Characterisation and performance of coconut fibre as packing material in the removal of ammonia in gas-phase biofilters

Data from the regular monitoring of a full-scale biofilter, filled with coconut fibre as packing material at a municipal solid waste treatment facility, were analysed to assess potential operational problems and to evaluate reactor performance in terms of ammonia removal, the target compound at the facility. Performance from year-round data was assessed based on ammonia removal efficiency (RE) and elimination capacity (EC). Reduced efficiencies were related to a low water content in the packed bed of the biofilter. Thus, a pilot-scale biofilter filled with coconut fibre as packing material was investigated for the treatment of ammonia. Biological activity of coconut fibre and biofilter performance were assessed during the operation of the pilot-scale biofilter under steady-state and transient conditions at inlet ammonia concentrations in the range of 45–300 ppmv and gas contact times of 36–19 s. A maximum EC of 12 g [NH3] m–3 h–1 at an 80% RE was found for a non-acclimated biofilter under transient conditions. A higher watering of the coconut fibre, as well as an acclimated biomass, allowed an EC of 33.3 g [NH3] m–3 h–1 at a 100% RE. Under transient and steady-state conditions nitrification inhibition was encountered, mostly affecting the conversion of nitrite to nitrate.