Water utility estimates (table 2) were used to calculate population equivalents in wastewater (PE-WW). The resident population estimate was calculated by multiplying the occupancy rate with the number of properties residing in the designated catchment area. Multi-occupancy buildings were also taken into consideration, including care-homes and university halls. Other additional inputs into the wastewater stream were also considered (e.g. commercial or industrial waste) by using certain water quality indicators (WQIs). For example, industrial PE was calculated via the supply flow to commercial properties and using estimates of 60 g biological oxygen demand (BOD) per capita per day. Chemical oxygen demand (COD) was used to calculate input from tankard waste, by observing the amount of COD present in the known volume of waste (assumption that there was 120 g of COD per capita per day).