Bioremoval of arsenic species from contaminated waters by sulphate-reducing bacteria.

A mixed culture of sulphate-reducing bacteria was used to study the bioremoval of arsenic species (As(III) or As(V)) from groundwater. During growth of a mixed SRB culture adapted to 0.1mg/L arsenic species through repeated sub-culturing, 1mg/L of either As(III) or As(V) was reduced to 0.3 and 0.13mg/L respectively. Sorption experiments on the precipitate produced by batch cultured sulphate-reducing bacteria (SRB-PP) indicated a removal of about 77 and 55% of As(V) and As(III) respectively under the following conditions: pH 6.9; biomass (2g/L); 24h contact time; initial arsenic concentration, 1mg/L of either species. These results were compared with synthetic iron sulphide as adsorbent. The adsorption data were fitted to Langmuir and Freundlich isotherms. Energy dispersive X-ray analysis showed the SRB-PP contained elements such as sulphur, iron, calcium and phosphorus. Biosorption studies indicated that SRB cell pellets removed about 6.6% of the As(III) and 10.5% of the As(V) from water containing an initial concentration of 1mg/L of either arsenic species after 24h contact.