The need for waste water treatment became apparent when it was realised that the Stockholmers’ wastewater was gradually polluting Lake Mälaren and Saltsjön (a part of the Baltic Sea).
In 1934, the first major waste water treatment works was inaugurated in Stockholm – the Åkeshov plant. The Nockeby plant was built during the 1960s and is located in a large 120,000 m3 rock cavity. Bromma Wastewater Treatment Plant is the name of both Åkeshov and Nockeby which are connected via a 600 metre long underground tunnel.
Waste Water from more than 320,000 people is treated at Bromma plant in several steps. Water mainly arrives here from Stockholms' northern and western parts as well as from Sundbyberg and parts of Järfälla and Ekerö. 126 000 m3 of wastewater is treated every day. The purified wastewater is then piped to Lake Saltsjön via a rock tunnel, passing by a powerplant where heat is withdrawn from the treated water by heating pump.
The most recent reconstruction was carried out at the turn of the millennium when nitrogen removal in the aeration tanks was improved.
Excavated into the rock of Henriksdalsberget, on the border between Stockholm and Nacka sits one of Stockholm Vatten och Avfall's Wastewater Treatment Plants. With an area of 300 000 m2 and approximately 18 kilometres of tunnels, Henriksdal Wastewater Treatment Plants is one of the largest in Europe built inside of a rock.
Henriksdal Wastewater Treatment Plant was inaugurated in 1941. At that time, it had the capacity to treat approximately 150,000 m³ of wastewater per day. Twelve years later, when the city had grown considerably and the population had increased, the works was extended in order to double its capacity. Later on, a chemical and a biological method were added to the treatment process and measures were taken in the 1990s to improve the treatment of nitrogen and phosphorus. The most recent reconstruction was completed in 2011 and comprises two new rock chambers – one for mechanical treatment and one for the reception of grease and other organic waste for increasing the production of biogas for vehicles.
250,000 m³ of wastewater is treated at Henriksdal Wastewater Treatment Plant every day. Water mainly comes here from Stockholm’s central and southern parts as well as from Nacka, Tyresö, Haninge and Huddinge.
Together with Bromma Wastewater Treatment Plant both treat wastewater from almost one million people as well as industrial companies in Stockholm,
Huddinge and six neighbouring municipalities.
The existing Henriksdal ventilation flue is part of Henriksdal Wastewater Treatment Plant. It is 80 metres high and vents air from Henriksdal Wastewater Treatment Plant. The air that is released is odour-free thanks to advanced treatment. The ventilation flue was built around 50 years ago and the entire ventilation flue was structurally reinforced in 2014-2015 to extend is service life for a further 50 years.
The Sickla facility is part of Henriksdal Wastewater Treatment Plant. Wastewater from the southern suburbs and municipalities are treated mechanically here (bar screen and sand trap). The water is then conveyed to Henriksdal via two large tunnels for further treatment. Digested sludge dewatering is also done in Sickla.
Sickla already has a 80 metre high ventilation flue. It rises up behind Hammarbybacken and the Sickla plant and you can see it from the South Link and Hammarby sjöstad.
The ventilation flue vents air from the Sickla plant today and when our tunnel is completed, it will vent air from the plant here and also air from the large tunnel that is planned from Lake Mälaren to Sickla. The air that is released is odour-free thanks to advanced treatment.
What can be malodorous in Sickla on the other hand is the sludge treatment that is done here above ground and outdoors. We are going to eliminate this sludge processing in our project to ensure that this odour will completely disappear in future.