Evidence for sewage contamination of the Sherwood Sandstone aquifer beneath Liverpool, UK

Urbanization of the Liverpool area in northwest England began in 1207 and the area was prosperous by the 1700s. As an area with a long history of urbanization, the objective of this study was to map the water quality of the underlying major Sherwood Sandstone aquifer with special attention to whether leaking sewers are contaminating the groundwater. The sewerage system in Liverpool has been extensive since the late nineteenth century, expanding along with the city. Twelve samples were collected from sites in Liverpool and analysed for several markers of sewage contamination, including the nitrogen isotope composition of dissolved nitrate, microbiological indicators, boron and major ions such as nitrate and potassium. The results showed saline intrusion and widespread contamination of the aquifer. The sewage 'fingerprint' was positively identified and provides the first conclusive evidence for sewer-derived contamination of Liverpool's groundwater.