Complex systems require a straightforward automation system. COWI performed detail design for all disciplines involved in VEAS’s sludge treatment plan.  

From wastewater to innovation

New framework agreement with Norway's biggest wastewater treatment plant


Each year, Norway’s largest wastewater treatment plant, VEAS, treats 100-110 million m³ of wastewater. The constant development of the plant capacity and the wish to be a leader in technology, have led to new framework agreements at the plant for COWI.

At Slemmestad in Asker Municipality, Norway, about one hour outside Oslo, lies VEAS (Vestfjorden Avløpsselskap). Each second, it receives around 11,000 litres of wastewater from 750,000 inhabitants, which travels through 42 kilometres of tunnels from downtown Oslo.

VEAS is the largest wastewater treatment plant in Norway. It treats wastewater from the owner municipalities and Nesodden Municipality.

Previously, COWI has carried out a lot of projects at the plant and recently won two framework agreements for VEAS. One covers building trades, including construction technology, fire safety, mechanical installations, outdoor environment, water, wastewater, stormwater, planning, environment, architecture and HSE. The other is a separate framework agreement covering electrical installations and automation.

Innovative actor leads to exciting solutions

Ole Tendal, who is responsible for the building trades framework agreement with COWI, considers VEAS an interesting customer to work for:

“VEAS is very forward-thinking. They are leaders in technology and operation and put a lot of effort into innovation. Among other things, they have a brand new biogas plant for liquid biogas, which will offer renewable biofuel to the transportation sector. This customer wants to be an industry leader, and that makes them incredibly exciting to work with for us, as a consultant,” explains Ole Tendal.

Behind these walls and in the caves of the plant, wastewater from Oslo, Bærum, Asker and Nesodden is treated.


Over the next four to six years, VEAS will invest in extensive plant rehabilitation and upgrade works – that must be carried out while the plant is in operation.

“When we’re dealing with these enormous volumes of water, you need great control systems,” explains Tendal.

VEAS chose to sign two parallel framework agreements with COWI and Norconsult for the building trades, and with COWI and Afry for the automation and electrical installations.


On a day with no rainfall, VEAS treats between 2,300 and 3,000 litres of wastewater each second. But the plant capacity is a whopping 11,000 litres a second. That amounts to 100-110 million m³ of wastewater a year.

  • The VEAS plant was constructed as a direct precipitation plant to remove phosphorous. Operation started in 1982, and at the end of the 1980s, 97 per cent of phosphorous was removed on average. 
  • In 1991, modification works began with the purpose of removing nitrogen. A dedicated treatment concept was developed – the VEAS concept for nitrogen removal – which resulted in a very compact plant.
  • In 2008, the so-called rainwater treatment plant was completed. That increased the capacity of the VEAS plant and reduced overflow at Lysaker by about 80 per cent.
  • VEAS introduced sludge digestion in 1993 and has always utilised the biogas for generating electricity and heat.
  • In June 2020, the production of liquid biogas for the transportation sector begins.

Get in contact

May Kristin Haugen

May Kristin Haugen
Head of Communication
Communication NO, Norway

Tel: +47 97745057