Modelling fate and transport of Escherichia coli and Cryptosporidium spp. using Soil and Water Assessment Tool

Viktor Johansson, Ekaterina Sokolova

Thursday 2 july 2015

17:15 - 17:30h at Asia (level 0)

Themes: (T) Hydro-environment, (ST) Impacts of pollutants on the water environment

Parallel session: 13G. Environment - Impact

Maintaining good quality of drinking water sources is essential as a part of drinking water management. Important steps are evaluation of source water quality and identification of contamination sources. Lately microbial organisms originating from faecal contamination have been increasingly identified as health risks and as an issue for providing safe drinking water. In Sweden, Lake Mälaren is a drinking water source for two million people. The aim with this study was to set up a hydrological model using Soil and Water Assessment Tool (SWAT) for a catchment area draining to Lake Mälaren in order to simulate transport and fate of faecal contaminants in the form of Escherichia coli and Cryptosporidium spp. oocysts. Sources of faecal contamination were identified through literature studies and contacts with local authorities. Calibration was performed on water flow in three different subbasins using SWAT-CUP. It showed an NSE between 0.18-0.44 and R2 between 0.26-0.53, whereas validation resulted in an NSE between 0.05-0.11 and R2 between 0.10-0.16. The modelling results showed that wastewater treatment plants were the dominating source of faecal contamination. Temporary spread of manure could also be seen as an important contributor. Catchment outlet concentrations of E. coli were higher than acceptable for Swedish bathing water quality and Cryptosporidium spp. oocysts outlet concentrations were in the same range as reported in other studies.