Evaluation of effective conditioners for enhancing sludge dewatering and subsequent detachment from filter cloth

Various types of materials (including ferric chloride, alum polymers, acids, wood chips, wheat dregs, diatomite, and coal ash) were used individually to condition a digested sludge from a brewery to investigate how adding these materials affected the dewaterability and adhesion of the sludge. Specific resistance (SR) to filtration, as an index of sludge dewaterability, and the mass of residue (MR) on the filter cloth after cake detachment, as an index of sludge adhesion, were measured to evaluate the effectiveness of conditioners. Among these additives, ferric chloride, alum, commercial organic polymers, and acids proved to be effective chemicals in reducing SR. However, only ferric chloride addition effectively decreased sludge adhesion. The optimum dosage of ferric chloride is around 15%, based on the original dry solids content of the sludge. Wood chips and wheat dregs were verified as suitable physical conditioners for both improving dewaterability and also reducing adhesion of sludge. These two inert materials also satisfy the requirements that conditioners be biodegradable, easy to obtain, and low cost, to maintain the potential utilization value of the resulting sludge cake.