Ozonation as a pre-treatment for anaerobic digestion of waste activated sludge: Effect of the ozone doses

The effect of different ozone doses was assessed in terms of biogas production, anaerobic digestion (AD) kinetics and concentration of amino acids (AA) and long chain fatty acids (LCFA) in the waste activated sludge (WAS). Four different ozone (O3) doses were used: 0.043 gO3/gTSS, 0.063 gO3/gTSS, 0.080 gO3/gTSS and 0.100 gO3/gTSS. The lower doses resulted in biogas production increases and faster kinetics in the AD of SS, while the higher doses led to poorer process performance. Ozonation of WAS resulted in a non-linear reduction of the AA concentration. The concentration of LCFA was also reduced with linear correlation with the ozone dose. The reaction products of LCFA (aldehydes) might be the cause of inhibition observed in the anaerobic digestion of WAS treated with higher ozone doses.