Hydria Water purifies snow removed from the streets of Oslo

Due to stricter environmental requirements, Oslo no longer has the option to simply dump the snow removed from the city’s streets in the fjord, as has been done in the past. The Terje snow-melting system is a climate-smart pilot project that NCC has developed on a commission by the City of Oslo, and purifies snow using Hydria Water’s screens.

Terje weighs 500 tonnes, is 50 metres long and 26.5 metres wide, and operates at a depth of 3.5 metres below the surface of the quay near the Akershus Fortress in Oslo, where it is docked from mid-December to March. During the high season, snow is dumped into Terje’s intake grills on the deck of the barge by up to 20 fully loaded lorries per hour, then purified in several steps. Sea water is used to melt the snow. Up to 1000 cubic metres of water is collected from a depth of 24 metres, where the water temperature is typically between 4 and 10°C in the winter. At a sea water temperature of 9°C, it is possible to melt roughly 1000 cubic metres of snow per hour; if it drops to 4°C, the rate of melting is approximately 500 cubic metres per hour.

The efficiency of the purification process is 70% on average, and over 90% of the heavy metals in the snow are removed. The first step is a sedimentation process, in which stones and gravel are screened out when the snow is mixed with sea water and run through Hydria Water’s screens. The water is then transported through purification channels equipped with micro filters and lamella clarifiers. Over a tonne of oil per season is also screened out before the purified water is eventually released back into the fjord.