Improving thermal dewatering characteristics of mechanically dewatered sludge: response surface analysis of combined lime-heat treatment.

In this study, disintegration of dewatered sludge (dry solids content [DS%] = 23 +/- 2) was studied to assess the possibility of enhancing the overall performance of a thermal dewatering processes. Powdered lime was used as an alkaline disintegrator. The combined effects of drying temperature, powdered lime dosage, and organic content on the thermal drying rate of dewatered sludge were investigated in a full-scale wastewater treatment plant. Effects of selected design parameters on the sludge drying rate were modeled using a response surface method. In addition, the possible interaction between lost on ignition and total organic carbon parameters also was investigated statistically. Specific resistance to filtration and free water contents of raw and disintegrated mixed sludge (DS% = 1.0 to 1.8) samples were compared statistically. The obtained results indicated that all of the selected design parameters have a significant effect on thermal dewatering characteristics, and the alkaline disintegration technique could remarkably improve thermal evaporation rate of dewatered sludge. These results are important because they could help to establish a sustainable sludge management model, which is critical in reducing environmental health risks.