Chromium (VI) removal using powdered activated carbon in activated sludge reactors

ANA MICAELA FERRO OROZCO; EDGARDO MARTIN CONTRERAS; NORA BERTOLA; NOEMI ELIZABET ZARITZKY

Campeche

Simposio; Fifth Latin American Biodegradation and Biodeterioration Symposium; 2004

Chromium is usually released by effluent discharge from steelworks, chromium electroplating, leather tanning and chemical manufacturing. The objective of this study was to evaluate the effect of powdered activated carbon (PAC) addition on the removal of hexavalent chromium by activated sludge microorganisms in batch reactors. Cr(VI) (as K2Cr2O7) concentrations of 5, 10, 25, 50, 75 y 100 mgCr/L and 4000 mg/L PAC were tested. The activated sludge used in this study was obtained from a laboratory scale completely mixed, continuous-flow activated sludge reactor. The following experiments were carried out: 1) Cr(VI) removal using activated sludge with and without carbonaceous substrate (lactose), 2) Cr(III) and Cr(VI) removal using PAC and, 3) Cr(VI) removal using activated sludge containing lactose and PAC. The presence of a carbon source was necessary to remove Cr(VI) by the microorganisms. Cr(VI) removal using activated sludge containing lactose and PAC was faster than that of Cr(VI) with PAC alone; Cr(III) removal in these systems was faster than Cr(VI). In the present work it was demonstrated that i) the biomass in activated sludges can be used as a detoxificant agent for wastewaters containing Cr(VI) concentrations lower than 25 mg/L, ii) the addition of PAC to activated sludges improved the removal of high chromium concentrations.