Mesophilic and thermophilic aerobic batch biodegradation, utilization of carbon and nitrogen sources in high-strength wastewater

This study compares organic and nitrogen removals of thermophilic and mesophilic aerobic processes. The experiments were performed in three 7.2 L sequential batch reactors (SBRs) operated at 30, 47 and 60 °C. Molasses based synthetic wastewater consisting chemical oxygen demand (COD): 11,200 mg/L, total kheljal nitrogen (TKN): 770 mg/L, ammonical nitrogen (NH4): 560 mg/L was the feed medium. Biokinetic parameters, COD, NH4+ and TKN removal efficiencies were compared under six different operating conditions. Five times lower sludge production and similar COD removal were observed in thermophilic SBRs compared to mesophilic SBR under 8.25 kg COD/m3 d loading rate. However at 24.75 kg COD/m3 d there were no differences in terms of sludge production while COD removals were varied as 59%, 80% and 82% at 30, 47 and 60 °C respectively. A mechanism was developed to understand the varying behaviors of thermophilic aerobic process. Stripping is the major mechanism for nitrogen removal in thermophilic SBRs.