Toxicity of electroplating metals on benzoate-degrading granules

Abstract

Toxicity of five electroplating metals on the activity of biogranules, which were obtained from an upflow anaerobic sludge blanket (UASB) reactor treating benzoate-rich wastewater, was investigated in this study. The methanogenic activities of the biogranules were measured in serum vials using wastewaters containing not only benzoate as substrate, but also individual heavy metals over a wide range of concentration. At 37°C, the toxicity, which increased with metal concentration, was in the following descending order: nickel > zinc > cadmium > copper > chromium. The biogranules exhibited higher resistance to metal toxicity than the flocculent anaerobic sludge. This is probably due to the densely packed nature of the biogranules, reducing the overall exposure of bacteria to the toxic metals in the bulk solution. This implies that granulation of biomass increases their resistance towards toxicants in the wastewater.