Continuous removal of sulfate and metals from acidic mining-impacted waters at low temperature using a sulfate-reducing bacterial consortium

Hanna Virpiranta,Ville-Hermanni Sotaniemi,Tiina Leiviskä,Sanna Taskila,Jaakko Rämö,D Barrie Johnson,Juha Tanskanen

doi:10.1016/j.cej.2021.132050

Abstract

The aim of this study was to develop a biological method for the simultaneous removal of sulfate and metals from acidic low-temperature mining effluents. A mixed consortium of cold-tolerant sulfate-reducing bacteria (SRB) and other microorganisms was immobilized on glass beads and exploited in an up-flow biofilm reactor for the continuous treatment of actual and synthetic mining-impacted waters (MIWs) with initial sulfate concentrations between 1580 and 5350 mg L-1. The proton acidity of the mine waters was neutralized by microbial sulfidogenesis. Metals present in the MIWs were precipitated either off-line or in-line, inside the reactor vessel. High sulfate reduction rates (SRRs), from 1000 to 4500 mg L-1 d-1 at a temperature of 11.7 ± 0.2 °C, were achieved (sulfate removal 43–87%). The bacterial consortium was found to be robust and resistant to changes in growth conditions during the bioreactor experiment. The relative abundance of SRB and the SRR increased at higher sulfate concentrations. Sulfidogenic bioreactors have the potential for treatment of acid mine drainage even at low temperature. It was demonstrated that neutral reactor conditions and high SRRs were maintained when acidic influent was fed into the reactor.

Highlights

Effluents from the mining industry are commonly characterized by having relatively elevated concentrations of soluble sulfate and transi tion metals, and are often moderately to extremely acidic [1,2]
Sulfate reduction was evidenced soon after continuous flow commenced by the precipitation of black CuS in the gas jar that received the off-gas produced in the bioreactor
Half of the sulfate present was reduced in the reactor during the treatment of both acid mine drainage (AMD) and acidic synthetic mine waters (SMWs) with initial sulfate concentrations of 1260 and 1580 Molybdenum (μg L-1) Nickel (mg L-1), respectively (Fig. 2)

Summary

Introduction

Effluents from the mining industry are commonly characterized by having relatively elevated concentrations of soluble sulfate and transi tion metals, and are often moderately to extremely acidic [1,2]. As a result, these waters can cause pollution of ground and surface waters and decrease the biodiversity in fresh waters [3]. Sulfate can be removed from water by membrane filtration or ion exchange processes These methods are efficient but have some disadvantages such as high costs, fouling of membranes, and the need for preprecipitation of the water and downstream treatment of the reject [6]. Biological treatment methods have been suggested for the removal of various contaminants [7] and the traditional bioreactors used for wastewater treatment have been developed significantly [8,9]

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Discussion

Conclusion