Bioelectrochemical hydrogen production from urban wastewater on a pilot scale

Abstract

Abstract Bioelectrochemical hydrogen production has been successfully achieved in laboratory-scale conditions with different substrates. However, scaling up microbial electrolysis cells (MECs) is not straightforward, and reported attempts have not been completely successful. This work presents the design, building, start-up and operation of an MEC pilot plant (130 L) based on a cassette configuration. The plant was started up in batch mode with acetate and glucose as substrates and operated for five months with different substrates (i.e. glucose, diluted raw glycerol and real urban wastewater). The best results were obtained in the last period with primary effluent from real urban wastewater. The hydrogen production increased to values higher than 4 L d−1 with a gas purity of 95%, a cathodic gas recovery of 82% and an energy recovery of 121% with respect to the electrical input. The organic matter removal efficiency was approximately 25% for a hydraulic retention time of 2 d with an organic loading rate (OLR) of 0.25 gCOD·L−1·d−1. It should be possible to achieve removal efficiencies around 75% with OLRs lower than 0.05 gCOD·L−1·d−1. These results are promising and represent an important step towards the industrial implementation of these systems.