Microbial electrochemical technologies (METs) have emerged as promising approaches for coupling wastewater treatment with energy and resource recovery. Considerable progress has been made in elucidating extracellular electron transfer, biofilm behavior, and electrode development, enabling laboratory systems to achieve high removal efficiencies under controlled conditions. Despite these advances, implementation in real treatment infrastructure remains limited. This review evaluates the progression of METs from laboratory studies to pilot-scale and field applications within the wider landscape of electrochemical wastewater treatment. The effects of reactor setup, material strength, and operational difficulty on performance at different scales are emphasized. Evidence from recent pilots consistently shows reduced energy recovery, along with challenges such as internal resistance, mass-transfer constraints, fouling, and cathode degradation. Laboratory-scale MFC systems have reported peak power densities of up to 23,000 mW/m2 and normalized energy recoveries of up to 1.2 kWh/kg COD removed under optimized, controlled conditions; however, pilot-scale systems typically recover only 0.01–0.05 kWh/kg COD removed, representing one to two orders of magnitude below laboratory-reported values. This contrast underscores the persistent gap between controlled experimental performance and operational reality. Proposed solutions, such as modular scale-out, membrane simplification, and the use of low-cost, replaceable materials, are assessed based on their maturity and practical applicability. Techno-economic and life-cycle analyses indicate that component longevity and integration strategy are often more decisive than peak electrochemical output. METs are therefore most likely to provide near-term benefits in hybrid or niche applications rather than as standalone replacements. Advancement toward wider implementation will require standardized metrics, long-term demonstrations, and engineering designs prioritizing robustness and maintainability.
Thobeka Pearl Makhathini (Sat,) studied this question.