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The latest sewage treatment plant discharge standard revision, the most complete viewpoint and collision!



Source: unknown Author: admin Date: 2019-06-24 09:15 Browse:

Reading guide

Since the release of the pollutant discharge standard for urban sewage treatment plant (Draft for comments), there has been a lot of heated discussion. Experts, design institutes and factory managers have their own opinions. Yuan Fang, what do you think?

Design case of sewage treatment plant under super high discharge standard

Opinions and consensus of factory director of first-line sewage treatment plant on Standards

1. To implement the new standard, the maturity of advanced processing technology should be considered

"The current standard of GB18918-2002 is actually stricter than that of most developed countries. In many parts of the country has not yet implemented a class a standard, and the introduction of such emission limits will result in many sewage treatment plants that have just been transformed for one year, and may have to be further transformed, "said Yang Chunrong of Yiwu water treatment Co., Ltd. For this standard, we need to consider the maturity of advanced treatment technology and whether the supporting equipment and implementation can keep up with it. The problems encountered in the process of future transformation also need to be considered in advance.

 

2. The new standard needs to consider the balance between the increase of power consumption, drug consumption, carbon source and pollutant reduction

The limit value of the draft has been raised a lot, which can be achieved by the mature water treatment technology. However, the following problems are the increase of power consumption, drug consumption and carbon source. Yan Guoqi, director of Qige sewage treatment plant of Hangzhou drainage Co., Ltd., said, "in the process of upgrading the sewage treatment plant from grade 1 B to level 1 A, we have personally felt a substantial increase in energy consumption and drug consumption.". The new energy consumption and drug consumption also contribute to carbon emissions, and the balance between the increase of carbon emissions and the reduction of final pollutants should be considered in the formulation of new standards.

3. Opinions and suggestions on the limit values of some index items in the draft

Fecal coliform group: it is suggested to delete or lenient regulation

In the draft, the limit value of fecal coliform in effluent is 1000 cells / L, which is lower than that of natural water (20000 cells / L) and waterworks. However, fecal coliform will rapidly propagate into natural water body, and its control is questionable. At the same time, several factory directors reported that although the assessment indicators clearly pointed out that 24-hour mixed samples should be used as monitoring water samples, at present, the assessment samples are still mainly instantaneous samples, and it may take one day to monitor after taking samples. "After adding sodium hypochlorite and chlorine to the sewage treatment plant, the fecal coliform group has reached the standard instantly, but it may exceed the standard after one day's division and reproduction. The sampling method and preservation method of monitoring water samples are worth studying," said Zhou Jianxin of Yiwu water treatment Co., Ltd. At the same time, according to the sewage treatment plant control indicators.

Cod: reducing from 50 mg / L to 30 mg / L is worth considering

TN, TP and BOD5 should be controlled, but cod index should be reduced from 50mg / L to 30mg / L. For sewage treatment, one is that the COD from the sewage plant has been removed, so the COD discharged into the river has little impact on dissolved oxygen; the other is that "carbon source needs to be added during nitrogen removal, which will lead to the increase of COD, and the simultaneous control of TN and COD is also a spear and shield", said Bao Zimao, operation director of China Water Services Co., Ltd.

SS: from 10 mg / L to 5 mg / L, the detection is difficult

It is difficult to detect the SS index of effluent when it is less than 10 mg / L, and it is more difficult to detect when the SS index drops to 5 mg / L. In practical experience, it is found that the error of sampling 100 ml for SS detection is very large, and the error of sampling 300-500 ml is small. When the actual index is 5 mg / L, it may exceed the standard.

Heavy metals: municipal wastewater treatment plant has no removal capacity

The directors of several sewage treatment plants have reported that the municipal sewage treatment plants generally adopt biochemical treatment methods, which basically have no removal capacity for heavy metals. It is difficult to increase heavy metal index in practical operation.

Selective control index: there are many indexes, and the wastewater treatment plant has no removal capacity

The draft proposed that the urban sewage treatment plant should sample and monitor all the items listed in Table 2 at least once a year, and the detected items should be included in the selected control items. In Table 2, there are 82 selective control indexes, which have many items and are expensive to detect. At the same time, even if it is detected, the activated sludge method of municipal sewage treatment plant can not control these indicators.

 

4. The test method conflicts with the actual practice in assessment or supervision

For the monitoring method, the draft and the previous requirements are "sampling frequency is at least once every 2 h, 24 h mixed samples are taken, calculated by daily mean value". The directors of several sewage treatment plants reported that in the actual assessment or supervision, the basic is instantaneous sampling, and this is the standard. The inconsistency between the implementation and the method also makes the sewage treatment plant "hard to say".

Expert opinion

Professor Shi Hanchang, Tsinghua University

First, is it necessary to reduce COD from 50mg / L to 30mg / L? In fact, strict standards have been set for total nitrogen, total phosphorus, COD, BOD5 and SS in sewage treatment. In addition to these indicators, are there any new indicators that we need to monitor? From the perspective of human life, if we go down to find pollution indicators, one is antibiotics and the other is endocrine disruptors. Now there are antibiotics in injections, medicines and dairy products of pigs, cows and sheep. These things will be discharged into the sewage through the human body. These indicators will gradually become the limiting indicators of sewage treatment in the near future. Cod is reduced from 100mg / L to 80mg / L, then to 60mg / L or even lower. In fact, the lower the COD is, the rest is often the substances with environmental risks and are not easy to degrade. Therefore, this is the reason why the new standard will further reduce COD.

Second, is the fecal coliform index necessary? At first, fecal coliform was considered as a representative of human intestinal bacteria or virus infection in water. However, it is very difficult to determine all kinds of bacteria, so the representative of fecal coliform group was selected as the limit value. For example, the drinking water limit is now 0 cells / L, and there was a standard less than 3 / L before. It actually represents the reduction of these microorganisms in the water body that are easy to cause intestinal diseases. Therefore, it is a representative and not only fecal coliform bacteria are controlled. Why choose fecal coliform group? Because it has relatively small impact on human body and requires low laboratory requirements. If other bacteria are selected, several layers of protection can be done. The index of fecal coliform group represents the impact of human fecal pollution on water.

Professor Li Ji, Jiangnan University

At present, the method in the standard for the determination of total arsenic is very complex, which is basically not used in the actual monitoring; in addition, the Standard Institute of the Ministry of environmental protection has not produced standard samples for a long time, these problems are also worth discussing. It is very difficult to set standards according to local conditions. I am also worried about the implementation of standards according to this.

Chen Jun, chief engineer of Jiangsu (Yixing) Environmental Protection Industry Technology Research Institute

These standards are related to the standards of sewage treatment and discharge. As an important indicator to measure the removal of organic pollutants, COD pollution has been solved after the invention of activated sludge process 100 years ago. There is no need to be too harsh on it, except for other purposes such as water reuse. Generally speaking, nitrogen and phosphorus pollutants need to be further stringent, especially in sensitive water areas. Today, we should consider the emerging pollutants, which is today's challenge, not the excessive pursuit of COD.

How to reach the standard? This actually involves an evaluation method, such as whether to adopt the annual value or monthly average value, or whether each water sample meets the standard, or whether a certain proportion of water samples meet the standard. This involves the technical performance and the thinking of different countries in managing environmental problems. For example, the European Union requires that the annual average of total nitrogen of sewage plants with a population of more than 100000 is less than 10mg / L Mixed sample. However, Germany, Austria and other countries use instantaneous samples, the total inorganic nitrogen is less than 13mg / L, but it is stipulated that one of the five consecutive water samples is allowed to exceed the standard, and the range of exceeding the standard should be less than 100% of the limit value. Therefore, the formulation of national emission standards should be based on the comprehensive consideration of national conditions, history, environment and technology. Many factory managers have mentioned fecal coliform, which is also measured in Canada, but is based on geometric mean rather than arithmetic mean. In a word, it's really a complex thing to consider when setting standards at the grassroots level.

Zheng Xingcan, chief engineer of North China Municipal Engineering Design and Research Institute

Any environmental problem is related to the economy. What kind of emission level the design reaches, what kind of investment is needed.

Secondly, the non biodegradable COD in the effluent, if it is a natural substance, will not cause the black odor of the water body. Therefore, if the COD requirement is forced to reach the level of 20mg / L, especially in the case of higher and higher concentration of sewage inflow in the future, such a high standard is a waste of money and money.

In my opinion, there is a more critical indicator for our current sewage treatment technology, namely, ammonia nitrogen index, which is directly related to black odor eutrophication. Moreover, if the ammonia nitrogen index of effluent can be lower than 1mg / L, the relevant COD and BOD will meet the corresponding requirements.

In terms of total phosphorus and total nitrogen, I have some different opinions from quite a few domestic experts. I think if the goal is to control algae growth and eutrophication, then we must pay attention to the proportion of nitrogen and phosphorus. If the total nitrogen can't be solved, the total phosphorus will not change.

From this point of view, in terms of eutrophication control of water body, total phosphorus is the first, ammonia nitrogen is the second, and total nitrogen index is the third. If these three indicators are controlled, the conventional indicators of sewage discharge will be controlled.

Chairman of bijianping water source

- "the standard of sewage treatment plant" is the standard of sewage treatment plant. "From class I to class V are water resources, if they go beyond class V, they are not water resources. Grade A is inferior to class V water, that is, liquid that can produce pollution. In other words, under the current national standard, where the sewage treatment plant is built, where the sewage is discharged, the black and odorous water body will be formed in the river basins and regions where the water environmental load is overloaded

China water network recently published a series of reports on Wen Jianping's views in the financial state weekly: "most of the supporters are enterprises with independent research and development of membrane technology. For them, the idea of "standard discharge" is deeply rooted and can not be considered from the perspective of water environment protection; Some water investment and operation enterprises in the industry, either because of their lack of innovative technology, or because of the long-term introduction of foreign technology, do not go to innovation, lack of in-depth understanding of the current innovative technology, always counter with the reason that the adoption of new technology will definitely increase the investment cost and is not in line with China's national conditions. ".

Xia Qingyuan, vice president and chief engineer of Chinese Academy of Environmental Sciences

The correct emission standard must be in the large-scale decision-making of water pollution control, reflecting the national technical and economic feasibility and promoting the combination of various environmental management means. It is necessary to oppose arbitrary tightening of emission standard limits, to create a special limit to seize the law enforcement space of environmental impact assessment, planning, especially pollution discharge permit, and even more oppose to deny the necessity of fine management of local standards and pollutant discharge permits with special "one size fits all" national standards. The task left for the emission standards is to study what the practical and feasible technologies of various pollutants treatment are, and put forward different basic levels of pollution control as the bottom line according to the national pollution control strategy. Instead of compiling standards in a room, we should seriously consult experts in various industries and urban sewage treatment plants to study the technologies applicable to harmless, resource-based and energy-saving sewage in China.

Dr. Liu Zhixiao, Beijing Capital Co., Ltd

1. To improve China's water environment, comprehensive consideration should be taken from the perspective of regional or urban healthy water circulation, instead of simply relying on improving the discharge standards of urban sewage treatment plants. It is necessary to comprehensively consider improving the popularization rate of pipe network collection, strengthening the collection and treatment of initial rainwater, and proper treatment of combined CSO; the setting of storage and detention tanks at different locations of combined pipe network; and the improvement of water environment in China; The storage and treatment of peak sewage at the inlet end of sewage treatment plant during rainstorm period; control of agricultural non-point source pollution and industrial wastewater point source pollution.

2. It is not suitable for China to formulate a unified emission standard across the Yangtze River and the south, and give priority to the formulation of local emission standards, while N and P indicators cannot be unified. For a specific sensitive area, it is suggested that the contribution of N and P pollutants to eutrophication in the specific water area should be scientifically evaluated in combination with the water environment capacity, and the variation rule and control measures of N / P ratio in the outbreak of water bloom should be studied, and then the scientific index control value and the limit of annual total emission should be formulated.

This standard is not applicable to rural sewage treatment facilities.

4. As for the revised standards, it is suggested to comprehensively consider the necessity of the level of discharge standards on improving the water environment and the sustainability of the "big environment": first of all, the level of emission standards will undoubtedly promote a large number of "high-rise" technology "swarm", which will intensify the government's purchase of services under the current local financial constraints In the case of limited capital investment, the investment of a series of comprehensive water environment treatment measures, such as rainwater treatment and pipe network popularization, will be affected. Secondly, high emission standards will greatly increase the consumption of energy consumption, chemicals, materials and equipment, which come from different upstream industries. These industries are actually contributing to environmental pollution, and are the main contributors of "carbon footprint" and major emitters of GHG. Therefore, this practice may shift or increase the direct pollution of upstream industries to the environment, which is actually against the ecological ethics.

5. Considering the correlation degree between emission indicators, it is not necessary to set emission indicators with high synchronous standards for SS, COD, TP and TN. Even if the high standard is adopted, it is suggested that only TP and TN should be limited. If the nutrient index is limited, the SS, COD and other indicators will achieve ideal removal efficiency. Otherwise, the simultaneous implementation of level restrictions on COD and Ss will increase unnecessary investment and operating costs, because these residual COD and SS are difficult to biodegrade, and have little harm to the receiving water body, and have no contribution to the overall improvement of the environment on a year-on-year basis.

6. When adopting high emission standards, it is suggested to consider using weekly average value, monthly average value, annual average value and other indicators for assessment. At present, the "special discharge limit" involved in the current revised discharge standard tends to the lot level of sewage treatment technology. In this case, the instability of the sewage treatment process should be taken into account in the formulation of the standard. The more strict the index is, the more difficult it is to reach the standard. It can refer to the assessment methods adopted by developed countries in Europe and the United States. In addition, the assessment of environmental protection departments is often instantaneous, which is unfair to the operating enterprises. In the current high pressure situation of environmental protection law enforcement, under the situation of huge pressure on the overall water price mechanism and local finance, the operation risk of enterprises is great.

7. Disinfection index: it is necessary to determine the disinfection method and fecal coliform group index in combination with the discharge and use of the tail water of the sewage plant.

8. Selective control index: the selection of indicators and the determination of index values should be scientific and reasonable.

Chairman of IWA, Dr. Helmut kroiss, Professor, Vienna University of Technology

The sampling methods in China's emission standards are different from those in Europe and the United States, and the requirements for the compliance rate are also different. Some European countries do not require 100% compliance. For example, Germany uses 4 or 5 consecutive samples to judge whether it meets the standard; Austria requires that the annual standard rate of daily average sample is 95%. When discharged into lakes, TP should be less than 0.5mg/l, and when discharged into rivers, TP should be less than 1.0mg/l. In some special waters, the discharge standards will be stricter.

When formulating the total nitrogen emission standard, the principle that the total nitrogen removal rate of inlet and outlet water should be greater than 70% is considered. In view of this principle, law enforcement agencies often refer to the annual average removal efficiency of total nitrogen, rather than based on the instantaneous emission value. For example, wastewater treatment plants that make efforts to reduce the infiltration of groundwater into the sewage pipe network often have higher effluent concentration than those with small actual inflow but serious groundwater infiltration, and the latter is the object of punishment by law enforcement agencies.

As far as I know, there is still a septic tank system in China, which will lead to low organic matter content in the influent of sewage treatment plant, and may also affect the carbon nitrogen ratio, thus affecting the efficiency of total nitrogen removal. However, in winter, the treatment efficiency of ammonia treatment plant in Tianjin should be divided into two parts: the temperature limit in winter and the time limit in winter.

At present, China's standard based on the standard of daily average mixed sample is very strict, which is bound to greatly increase the investment of sewage treatment plant, but in fact, the improvement effect on the overall water environment is very limited.

Judging from long-term experience, if the sewage treatment plant can operate stably, the traditional activated sludge process can remove 94% of the influent cod (under the condition of complete nitrification). If the secondary sedimentation tank is well designed, even if no additional follow-up treatment is required, the effluent COD of 20 mg / L or 30 mg / L proposed in some Chinese standards can be achieved; without post filtration process, BOD can not reach 4-6 mg / l every day. The biological flocs in the effluent of the secondary sedimentation tank are the final determinants of the concentrations of BOD, SS and TP. The implementation of China's strict TP emission limits requires the use of chemical phosphorus removal. In Switzerland, TP is stable less than 0.3 mg / L after chemical flocculation filtration. I am not sure whether the traditional sand filtration can meet the requirement of daily effluent TP stability less than 0.2mg/l. In blue plains wastewater treatment plant in the United States, the monthly average value of TP is less than 0.1 mg / L, which is achieved through membrane filtration process.

For ammonia nitrogen removal, our institute has developed a series of design and operation models to achieve such strict emission limits. From the economic point of view, it is recommended that 95% or even 97% of the ammonia nitrogen emission standard rate can save considerable investment. In fact, even if the ammonia nitrogen is not 100% up to standard, there is no substantial impact on the overall water environment of receiving water and possible water reuse.

According to the characteristics of water quality in China, I think the total nitrogen will not meet the standard without additional carbon source. Under such strict standards, it is difficult to realize the self-sufficiency of energy consumption of sewage treatment plant. Autotrophic nitrogen removal process (ANAMMOX) will be a technical means, which can effectively reduce energy consumption, but it is the latest process, and there are many challenges to be solved. In view of the climate conditions in Beijing and Tianjin, I don't know whether the mainstream anammox can stably meet such strict local emission standards, but in the future, mainstream anammox can become a solution.

If based on the traditional activated sludge process, considering the influent water quality and discharge standards, China's sewage treatment plants can not achieve self-sufficiency in energy consumption. This conclusion can be calculated by many models. In China's serious water shortage areas such as Beijing and Tianjin, the standard discharge of sewage and the effective reuse of water are more important than the realization of energy self-sufficiency of sewage treatment plants.

From the perspective of greenhouse gas emissions, China's septic tank system has many disadvantages. In addition to the large amount of methane produced by the septic tank itself, the carbon nitrogen ratio of the sewage treatment plant is insufficient, which also limits the efficiency of denitrification process and releases N2O.

Generally speaking, the existing technical means can meet the increasingly stringent requirements of China's sewage discharge standards. However, from the perspective of protection of receiving water, controlling non-point source pollution should be more effective.

Opinions of Design Institute

Northeast China Municipal Engineering Design and Research Institute

Opinions and suggestions:

1. The standard preparation method is based on China's standard preparation specifications. Has the in-depth investigation been carried out, including going out to Europe and the United States and other developed countries to see how the standards of others are put forward and why the water system and environment of other people are so good, but the effluent standard is much lower than the national index; To avoid the phenomenon of raising standards when it comes to revising standards, imagine how our standards will be revised in the next decade?

2. What is the basis for setting the emission standard limits of organic matters and nutrients? For the current situation of water pollution in China, what standards should be formulated? EPA of New York State has analyzed and calculated the self purification capacity of water body through the continuous research on the Hudson River System in New York City for more than ten years, and finally determined that each sewage treatment plant in New York City should pay more attention to the pollution of water system We believe that this method is scientific and reasonable.

3. Whether the basic method of sewage treatment in urban sewage treatment plant should still be biological treatment. If we accept this idea, we should consider the removal of any harmful substances, which should be within the scope of biological treatment. If the substances that cannot be removed by conventional treatment can not be removed, the relevant specifications should be revised to include these substances in point source treatment. We believe that the discharge standards of various pharmaceutical wastewater are relatively scientific.

4. We believe that the national standard is the highest standard used in the design, and the use of the standard should be clear and clear, without ambiguity and ambiguity, which will bring adverse impact on the implementation of the standard. For example, section 4.2.2 of the standard stipulates: "since January 1, 2018, the existing urban sewage treatment plants in the sensitive area shall implement class a standard in Table 1; For the existing urban sewage treatment plants outside the sensitive area, if the proportion of industrial wastewater received and treated is less than 80%, the first level B standard in Table 1 shall be implemented; if the proportion of industrial wastewater received and treated is more than 80%, the secondary standard in Table 1 shall be implemented. " We think that it is difficult to determine and implement the 80% standard. If a sewage treatment plant is built in a drainage area and the proportion of industrial wastewater is 79%, it is still very difficult to implement level I b; If 81% of industrial wastewater is accepted and treated, and 79% of industrial wastewater will be accepted and treated in a few years, it will be upgraded immediately. Most importantly, which department will determine the 80% proportion?

5. We hope to further clarify section 4.2.4 that "in areas where the land development density is already high, the environmental carrying capacity is beginning to weaken, or the environmental capacity is small, the ecological environment is fragile, and it is easy to cause serious environmental pollution problems and need to take special protection measures, the pollutant discharge behavior shall be strictly controlled, and the urban sewage treatment plants in the above-mentioned areas shall implement the special measures for water pollutants Emission limits ". Which agency is responsible for the adjudication rights and responsibilities?

6. The wastewater in most countries in the world is the secondary treatment standard. The mainstream technology is biological treatment process based on activated sludge process. The effluent COD of secondary treatment process is usually less than 60mg / L. COD of many countries in the world is basically within this range. Considering some external influences, COD will be slightly higher, which is a kind of spirit of seeking truth from facts. Through the enhancement of natural microorganisms (activated sludge), we have achieved the treatment that requires a long time and large space in nature, and has completed the proper treatment of organic matters. The COD in the secondary effluent has little oxygen consumption, and no longer causes the oxygen consumption of natural microorganisms to cause black odor in the water body. It seems that there is no need to eliminate that little bit of COD through high investment, on the contrary, these inputs are in the 1 To a certain extent, it increases the carbon footprint of sewage treatment (caused by power consumption and material consumption). In particular, we do not want to see the sewage treatment plant turned into a chemical plant in order to remove a little bit of inert COD index.

7. Section 4.2.2 of the standard stipulates: "from January 1, 2018 If the proportion of receiving and treating industrial wastewater is more than or equal to 80%, the secondary standard in Table 1 shall be implemented. " For industrial parks, even if the nature of COD removal is complex, it is still very difficult to implement the standard. Can you change your mind and remove these stubborn COD from the source!

8. Support the updating of standards related to the emission control requirements of air pollutants, so as to avoid the occurrence of "NIMBY effect" phenomenon, and the detection means are still very inconvenient. It is suggested to prepare the necessary means for the sewage treatment plants to realize the emission standards for removing air pollutants and realizing the emission standards.

9. In item 12 of Table 1, does the requirement of fecal coliform count mean that the sewage treatment plant needs to be disinfected from time to time? Is this necessary? Is it necessary for any drainage system to meet this requirement? It is suggested to study it carefully.

10. It is difficult for us to find out the administrative divisions of 62 state-controlled lakes and reservoirs and 212 districts and counties in 56 prefectures and cities in 11 coastal provinces.

Tianjin municipal engineering design and Research Institute

1, 4.2.1. Since July 1, 2016, the newly-built urban sewage treatment plant shall comply with class a standard in Table 1. For Industrial Park sewage treatment plants, wastewater treatment plants with a high proportion of industrial wastewater, and township sewage treatment plants, it is difficult to implement, so it is suggested to relax to class a B standard.

The proportion of industrial wastewater in Article 2 and 4.2.2 is 80%, which can not be determined as pollutant concentration or flow rate, so it should be clear. According to the provisions, this article can be used as the standard for the construction of sewage treatment plant. Since the water from the sewage plant is variable, if the proportion exceeds the standard during the operation of the sewage treatment plant, the discharge standard can be appropriately relaxed after the sewage treatment plant applies.

It is proposed to change 80% to 60%.

3. Total nickel and benzo (a) pyrene are added to the basic control items of the new standard. It is difficult to detect these two indicators for many township sewage treatment plants and county-level environmental protection departments. The reason for adding the two original selected control items to the basic control items in the compilation instructions is that these two items have a high detection rate in the detection of typical sewage treatment plants, but the current sewage treatment workers have a high detection rate The high detection rate is due to the poor control of industrial point source, so it is suggested that these two indicators should still be selected control projects.

4. In Table 2 of 4.2.4, the newly added total aluminum index is 0.2mg/l. Considering that the aluminum index in the sanitary standard for drinking water (GB5749-2006) is 0.2mg/l, aluminum salt is sometimes added in wastewater treatment process, and aluminum salt may also be added in water of some industrial enterprises, so it is suggested to relax it to 0.5mg/l.

The high allowable concentration value of air pollutant emission at plant boundary in Table 3 of Article 5 and 5.1. As the distance between sewage treatment plant and urban residential area is different, it is suggested to use the original classification standard in the standard. For the environment sensitive areas, more stringent requirements can be put forward through the EIA.

6. It is suggested that the original standard should be retained according to the requirements of the removal rate for the wastewater treatment plants with Cod greater than 350 mg / L, and the requirements for the wastewater treatment plants with total nitrogen more than 60 mg / l should be added according to the requirements of the removal rate or carbon nitrogen ratio.

7. 6.3 if a special agency is entrusted for sludge treatment, the sludge discharged from the factory shall meet the requirements of 1 ~ 4 control items in Table 4.

The two indexes of fecal coliform group value and total bacterial count can not be reached for dewatered sludge. If the dewatered sludge needs to be treated, the significance of entrusting a special agency for treatment does not exist. It is suggested that the ex factory sludge meet the requirements of 1 ~ 2 in Table 4. Because it is entrusted to professional institutions for management, environmental risk is easier to control.

8. China has a wide area and is in the process of rapid industrialization and urbanization, and the source of sewage from sewage treatment plants is complex. At present, sewage treatment is mainly microbial treatment process, which is affected by many factors such as incoming water, temperature, operation status, etc. it is recommended to adopt the method of the United States, France and other countries, and the weekly or monthly average value of water sample detection or the assurance rate of reaching the standard should be adopted It can not only control the weight of pollutants entering the environment, but also reduce the operation cost of sewage treatment plant.

If the standard guarantee rate is adopted, 85% ~ 90% is recommended.

9, 7.4.2 table 5 chemical oxygen demand is determined by potassium dichromate method. There is no problem for the influent water. Since the water quality is close to the surface water after full treatment, it is recommended to use potassium permanganate method to measure the effluent, which is mainly to reduce the impact of excessive use of potassium dichromate on the environment, and the potassium permanganate method is also used in Japan. As long as the same standards are used across the country, comparisons can be made.

10. The pollutant discharge standard of sewage treatment plant involves many factors, such as sewage treatment fee, enterprise operation cost, resident water fee and so on. After the implementation of the new standard, the cost of sewage treatment is conservatively estimated at 1 / 0 ~ 3.0 yuan / m3, Most sewage treatment plants are between 1.2 and 1.8. At present, the domestic sewage treatment fee of most urban residents in China is less than 0.5 yuan, and there are about 10% - 15% groundwater in urban sewage treatment plants. It may be necessary to treat initial rainwater in the future. Therefore, it is suggested to reduce the scope of application according to the special discharge limit and class a standard, otherwise it is difficult for the sewage treatment plant to maintain normal operation.

At the same time, it should also be considered that in order to make the sewage treatment plant meet the standard, a large amount of carbon sources, chemicals and power consumption are needed, which will indirectly produce pollution and increase carbon dioxide emissions.


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