Enhancement of anaerobic biodegradability and filterability of biological sludge by means of electro-oxidation process

Abstract

This study deals with pre-treatment of biological sludge by electro-oxidation process. Disintegration used before anaerobic digestion processes for improving biodegradability of sludge, and conditioning used to increase mechanical dewatering performance of sludge were chosen as pre-treatment methods. The effect of electro-oxidation on polymer requirement of sludge in chemical conditioning processes was also evaluated. Titanium electrode coated with Ruthenium dioxide (Ti/RuO2) and stainless steel electrode was used as anode and cathode, respectively in electro-oxidation experiments. Disintegration and conditioning performances of the method were evaluated with disintegration degree (DD) and percent decrease in capillary suction time (EcsT) parameter using response surface methodology (RSM). Optimum conditions were determined as 20 volt for 30 min for disintegration (DD=33.4%), addition of supporting electrolyte (10 g/L Na2SO4) provided to improve disintegration performance of sludge (DD=40.8%), also. Biochemical methane potential (BMP) results indicated that electro-oxidation improves the biodegradability of sludge. An increase of 39.6% methane gas production in electro-oxidized sludge was reached, comparing to the raw sludge at the end of the 40 days of incubation. Optimum conditions were determined as 30 V and 20 min for conditioning (E-CST=32.1%) and 50% decrease in polymer requirement of sludge with this application.