A coal slag-packed biotrickling filter inoculated with autotrophic sulphide oxidizing and ammonia oxidizing bacteria was successfully operated for co-treating hydrogen sulphide (H2S) and ammonia (NH3). Excellent removal efficiencies of H2S (98.5%) and NH3 (99.9%) were obtained at loadings of up to 120 g H2S m(-3) h(-1) and 80 g NH3 m(-3) h(-1), respectively. The inhibitory effects of selected pollutants and metabolic products on the treatment performance were evaluated through mass balance and bacterial community analyses. The presence of NH3 significantly affected the composition of metabolic products of sulphide oxidation. Elemental sulphur was the dominant metabolite that ranged from 35% to 65%, whereas the amount of sulphite and thiosulphate generally increased up to 20%. However, a similar trend in the distribution of by-products to the results of nitrogen mass balance from sole NH3 removal was observed. The predominant bacteria were also changed with different loading ratios (H2S:NH3). (C) 2015 Elsevier B.V. All rights reserved.