Ozone as a Catalyst of Surplus Activated Sludge Hydrolysis for the Biogas Production Enhancement

Abstract

The biogas produced in the methane fermentation is valuable due to its use as a renewable energy source. A promising method of biogas production intensification is sludge flocs disintegration via ozonation. The aim of this study was to check the impact of the ozonation on the efficiency and kinetics of biogas production from surplus activated sludge (SAS). Processes were carried out batchwise at 37 °C. The following analyses were performed: pH, alkalinity, dry matter, dry organic matter, chemical oxygen demand, total organic carbon, total nitrogen, elemental analysis (CHNS), the biochemical potential of methane by NIR spectroscopy, and the amount and composition of biogas. The results showed that the ozonation process had no effect on the elemental composition and chemical structure of SAS. The chemical formula of SAS (C2.97H4.68O1.20N0.3) and a simplified equation describing the methane fermentation process were determined. Ozonation caused the hydrolysis of some organic compounds from sludge flocs and increased the efficiency of biogas production. The methane content in biogas was higher by about 2.5%, while the amount of produced biogas rose by up to 21% for the ozonized sludge. The kinetic constants of first-order reaction were between 0.219 and 0.323 d−1, with an upward trend due to ozonation.