Improvement of the sludge dewaterability conditioned by biological treatment coupling with electrochemical pretreatment

The effects of biological conditioning coupling with electrochemical pretreatment (EP-BC) on the dewaterability of waste activated sludge (WAS) and its mechanism were investigated in this study. The capillary suction time (CST) was considered as one of the main parameters to estimate the sludge dewaterability. Results indicated that the optimal conditioning parameters were as follows: biological conditioning with 10% DS (dried solid) mixture substrate of elemental sulfur and ammonium ferrous sulfate at a ratio of 3: 7 (S-0\Fe2+, w/w), and the electrochemical pretreatment (voltage 20 V, electrolysis time 5min) was applied. Highest CST reduction of 67.3% was achieved with EP-BC treatment for 12 h. Otherwise, the effects of EP-BC treatment on zeta potential, viscosity, pH and EPS property were also analyzed to illustrate the potential mechanisms of the sludge conditioning. The removal of protein in EPS was considered to be the key factor to improve the sludge dewaterability. Furthermore, high-throughput sequencing analysis indicated that Acidocella, Nitrospira, Alicyclobacillus and Rhodanobacter were the dominant bacteria genera in the treatment which played an important role in biological conditioning process. Thiobacterales could be enriched by EP-BC process well to enhance the sludge dewateriability. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.