as long as the operation is properly debugged, the ammonia nitrogen removal efficiency has a large room for improvement, and the technical and economic rationality is also guaranteed.
The basic reserve of ammonia nitrogen as a national binding indicator is basically mature
Water pollutants suitable for total national control must meet the following conditions: regional rather than local pollutants; can be monitored, statistic, evaluable, and have a basis; the control object is a primary pollutant, preferably not Mixed pollutants; there are ways to control emission reductions, and the emission reduction technology is economically reasonable and the economic burden can be tolerated. According to the characteristics of ammonia nitrogen pollutants, ammonia nitrogen belongs to primary pollutants. According to the current situation of ammonia nitrogen pollution in China, ammonia nitrogen belongs to regional rather than local pollutants. Since the "11th Five-Year Plan", China has achieved certain accumulation in the construction of pollutant monitoring capacity, the integrity of emission statistics, the formulation of emission reduction targets and the implementation assessment. It is possible to incorporate ammonia nitrogen into the "Twelfth Five-Year Plan" binding index.
Since 2001, China's environmental statistics have increased the indicators of ammonia nitrogen emissions in urban areas, thus improving the statistical data of point source ammonia nitrogen. The national pollution source surveyed the total discharge of major pollutants in the country, found out the watershed, regional and industry characteristics and governance of the pollution source, mastered the discharge status of agricultural source pollutants, and the accuracy of ammonia nitrogen emission data was further improved. With the dynamic update of pollution source census data and the continued improvement of the future environmental statistical survey system, the interface between the census results and environmental statistics will further consolidate the data base of total ammonia nitrogen control.
In 2007, the environmental statistics of national wastewater in the national wastewater emissions of 1.324 million tons (excluding agricultural sources). Among them, industrial ammonia nitrogen emissions are 341,000 tons, accounting for about 26% of total ammonia nitrogen emissions. The ammonia nitrogen emission in urban life is 983,000 tons, accounting for more than 74% of the total ammonia nitrogen emissions. The proportion of domestic pollutants has increased year by year, from 64.95% in 2005 to 74.30% in 2007. According to the national survey of pollution sources in 2007, the ammonia nitrogen emissions from agricultural sources are about 314,000 tons (of which planting and large-scale livestock and poultry farming account for 93%). Different from total nitrogen source, the source of agricultural sources and non-point source contributes less to ammonia nitrogen than to total nitrogen. It also controls the total amount of ammonia nitrogen to be one step ahead of total nitrogen control. Based on industrial plus living sources, supplemented by key agricultural sources such as large-scale livestock and poultry farming, it can basically cover the key points of total ammonia nitrogen emissions. In fact, the “Eleventh Five-Year Plan†of the Huaihe River Basin in China has explicitly included the ammonia nitrogen index in the planning target.
COD and ammonia nitrogen pollution emissions have a high degree of homology, and the total ammonia nitrogen control is basically similar to the COD control mode. At present, various COD pollution reduction systems and technical measures have played an important and fundamental role in the prevention and control of ammonia nitrogen pollution. During the “Eleventh Five-Year Plan†period, the construction of “three major systems†for pollution reduction has been improved to a certain extent. The comprehensive implementation of COD pollution reduction has laid a foundation for ammonia nitrogen pollution reduction, and is also conducive to the implementation of ammonia reduction work.
How to effectively reduce ammonia nitrogen emissions?
Improve ammonia nitrogen emission standards and promote the improvement of ammonia nitrogen pollution prevention and control
At present, there are 26 current water pollutant discharge standards in China that stipulate control standard values ​​for ammonia nitrogen emissions. In general, China's current national and local standards for ammonia-nitrogen emissions are released earlier than the standards of the past, and their ammonia nitrogen control requirements can no longer meet the current local environmental management requirements; and the local standards issued in recent years can basically meet Local environmental management work requirements. According to the low standard of ammonia nitrogen emission standards of existing industrial enterprises, the national environmental quality standard system should be improved, the work system (repair) of industrial pollutant discharge standards should be strengthened, and the scope of application of general-purpose and comprehensive pollutant discharge standards should be narrowed. Comprehensively review and revise emission standards with long implementation time, improve ammonia nitrogen emission control requirements, urge enterprises to conduct advanced treatment, and improve industrial ammonia nitrogen treatment.
Considering that the actual influent ammonia nitrogen concentration in industrial enterprise wastewater treatment facilities is very high, many enterprises face difficulties in obtaining ammonia water, and the characteristics of sewage in different industries are not the same. They should avoid across the board and propose “upgrading upgrade†based on technical and economic feasibility. To reflect the requirements for water quality, we must also consider the actual economic affordability and processing level of each industry. Through the “upgrading upgrade†to promote enterprise upgrading and transformation, industrial ammonia nitrogen emission levels are expected to be further reduced.
Promote the construction and upgrading of urban sewage treatment facilities, and greatly enhance the role of ammonia reduction
Due to the large changes in the amount of influent water, the influence of industrial wastewater, and the high concentration of influent SS (solid suspended solids), the removal effect of ammonia nitrogen in wastewater treatment process in China is not satisfactory. Most sewage treatment plants in China lack effective means to control ammonia nitrogen. The presence or absence of nitrification is largely dependent on the natural replacement of nature in spring, summer, autumn and winter. The effect of some sewage treatment plants to increase nitrification is simply to reduce mud discharge or Increasing the amount of aeration is far from achieving optimal operation. Some old sewage treatment plants did not consider the function of nitrification at the beginning of construction. Only a simple COD removal function, the effluent ammonia nitrogen of the sewage treatment plant is higher. The aeration tanks of these sewage treatment plants have a small volume and cannot meet the sludge age requirements required for nitrification; the sedimentation tank volume is too small to meet the high sludge concentration required for nitrification; the capacity of aeration equipment is low, up to no The amount of oxygen required for nitrification.
Through the synergistic effect of COD emission reduction in sewage treatment plants and upgrading and strengthening the ammonia nitrogen removal efficiency of living sources, ammonia nitrogen emissions can be effectively reduced. On the one hand, we will tap the potential and focus on improving the load rate and operation level of existing facilities. According to the water quality of the river basin, if it is conditionally modified, it will continue to increase the function of nitrogen and phosphorus removal in urban sewage treatment plants in phases; the sewage treatment plants that are discharged into closed waters and have direct impact on the water quality of coastal waters should be selected. The treatment process with enhanced phosphorus and nitrogen removal functions is encouraged to encourage the new sewage treatment plant to remove total nitrogen from the water as one of the pollution control indicators; the load rate is low, the sewage collection pipe network is improved, and the load rate is improved through the improvement of the pipe network. On the other hand, it will comprehensively start the construction of county sewage treatment plants, promote the construction of decentralized sewage treatment facilities in rural areas, and encourage qualified areas to construct rural decentralized sewage treatment facilities according to local conditions. At the same time, we will vigorously promote wastewater reclamation and utilization in the area of ​​water shortage, encourage other areas to carry out wastewater recycling, and focus on improving wastewater recycling.
It should be noted that the nitrifying bacteria group has a slow proliferation rate and it is difficult to maintain a high biological concentration. It is necessary to simultaneously carry out sludge reflux and nitrification liquid reflux. When denitrifying, it is necessary to additionally add a carbon source (such as methanol) and alkali, which requires co-ordination. In order to solve this problem, the old sewage treatment plant should be upgraded, and enterprises should be encouraged to adopt technical measures to reduce energy consumption in the sewage treatment process, eliminate backward technologies, optimize operation, and optimize ammonia nitrogen emission reduction.
Focus on key industries, increase industrial restructuring, and strengthen industrial pollution control
Many industrial wastewaters have high COD influent, and the proportion of refractory COD is too high. The easily degradable organic carbon source accounts for about 10% of COD. The available carbon source can not meet the needs of biological nitrogen and denitrification, which causes industrial wastewater treatment plant. It is difficult to reach the standard of ammonia nitrogen and total nitrogen in the effluent. According to the 2007 China Environmental Statistics Annual Report, in 2007, the industrial ammonia nitrogen removal rate was 60.3%, which was 10 percentage points lower than the industrial COD removal rate; the domestic ammonia nitrogen emission was 983,000 tons, and the removal rate was only 26.1%, which was better than urban life. The COD removal rate is 13% lower; according to the analysis of the ammonia nitrogen removal rate of the main ammonia nitrogen emission industry, except for the petrochemical industry removal rate of more than 90%, other industries have potential for improvement.
The structural problems of pollution from ammonia-nitrogen pollution are prominent. The ammonia nitrogen emissions of chemical industry, non-ferrous metals, petrochemicals, agricultural and sideline foods, and textiles account for 85.9% of the total industrial emissions. The chemical industry is the main emission industry of ammonia nitrogen, accounting for more than 40% of the total ammonia nitrogen emissions of industrial enterprises, followed by papermaking, food processing, textile, ferrous metallurgy, petrochemical and food manufacturing industries, and the industrial sector with high ammonia nitrogen wastewater discharge problems. oil refining, chemical fertilizer, inorganic chemicals, pesticides, iron alloy, glass, food and feed production. In addition, the amount of ammonia nitrogen in the wastewater discharged from the farm and the landfill leachate produced by the landfill is also high. Focus on chemical, nonferrous, petrochemical, agricultural and non-staple food, textile and other key industries, can effectively control the total amount of industrial ammonia nitrogen emissions.
In accordance with the order of controlling the newly added quantity and reducing the stock, first of all, strict environmental access standards in the project approval stage, reasonable control of the industry development speed and economic scale, and more “subtraction†in the incremental part of the source pollutants to control ammonia nitrogen pollutants. New increments; Secondly, strictly implement the national industrial policy, increase the adjustment of industrial structure, and implement mandatory clean production audits for key industries and key river basins according to law, and should close and eliminate the level of clean production; third, grasp Good end-of-business governance, strengthen the operation and supervision of pollution control facilities, and ensure that industrial enterprises achieve comprehensive and stable discharge standards.
Multi-pronged approach, comprehensive pilot, vigorously prevent and control agricultural source pollution
In some areas, only considering the ammonia nitrogen reduction of industrial point sources and urban living pollution sources can not guarantee the comprehensive compliance of environmental function zones. To fundamentally alleviate the problem of ammonia nitrogen pollution, it is necessary to gradually incorporate the main agricultural sources of ammonia nitrogen pollutants into control. Due to the lack of basic work, the lack of engineering supervision, the difficulty of implementation of management objects, and the lack of governance methods, agricultural sources will be the key areas for the prevention and control of water pollution in the “Twelfth Five-Year Planâ€. This is true for COD as well as for ammonia nitrogen pollution control.
At this stage, agricultural source management should focus on large-scale livestock and poultry farming, implement various management systems and policy measures, and carry out pollution prevention and control of large-scale livestock and poultry farms (communities) and livestock and poultry. Large-scale livestock and poultry breeding enterprises are managed with reference to point sources, and strict requirements are made for the stable discharge of ammonia nitrogen. For the free-range livestock and poultry farms, comprehensive utilization is the main measure to promote the biological treatment technology of livestock and poultry manure and develop ecological agriculture. For the prevention and control of agricultural non-point source, the management measures are mainly used to prevent and control from the source, and the conditions are allowed to be supplemented by engineering measures to actively carry out pilot projects. By promoting the method of soil testing and fertilization, the planting area of ​​organic agricultural products will be expanded, and the amount of chemical fertilizer applied in agriculture will be reduced. Promote the development, production, transportation and sales of slow release ∕ controlled release fertilizers, improve the structure of fertilizer products, and improve nitrogen utilization. Study and establish a comprehensive scale of livestock and poultry farms - organic fertilizers - farmers - farmland operation models and channels, to achieve coordinated reduction of point source sources, while promoting sustainable agricultural development.
Galvanized (galvanizing) flange is the flange surface covered for zinc for better anti-rust method than light oil coated, galvanizing have hot dip galvanized and cold galvanized two method, hot dipped galvanizing for zinc thickness on flange is much bigger than cold galvanizing, so hot dip galvanized flange price is expensive and much higher than cold galvanized for flanges.
Galvanized Flange, hot dipped galvanized flange, cold galvanized flange, galvanizing flange, zinc coated flange
Jinan Hyupshin Flanges Co., Ltd , https://www.iflange.com