Application of Fruit Wastes as Cost-Effective Carbon Sources for Biological Sulphate Reduction

We conducted a study dealing with the economical application of sulphate-reducing bacteria (SRB) for the treatment of sulphate-rich wastewater. In this study, four types of frequently available fruit wastes were employed as carbon sources for economical cultivation of the SRB and consequent reduction of sulphate from artificially prepared sulphate-rich wastewater. The bacterial species employed in this study were isolated from a leading wastewater channel in Pakistan and characterized phenotypically as well as genotypically. The bacterial identities were proved after BLAST analysis and construction of phylogenetic tree. Among all of the SRB species employed for sulphate reduction, Desulfovibrio fructosovorans-HAQ2 was found as the leading sulphate reducer and reduced sulphate maximally to 29% (0.51 ± 0.02 g L−1), 76% (1.51 ± 0.07 g L−1), 41% (0.83 ± 0.02 g L−1), and 63% (1.25 ± 0.02 g L−1) using apple peelings, apple pomace, mango peelings, and watermelon rind, respectively, in a 60-day trial of anaerobic incubation. In the present study, apple pomace appeared as the most suitable carbon source only for Desulfovibrio fructosovorans-HAQ2, while any of the other three bacterial species could not reduce sulphate more than 34% using this substrate. However, on average, watermelon rind was found as the most appropriate carbon source for the cultivation of SRB and all the SRB species reduced sulphate efficiently in the range of 40–63% using this carbon source. Our findings of the present study prove the productive utility of fruit wastes for developing cost-effective and environmental-friendly remedial strategies.