Production of hydrogen from domestic wastewater in a pilot-scale microbial electrolysis cell
Addressing the need to recover energy from the treatment of domestic wastewater, a 120-L microbial electrolysis cell was operated on site in Northern England, using raw domestic wastewater to produce virtually pure hydrogen gas (100 ± 6.4 %) for a period of over 3 months. The volumetric loading rate was 0.14 kg of chemical oxygen demand (COD) per cubic metre per day, just below the typical loading rates for activated sludge of 0.2–2 kg COD m−3 day−1, at an energetic cost of 2.3 kJ/g COD, which is below the values for activated sludge 2.5–7.2 kJ/g COD. The reactor produced an equivalent of 0.015 L H2 L−1 day−1, and recovered around 70 % of the electrical energy input with a coulombic efficiency of 55 %. Although the reactor did not reach the breakeven point of 100 % electrical energy recovery and COD removal was limited, improved hydrogen capture and reactor design could increase the performance levels substantially. Importantly, for the first time, a ‘proof of concept’ has been made, showing that this technology is capable of energy capture as hydrogen gas from low strength domestic wastewaters at ambient temperatures.
KeywordsMicrobial electrolysis cell Hydrogen Wastewater Energy
The authors would like to thank the staff at Northumbrian Water Limited, Andrew Moore, Steve Robson and Laura Stephenson, as without their support this project would not have been possible. The authors also thank Christine Jeans for preparing the reactor diagrams. This work was financially supported by the Engineering and Physical Sciences Research Council and Northumbrian Water Limited.
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