Urban treatment plants produce a large amount of sludge every day, which is difficult to treat because of its high moisture (more than 80%), large volume and easy to decay and stink With the increasing output of municipal sludge and industrial sludge year by year, many EU countries have formulated and implemented relevant environmental laws and regulations to prohibit the landfill of sludge containing biodegradable organics and encourage its incineration The best feasible technology guidelines for pollution prevention and control of sludge treatment and disposal in urban sewage treatment plants (Trial) (2010) and the best feasible technology guidelines for sludge treatment and disposal in sewage treatment plants (Exposure Draft) (2008) issued by the Ministry of environmental protection of China clearly regard sludge incineration as one of the best feasible technologies for sludge treatment and disposal in China. This method is a sludge disposal technology with the advantages of reduction, harmlessness, recycling and energy recovery, However, at present, the moisture content of sludge after mechanical dehydration is relatively high, which makes it difficult to burn sludge

In order to effectively dehydrate the sludge, physical and chemical conditioning methods are often used to pretreat the sludge Chemical conditioning method has become one of the most commonly used methods because of its simple operation, low price and remarkable effect. Among them, the commonly used chemical conditioning agents include inorganic coagulants (such as FeCl3, Cao, AlCl3, etc., with the addition amount of 5% ~ 20% of the dry solid volume of sludge), organic polymer coagulants (PAM, etc., with the addition amount of 0.1% ~ 0.3% of the dry solid volume of sludge) and Microbial coagulants Because a single chemical conditioner is often difficult to achieve the ideal effect of sludge dewatering, in recent years, scholars at home and abroad have tried to use composite conditioners or combine a variety of conditioners to improve the deep dewatering performance of sludge. Among them, the most common is the mating use of Cao with iron salt and aluminum salt It can be seen that the application of conditioner can effectively reduce the moisture content of sludge, which means that the objects of sludge treatment in the future are mostly deeply dehydrated sludge