Sludge profiling at varied organic loadings and performance evaluation of UASB reactor treating sewage

• Long term performance of pilot-scale UASB reactor was investigated under ambient conditions.
• Sludge bed profiles were determined at different organic loading and biogas production rates.
• Specific methanogenic activity was investigated.
• Experimental results were verified with sludge bed model.

An up-flow anaerobic sludge blanket (UASB) process was investigated for the treatment of domestic wastewater using a 60 l pilot scale reactor. The treatment performance was analysed at 8 h hydraulic retention time under ambient condition (8–40 °C). Biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) were used to evaluate the performance of organic matter and suspended solids removal. Specific methanogenic activity and solids concentration along the sludge bed height were determined to evaluate sludge quality. An average of 65–85% BOD, COD and TSS removal were achieved under different organic loadings 0.57–6.35 kg [COD] m−3 d−1. The removal of organic matter showed a linear correlation with organic loads. The methanogenic activity decreased at lower organic loads. In addition, at low organic loads, high variations in COD reduction and low gas production were observed.