Sludge "bathing and disinfection" can turn waste into treasure, and "productization" is the fundamental solution

my country's sewage treatment rate has exceeded 90%, but the treatment rate of sludge produced after sewage treatment is not high. The phenomenon of "heavy water and light sludge" is serious across the country. In particular, the problem of sludge product outlet has always restricted the development of sludge aerobic fermentation industry. A recent interview by reporters found that my country is accelerating the promotion of sludge disposal productization to create conditions for the resource utilization of sludge. The industry believes that only when sludge treatment and disposal is "productized" and eventually put on the market can the outlet of sludge be fundamentally solved.

"Heavy water, light mud"

Sludge treatment becomes the shortcoming of the industry

Wastewater treatment has always been a hot spot for environmental governance. In recent years, the national sewage treatment rate has exceeded 90%. However, a large amount of sludge is also produced during sewage treatment, which contains a large amount of harmful substances. However, due to the lack of treatment technology, sludge has become an industry problem that needs to be solved urgently. The phenomenon of "heavy water, light mud" is serious across the country. The treatment rate of sludge produced after sewage treatment is not high. In many places, sludge is usually transported to the suburbs for simple landfill treatment.

According to the plan formulated during the "12th Five-Year Plan" period in my country, the national planned construction of urban sludge treatment and disposal scale is 5.18 million tons per year. However, among the five tasks of "pipeline network, new construction of sewage treatment plants, upgrading and transformation of village sewage treatment plants, sludge treatment and disposal, and recycled water", only the task of sludge treatment and disposal has not been completed, and the road to sludge treatment and disposal is still long and arduous.

"The main means of sludge treatment at present are landfill, incineration, and resource treatment and utilization." Engineers from Hubei Xiangyang Guoxin Tianhui Energy Co., Ltd. introduced that at present, in some European countries, the application of anaerobic, dry incineration and other related technologies for sludge treatment is very mature, but the cost is relatively high. In China, sludge treatment in some places still adopts landfilling and lacks formal treatment channels.

According to environmentalists, sludge is one of the main sources of solid pollution in my country's cities and towns, containing a large number of complex and harmful components such as viruses, pathogens, microorganisms and heavy metals. If sludge is not properly handled, such as random landfill or stacking, it will seriously pollute groundwater, surface water, surrounding environmental sanitation and air, breed pests and diseases, and bring very severe secondary environmental pollution problems. Many villages "surrounded" by sludge and garbage have become "cancer villages" or villagers have been forced to move away.

Industry insiders believe that the high cost of resource utilization of sludge treatment is the main limiting factor in the industry. It is understood that the sludge transportation stage alone has become a key link in limiting the large-scale continuous operation of sludge aerobic fermentation. Because in the entire sludge disposal process, sludge transportation is the link with the most personnel, the highest labor intensity and the lowest degree of automation in the entire aerobic fermentation process.

Promote "productization"

Sludge treatment has a way out

Yang Xiangping, president of the National Sludge Treatment and Disposal Promotion Association, said that only by "productization" of sludge treatment and eventually pushing it to the market can the way out of sludge be fundamentally solved. He proposed to upgrade my country's previous sludge treatment of "reduction, stabilization, harmlessness, and resource utilization" to "five transformations", that is, to add "productization".

The reporter saw a sludge treatment method at the Xiangyang Sludge Treatment Plant of Guoxin Tianhui Energy Co., Ltd., which covers an area of ​​30 acres. It is reported that this treatment method is in the leading position in environmental protection standards and technical levels in the international harmless disposal technology. The specific method is that after the sludge and kitchen waste are collected and transported, they are "washed" by low-energy 170℃ high-temperature hot water hydrolysis for disinfection and deodorization. Then high-concentration medium-temperature anaerobic digestion is carried out. This process is like "refining elixir" and takes 20 days. In this process, about 30% to 40% of the total solid sludge will be "digested and eaten".

As for the remaining "hard bones" biogas residue, it will be "transformed" into organic sludge particles after being dried with waste heat. The energy consumed by using waste heat and solar energy for drying is only 1/4 of that of traditional thermal drying methods, which greatly reduces the drying cost.

These organic sludge particles are finally uniform in size of soybeans. The 60 tons of organic sludge particles produced every day are reused by the land for soil improvement and landscaping. The biogas produced can't "run away" either. After purification and compression, it generates green and environmentally friendly CNG biomass gas for use by urban taxis.

The reporter could not smell any abnormal odor at the scene, nor could he see any excess residual slag. The sludge garbage was handled cleanly. In the woods next to the factory, the seedlings absorb organic biogas fertilizer, and they are lush and full of vitality. Here, through energy recovery and resource utilization, carbon dioxide emissions can be reduced by about 60,000 to 80,000 tons per year. Through the use of biomass gas, it is equivalent to saving 5,500 tons of standard coal per year.

In order to promote the productization of sludge disposal and solve the bottleneck problem of sludge disposal and transportation, Tang Hongbo, engineering operation director of Beijing Zhongke Bolian Environmental Engineering Co., Ltd., said that my country has currently explored the construction of ideas based on the Internet of Things and Industry 4.0, integrating sludge intelligent transportation, intelligent fermentation, intelligent deodorization, intelligent control platform and resource utilization, realizing intelligent control and unattended aerobic fermentation process, which can greatly improve the operating environment, reduce labor costs, and control the secondary environmental pollution of sludge facilities.

It is reported that this project uses the world's first automatic feeding and discharging robot, embedded with artificial intelligence technologies such as automatic positioning, remote monitoring, and human-computer interaction, and realizes unattended, precise feeding and discharging, and remote intelligent control. The automatic feeding and discharging robot fills the gap in sludge intelligent transportation and breaks the bottleneck of fully automated control of sludge aerobic fermentation engineering.

Professionals suggest that sludge treatment equipment is an important guarantee for the quality of sludge treatment products. It is necessary to adopt an industrial development model and focus on the stabilization, reliability and standardization of equipment.

Sludge industrialization

It requires multiple efforts to innovate models

In order to alleviate the contradiction between sludge production and lagging sludge treatment capacity, my country has issued a series of policies and plans in recent years. At present, the technical route and industrial policy of sludge treatment in my country are gradually becoming clear, and industrialization and marketization are about to start.

Experts said that sludge disposal is now receiving more and more attention, and the technology, policy and operation mode of sludge disposal will have breakthroughs in the near future. The sludge treatment and disposal industry is expected to enter a stage of rapid growth under the promotion of policies.

In order to explore the outlet of sludge products, some sludge disposal companies in the industry are currently trying the "engineering general contracting + trusteeship operation" business model. It is to give full play to the technical advantages of professional companies, adopt the engineering technology of professional companies, and after the construction is completed, professional companies will be entrusted to operate, so as to reduce operating costs, reduce difficulties and risks for owners, and avoid "sunbathing" projects with abnormal or even idle engineering operations.

Chen Tongbin, vice chairman of the National Sludge Treatment and Disposal Promotion Association, said that it is recommended to promote this model nationwide to improve the quality and operation efficiency of projects and promote the healthy development of the sludge treatment and disposal industry.

Zhang Linwei, deputy director of the Urban Construction Department of the Ministry of Housing and Urban-Rural Development, suggested that the sewage treatment system also needs to increase the COD concentration of the sewage treatment plant inlet water to create conditions for the resource utilization of sludge, and ultimately achieve "where the sludge comes from and where it goes back to".

Many experts said that sludge treatment should always put harmlessness and control of environmental risks first, adopt advanced and mature technologies and processes, and gradually promote the realization of 100% "five-in-one" treatment of sludge across the country.