Effects of Trivalent Chromic Ions with Different Concentrations on Settling Volume (SV) of Activated Sludge in the Settling Period of SBR Process

Abstract

Aiming at the toxicity effect of trivalent chromic ions on activated sludge in SBR process system, by determination of the settling volume SV, the effects of trivalent chromic ions on sludge settling volume SV in the settling period of SBR process was studied. The results show that trivalent chromic ions will make the sludge volume increase under low chromium load. Moreover, the sludge volume will increase with increasing chromium load, but the settling volume of the activated sludge at 30 min begins to increase in waves as chromium load continues to increase. When the chromium load increases to a certain level, the settling volume of the activated sludge at 30 min continues to decline in waves and is finally lower than the sludge settling volume of the contrast system at 30 min. The experiment suggests that trivalent chromic ions have toxicity and flocculation effects to the activated sludge, and the interaction of the two effects leads to the change of the activated sludge in waves as the chromium load increases.