Abstract Description

Industrial wastewater pollution is a global concern due to industrialization and urbanization in developing countries like South Africa. Heavy metals discharged from industrial processes contaminates water rendering it toxic when metals are dissolved at high concentrations and thus posing serious threats to environmental health affecting soil, air and water. Limited research has been conducted on the use of indigenous bacteria that thrive in extreme industrial wastewater conditions for their applications in the removal of heavy metal for their recovery and valorization. The current study examines the use of indigenous bacteria for bioremediation of industrial wastewaters with interest in recovering valuable heavy metal for their valorization. Microcosm studies were conducted to uncover the bioremediation potential of indigenous bacteria. Wastewater samples were collected from three industrial sites where heavy metals were reported in high concentrations. Water chemistry was determined by analyzing water samples using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Bacterial diversities in the three sites were compared using metagenomic approach combining both molecular biology and bioinformatics techniques. Bacterial consortia from the water samples were enriched in nutrient and Postgate medium B for minimum inhibitory concentrations (MIC) and maximum tolerance concentrations (MTC) test with three metals of interest: Zinc (Zn2+), Lead (Pb2+) and Copper (Cu2+) supplemented in the media in increasing concentrations. Bacterial growth and metal precipitation dynamics were monitored at different maximum metal concentrations: 2500 mg/L for Zinc (Zn2+), 500 mg/L for Lead (Pb2+), and 200 mg/L for Copper (Cu2+) which proved high tolerance by the enriched bacteria as compared to previously reported studies in literature. Effects of pH on metal precipitation were also evaluated by subjecting the consortia to three pH conditions: 3, 7, and 9. The chemical analysis from Inductively Coupled Plasma Mass Spectrometry (ICP-MS) indicated different metals (Zinc (Zn2+), Strontium (Sr2+), Aluminum (Al3+), Iron (Fe3+), Vanadium (Vn5+)) and sulphate (SO42-) ranging from (1 061 mg/L to 6 115 mg/L). The results from Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) demonstrated that indigenous bacterial consortia use different mechanisms, primarily biosorption for Lead (Pb2+), bioaccumulation, biotransformation and biosorption for Zinc (Zn2+), and biosorption for Copper (Cu2+) removal from their dissolved state. These findings further prove the potential and effectiveness of using indigenous bacteria for the removal of toxic heavy metals from water contaminated by industrial waste.