Performance of an immobilized cell biofilter for ammonia removal from contaminated air stream

The performance of a lab scale biofilter packed with biomedia, encapsulated by sodium alginate and polyvinyl alcohol was used for treating ammonia (NH3) gas at different loading rates. The metabolic end products during NH3 oxidation were NH4+, NO3- and NO2-. It is noteworthy to mention that the immobilized cell biofilter required no separate acclimatization period and showed high removal efficiencies during the start of continuous experiments. The removal efficiency was nearly 100% when ammonia loading was 4.5 g m−3 h−1 and the maximum elimination capacity achieved in this study was 5.5 g NH3 m−3 h−1 at a loading rate of 7.5 g m−3 h−1. Shock loading studies were carried out to ascertain the response of the immobilized cells to fluctuations in inlet concentration and flow rate. The inlet loading rates were varied between 0.05 and 6 g NH3 m−3 h−1 during this phase of operation. The biofilter responded effectively to these shock loading conditions and recovered rapidly within 4–8 h. Pressure drop values were consistently less and insignificant. The results from this study indicated that this immobilized cell biofilter could be considered as a potential option to treat NH3 under steady and transient state operation.