Immobilisation of Arsenic in Anaerobic Environment

Abstract

Nowadays, the main method applied to remediate As contaminated soil is excavation and landfilling. Soil treatments normally are implemented under aerobic conditions. This study was conducted to investigate the possibility of stabilizing As in reducing conditions by adsorption to and co-precipitation with Fe-sulphides or formation of amorphous As-S phases. The sulphide formation is considered to result from the activity of sulphate reducing bacteria (SRB) present in sludge as a part of their metabolism. The bacteria produce sulphide by reducing sulphate and oxidizing organic compounds. A total of 36 bottles were prepared, 18 of them are considered as sample bottles and did not contain sludge or Na-lactate (organic source) together with soil. The bottles amended with sludge contained 4.5 g/l of sulphate and 3.5 g/l of Na-lactate. The results showed that the concentration of dissolved As was dramatically higher in the bottles amended with sludge, probably due to insufficient SRB activity or the necessity of having a longer-term experiment.