Chemical engineers at University College Dublin (UCD) have developed new technology to save energy in wastewater treatment. Our approach targets a particularly wasteful step in wastewater treatment. Conventionally, this step involves forcing oxygen bubbles through the wastewater ‘sludge’ in order to support bacterial growth. The bacteria then absorb contaminants and nutrients from the water, thereby helping to clean it so it can be released back into the environment or recycled for human use. My research group at UCD’s School of Chemical and Bioprocess Engineering has developed an alternative technology: membranes that diffuse or ‘breathe’ oxygen and thereby directly support biofilms of bacteria. Our studies show that this membrane-aerated biofilm reactor (MABR) technology can save up to 75 per cent of the energy conventionally needed to support bacteria in their wastewater treatment role. In 2014, OxyMem (the UCD spin-out company) delivered the first commercial MABR technology to the market, and it is now reducing energy use for wastewater treatment in numerous countries.