Application of a compact trickle-bed bioreactor to the biodegradation of pollutants from the ventillation air in a copper-ore mine

Selected results are presented of an on-going project conducted by Ekoinwentyka Ltd. with the aim to design, test and apply a compact trickle-bed bioreactor – operated in a biofiltration system with circulating salt solution – to the biodegradation of VOCs, mercaptans and H2S contained in the ventillation air in a copper-ore mine at a depth of 1000 m underground. The experiments were performed using a 48 dm3 semi-industrial scale bioreactor in which gas and liquid phases flowed co-currently in downward direction through a bed made of polyethylene rings. The bioreactor was inoculated with a co-culture of microorganisms including bacterial strains found in the cooper-ore mine and adopted to chosen pollutants. laboratory tests, biodegradation of 4-components VOC mixture (acetone, styrene, benzene, vinyl acetate) and 8-component pollutant mixture (VOCs + xylene, H2S, dimethyl sulfide, dimethyl disulfide) was studied. In the gas-flowrate range 2.0–15.0 m3/h and at a specific pollutant load up to 40 g/(m3h), values of the efficiency of pollutant removal above 80% were measured for all mixture components except benzene which caused bioreactor poisoning at a specific load above 5 g/(m3h). Possible consequences of a fatal pollutant overload and the time required for regenerating the microorganisms and returning to stable process conditions were also investigated. copper-ore mine, it was found that pollutant concentration in the ventillation air was normally low not exceeding values attained during laboratory tests but temporary bursts of very high H2S concentration were also detected. An increase in H2S concentration to 1000 ppmv lasting for 1 h caused bioreactor poisoning but after H2S concentration returned to normal, stable process conditions were restored within 45 min. basis of experiments carried out both in the laboratory and copper-ore mine, acceptable values of parameters of the biodegradation process were determined. Despite harsh working conditions that are characteristic of the copper-ore mine 1000 m deep, the experimental set-up has been working reliably for several months and a high efficiency of pollutant removal has been achieved.