The population equivalent of those served by the WWTP (PE-WW) was estimated by Wessex Water (Table ). By multiplying the number of properties in the catchment area by occupancy rate (set at district level), the resident population estimate was determined. The resident population also considers the number of multi-occupancy residencies that fall within the catchment area, including care homes, residential schools, university halls, and military bases. As a UNESCO world heritage site, Bath has a thriving tourism input. Tourists were considered as non-resident population, and due to challenges estimating input of day-trippers to the catchment area, they were not included.