During the 12th Five-Year Plan, the sludge market was not as expected. Policy weakness, the payment mechanism is not clear and other factors led to a marked decline in the market. Sludge treatment enterprises a project a year embarrassing situation continues to emerge, the industry self-deprecating in the "dark before dawn." The anaerobic digestion technique, which has been "picked up" again, seems to be turning the sludge treatment into a turning point.

Four plight bad song? Sludge anaerobic technology actually digs the gold opportunity

Seven months time, 19,000 tons of sludge was dumped in Mentougou District of Beijing, resulting in serious pollution of 44 acres of woodland. In April 2016, Beijing No. 1 Intermediate People's Court finally ruled that the related personnel acts constituted crimes of environmental pollution. This is not the first incident in the sludge treatment industry. The sewage sludge from sewage treatment plants has not been safely disposed of and it has become a commonplace problem. When public opinion criticism comes one after another, the experts in the industry are feeling that the industry handling and government regulation are "clever and brutal."

"I have not talked about the sludge for a long time and I really have nothing to talk about." Wang Hongchen, vice president of the School of Environment at Renmin University, once declined to be interviewed. He was tired of calling for the same thing from year to year, but with no progress. "Why do I talk about the problems six or seven years ago, are still there now? Just a few people in our industry are yelling that there is no breakthrough in the periphery."

From the 1970s to explore the construction of sewage treatment plant in China so far, more than 40 years. Sludge problems from scratch, from only a few people in the industry concern gradually into the public view. A group of sludge experts, including Wang Hongchen, shouted loudly at one side and then passed by another for five years and another five years.

Fortunately, anaerobic digestion of sludge that has been neglected in the country is being "picked up" again.

Application Status of Sludge Anaerobic Digestion

According to public information, sludge treatment methods are mainly sanitary landfill, incineration, composting, resource utilization and other methods, and anaerobic digestion technology due to have the energy recovery, reduce environmental hazards function has become the most widely used in the world sludge stabilization And resource-based approach. At present, there are about 36,000 anaerobic digestion reactors in Europe, accounting for about 40% -50% of sludge treatment volume. In the UK, about two-thirds of sludge is treated with anaerobic digestion. According to the survey conducted by the U.S. Environmental Protection Agency, the prevalence of anaerobic digestion in U.S. sewage plants is about 60%. Most Japanese sewage treatment plants also use anaerobic digestion to treat sludge.

However, the treatment of sludge in our country, according to professor Dai Xiaohu Tongji University, with the population growth and sewage treatment capacity upgrade in 2014 China's municipal sludge production reached 102,100 tons / day, but about 75% of the Sludge has not undergone any stabilization or decontamination, only simple landfilling and random dumping, 15% of the sludge used in incineration and building materials, 10% of the sludge used harmless, stable Land and land use.

However, sludge anaerobic digestion technology started earlier, but the technology application developed slowly, and there is still a big gap between developed countries. According to the survey, as of September 2015, China has built a total of 3,830 urban sewage treatment plants with a total wastewater treatment capacity of 162 million m3 / d, but only about 60 in Beijing, Shanghai, Tianjin, Chongqing, Qingdao, Shijiazhuang and Zhengzhou Block sewage treatment plant sludge anaerobic digestion process, and normal operation of only about 20. Most sludge anaerobic digestion project is not running or stoppage, such as Beijing Gaobeidian water sludge sludge anaerobic digestion project, though it is China's earliest construction, the largest, most complete design, the operation of up to 10 years Of the project, but stopped before the 2008 Olympic Games.

There are many problems to be solved

So why? Chen Tongbin, director of the Center for Environmental Rehabilitation, Institute of Geographic Sciences and Natural Resources Research, CAS, once gave his opinion on this issue. The first is that sludge anaerobic digestion technology has a large investment in sludge disposal. The relevant engineering experience of sludge digestion in China Small, large-scale sludge digestion equipment are mostly imported from abroad, the basic investment and operating costs are higher.

Second, sludge anaerobic digestion in addition to the need to invest a lot of money to build digestion facilities, but also need to invest a lot of money to build supporting facilities, sludge after anaerobic digestion can only reduce the quality of about 1/3 to 1/2 . From the point of view of the entire industrial chain of sludge disposal, anaerobic digestion has not reached the final disposal purpose, leaving a large amount of remaining sludge residue to be treated by other technologies. The resulting digestion fluid COD concentration is very high, the need to establish a supporting sewage treatment facilities or return to the sewage treatment plant. This requires significant additional investment and operating costs. Therefore, the construction of digestion treatment project can not only consider the investment of digester and operating costs, but also consider the other supporting conditions of investment and operating costs.

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