The "2024 National Sludge Treatment and Disposal Industry Technology Innovation Strategic Alliance Annual Meeting" was held in Shenzhen from October 10-12, 2024. More than 350 people from senior experts in the industry, water companies, design institutes, equipment manufacturers, etc. attended the meeting. The meeting pointed out that the current annual sludge output in China exceeds 80 million tons (80% moisture content), it is expected to exceed 100 million tons by 2025, and the sludge will enrich 50% of the pollutant substances in the sewage, which will bring a great burden to the city. Therefore, our country's sewage has entered the era of stock improvement, quality and efficiency, and sludge treatment and disposal still have a long way to go.
1. Sludge treatment and disposal technology
Common sludge treatment technologies mainly include thermal drying, deep dehydration, anaerobic digestion, synergistic digestion, aerobic fermentation, and lime stabilization technology.
Common sludge disposal technologies mainly include separate incineration, collaborative incineration, carbonization, and cement kiln collaborative disposal technology.
Common mechanical dewatering technologies for sludge include plate and frame filter presses, belt filter presses, stacked screw dewatering machines, centrifugal dewatering machines, and high-pressure belt dewatering machines.
Common thermal drying technologies for sludge include electric heating belt drying, low temperature (heat pump) belt drying, paddle-type sludge drying, and disc-type sludge drying.
Common sludge incineration technologies include collaborative incineration in cement kilns, mixed incineration in thermal power plants, mixed incineration in waste power plants, and separate incineration of sludge.
PART 02 Domestic representative process route
The Way of Beijing
Beijing's current mature process route is “hot water hydrolysis + anaerobic digestion + plate and frame dehydration + crushing + formula deep processing resource utilization”. Due to policy restrictions, building materials, incineration, and composting cannot become Beijing's sludge disposal methods. Therefore, Beijing's sludge resource utilization methods are mainly forest land utilization, mine restoration,Landscaping, saline-alkaline land improvement.
The Way of Shanghai
The process route adopted by Shanghai is “dehydration + drying + incineration + fly ash resource utilization”. In 2023, Shanghai will achieve zero sludge landfill and 100% incineration harmless treatment, of which independent incineration accounts for 82.3%, and mixed incineration in power plants accounts for 7.4%., Garbage mixing and burning accounted for 10.3%. The general ash produced by incineration is shipped out for resource utilization, and a small part of hazardous fly ash is disposed of as hazardous waste.
Jiujiang Way
At present, it is generally believed that the low concentration of sewage water quality in the southern region and the low content of organic matter in the sludge produced are not conducive to anaerobic digestion and treatment. Jiujiang adopts the introduction of food waste and other exogenous organic waste and sludge for collaborative treatment and disposal, using “pretreatment + anaerobic digestion + centrifugal dehydration of biogas residue + low temperature waste heat drying+ The technical route of ”resource utilization" not only solves the problem of low organic matter content in sewage sludge, but also solves the problem of pollutant disposal in urban areas such as food waste, sick and dead livestock, expired food, and garden waste.
Zhengzhou Road
Zhengzhou City adopted the dual-route model of “anaerobic digestion + thermal drying” and “aerobic composting + resource utilization” 23 years ago, but encountered the problem that the final way out of the sludge is difficult, especially aerobic composting, which occupies a large area and has a poor environment. Add accessories and high treatment costs. Therefore, the latest sludge pyrolysis and gasification technology has been adopted on the road of energy and resource utilization of sludge. After the sludge is dried, under high temperature (1100℃) oxygen-poor conditions, it reacts with the gasifier to generate combustible gas and slag. Pyrolysis combustible gas can be used for drying and power generation, and slag can be used to make slag.The resource utilization of concrete, slag bricks, slag blocks, etc. solves the ultimate way out problem.
PART 03 Outlook on Sludge treatment and disposal technology
Hang Shijun, a member of the Strategic Committee of the National Sludge Industry Alliance, spoke at the meeting. On the basis of the four aspects of traditional sludge treatment and disposal: “Reduction, stabilization, harmless, and resource”, he also proposed “4+1", that is, “reduction, stabilization, harmless, and resource”.+ The concept of “low carbonization”, as well as the new ideas of reducing the amount from the source and upgrading the dimension from the end, turn sludge into "waste” into “resources". End-resource utilization such as sludge collaborative incineration and sludge carbonization are still the technical direction pursued by the sludge treatment and disposal industry. At the same time, advanced improvements such as AOA are used to improve sewage.The treatment process to achieve the reduction of sludge at the source of the biological pond is more worthy of attention.
Now Mr. Zhang Yue of the Strategic Committee of the National Sludge Industry Alliance adheres to his consistent style of being quick-talking and quick-talking. At the meeting, he said that the current processing capacity of our country's sewage treatment plants has reached 80 billion tons per year, and the sewage treatment capacity is actually surplus. Many sewage treatment plants collect river water and rainwater, and the sewage pipe network improves the quality and increases.Efficiency work should also be vigorously promoted. The treatment of sewage as recycled water has only ecological and environmental benefits, and there is no direct economic benefit. The resource utilization of sludge can only make money. At the same time, it goes the other way, jumping out of the current conventional route of recycling C and TP resources in sludge and changing it to recycling NResources, and successfully tested the product, which opened up new ideas for everyone.
