Queensland has extensive shale oil reserves, which if developed would supply Australia petroleum requirements for the next century. The technology used to develop these resources is in the developmental stages and a trial is currently being conducted at the Stuart Shale reserve north of Gladstone to establish the projects viability. Environmental concerns are paramount to the success of the project, with emission control, both liquid and gas, requiring attention in the production phase. One of the major liquid emissions is sour water, which is a waste product produced in the retorting and refining stages. Sour water poses an environmental risk, through its unpleasant odour and complex mix of polar organic compounds and is produced in such large volumes that conventional waste treatment techniques are not appropriate.Various systems are being investigated involving the use of native microorganisms to biodegrade the sour water. One such system is an aerobic column trickling filter, in which the sour water is trickled through a bed of shale ash/overburden. Previous research has established that low volumes of sour water are effectively treated in a trickling filter, with significant reductions in influent concentration (typically 98%) being observed. These studies however have not conclusively shown that this reduction is a direct result of biodegradation, relying instead on anecdotal evidence to suggest that biodegradation is occurring. This study uses a dedicated gas analysis system to continuously monitor the CO2 and CH4 concentrations in the column headspace. If biodegration is occuring in the system then the CO2 concentration would be expected to rise. This would be seen as conclusive proof of biodegradation.The results of the study show reveal:· Conclusive proof biodegradation does occur within the column· An excessive amount of carbon is leaving the column when compared with the influent TOC values. This is possibly a result of the microbes utilising the carbon in the shale ash/overburden· The microbe growth is concentrated at the top of the column. After several months of operation this resulted in blockage.· A possible oxygen threshold concentration below which microbial growth is retarded.