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Three treatment methods work together to promote the utilization of sludge resources

In June 2021, the National Development and Reform Commission issued the "14th Five-Year" Urban Sewage Treatment and Resource Utilization Development Plan, which clearly stated that by 2025, the direct discharge of domestic sewage and the blank area of collection and treatment facilities in urban built-up areas will be basically eliminated , The national urban domestic sewage centralized collection rate strives to reach more than 70%; by 2035, the urban domestic sewage collection pipeline network will be basically covered, the urban sewage treatment capacity will be fully covered, and the harmless treatment and disposal of sludge will be fully realized. Therefore, the successive promulgation of national policies has effectively promoted the rapid development of China's sludge resource utilization market.


It can be seen that the utilization of sludge resources is about to become a major development trend in China's sewage treatment industry during the "14th Five-Year Plan" period. With the advancement of urbanization and the rapid development of cities, domestic sewage treatment plants are paying more and more attention to the resource utilization of sludge in the process of upgrading and upgrading and zero discharge of sewage. Therefore, how to scientifically and effectively utilize sewage as a resource? This has become the primary problem facing the sewage treatment industry.


At present, domestic sewage treatment plants use pre-treated sludge mainly through "sludge incineration, sludge composting, and sludge building materials utilization" Three treatment methods are included to realize the resource utilization of sludge.


1st





Dewatered sludge incineration treatment

Dewatered sludge incineration is a common method of sludge treatment in domestic urban sewage treatment plants. It mainly uses two processes of dehydration and incineration to basically achieve the purpose of harmlessness, resource utilization and reduction of sludge.


The role of dehydrated sludge incineration disposal: Dewatered sludge incineration not only reduces the energy consumption of sewage treatment plants in the sewage treatment plant, but also realizes the harmless treatment of sludge and avoids secondary pollution. The treated sludge is piled and compacted, which reduces the land occupation area and reduces the combustibility. Loss of waste and ash.


Implementation plan for incineration of dehydrated sludge: The incineration of dehydrated sludge requires three key processes: sewage crushing and conveying system, sludge incineration system, incineration ash collection system, and flue gas purification system. The sludge crushing and conveying system means that the dehydrated sludge cake is crushed and processed by the ring hammer crushing equipment, and then stored in the dry sludge storage, and put into the boiler by the shaftless screw feeding equipment. As a key process of dewatered sludge incineration, the sludge incineration system refers to a series of treatments of dewatered sludge through the application of a circulating fluidized bed boiler. Incineration ash collection system and flue gas purification system means that large-scale soot, nitrogen dioxide and sulfur dioxide will be formed during the incineration and disposal of dehydrated sludge. The municipal sewage treatment plant will collect incineration ash and slag and purify the flue gas through a series of treatments. , Effectively avoiding secondary pollution caused by sludge incineration.


2nd





Sludge composting technology

Sludge composting technology refers to the process of transforming unstable organic matter in the pile into relatively stable organic matter through the life activities of aerobic microorganisms under aerobic conditions, while reducing the content of volatile organic matter and eliminating odors. It has low energy consumption. , The characteristics of low toxicity of gas products.

Control factors of sludge composting: The control factors of sludge composting technology include ventilation, moisture content, temperature, pH value and carbon to nitrogen ratio (C/N). Ventilation is particularly important in the sludge composting process, which determines the available oxygen content of microorganisms, and affects the moisture content, temperature and pH of the pile. Therefore, if the ventilation volume is too small, it is easier to form a local anaerobic environment, resulting in low aerobic microbial activity, resulting in unsatisfactory composting effect; too large ventilation volume will take away excessive moisture and temperature, resulting in the stack temperature not reaching the standard , The effect of killing pathogenic bacteria will be unsatisfactory.

Therefore, optimizing aeration is the main technical difficulty for improving sludge composting under aeration. In short, ventilation, moisture content, and C/N provide necessary raw materials for the life activities of microorganisms in the composting process, while temperature and pH affect the activities of microorganisms.

3nd





Utilization of sludge building materials

The sludge contains 20%-30% of inorganic substances such as silicon, aluminum, iron, calcium, etc., which can be made into building materials such as bricklaying, ceramsite, cement, activated carbon, and biochemical fiberboard through wall breaking and mixing refining technology. Used in building construction. After the dewatered sludge is broken through the wall, it is crushed and mixed with coal gangue, fly ash, construction waste, etc., and then begins to age. The aged material is refined and passed through a brick extruder, a blanking machine, and an annular furnace. Firing and other treatment processes, firing into building materials and bricklaying.

From the perspective of the wide application of sludge bricks, sludge ceramics and other materials in engineering, sludge building materials have a broad space in the domestic building materials market. With the improvement of sludge building materials utilization technology and the successive introduction of government sludge disposal subsidy policies, domestic sewage treatment plants will continue to promote the utilization of sludge building materials, improve the technical level of sludge building materials utilization, and realize the leapfrog development of sludge building materials utilization.

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