Effect of heavy metals on the upflow anaerobic sludge blanket process

This study examined the effects of ionic chromium, cadmium, lead, copper, zinc, and nickel on methane production and volatile fatty acid (VFA) production in an upflow anaerobic sludge blanket (UASB) reactor using serum bottle assays. The granular seed sludges were acclimated with glucose by continuous feeding. According to experimental results, effects of the metals relied on the sludge zones, VFA types and metal types. The metal concentrations that caused 50% inhibition of methane production and total VFA production ranged from 210 similar to 2640 mg/L and 350-->>5000 mg/L, respectively. The metals' relative toxicity to total VFA degradation was in the order of Cu>>Cr>Cd>>Zn>Ni>Pb and Cu>>Cdis-approximately-equal-toCr>>Ni>Zn>Pb for bed and blanket sludges, respectively. Our results also confirmed copper and lead to be the most toxic and least toxic metals tested, respectively. In UASB biogranules, the organisms responsible for methane production were less resistant to metal toxicity than those responsible for VFA production.