AEROBIC BIODEGRADATION OF AZO DYES IN BIOFILMS

Factors affecting biofilm removal of azo dyes from a synthetic, municipal-type wastewater were investigated using lab-scale, rotating drum biofilm reactors. Among the three azo dyes studied - Acid Orange 8, Acid Orange 10, and Acid Red 14 - only AO-8 degraded aerobically. The azo bond cleavage occurred very easily for all three dyes under anaerobic conditions. AO-8 removals ranged from 20% to 90%. Statistically designed experiments were used to characterize the response of pseudo-steady state biofilms. Two AO-8 removal rate maxima were identified - one at high bulk-phase dissolved oxygen and low COD removal flux, and the other at low dissolved oxygen and high COD flux.