Removal of pollutants from the air in a copper-ore mine using a compact trickle-bed bioreactor

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 to the biodegradation of H2S and VOC mixture present in the air in a copper-ore mine at a depth of 1,000 m underground. The experiments were performed using a 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 developed by Ekoinwentyka Ltd. especially for the chosen pollutants and bacterial strains found in the cooper-ore mine. During the period of test operation of the bioreactor in a mine corridor, it was found that pollutant concentration in the air was normally moderate but temporary bursts of very high H₂S concentration were also observed. An increase in H2S concentration to 40 - 60 ppm usually caused a drop in biodegradation efficiency but once the concentration returned to its normal range below 38 ppm, stable process conditions were restored quickly. Despite harsh working conditions that are characteristic of the copper-ore mine 1000 m deep, the experimental set-up has been operated reliably for several weeks and a satisfactory level of the efficiency of pollutant removal (the factor of H₂S conversion typically in the range 80 - 100 % and that of VOC conversion 90 - 100 %) has been achieved.