Sequential anaerobic-aerobic treatment of sulphur rich phenolic leachates

Sequential biological anaerobic-aerobic treatment of oil shale ash dump leachate was studied using laboratory-scale reactors and bioassays. The COD of the leachate wad 2.0-3.0 g dm -3 . The leachate was known to contain several phenolic compounds and to have a high sulphur concentration. The proportion of the leachate in the feed of the biological process was gradually increased during a 309 day test period. With 100% leachate in the feed, COD removal was 35% in the anaerobic stage while in the combined process the COD and BOD 7 removals were up to 75% and 99%, respectively. The removal of total phenols was insignificant in the anaerobic stage, while up to 85% removal was obtained by the combined anaerobic-aerobic process. In the anaerobic stage, degradation of organic compounds was mainly a result of sulphide production. The results demonstrated that the leachates were amenable to biological treatment