Hexavalent Chromium Removal Efficiency of Chromium Resistant Bacteria in Tannery Industrial Wastewater

Abstract

Hexavalent chromium (Cr (VI)) contamination in the environment has become a serious
problem worldwide. The study was conducted by considering pollution of wastewater in
tannery industrial area by Cr (VI). Innovative bioremediation based on the biological method
is one of technology for the removal of toxic metals from the environment. Hence, this study
has investigated to remove the hexavalent chromium in tannery industry wastewater using
chromium resistant bacteria isolated from the tannery wastewater. Chromium resistant
bacteria were isolated, screened and characterized. About twenty-five bacterial isolates were
obtained from Cr (VI) LB agar culture medium supplemented with different concentrations of
(50-500 mg/L). Among the twenty-five bacterial isolates two strains (C5 and C6) were
selected based on the level of Cr (VI) tolerance and designated as C5 and C6.
Sequencing of 16S rRNA identified as Bacillus cereus and Bacillus amyloliquefaciens
respectively. Chromium reduction assays of the isolates were performed using 1, 5 diphenycarbazide (DPC) at various temperatures (25˚C, 30˚C, 35˚C and 40 ˚C) and pH (4, 6
and 9). Results shown that both isolates (C5 and C6) have better removal efficiency chromium
concentration up to 300 mg/L from the effluent. The FTIR analysis of the bacterial biomass of
C5 and C6 grown in LB broth with and without Cr (VI) (100 mg/L) has shown several
absorption peaks indicating the presence of different functional groups including hydroxyl,
amines (-NH2) alkene (C=C), alkyene and sulfamide bond (S=O) at different wavelengths. In
this study, it is reported that the bacterial isolates from tannery wastewater are, therefore,
useful as a bioremediation agent.