The status quo of sludge disposal in China is worrying, and the treatment is less

Time: 2013-11-12 Source: China Environmental Protection Network

 

The State Council's "Opinions on Strengthening Urban Infrastructure Construction" proposes that by 2015, the rate of harmless disposal of municipal sludge should reach 70%. This goal has been lowered compared to the previous one, but experts believe that it is still difficult to complete the judgment of the current policy implementation. Previously, the “12th Five-Year Plan for Urban Wastewater Treatment and Recycling Facilities Construction” proposed that by 2015, the treatment rate of sludge in the municipalities, provincial capitals and cities with separate plans reached 80%, and other cities It reaches 70%, and the county and key towns reach 30%.

 

As the sewage treatment rate has increased year by year, the amount of sludge generated has increased rapidly, but the problem of sludge treatment and disposal has not been properly solved. Why is the road of sludge disposal in China so rough? How to choose the technical route to reduce and stabilize sludge? What are the efforts to solve the problem of sludge treatment and disposal? This edition will comprehensively analyze the opinions of experts in the industry and explore the pollution. The solution to mud disposal.

 

At present, China's sewage treatment capacity has reached 140 million tons / day, but there are still some confusion in the sludge treatment and disposal work, progress in technical choices, engineering implementation is slow.

 

China's sludge disposal road has been very uneven, sludge production has been increasing, and sludge treatment and disposal capacity is also increasing, but the two "increased" rates are not the same. Therefore, the overall situation of sludge disposal in China is relatively worse. Most of the sludge is not properly disposed of, but simply disposed of and buried, which will cause secondary pollution and seriously affect the environmental treatment effect.

 

About 50 of the cities in Beijing and Shanghai have sludge digestion facilities, but only a dozen are in operation. In the process of sludge digestion, there are some technical problems in China, but the most important ones are insufficient practical experience, insufficient policy support, and lack of operational methods.

 

In foreign countries, the trend of sludge treatment is still returning to land, and the share of landfill is small. In the 1990s, land use in US sludge was only 30%, and in 2005 it reached 66%. Therefore, in foreign sludge treatment and disposal, digestion is common, landfill is being gradually banned, incineration is gradually decreasing, and in digestion technology, heat drying and composting are the main technical routes.

 

The situation in China is just the opposite. In 2009, the proportion of sludge landfill in China was about 52%, and the others were less than 30%. Although the harmless disposal technology has developed in recent years, the total amount of sludge has increased, and the landfill ratio has reached 62%, and the others are less than 20%. This shows that at present, sludge treatment and disposal in China is slow and does not match the progress of sewage treatment.

 

The sludge disposal is not in place. Is it a financial problem? In fact, the capital demand for sludge treatment and disposal facilities is limited relative to the overall investment in sewage treatment. The key point is that operating costs have made some local governments unable to do so.

 

For the sludge treatment and disposal work in China, the following suggestions are made:

 

First, raise awareness of sludge treatment and disposal. The sludge can no longer be used as a potential temporary transition problem, but should be used as a national hard energy-saving emission reduction indicator, along with the sewage treatment COD emission reduction targets during the 11th Five-Year Plan period, and become a country. Act, and effectively increase the intensity;

 

Second, the improvement of management policies and regulations, sludge treatment and disposal involve all aspects, and all departments need to coordinate and cooperate;

 

Third, formulate sludge treatment and disposal planning, sewage treatment planning and sludge should be integrated and integrated, and it is not possible to build a sewage treatment plant and throw away sludge disposal. Now many provinces and cities do not have relevant plans. If there is no sludge facility construction plan, site selection will be a problem;

 

Fourth, sludge treatment must be implemented in parallel with wastewater treatment. In the future, during the "Twelfth Five-Year Plan" period and the "Thirteenth Five-Year Plan" period, thousands of sewage treatment plants will probably be built. If there is no sludge disposal project, it should not be approved;

 

Fifth, pay close attention to the implementation of sludge operating costs, it is recommended to purchase public services to solve the problem of insufficient operating costs. On the specific technical route, it is recommended to choose sludge digestion first. It can also consider biological drying and heat drying processes. In a certain stage, it can develop some co-processing with thermoelectricity, cement and building materials, but this is only short-term behavior, long-term The behavior should still be in the system of sludge digestion.

 

In addition, it is necessary to scientifically supervise upstream wastewater discharge and downstream sludge disposal, and start with the entire indicator, responsibility, policy and supervision, and build a complete management chain so that sludge treatment and disposal can develop rapidly.

 

According to the “Best Available Technical Guidelines for Pollution Control of Sludge Treatment and Disposal in Urban Sewage Treatment Plants (Trial)” issued by the Ministry of Environmental Protection, medium-temperature anaerobic digestion and aerobic fermentation are the best viable technologies for sludge treatment and pollution prevention, and sludge land use And dry incineration is the best feasible technology for sludge disposal pollution prevention.

 

The development of anaerobic digestion has become a very mature technology, and large digester has been widely used in China. Urban sludge has great potential for anaerobic digestion to produce biogas, but there are still many problems in actual operation. The state has proposed the idea of ​​purchasing public services from society, but companies in the field of anaerobic digestion have not really entered this market. To solve this dilemma, it is necessary to allow competent companies to quickly enter the market and dispose of urban sludge in an industrialized manner.

 

Aerobic fermentation was a relatively extensive method in the early stage. Now it has basically realized large-scale engineering, localization of equipment, intelligent control and sludge stabilization. At the same time, relevant national policies also encourage land use for sludge, providing opportunities for the development of this approach.

 

However, China's national conditions are different from those of Europe and the United States. How to transport aerobic fermented compost to the field is a problem to be considered. The sludge becomes a fertilizer after aerobic fermentation, and the fertilizer is used by the land. In the middle, it has to go through a long logistics chain such as sludge storage, transfer, and dispersion. If there is no such logistics chain, the sludge land use is an empty talk. That is to say, people who engage in urban sludge need to be more involved in agriculture, and more consideration of the logistics chain can extend the industrial chain, thus opening up the technical route of sludge land use.

 

Therefore, it is a good example to promote system solutions in sludge treatment and disposal, and use government procurement to drive the market. The “Technical Policy for Sludge Treatment and Pollution Prevention and Control in Urban Sewage Treatment Plants (Trial)” clearly stipulates that sludges that meet the standards are encouraged to be used for land improvement and landscaping, and are included in the government procurement list. However, this policy is not currently sufficient. The government should promote the formation of the market in terms of demand.

 

In short, the problem of sludge treatment and disposal has long been caused by the collective absence and dereliction of duty of government functional departments and technology circles. Sludge treatment includes sludge reduction, stabilization and decontamination. This should be the task completed in the construction of sewage treatment plants, but we have not treated sludge treatment as an essential part of sewage treatment. .

 

Landfill, incineration and utilization are the main methods of sludge disposal, and each treatment approach faces different problems.

 

The main problem with landfills is carbon emissions and low land resources. Organic matter is buried underground, producing a large amount of methane gas, and carbon emissions increase rapidly. The resulting methane can be collected, but theoretically only 40% can be recovered. Nowadays, land resources are very small, and urban sludge may need to be transported to a distance of 100 kilometers to find landfill sites, and the transportation distance is too long.

 

The sludge contains organic matter and inorganic nutrients, but there are also pathogens, heavy metals, persistent organic matter, etc. Can it be used to make a profit and realize the use of resources? A lot of research and practice in the West prove that the answer is yes, but this is a meticulous work. based on. The sludge column of the EU Environment Council website clearly mentions that sludge is a good thing, but there is a risk that it needs to be returned to the land after controlling the risk.

 

Although the official approval of sludge for agricultural use, there are also many objections. Therefore, European and American countries have conducted in-depth research on the agricultural utilization of sludge and formulated strict standard specifications. For example, as early as 1986, the European Union formulated the "Sludge Agricultural Standards" (86/278/EEC) to make strict regulations on related issues, such as when the land after using the sludge cannot grow vegetables, when can't Harvest and so on. In contrast, China's standard norms and details of intermediate links are too little, and the corresponding management supervision is not in place, so it is not easy to say that sludge can be used for agriculture.

 

From 2007 to 2010, the European Union organized the strength to evaluate the “278” procedure. The result of the evaluation is that since the implementation of the regulations for sludge entering the land, there is no scientific literature to prove the environmental or health risks caused by agriculture. In 2011, the EU proposed two different land-use options for sludge, which are still in the process of soliciting opinions. They plan to release new sludge standards this year, which specify detailed standard limits, monitoring frequencies, and more.

 

The famous American 503 bill was promulgated in 1993 and was amended twice in 2001 and 2007. The heavy metal related indicators were strictly regulated. Because the domestic opposition voice is relatively large, the US organization of chemistry and toxicologists evaluated the 503 bill. The final conclusion is that there is no scientific evidence that the bill does not protect public health. It is recommended that the EPA should regularly track, monitor, and evaluate organic chemical pollutants and pathogens. . Based on this evaluation, EPA has conducted a systematic assessment of sludge land use every two years since 2005, involving indicators including heavy metals, inorganic ions, persistent organics, pharmaceuticals and artificial care products. In other words, the United States encourages sludge to return to the land while not hesitating to increase supervision.

 

All in all, agricultural utilization is a high-level way of sludge treatment and disposal. On the basis of strict treatment, through scientific evaluation, tracking and supervision, it is possible to realize the use of resources, control risks, and pros and cons. This is an ecological, sustainable and recyclable good thing, but it is very troublesome and needs to be done seriously.

 

Another method of disposal is incineration. Sludge incineration is not a bad thing, but there are more problems and the opposition is very loud. I believe that incineration is a helpless choice. Before the establishment of a standardized sludge agricultural technology system and management system, incineration is an important means to temporarily solve the sludge problem.

 

Where does the sludge eventually go? Landfill is a passive and simple disposal. Incineration is a helpless transitional treatment, and scientific agricultural use is an active high-level disposal. Therefore, landfills are definitely better than littering, but the site has to be found; incineration is certainly better than landfilling, but it is better to control the flue gas; agricultural use is better than incineration, but it must be strictly managed.

 

Based on the above conclusions, what should we do? First of all, no matter how to deal with it now, it is better than dumping it. Secondly, we need to test the sludge components in a down-to-earth manner. The danger of sludge has been said, but few cities can get the data of sludge mud. No data can be talked about.