Flow proportional sampling of stormwater

Gustav Myhrman, Mälarenergi AB, 2020-03-31

Deliverable No. 56. 31/03/2020 (Action C9)

Full report (in Swedish)


Within the framework of LIFE IP Rich Waters, flow proportional sampling of stormwater has been carried out at 9 locations within the city of Västerås.

Stormwater has been analysed for phosphorus, metals, oil, PAHs and phosphate phosphorus. Sampling has also been taken on suspended material. The various sampling sites have then been classified according to land use upstream of the sampling well. Measured concentrations of contaminants were then calibrated to compensate for variations in flow during the sampling period.

The results show that the highest concentrations are generally obtained during the summer months. Previous studies have shown the opposite, that the highest levels are usually measured during the winter.

The explanation for the higher levels during the summer could be more intense rain that flushes more substances in the stormwater in a shorter time during the summer months. Also longer periods of no rain will allow substances to accumulate for a longer period on the ground.

The results also show that the two locations in central Västerås have consistently higher concentrations of metals in the stormwater than the other locations.

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