Because the sludge has the properties of high water content and loose particle structure, the sludge disposal process often requires a lot of costs. Usually, a series of pre-treatments are carried out before the sludge is dried and incinerated to change its characteristics and reduce operational difficulties. Pre-treatment can be divided into physical pre-treatment, chemical pre-treatment and biological pre-treatment according to different treatment mechanisms. Various pre-treatments can improve the dewaterability of sludge, reduce the content of pathogenic bacteria, and promote the hydrolysis of organic matter to increase the decomposability.

1. Physical pre-treatment Physical pre-treatment is a method of changing the structure of the rubber feather by applying energy, mainly using temperature changes (such as heat treatment, freezing and thawing treatment, sunshine method), high-frequency crushing (such as ultrasonic oscillation), mechanical stress (such as Mechanical grinding, high pressure method), electromagnetic waves (such as ultraviolet radiation, electron beam radiation) and other principles to destroy the original highly loose form of the rubber plume, so as to improve the effect of dehydration or disinfection and hydrolysis. Heat treatment Heat treatment directly destroys the sludge plume through a large amount of heat energy, and promotes the death of bacteria and the release of organic matter. The heat treatment temperature is generally above 70°C and lasts for at least 30 minutes to ensure the treatment effect. Heat treatment is considered to be a pre-treatment method suitable for disinfection and sludge hydrolysis, and the treated sludge can meet the sludge standard recognized by the foreign environmental protection agency. The disadvantage is that it consumes a lot of energy. There are many methods of heating treatment, including direct steam injection method, resistance heating method, microwave heating method and indirect heating method. The steam injection method can make the sludge particles directly contact with heat energy, but the volume of the sludge will be increased after a large amount of steam is condensed; resistance heating and microwave heating require a lot of auxiliary equipment, and the operation is more difficult; in comparison, the use of other Indirect heating of the waste heat recovered by the facility is a relatively simple and economical treatment method. Freeze-thaw treatment Freeze-thaw treatment is a new method of sludge disposal developed in recent years. After the sludge is frozen and then melted, the originally loose particles will become large and dense, the sedimentation will be rapid and the sediment volume will become smaller, and its dehydration property will be greatly improved. The filtering effect of the sludge treated by freeze-thaw is greatly improved. Freeze-thaw treatment is suitable for all kinds of sludge, but the sludge must be frozen at a slow freezing rate to achieve the desired effect. It is mainly suitable for areas where the temperature is below 0 ℃ in winter, such as northeast my country. It is only necessary to spread the sludge layer outdoors in the first year, and after the ice melts in the spring, the water will automatically be separated from the solid by permeation or evaporation. Using this method to treat sludge is simple and economical, and can greatly save costs.

2. Chemical pre-treatment Chemical pre-treatment is the effect of coagulation and precipitation of sludge by adding Kun chemical reagents, disinfection and hydrolysis of sludge particles. General chemical reagents include acids, metal salts, surfactants, and polymer polyelectrolytes. The agents that promote disinfection and hydrolysis include alkalis, strong oxidants (such as ozone), potassium permanganate, and some biological reagents. Acid-base treatment in the activated sludge tank, the pH will obviously affect the new metabolism of microorganisms, change the shape and dehydration of the gel plume; in the waste sludge without biological flocculation and microbial metabolism, the acid-base environment will also affect the gel The form of organic matter in the feathers and the aggregation between particles.