HYDRODYNAMIC CHARACTERISTICS IN AEROBIC BIOFILM REACTOR TREATING HIGH-STRENGTH TRADE EFFLUENT

Four 3-L aerobic biofilm reactors (ABR1, 2, 3, and 4) treating a high- strength food-processing waste water (10 g chemical oxygen demand [COD ] /L) were subject to reactor liquor recirculation rates of 1, 3, 15, and 30 L/h, respectively. Treatment performance in term of COD removal rates of ABR1, 2, and 3 were similar at hydraulic loads of 2.0 g COD/ L/d and below. At higher organic loads, ABR3 could achieve a COD remov al rate that was over two times higher than that of ABR1 and 2. ABR3 c ould be operated at a maximum organic load that was two times higher t han that of ABR1 and 2. ABR4 experienced a biofilm sloughing from the packing medium at the beginning of operation. Tracer studies showed th at recirculation rate of 1 L/h resulted in a plug-flow pattern in the packed bed of the reactor. On the other hand, recirculation rate of 15 L/h, which was equivalent to recirculating the reactor liquor five ti mes per hour, provided effective mixing in the packed bed. Superior pe rformance of ABR3 was attributed to the effective recirculation of rea ctor Liquor, which diluted and distributed the influent, particularly the oil and grease components.