Evaluating the effects of pH and temperature on sulphate-reducing bacteria and modelling of their effects in stirred bioreactors

ABSTRACT

Sulphate (SO4) abundance in the earth’s crust contributes largely to industrial wastewater contamination lowering the pH, which exuberates the dissolution of metals forming acidic drainages. Biological sulphate reduction as a remediation process can be affected by factors such as pH, temperature and high sulphide concentrations. In this study, sulphate-reducing bacterial community enriched from mine wastewaters was applied in semi-automated bioreactors to assess the effects of these factors on microbial sulphate reduction capacities. Low pH (3.5) and temperature (10°C) were observed to promote the toxicity of sulphur-reduced species on the consortium while mesophilic temperature (25°C) and near neutral pH (6.2) were observed to induce optimum SO4 reduction attaining a maximum of 95% SO4 reduction. Obtained SO4 reduction dynamics data was then applied in formulating a unique non-competitive inhibition equation that models biogeochemical events during SO4 reduction under varied pH and temperature conditions and predicts the efficacy of a bioremediation system.

KEYWORDS:

• Bacterial consortium
• biogeochemical modelling
• Bio-precipitation
• bioreactors
• bioremediation
• sulphate reduction
• water contamination

Acknowledgments

The authors would like to acknowledge TIA for financial support and the involved departments at the University of the Free State (UFS), Central University of Technology, Free State (CUT), University of Kwa-Zulu Natal (UKZN), University of Pretoria (UP) where resources, infrastructure and equipment were used in conducting the experiments and preparing the manuscript. Authors finally acknowledge the three mining companies in South Africa for granting access to collect samples and the Institute of Groundwater Studies (IGS) at the UFS for assistance with chemical analysis of water samples.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Conceptualization: E.v.H., J.C. and K.M.; Experimental work: K.M.; Data interpretation and analysis: K.M., E. vH., J.C., E.C.; Model formulation: A.A., J.C. and K.M.; Writing of the manuscript: K.M., J.C., E. vH., E.C., Z.K., M.M., J.U.; Project Administration: E.vH. Funding Acquisition: E.vH., and J.C. All authors have read and agreed to the published version of the manuscript.

Data availability statement

Data used and presented in this study can be made available upon requests to the corresponding authors.

Additional information

Funding

The study was supported by the South African BioDesign Initiative (SABDI) Under: SABD 16/1070.