Analysis of heavy metals inhibition on methanogenic activity inside an expanded granular sludge bed reactor

Proceedings su CD (senza ISBN) del Congresso “VI International Congress: Valorization and Recycling of Industrial Waste”, L’Aquila (I), 27-29 giugno 2007. - The scope of this project is the evaluation of specific toxicity of heavy metals inside an anaerobic digestion process, using a pilot-scale EGSB (Expanded Granular Sludge Bed) reactor on stationary state. Cu+2, Ni+2 and Cr+3 ions were separately considered and their effects on the anaerobic activity were analyzed by the measurement of methane production rate and the removal of COD (chemical oxygen demand). A concentration of 50 mg/l of heavy metals was used in all the experiments. Feed was constituted by a solution of sodium acetate and ethanol to obtain 3000 mg/l of COD. Experiments showed that biomass has a higher sensitivity for copper and much more slight for nickel and chromium respectively. Moreover, copper inhibition has been demonstrated to be less significant if a clean feed had been provided to the system before copper addiction.