Digested wastewater sludge dewatering process using water treatment plants chemical sludge and walnut shell activated carbon powder

In this study, the feasibility of employing polyelectrolyte simultaneously by thickened sludge of water treatment plants (STS), water treatment plant dewatered sludge (DBS), and walnut shells activated carbon powder (WSCA) was investigated in a laboratory scale for wastewater sludge dewatering process. Compressibility, filtration yield, specific resistance to filterability (SRF), time to filter (TTF), extracellular polymeric substances (EPS), zeta potential, and particle size have been considered as the most important affecting parameters. Singly used cationic polyelectrolyte decreased SRF and TTF by 52% and 44%. Combining WSCA, STS, and DBS with cationic polyelectrolyte reduced the SRF to 91, 78, and 75%, and the TTF to 73.5, 59, and 46%, respectively. By destroying the EPS and decreasing the rate of protein/polysaccharides, WSCA, STS, and DBS reduce zeta potential (85, 91, and 86%). Moreover, its use decreased the compressibility coefficient by 58, 50, and 56%, and increased the filtration yield by 523, 269, and 160%, respectively. The WSCA acts significantly as a physical conditioner and increases particles' mean size significantly more than any other conditioner and improved filtration yield which has the most effect on the wastewater sludge dewatering process. The STS and DBS act as physical–chemical conditioners, neutralizing surface charges, and making porous sludge.