Abstract

Laboratory scale bioreactors were used to investigate the treatment of arsenic species deliberately contaminated groundwater. A mixed culture of sulphate-reducing bacteria (SRB) with molasses as carbon source was immobilised on a polystyrene support matrix. The artificial groundwater contained either As(III) or As(V) at concentrations of 20, 10, 5, 1 or 0.1 mg/l as well as 0.1 mg/l of a mixture with As(III) accounting for a total of 20, 30, 40, 60 and 80%. More than 90 and 60% of the As(V) and As(III), respectively, were removed by the end of a 14-day experiment. Total arsenic had been reduced to below the WHO acceptable level of 10 µg/l when the proportion of As(III) was 20 and 30%, while at 40% As(III), this level was reached only after 21 days treatment. The efficiency of As(III) removal was increased by first oxidising it to As(V) using MnO₂.

Key words: Arsenite, arsenate, bioreactor, polystyrene, sulphate-reducing bacteria.

Abbreviation

SRB, Sulphate-reducing bacteria; CPD, critical point drying; Eh,redox potential; WHO, world health organization; ESEM, environmental scanning electron microscopy.