Life cycle assessment of drinking water and wastewater treatment works in mainland Scotland.

Assessing the global warming potential (GWP) of water treatment systems is vital for reducing the carbon footprint of the water industry and aiding the net zero target. The approach of life cycle assessment (LCA) was used to determine the GWPs of four drinking water treatment works (DWTW) and one wastewater treatment works (WWTW) on the Scottish mainland. The results were compared with a previous study on the DWTWs and WWTWs of five Scottish islands which used the same method (LCA), modelling and context as the mainland work. The GWPs for the DWTW ranged from 0.09 to 0.27 kg CO-eq/m and for the WWTW was 0.44 kg CO-eq/m which were generally much smaller than that for island systems whose GWPs ranged from 0.18 to 0.79 kg CO-eq/m for DWTWs and 0.51 to 1.14 kg CO-eq/m for WWTWs. The largest contributor is the electricity consumption for all the mainland systems and asssociated footprints are smaller than that for island systems. By comparing Scottish mainland and island systems, the suitability of mainland systems for rural island systems is discussed. In terms of carbon abatement in the water industry, post treatment processes such as sludge reduction or resource recovery as well as the use of increased renewable energy sources would benefit both mainland and island water treatment works.