Evaluation of Cr(VI) Reduction Using Indigenous Bacterial Consortium Isolated from a Municipal Wastewater Sludge: Batch and Kinetic Studies

Abstract

Hexavalent Chromium (Cr(VI)) has long been known to be highly mobile and toxic when compared with the other stable oxidation state, Cr(III). Cr(VI)-soluble environmental pollutants have been detected in soils and water bodies receiving industrial and agricultural waste. The reduction of Cr(VI) by microbial organisms is considered to be an environmentally compatible, less expensive and sustainable remediation alternative when compared to conventional treatment methods, such as chemical neutralization and chemical precipitation of Cr. This study aims to isolate and identify the composition of the microbial consortium culture isolated from waste activated sludge and digested sludge from a local wastewater treatment plant receiving high loads of Cr(VI) from an abandoned chrome foundry in Brits (North Waste Province, South Africa). Furthermore, the Cr(VI) reduction capability and efficiency by the isolated bacteria were investigated under a range of operational conditions, i.e., pH, temperature and Cr(VI) loading. The culture showed great efficiency in reduction capability, with 100% removal in less than 4 h at a nominal loading concentration of 50 mg Cr(VI)/L. The culture showed resilience by achieving total removal at concentrations as high as 400 mg Cr(VI)/L. The consortia exhibited considerable Cr(VI) removal efficiency in the pH range from 2 to 11, with 100% removal being achieved at a pH value of 7 at a 37 ± 1 °C incubation temperature. The time course reduction data fitted well on both first and second-order exponential rate equation yielding first-order rate constants in the range 0.615 to 0.011 h−1 and second order rate constants 0.0532 to 5 × 10−5 L·mg−1·h−1 for Cr(VI) concentration of 50–400 mg/L. This study demonstrated the bacterial consortium from municipal wastewater sludge has a high tolerance and reduction ability over a wide range of experimental conditions. Thus, show promise that bacteria could be used for hexavalent chromium remediate in contaminated sites.

Screening and Evaluation of Chromium (VI) Tolerant Bacillus sp. from Industrial Areas of Ranipet, Tamil Nadu for Bioremediation of Chromium Contaminated Soil

“…Similar studies of Cr (VI) tolerance through reduction were observed at 3,700 mg/l at pH 7 as described by Princy et al (2020). Mixed culture could reduce Cr (VI) at concentration up to 400 mg/l as reported by Kholisa et al (2021).…”

In Situ Bioreduction of Hexavalent Chromium‐Contaminated Water Using a Microbial Culture Barrier

“…The sample was then centrifuged for 10 min at 6000 rpm (2820 g ), using a Minispin® Microcentrifuge (Eppendorf, Hamburg, Germany) to remove the suspended solids. The sample was then analyzed in a UV‐vis spectrophotometer (WPA, Light Wave II, and Labotech, South Africa) at the wavelength of 540 nm, using the diphenylcarbazide (DPC) method as described by Kholisa and Chirwa 8. The total chromium in each sample was measured using a Varian AA – 1275 Series flame atomic adsorption spectrophotometer (AAS) (Varian, Palo Alto, CA, USA) at a wavelength of 359.9 nm.…”

“…Bioremediation of Cr(VI)-contaminated environments using microorganisms appears to be a more economical and environment-friendly treatment method. The ability of bacteria to reduce Cr(VI) has been reported to depend on numerous envi-ronmental parameters that affect the transformation of Cr(VI), such as the pH and the temperature [6,7]. However, many of these studies were done in batch systems and would offer challenges on the large scale.…”

Multi-Walled Carbon Nanotubes Modified NiCo2S4 for the Efficient Photocatalytic Reduction of Hexavalent Chromium

“…In the past decades, water resource pollution has become more and more severe with industrialization development [1]. Heavy metal pollution due to the massive application of heavy metals in industry is gaining widespread attention [2,3]. Among them, hexavalent chromium (Cr(VI)) is often used as an essential raw material in electroplating, pigment processing, leather making, photographic, textile, and other applications.…”