With the increase of urban population in our country and the expansion of its scale, the difficulty of urban sewage treatment is increasing day by day. Sewage treatment will produce more solid waste and its disposal becomes a major challenge nowadays. Experts believe that the difficulty of sludge disposal project is greater than the difficulty of sewage treatment. As of the end of September 2015, 3830 WWTPs have been built up in cities and towns across the country, with a capacity of 162 million m3 / d and an associated sludge exceeding 30 million tons per year. Statistics from the Ministry of Housing and Urban-Rural Development as of the end of 2014 shows that about 56% of the sludge is decontaminated by sanitary landfill, fertilizer production, incineration and building materials, and nearly half of the sludge still can not be decontaminated. Sludge problems have become a bottleneck in the field of wastewater treatment. As more sewage treatment plants are put into use, sludge emissions are increasing. The issue that we are extremely eager to solve is the imminent development of equipment and research on sludge disposal, municipal sludge disposal and treatment technologies. In recent years, with the full implementation of China's major projects of water pollution control and control technology and large-scale construction of sewage treatment facilities, sludge recycling and disposal of equipment and technology has been rapid development, to solve the sludge problem provides a very powerful Technical support. Pretreatment Sludge belongs to the colloidal structure of hydrophilic material, is very easy to form filamentous bacteria and bacteria micelles, a large number of breeding process can allow the formation of filamentous bacteria and micelles adsorption more water and sludge expansion, eventually leading to pollution Mud has the characteristics of easy dehydration and high water content. Studies have shown that the sludge after dehydration can reduce its moisture content to about 50%, compared to the current centrifuge and belt filter, up to about 60% capacity reduction rate. After the technology promotion of high dryness sludge dewatering can greatly reduce the sludge disposal and disposal costs. Traditional pretreatment methods are usually dehydration, digestion, conditioning, cracking, concentration, etc., usually the traditional and treated sludge still has a moisture content of about 80%, an increase of sludge follow-up costs. In the future, the new direction of sludge disposal and treatment is resource treatment, and the premise of sludge resource recovery must give sludge economical and efficient high-dryness dehydration. Dry dehydration methods are mainly electro-dewatering method, plus mechanical pressure filtration after lime and heat drying method. Electro-osmosis has a high dewatering effect on sludge of 60% -80% high water cut, which results in poor dewatering effect on sludge with low moisture cut of 40% -60%, with more expensive equipment costs. Sludge in the water will be added to absorb the release of lime hydration release a lot of heat, moisture will be quickly evaporated. Heat drying method has the characteristics of large equipment volume and energy consumption, the wall of the instrument is easy to stick to the sludge, resulting in reduced heat transfer efficiency. The above-mentioned sludge treatment method is mainly for high-degree-dehydration sludge treatment and microbial cell structure to be destroyed, although the sludge volume can be reduced, but the secondary pollution and high cost shortcomings are obvious. Sludge resource utilization From the perspective of urban ecological environment protection, resource development and utilization, and economic development, resource utilization is the most ideal method for urban pollution treatment. The practice and research on the utilization of urban sludge resources should be strengthened. The problems of sludge disposal To be solved, urban ecological and environmental pollution should be avoided, and the cost of disposal should be saved. Only in this way can we get a better social, economic, environmental and ecological environment, which is in line with the necessary development trend and requirements of urban sustainable development. Energy Use: Sludge fermentation sludge can be used as chemical raw materials and fuels. Sludge gas from digesters can be used as a clean fuel and can be easily transported and stored. Sludge gas per square of heat about 20850 ~ 25020kJ, equivalent to 1kg of coal heat. Sludge gas is the main component of CO2 and CH4, removal of CO2 and purifying gas can be obtained after a variety of chemical products CH4. Reduction technology: sludge is easy to secondary pollution, malodour, heavy metal accumulation, high water content, high pathogen load characteristics, and now "Sinotrans landfill" approach to land protection and urban health requirements far can not be met. Nowadays, the most urgent and common needs of sludge treatment are large-scale reduction. Sludge utilization is a long-term and can not be ignored goal. How to take into account the future development of resource-based and current demand to meet the reduction requirements of sludge technology route selection and formulation of the key to disposal strategy. Sludge reduction technology to control dissolved sludge, biofouling sludge reduction technology, chlorination combined with sludge reduction technology, ozonation combined with sludge reduction technology, ultrasonic combined sludge reduction technology , Alkali-thermal reduction of sludge reduction technology, aerobic - anaerobic cycle of sludge reduction technology, solution plus uncoupler sludge reduction technology is the current study of sludge reduction Technology. Sludge Incineration Technology: Sludge incineration is the most thorough reduction technology. After incineration, the volume of sludge can be reduced by 90% or less to become stable and inert ash, which can be fully utilized in building materials so that it can be used in real In the sense of resource recycling, decontamination and stabilization, incineration sludge heat can be reused during the wet sludge drying process, which is very beneficial to the recycling of sludge biomass energy. In the current large-scale international cities, Methods As the mainstream sludge treatment methods. However, sludge drying incineration has the characteristics of complex processes and large scale of the project, with high operating costs and construction costs, in today's application and promotion of the technology there are still great difficulties. So, from the point of view of reducing the cost of operating and constructing a sludge disposal facility, the use of co-incineration in existing kilns should be encouraged. In recent years, sludge incineration equipment and technology have been developed rapidly, sludge co-incineration technology, wet sludge circulating fluidized bed incineration technology, heterogeneous fluidized bed sludge incineration technology and other representative results continuously Be used. Among them, the heavy fluidized bed sludge incineration technology mainly uses quartz sand bed material, the calcium-based material is added to the fluidized bed, combined with the furnace combustion temperature control and other means of large sludge agglomeration in the fluidized bed The deposition to be effective to eliminate. Sludge co-incineration technology is mainly the use of other substances in the existing industrial incinerator sludge will be mixed incineration. Now, cement kiln incineration, waste incineration plants and thermal power plants have completed the project demonstration, the amount of flue gas pollution control and furnace impact is the focus of current research and development. Nantong Weizhuo Environmental Protection Equipment Co.,Ltd , https://www.natongcwz.com
Discusses China's sludge disposal and resource utilization