Dewatering Mechanism and Mercury Distribution of Sludge Pretreated by Electrolysis
The sludge was pretreated by using Ti/RuO2-IrO2 electrode as the anode, the dewatering mechanism, the influence of direct oxidation and the potential oxidizing substances produced in the process of electrolysis, such as oxygen, hydrogen peroxide, ozone and hydroxyl radicals, on the extracellular polymeric substance (EPS) of sludge was studied. There were O2 and OH- produced but no H2O2 and O3 under an external electric field. O2 had no obvious effect on the degradation of polysaccharides (PS) and proteins (PN);OH- content was positively correlated with current density and the degradation of EPS was main caused by oxidation of OH-. The reduction of the water content (WC) was mainly attributed to the OH- responsible for attacking and disrupting floc structure and cell membranes, increasing the concentration of EPS, and degrading some PN and PS. The capillary suction time (CST) of the sludge treated by electrolysis was higher than those of the untreated sludge due to the increase in EPS content and the decrease in the size of sludge floc during electrolysis. The HgO in the sludge entered the water phase more and was oxidized during the electric dehydration process, and the elemental mercury was oxidized into Hg2+ under the action of OH-.
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