Electrified bioreactors: the next power-up for biometallurgical wastewater treatment

Abstract

Over the past decades, biological treatment of metallurgical wastewaters has become commonplace. Passive systems require intensive land use due to their slow treatment rates, do not recover embedded resources and are poorly controllable. Active systems however require the addition of chemicals, increasing operational costs and possibly negatively affecting safety and the environment. Electrification of biological systems can reduce the use of chemicals, operational costs, surface footprint and environmental impact when compared to passive and active technologies whilst increasing the recovery of resources and the extraction of products. Electrification of low rate applications has resulted in the development of bioelectrochemical systems (BES), but electrification of high rate systems has been lagging behind due to the limited mass transfer, electron transfer and biomass density in BES. We postulate that for high rate applications, the electrification of bioreactors, for example, through the use of electrolyzers, may herald a new generation of electrified biological systems (EBS). In this review, we evaluate the latest trends in the field of biometallurgical and microbial-electrochemical wastewater treatment and discuss the advantages and challenges of these existing treatment technologies. We advocate for future research to focus on the development of electrified bioreactors, exploring the boundaries and limitations of these systems, and their validity upon treating industrial wastewaters.

Fig. 1

Syntrophic relationship and metal(loid) removal mechanisms at play in biological systems for the treatment of sulfate containing metallurgical wastewaters. CCC, complex carbon chains; SCC, short carbon chains. Green arrows denote pathways that can be electrified.

Fig. 2

Overview of possible hypothetical flowsheets using multiple biometallurgical wastewater treatment technologies. (A) Arsenoteq/Thioteq Scorodite, (B) Sulfateq, (C) Thiopaq, (D) Thioteq or BioSulphide with selective recovery, (E) BioMeteq or ABMet. These conceptual flowsheets are non‐limiting as multiple iterations, sequences, combination, gas recycles and liquid recycles are possible.

Fig. 3

A hypothetical example of electrified biological systems (EBS) applied to existing biometallurgical wastewater treatment technologies. (A) Arsenoteq/Thioteq Scorodite, (B) Sulfateq and (C) Thiopaq. This conceptual flowsheets is non‐limiting as multiple iterations, sequences, combination, gas recycles and liquid recycles are possible.

Fig. 4

Reduction rates achieved by passive treatment (generation I), active treatment (generation II) and bioelectrochemical systems (BES, generation IIIa) reported in peer‐reviewed journals and the innovations between each generation (Dvorak et al., ; Smul et al., ; Waybrant et al., , ; Chang et al., ; Cocos et al., ; Skousen and Ziemkiewicz, ; Zagury et al., ; Liamleam and Annachhatre, ; Van Houten et al., ; Su et al., ; Coma et al., ; Luo et al., ; Sánchez‐Andrea et al., ; Sharma et al., ; Pozo et al., , , , ; Blázquez et al., , ; Teng et al., 2016).