Enhancing the MTE dewatering of sewage sludge by conditioning with brown coal

Dewatering of sewage sludge is an important part of proper sludge management practice. It is becoming a more challenging issue for water industries as new regulations on sludge disposal are being imposed. In this paper, the application of mechanical thermal expression (MTE) to dewater sewage sludge and the conditioning of sludge by mixing with brown coal are investigated. Raw sludge, sludge flocculated with polyelectrolyte and flocculated sludge with further conditioning by mixing with brown coal are investigated at a range of processing conditions in an MTE cell. Dewatering performance is measured by determining the sludge water removal and specific cake resistance of the filter cake for various test conditions. Both flocculation of sludge with polyelectrolyte and mixing of sludge with brown coal improve the dewatering rate. However, the sludge which is flocculated prior to mixing with brown coal gives the best dewatering performance in a compression cell at room temperature. Increases in both the applied pressure and the amount of coal are found to have a positive effect on sludge dewaterability.