Anaerobic and aerobic biodegradation of chlorophenols using UASB and ASG bioreactors

Chlorophenol degradation was studied by combined anaerobic-aerobic treatmen ts as a single or multi-substrate system. 2,4-Dichlorophenol (2,4-DCP) was degraded to the extent of 52 and 78% in up-flow anaerobic sludge blanket (U ASB) and aerobic suspended growth (ASG) reactors respectively, at organic l oading rates of 0.18 kg/m(3)/day and hydraulic retention time of 26.4 h in the presence of glucose. The UASB represents the dominating facultative ana erobic microbial population. When the effluent from the anaerobic reactor ( UASB) was subjected to aerobic treatment on the ASG reactor, 2,4-DCP and CO D removals of 86 and 95% respectively were achieved. Aerobic degradation of chlorophenol by acclimated mixed bacterial isolates was found to be sequen tial: 2-Chlorophenol (2-CP) and 4-CP were degraded first, followed by 2,4-D CP and 2,4,6-Trichlorophenol (2,4,6-TCP) while the contrary was obtained in anaerobic degradation. In anaerobic degradation by acclimated mixed bacter ial cells, 2,4-DCP and 2,4,6-TCP were degraded first followed by mono-chlor ophenols. The anaerobic/aerobic bioreactors were most efficient when operat ed in sequence (series) rather than in parallel.