In this research, the salinity effects on mechanical dewatering, freeze/thaw conditioning and electro-osmosis dewatering were investigated in terms of specific resistance in filtration (SRF), time to filter (TTF) and solid content of one biological sludge. Three levels of salinity, 5,000, 10,000 and 20,000 ppm, were studied and typical coagulant chemicals such as alum and organic polyelectrolytes were used for some tests. The experimental results show that increase salinity can decrease the SRF and TTF in mechanical dewatering, and increase the final solid content of the dewatered sludge. At salinity of 10,000 ppm or higher, the results obtained are comparable to those obtained with chemical addition as the performance of chemicals on sludge SRF and TTF is limited at high salinity. Duri...[ Read more ]

In this research, the salinity effects on mechanical dewatering, freeze/thaw conditioning and electro-osmosis dewatering were investigated in terms of specific resistance in filtration (SRF), time to filter (TTF) and solid content of one biological sludge. Three levels of salinity, 5,000, 10,000 and 20,000 ppm, were studied and typical coagulant chemicals such as alum and organic polyelectrolytes were used for some tests. The experimental results show that increase salinity can decrease the SRF and TTF in mechanical dewatering, and increase the final solid content of the dewatered sludge. At salinity of 10,000 ppm or higher, the results obtained are comparable to those obtained with chemical addition as the performance of chemicals on sludge SRF and TTF is limited at high salinity. During freeze/thaw conditioning, a negative effect of salinity on SRF and TTF was obtained. The extent of salinity effect is lower than the case found in the sludge without freeze/thaw conditioning. The performance of chemicals on SRF and TTF improvement is similar to that without freeze/thaw conditioning. However, the chemical effect on increasing the sludge final solid content is not as significant as that without freeze/thaw conditioning. In the electro-osmosis dewatering, the solid content of dewatered sludge increases with salinity and electric field strength. The electro-osmosis dewatering, however, is inhibited by a high salinity level of sludge.