Bioremediation of hexavalent chromium from wastewater using bacteria-a green technology.

Abstract

Hexavalent chromium has high toxic effect on the ecological system. The aim of the present study is to isolate and characterize the bacteria that can reduce the toxicity of hexavalent chromium from liquid effluent. The bacterial isolate was identified as Bacillus sp. ltds1 after 16S rRNA gene sequencing, and annotation has been submitted in National Center for Biotechnology Information (NCBI) GenBank. The bacterial strain was found able to grow in Luria Broth medium at 100mg/L Cr6+ concentration. A maximum Cr6+ bioremediation (95.24 ± 2.08 %) could be achieved using the said isolate at 40mg/L, pH 7, and inoculum concentration 4 % at 24h. The residual chromium was found in the form of less toxic trivalent chromium (Cr3+), which confirms that the bacterial isolate can transform toxic Cr6+ to non-toxic Cr3+. Fourier Transform Infra-Red (FTIR) study was performed to analyze the functional groups and overall nature of chemical bonds involved in the remediation process, whereas, Energy-Dispersive Spectroscopy (EDS) studies of native and treated cells showed the changes in elemental composition in response to metal stress. Artificial Neural Network (ANN) based prediction model is developed based on experimental points. The developed model was found to predict the bioremediation of Cr6+ at various operating conditions. Particle Swarm Optimization (PSO) is used to optimize the variables like the initial concentration of metal, pH, temperature, and inoculum concentration for the said bacterial strain. The results showed that the isolate could be applied as a potential bioremediation agent for Cr6+ removal.