| The presence of heavy metals in both domestic and industrial wastewaters is of increasing concern to researchers because of their known toxicity to plant and animal life and their ability to bioaccumulate up the food chain.; Batch experiments were conducted in a bench scale rotating biological contactor in order to determine the primary removal mechanism(s) of chromate and copper from the bulk liquid. In addition, the effects, if any, of pH, initial substrate concentration, initial metal concentration and the quantity of biomass present on heavy metal removal were investigated. Results of these experiments indicate that pH, initial substrate concentration, initial metal concentration and the quantity of biomass present all affect, either directly or indirectly, the extent of chromate and copper removal from the bulk liquid in a bench scale RBC system. Percent removals of copper were generally higher for copper than for chromate. Whereas copper will readily form surface complexes with organic matter, a two step removal process was proposed for chromate. First, diffusion into an inner anaerobic layer of biomass. Secondly, reduction of the soluble chromate into the highly insoluble trivalent chromium within the anaerobic layer.; Biofilm thickness and the extent of oxygen penetration into the biofilm were found to be important in the extent of chromate removal from the bulk liquid. Using a simple model, the aerobic layer of biofilm on the experimental RBC unit was calculated to vary between 2.0 {dollar}times{dollar} 10{dollar}sp{lcub}-2{rcub}{dollar} mm to 3.0 {dollar}times{dollar} 10{dollar}sp{lcub}-2{rcub}{dollar} mm.; In addition, diffusional limitations of chromate and copper ions into the biofilm appear to occur. |
