Activated Sludge Process Response to Variable Inputs of Volatile Organic Contaminants

Laboratory-scale activated sludge treatment systems were operated under dynamic loading conditions to investigate the non-steady state behaviour of volatile organic contaminants (VOCs) under controlled conditions. Four step tests were conducted in which an incremental increase in the concentrations of selected contaminants was applied to the reactor feed from background levels of about 15 µg/L to levels of about 100 µg/L for a duration of approximately three hydraulic retention times. Although it was not possible to define the relative contributions of stripping and biodegradation to the removal of the test VOCs, different mechanisms are responsible for the removal of short-term, non-steady state inputs of chlorinated and non-chlorinated VOCs. No apparent effect of SRT or HRT on VOC removal was observed at the conditions tested.