Effect of 1-25 mg/l of influent Cr(VI) concentrations on true biomass yield (Y(t)) and decay coefficient (k(d)) of activated sludge units was investigated in this study. To this purpose, completely mixed, once-through laboratory scale activated sludge units with acclimated cultures were operated. After obtaining dilute-out curves for each Cr(VI) concentration, the values of Y(t) and k(d) were determined. The results revealed that presence of Cr(VI) caused stimulatory effects on biomass yield and maintenance up to the Cr(VI) concentration of 25 mg/l. Lower Cr(VI) concentrations exerted higher stimulation of the system. Extended oxidation due to the presence of Cr(VI) and/or increased synthesis of cellular material due to the stimulatory effects of Cr(VI) were thought to be the mechanisms of the observed stimulation. Copyright (C) 1999 Elsevier Science Inc.
- Activated sludge
- Biomass yield