Application of sequencing batch biofilm reactor for treatment of sewage wastewater treatment: effect of power failure

The operational performance of the sequencing batch reactor (SBR) and sequencing batch biofilm reactor (SBBR) for treating the university campus wastewater was evaluated. The effects of power failure on performance of processes were investigated by comparing chemical oxygen demand (COD) and total suspended solids (TSS) removal, sludge settling properties and microorganism's morphological properties by using SEM photos. The experiments were carried out at four 2-L reactors made from plexiglas. Three in four reactors were operated as SBBR. SBBRs were filled with the kaldnes biomedia K1 to 40, 50 and 60% of the volume of empty reactor. SBR and SBBRs were operated at 6/24 h cycling periods on a day that consisted of wastewater fill (30 min), reaction (4 h), settling (1 h) and draw (30 min), summed up to 6 h with the hydraulic residence time of 7.5 h. The effect of filling ratio on SBBR performance was also determined. In normal operation, average COD removal rates were calculated as 86, 88.5, 90.6 and 94.2% for SBR, SBBR1, SBBR2 and SBBR3, respectively. Power failure is one of the most encountered problems in the small wastewater treatment plants. Its effect was observed at 1 cycle as short term and 4 cycles as long term. Besides the negative effects of the power failure on COD and TSS removal, it also affects sludge settling properties. While interruption time is increased, recovery took much more time than expected to reach steady state conditions for all the reactors. However, the presence of biofilm restricted the adverse effect of power failure. SEM photos and better effluent quality supported these findings.