Municipal sewage sludge is solid, semi-solid and liquid waste generated in the sewage treatment process. The sludge composition is complex, including solid particles such as fibers, sediments and animal and plant residues mixed into domestic sewage or industrial wastewater. A solid substance of coagulated flocs, various colloids, organic matter, and adsorbed metal elements, germs, microorganisms, and eggs. If these sludges are discharged or disposed of improperly, they will cause serious pollution to the surrounding environment. Therefore, it is of great significance to seek economical and effective reduction, harmless and resource sludge treatment technologies.
With the acceleration of urbanization in China, the number of urban sewage treatment plants has increased year by year, and the sewage treatment capacity has gradually increased, and the production of sludge has also increased dramatically. According to the survey, as of the end of September 2010, a total of 2,631 sewage treatment plants have been built in cities, counties and some key towns, and the daily sewage treatment capacity has reached 1.22×108 m3. The urban sewage treatment project under construction in the country has reached 1849. The total design capacity is about 0.466×108m3/day. According to the sludge yield of 3.8%, the daily sludge discharge is about 6.4×106m3. The sludge disposal method of most sewage treatment plants is to transport the sludge to the landfill or form it directly by proper concentration. On the one hand, it is easy to cause secondary pollution, on the other hand, the useful resources in the sludge are lost, resulting in waste of resources.
Obviously, with the construction of urban sewage treatment plants, how to properly treat and dispose of sludge will become more and more important. At present, China’s traditional sludge disposal methods include landfill, incineration, and direct land use. These treatment methods do not effectively utilize the sludge, and there are many social and environmental problems, not sludge disposal. The best way. Therefore, the search for appropriate resource utilization methods is the most important research in sludge treatment and disposal.