Sarah Constance Motshekga
Nitrogen (N) and phosphorus (P) are essential nutrients for all living organisms and at a larger scale for the productivity of several organisms within the ecosystem. Their recovery from wastewater is crucial to address the environmental eutrophication and the unsustainable mining of finite nutrient resources. Bioelectrochemical systems (BES) have emerged as adaptable technology capable of supporting simultaneous nutrient recovery, wastewater treatment and bioenergy production. The primary goal of BES, commonly referred to as a microbial electrolysis cell (MEC), is the production of bioenergy, primarily methane and biohydrogen while treating wastewater in the anodic chamber. With the adoption of improved reaction kinetics, the potential of BES to create sporadic compounds and high-value derivatives has been extensively studied in recent decades. This review discusses the recent developments in the recovery of N and P using BES, shifting the focus from mere removal to value-added product recovery. Recovery efficiencies are promising with studies reporting up to 96 % N recovery as ammonia and 95 % P recovery as struvite. However, the present analysis highlights that these high efficiencies are often achieved under optimized laboratory conditions and are still challenging to replicate in real-world applications. Key barriers include high energy requirements for N recovery, interference from competing ions limiting P precipitation and operational instability due to membrane fouling and fluctuating wastewater composition. The review asserts that the path to commercial viability requires dedicated focus on the development of cost-effective hybrid systems, scalable reactor designs and validating long-term performance with industrial wastewater. The review provides a critical framework to guide prospective research and innovation towards making BES a technically and economically viable platform for sustainable nutrient recovery. • BES recovers >95 % nutrients from wastewater in the lab. • Struvite purity is compromised by competing ions. • High energy cost for N recovery remains a major barrier. • BES integration with established technologies is crucial for scale-up. • Real-world application is hindered by competing ions and fouling.