Methanogenesis inhibition by phosphorus in anaerobic liquid waste treatment

Abstract The effect of a sudden influent phosphorus concentration increase on a completely mixed reactor of an anaerobic liquid waste treatment process was evaluated. Chemical oxygen demand (COD), volatile fatty acids (VFA), suspended solids, pH and gas production were measured for process monitoring. Optical and scanning electron microscopic observations were also performed. Kinetic parameters were estimated from substrate and microorganisms concentrations, mass balances and experimental data. After phosphorus concentration increase, VFA concentration enhanced by 500% approximately and COD removal, gas production, bacterial growth coefficient (Y) and maximum bacterial growth rate (μmax) decreased 20%, 18%, 54% and 35% respectively. An excessive growth of filamentous microorganisms was also observed. The equilibrium established between acidogenic and methanogenic microorganisms was visibly affected causing a decrease of methanogenic activity. The experimental results showed that phosphorous arises as a methanogenesis inhibitor and a growth factor for filamentous microorganism under anaerobic conditions.