Effectiveness of electrooxidation process for stabilizing and conditioning of urban and industrial wastewater sludge

The objective of this research was to investigate the performance of an electrochemical process for enhancing dewaterability and stabilize wastewater sludge from paper mill industry (PMS) and municipal wastewater (MWS) treatment plants. The treatment was conducted using 13.2 kg of sulfuric acid (H2SO4) per ton of dry sludge (TDS) and 200 kg of NaCl/tds as electrolytes, at a current intensity of 8A for 60 min. The process was efficient for increasing the dryness of PMS with an average value of 25.3 +/- 1.2% (w/w). By comparison, the electrochemical treatment using MWS allowed increasing the dryness to 33.4 +/- 1.4% (w/w). Simultaneously, the process was found to be effective in removing pathogen indicators (abatement > 4 to 5 log units of total and fecal coliforms) using either PMS or MWS. At the same time, it preserved the fertilizing properties of sludge by maintaining the concentration of P(tot), N-TKN and COD in dewatered sludge. The substitution of sodium chloride (used as electrolyte) by sodium sulfate (Na2SO4) combined with hydrogen peroxide (H2O2) allowed reducing the formation of organo-chlorinated compounds: more than 50% of chloroform was reduced, 86% of toluene was reduced and 59% of phenolic compounds was reduced.