Microbiological runoff water quality from a green roof and in an open stormwater system / Mikrobiologiska föroreningar i avrinningsvatten från ett grönt tak och i ett öppet dagvattensystem

Microbiological quality of stormwater runoff from a green roof and in an open stormwater system in Augustenborg, Malmö, Sweden was studied. Since the stormwater is managed in an open system there is a possibility of human contact with that water and a potential risk for public health. Four locations have been selected as sampling points: a green roof, a ditch, and two ponds. E. coli, total coliforms, Pre. Clostridium perfringens, and intestinal Enterococci are used as microbiological indicators to evaluate the potential stormwater contamination of fecal origin. Grab stormwater samples have been collected after rain events during 6 May, 24 October, and 26 November 2009. Comparison of obtained results is done between sampling sites, between sampled precipitation events, and between different indicators. The obtained results are also compared with bathing water standard for EU countries and guidelines for surface water quality by the Swedish Water & Wastewater Association. The highest concentration of microbiological indicators was found in water samples taken from the ditch. The least polluted stormwater samples were collected in the pond 1. The green roof runoff was contaminated by total coliforms and intestinal Enterococci. Most of the collected samples did not meet the standards for bathing water quality, except for the pond 1. In general, the stormwater in Augustenborg open system can be judged as polluted water from a microbiological point of view. There is a need for further research for better linkage between microbiological contamination in stormwater, rainfall intensity, and a season.