Abstract:
The study focused on determining the microbial precipitation abilities of bacterial strains
that were isolated from an industrially obtained Pb(II)-resistant microbial consortium. Previous
research has demonstrated the effectiveness of the consortium on the bioprecipitation and adsorption
of Pb(II) from solution. The bioremediation of Pb(II) using microbial precipitation provides an alternative option for Pb(II) removal from wastewater. Both strains, Klebsiella pneumoniae and Paraclostridium
bifermentans, were successfully isolated from the consortium obtained from a battery recycling plant
in South Africa. The experiments were conducted over both 30 h and 5 d, providing insight into the
short- and long-term precipitation abilities of the bacteria. Various initial concentrations of Pb(II)
were investigated, and it was found that P. bifermentans was able to remove 83.8% of Pb(II) from
solution with an initial Pb(II) concentration of 80 mg L−1
, while K. pneumoniae was able to remove
100% of Pb(II) with the same initial Pb(II) concentration after approximately 5 d. With the same
initial Pb(II) concentration, P. bifermentans was able to remove 86.1% of Pb(II) from solution, and
K. pneumoniae was able to remove 91.1% of Pb(II) from solution after 30 h. The identities of the
precipitates obtained for each strain vary, with PbS and Pb0 being the main species precipitated by
P. bifermentans and PbO with either PbCl or Pb3(PO4
)2 precipitated by K. pneumoniae. Various factors
were investigated in each experiment, such as metabolic activity, nitrate concentration, residual
Pb(II) concentration, extracellular and intracellular Pb(II) concentration and the precipitate identity.
These factors provide a greater understanding of the mechanisms utilised by the bacteria in the
bioprecipitation and adsorption of Pb(II). These results can be used as a step towards applying the
process on an industrial scale.
