REMOVAL OF LEAD AND CHROMIUM FROM AQUEOUS SOLUTION BY BACILLUS CIRCULANS BIOFILM

The different methods are used for the removal of heavy metals as important contaminants in water andwastewater. biosorption is an alternative to traditional physicochemical in removing toxic metals fromwastewaters and groundwater resources. in this study biosorption of lead and chromium ions fromsolution was studied using bacillus circulans isolated from anzali wetland in batch and biofilter modesand optimum conditions were determined. the experimental results showed 900-950 mg/l and 1050-1100 mg/l, for minimum bactericidal concentration and minimum inhibitory concenteration for lead andchromium, respectively. results of metal concentration in solution containing 500 mg/l in batch cultureshowed a reduction about 65% and 48% in five and four days for lead and chromium, respectively. thehighest value of lead and chromium uptake in solution with 500 mg/l was 78% and 40% in biofiltermode, respectively. the biosorption of lead and chromium were increased up to ph=5.5, 6, 5.5 and 7,respectively. in the other hand, maximum sorption occurred at neutral ph. there was a significantdecreasing of biosorption levels by lowering ph fewer than 3. accumulation of lead and chromium wasdetermined by scanning electron microscopy analysis of the biofilm exposed to 500 mg/l metalconcentration. based on this analysis, the highest metal concentrations were observed in regions withincluding bacteria.