Research Of Sludge Dewatering And Drying

Sludge is secondary product of sewage treatment plant of sewage treatment. With the increasing amount of population and the development of industry, the sludge quantity increases greatly. Thus sewage sludge plants treat larger amount of sewage sludge and the treatment degree is improved. To prevent the secondary-pollution caused by sludge and ensure the normal operation of the sewage sludge treatment plants and the treatment effects, we must have a reasonable sewage sludge treatment and disposal method in urban sewage treatment. In the sludge disposal process, how to reduce the sludge moisture content is the key to solve the problems in the sludge treatment.Domestic and international researches and practices show that many methods have been applied in sludge treatment, including direct and indirect heat drying, but using these approaches to reduce water content to below40%after drying is difficult. Nowadays, sludge pretreatment technologies based on physical, chemical and biological methods is emerging as promising methods for waste activated sludge treatment. And sludge pretreatment had many advantages, it may affect water distribution on the surface of biological sludge particles and futher affect sludge dewaterability. The research of treating municipal sewage sludge by using chemical pretreatment combined with vacuum drying、thermal drying process was presented in this paper.In this paper, the drying characteristics of sludge is explained and the study results show that when acetone contents are0%、30%、60%, pressure degrees are20mmHg、120mmHg、220mmHg, temperatures are95℃、80℃、65°C,the sludge moisture content is reduced to the scope from68.88%to1.16%.In this study, attention is focused on drying characteristics analysis over different ranges of acetone rates、vacume degrees and dry temperatures and modeling of sewage sludge drying process by using mathematical models. Thin layer mathematical drying models which predict the effects of drying were compared according to their coefficient of correlation to estimate drying curves. In addition, the temperature dependence of the effective diffusivity coefficient was expressed by an Arrhenius type relationship. The effective diffusivity varied between0.12×10-9m2/s and7.69X10’9m2/s with an activation energy of55.209kJ/mol and25.936kJ/mol respectively for sludge and sludge pretreated by acetone. This result demonstrates that acetone pretreatment can reduce drying activation energy by53.022%.The experiment also synthesis surface active agent dosage form filter aid p-cresol resin, add hydrotropy agent to a phenol resin as dissolvant, the filter aid agent can realize the hydroscope of sludge particles surface area and it’s foaming ability is not strong. Adopt maximum bubble pressure method to measure the surface tension, and the surface tension is reduced that indicates the filter aid agent have surface activity. This research have found that using the method of the suction filter reduction can reduce the sludge moisture content by3.8%in5min under5ppm PCN and vacuum degree0.04MPa,...