Modeling of electrochemically-activated denitrifying biofilms

The ability of an electrode-biofilm system to reduce nitrate has been experimentally demonstrated. In this system, a denitrifying biofilm is attached to an electrode and the H₂ produced by the electrolysis of water is used for the reduction of NO₃^- to N₂ gas. Complete denitrification was achieved in the presence of an electric current. A steady-state biofilm model describing the system is presented. The model takes into account the mass transfer rates, biological reaction rates and electrochemical reaction rates of H⁺, OH^-, H₂, NO₃^- and supporting electrolytes. The denitrification rates calculated using the model are in fairly good agreement with experimental results. The net denitrification rate is affected significantly by the electric current and its response can be divided into three regions, namely, the "linear", "plateau" and "decline" regions. The overall feasibility of the electrode-biofilm system is theoretically demonstrated.