Effects of cycle time and fill time on the performance of an anaerobic-anoxic-aerobic-fed batch moving-bed reactor.

Performance of a fed batch moving-bed reactor system arranged in anaerobic (B1)-anoxic (B2)-aerobic (B3) mode was investigated using cycle time (18-36h), gradual fill time (total 5-18.5 h; B1: 1-3.7 h; B2 and B3: 2-7.4 h each) and instantaneous fill time as variable parameters. During cycle time variation, total hydraulic retention time changed from 4.5 to 9 days (B1: 2.25-4.5 days; B2 and B3: 1.13-2.25 days each). Synthetic wastewater contained phenol (1500 mg/l), thiocyanate (SCN(-)800 mg/l at gradual fill and 100 mg/l at instantaneous fill) and ammonia (NH4(+)-N 500 mg/l). Phenol and chemical oxygen demand (COD) removals in B1 increased with increase in cycle time and gradual shorter filling showed higher performance than gradual long filling and instantaneous filling. In B2, simultaneous removals of phenol, SCN, COD and NO3(-)-N were achieved and effects of cycle time and fill times were not profound. In B3, NH4(+)-N removal efficiency increased with increase in both cycle time and gradual fill time. The minimum cycle time of 30 h and total hydraulic retention time of 7.5 days and total fill time of 12.5 h were recommended. A modified Stover-Kincannon model showed the highest correlation for removal of substrates in B1, B2 and B3.