9 An Insight into Microbial Remediation of Hexavalent Chromium …
219
9.6 Case Studies
The utility of microbial species isolated from chrome liquor, tannery waste, effluent
treatment plant, and serpentine soil is studied by many researchers for the removal
of Cr
6+ (Table 9.1). These species found suitable not only to remove toxic chromium
from water but also to reduce chemical and biological oxygen demands.
• Verma et al. (2009) isolated different species of Bacillus like B. brevis, and B
subtilis to ascertain their comparative effectiveness to reduce Cr
6+ in the concentration range of 160–180 mgL
−1 . And, B. coagulans was not found effective to
reduce Cr
6+ in that range in comparoson with the other two strains.
• Ahmad et al. (2010) constructed a pilot-scale bioreactor (Chrom-BacTM) inoculated with Acinetobacter haemolyticus microbial strain and found a complete
reduction of 17–81 mgL
−1 of Cr
6+ from electroplating water. They stated that, the
performance of Chrom-BacTM was not affected by different factors like in the
fluctuation of pH (6.2–8.4) and nutrient temperature (30–38 °C). The technical
feasibility of a Chrom-BacTM system was demonstrated at 200 L pilot scale.
• According to Wani et al. (2019), Pseudomonas entomophila MAI4 bacterial strain
was isolated from industrial effluent, showed significant removal of Cr
6+ at the
controlled laboratory environmental condition and concentration dose of 100 ppm,
and showed 80% Cr
6+ reduction efficiency in the original industrial wastewater.
9.7 Conclusion
The chapter sheds light on the applicability of microbes toward reducing Cr
6+
from water in both aerobic and anaerobic conditions. The reduction of Cr
6+ can be
achieved effectively by microbial systems for the water containing Cr
6+ in appropriate amounts. As described in the chapter, the metal tolerance and resistant potential
in microbes not only depend on that particular microbial species, but also on the
environmental conditions and provided nutrient medium.
There are numbers of aerobic and facultative microbes that found suitable for
Cr
6+ reduction; but in the economical point of view, aeration at field level is not costeffective. Microbial reduction of Cr
6+ can be improved by prior acclimitization of
aerobic and anaerobic Cr
6+ tolerating microbes before their application in batch
or continuous or hybrid bioreactor system. As only few works have done on the
anaerobic microbial remediation of Cr
6+ , there exist a research gap that need to be
addressed. Further, studies should be done on recovering Cr from Cr
6+ reducing
sludge/microbial biomass in a economic, feasible process with least environmental
footprint.
219
9.6 Case Studies
The utility of microbial species isolated from chrome liquor, tannery waste, effluent
treatment plant, and serpentine soil is studied by many researchers for the removal
of Cr
6+ (Table 9.1). These species found suitable not only to remove toxic chromium
from water but also to reduce chemical and biological oxygen demands.
• Verma et al. (2009) isolated different species of Bacillus like B. brevis, and B
subtilis to ascertain their comparative effectiveness to reduce Cr
6+ in the concentration range of 160–180 mgL
−1 . And, B. coagulans was not found effective to
reduce Cr
6+ in that range in comparoson with the other two strains.
• Ahmad et al. (2010) constructed a pilot-scale bioreactor (Chrom-BacTM) inoculated with Acinetobacter haemolyticus microbial strain and found a complete
reduction of 17–81 mgL
−1 of Cr
6+ from electroplating water. They stated that, the
performance of Chrom-BacTM was not affected by different factors like in the
fluctuation of pH (6.2–8.4) and nutrient temperature (30–38 °C). The technical
feasibility of a Chrom-BacTM system was demonstrated at 200 L pilot scale.
• According to Wani et al. (2019), Pseudomonas entomophila MAI4 bacterial strain
was isolated from industrial effluent, showed significant removal of Cr
6+ at the
controlled laboratory environmental condition and concentration dose of 100 ppm,
and showed 80% Cr
6+ reduction efficiency in the original industrial wastewater.
9.7 Conclusion
The chapter sheds light on the applicability of microbes toward reducing Cr
6+
from water in both aerobic and anaerobic conditions. The reduction of Cr
6+ can be
achieved effectively by microbial systems for the water containing Cr
6+ in appropriate amounts. As described in the chapter, the metal tolerance and resistant potential
in microbes not only depend on that particular microbial species, but also on the
environmental conditions and provided nutrient medium.
There are numbers of aerobic and facultative microbes that found suitable for
Cr
6+ reduction; but in the economical point of view, aeration at field level is not costeffective. Microbial reduction of Cr
6+ can be improved by prior acclimitization of
aerobic and anaerobic Cr
6+ tolerating microbes before their application in batch
or continuous or hybrid bioreactor system. As only few works have done on the
anaerobic microbial remediation of Cr
6+ , there exist a research gap that need to be
addressed. Further, studies should be done on recovering Cr from Cr
6+ reducing
sludge/microbial biomass in a economic, feasible process with least environmental
footprint.