Water Supply

Kakolanmäki Wastewater Treatment Plant

A 471,000 cubic meter rock field was excavated near the center of Turku for construction of the Kakolanmäki Wastewater Treatment Plant. When completed, the wastewater treatment plant replaced five old treatment plants and also reduced the region’s effluent load to the sea by 30–50%.

The sludge separated during the treatment produces biogas, which is used for district heating. The Kakola Heat Pump Plant also uses the waste heat from the treated wastewater.

The adjacent, valuable old buildings housing the Kakola Prison, created challenges for the excavation. Design and construction of the wastewater treatment plant particularly considered the location in the urban environment and near our valuable archipelago.

Kakola Heat Pump Plant

The Kakola Heat Pump Plant uses the waste heat from the Kakolanmäki Wastewater Treatment Plant and produces both district heating and district cooling for properties in Turku. So the heat pump plant gets its energy from a renewable energy source!

The Kakola Heat Pump Plant has been excavated in the rock in connection with the Kakolanmäki Wastewater Treatment Plant. Upon completion, the heat pump plant reduced the consumption of fossil fuels and greenhouse gas emissions in the area, as it could partially replace the use of coal at the Naantali Power Plant.

Viikinmäki Wastewater Treatment Plant

The Viikinmäki Wastewater Treatment Plant, built mainly inside the rock, was commissioned in 1994 and is the largest wastewater treatment plant in Finland and the Nordic countries.

The Viikinmäki Wastewater Treatment Plant process is based on the activated sludge method, in which the organic matter from the sludge is digested, producing energy.

Rockplan has been involved in both the original design of the Viikinmäki Wastewater Treatment Plant as well as in its later expansion phase. In the expansion, space was excavated for a new biological post-filter and a new treatment line, keeping the treatment plant is in operation throughout the excavation. The expansion increased the plant’s nitrogen removal capacity to the level of 70%, as required by the authorities.

Sewage Tunnels at the Blominmäki Wastewater Treatment Plant

The sewage tunnels of the Blominmäki Wastewater Treatment Plant consist of an inlet tunnel leading to the treatment plant and a discharge tunnel leading out of the treatment plant. A total of about 20 kilometers of inlet and discharge tunnels and associated access tunnels will be excavated.

In addition to the tunnels, the contract includes maintenance and emergency exit shafts that are critical for safety, the Suomenoja Acceleration and Drainage Pumping Station built within the rock as well as its associated above-ground shaft access buildings, and a challenging connection to the existing offshore tunnel. The offshore tunnel directs treated wastewater 15 kilometers to the sea.

Rockplan was also involved in the general design phase when a suitable site was sought for a new wastewater treatment plant in Espoo. There were five alternative locations under review.

The contracts are estimated to be completed in the summer of 2021. In 2022, the new Blominmäki Wastewater Treatment Plant will treat wastewater from 400,000 inhabitants in the Espoo, Kirkkonummi, Siuntio and West Vantaa areas.

Sulkavuori Central Wastewater Treatment Plant

Construction of the Sulkavuori Central Wastewater Treatment Plant began in 2018 and is expected to be commissioned in 2024. The Sulkavuori Central Wastewater Treatment Plant will be excavated in rock to create stale conditions for the operation of the treatment plant, so that treatment processes are not disturbed or slowed down due to weather variations.

The planned Central Wastewater Treatment Plant uses the latest treatment technologies in order to keep the discharge load on the lake to a minimum. The activated sludge process is supplemented by sand filtration and UV disinfection. The treated wastewater is led to Lake Pyhäjärvi by means of a tunnel excavated in the bedrock and a discharge pipe.

The progress of the excavation of the Sulkavuori Central Wastewater Treatment Plant can be monitored through the environmental monitoring system, EMO (Environmental Monitoring Online), developed by Kalliotekniikka Consulting Engineers Oy.

In the design of the Sulkavuori Central Wastewater Treatment Plant, special attention has been paid to a possible future expansion.