Inhibition of the acetoclastic methanogenic activity by disinfectants used in the washing of pharmaceutical industry equipment

The pharmaceutical industry uses different types of disinfectants in the washing processes of different equipment, which become part of the wastewaters generated in the production processes. The nature of these compounds can diminish the biodegradability of the effluents; hence, this is an important issue to consider during the design and operation of treatment processes. This study establishes the kinetic parameters for three commercial disinfectants, using anaerobic sludges as inoculum. The doses for the active principle (quaternary salt) that yield a 50% reduction of the specific methanogenic activity of the inoculum were 1.6 x 10^-3 kg · m^-3 for benzalkonium, 8.4 x 10^-3 kg · m^-3 for bactium, and 154 x 10^-3 kg · m^-3 for anibac. The three disinfectants induced a mixed-type inhibition on the anaerobic biodegradability of sodium acetate, the main precursor of methanogenesis during anaerobic digestion.

Keywords: anaerobic digestion, disinfectants, acetoclastic methanogenic, inhibition constants.