Abstract:
The study focused on determining the microbial precipitation abilities of two bacterial strains, Paraclostridium bifermentans and Klebsiella pneumoniae isolated from an industrially obtained microbial consortium. Previous research has demonstrated the effectiveness of the consortium in the bioprecipitation of Pb(II). The bioremediation of Pb(II) provides an alternative and less costly method for lead removal from solution. A proof of concept was determined in a long duration study over 100 h wherein the bioprecipitation abilities of the strains were determined. It was concluded that approximately 84 % and 100 % of Pb(II) was removed from solution in experiments containing 80 mg/L initial Pb(II) concentration over 100 h, with P. bifermentans and K. pneumoniae respectively. The mechanisms of precipitation were further investigated with a short-term study, since it was observed that precipitation occurred in under 18 h in the long duration study. This shorter study was conducted over 30 h with nine sampling intervals and indicated removal percentages of approximately 86 % and 91 % for samples containing 80 mg/L initial Pb(II) concentration after 30 h for P. bifermentans and K. pneumoniae respectively. The precipitate identity was determined to be PbS and Pb(0) for samples containing P. bifermentans while samples containing K. pneumoniae contained precipitates of PbO and either PbCl or Pb3(PO4)2. An investigation into the extracellular and intracellular Pb(II) concentration led to the observation that a rapid detoxification mechanism such as biosorption is present in the microbes within the first 6 h of the experiment. These mentioned factors provide a greater understanding of the mechanisms utilised by the bacteria in the bioprecipitation and adsorption of Pb(II), and can be used as a step towards applying the process on an industrial scale.
