A dynamic model for ammonia abatement by gas-phase biofiltration including pH and leachate modelling

A dynamic model of ammonia removal by gas-phase biofiltration is presented. Complex biodegradation kinetics including inhibitions and oxygen limitation were used. Since pH has a strong influence on kinetic parameters and governs the process of ammonia absorption into the biofilm, proton concentration (H+) was included as a state variable in the model. Different approaches to model pH variations in biological systems can be found in literature. Amongst the different approaches tested for modelling pH variations during ammonia biofiltration, an ion balance method based on the electroneutrality condition in the biofilm was chosen in this work. This approach was demonstrated to be reliable and efficient to describe pH profiles in gas-phase ammonia biofiltration. The biofilter model was implemented in a home-made simulation environment developed in MATLAB. Model evaluation was performed by comparison of model predictions with experimental data obtained in a pilot-scale biofilter. The model was able to predict qualitatively and quantitatively the behaviour of the system under dynamic conditions, particularly for pH, nitrite, nitrate and ammonium measured in the leachate of the pilot-scale biofilter.