Sequential anaerobic–aerobic treatment of sulphur rich phenolic leachates

Abstract

Abstract Sequential biological anaerobic–aerobic treatment of oil shale ash dump leachate was studied using laboratory‐scale reactors and bioassays. The COD of the leachate was 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.