Bacterial sources, pathways and management strategies for urban runoff

The microbiological quality of diffuse impermeable surface runoff is described in terms of bacterial densities and pathogens observed within urban catchments in North London and Milton Keynes and the use of somatic bacteriophages as faecal indicators are evaluated. The studies show the occurrence of faecal indicator organisms (FIOs) and pathogens to be ubiquitous in stormwater runoff from all types of urban land use surfaces, with the possible exception of major highways. Urban catchments in North London show a progressive downstream increase in FIOs and pathogens consonant with increasing urbanization and incidence of stormwater outfalls and combined sewer overflows (CSOs). Surface water FIOs and pathogens appear to be predominantly of non-human origin being primarily derived from animal and bird sources, although the effect is over-ridden in the presence of misconnections and CSO discharges. A combination of infrastructure improvement, end-of-pipe detention, source control and more robust local authority regulation is recommended for effective management and remediation of bacteriological urban water quality.