Updating Stockholm’s wastewater treatment system to meet future needs

Photo: SVOA

To cope with Stockholm’s rapid population growth and be able to meet the increased environmental requirements set to come, the city’s wastewater treatment system needs to be upgraded. This is a complex project, involving – among other things – the construction of new sewage tunnels that will connect the wastewater systems from various parts of the growing metropolis, as well as expanding the existing treatment plant in Henriksdal into nearby Sickla, where one of the most cutting-edge wastewater facilities in the world is set to be built. 

Regional Manager Peter Johansson believes that Bravida’s experience in complex heating, plumbing and ventilation installations was a key factor in persuading Veidekke to choose it as an installer for this project.

“Bravida plays an important role in society with its installation services and we are involved in many of Stockholm’s ongoing infrastructure projects. We are very happy to be part of yet another assignment within this project, in which we are already involved through installation work on Henriksdal’s biolines and the sewage tunnel,” he says.

Expansion and renovation
At the moment, all wastewater from Stockholm’s southern suburbs is pumped out to the Sickla facility, where the first purification stage – coarse purification – is carried out inside the rock. It is then sluiced on to the nearby Henriksdal treatment plant to undergo the rest of the treatment process. The plan now is to expand the Sickla plant so that it can also receive wastewater from Stockholm’s western suburbs – through a sewage tunnel spanning several kilometres, which is also currently being built. At the same time, the Henriksdal treatment plant is being updated and future-proofed. The new state-of-the-art treatment technology being used will make the wastewater even cleaner, which in turn will reduce the amount of phosphorus and nitrogen that contribute to eutrophication in lakes and oceans. 

A complex project
The work required to upgrade the wastewater treatment system is complex, not least because of all the different parties involved. According to Peter Johansson, the fact that the heating and plumbing and the ventilation are all being organised by the same team is a big advantage for the customer. 

“This means that Veidekke has one point of contact instead of two,” he says, “So there will be shorter decision-making pathways and it will save a lot of time as both disciplines will work together and understand the challenges each other is dealing with”.  

One of the biggest challenges for Bravida in this project is the logistics surrounding the building material. The material storage system is divided into three different parts to help make the logistics process flow as smoothly as possible. A warehouse for smaller deliveries is located next to a technical building, which is also included in the contract. A second warehouse is located just outside the site and is intended for time-critical deliveries that need to be secured before production. The third warehouse is a just-in-time storage facility for all the different jobs that take place inside the rock. Logistically, a major issue here is that trucks have to bring in new deliveries every night to make sure that the next day’s material is ready to be transported down into the rock when the installers start work early in the morning. And as if coordinating between all the different warehouses were not enough of a challenge, the treatment plant is also fairly centrally located in Stockholm, near a busy road that is often congested with traffic.

“What unforeseen events do we need to take into account? How can we influence traffic situations and the ability of other parties involved to get deliveries in on time? We will have to spend a lot of time thinking about those types of questions before construction starts,” says Peter Johansson.  

Sustainable working environment
Bravida will have up to seven employees and between 30 and 40 installers working on this project. When it comes to securing the right skills, welders are in rather short supply in Sweden. Bravida and the other contractors involved also have the important task of ensuring a sustainable and safe working environment. 

“We will work hard to ensure that all our employees have good, sustainable working conditions. For example, the installers are only allowed to work a 36-hour week because they are working underground without natural daylight.” 

The entire treatment development, including both the Sickla facility and the nearby Henriksdal plant, is estimated to be ready to go operational in 2031. When it does, it will be able to boast that emissions of, nitrogen, for example, will be reduced by 40 percent, and the proportion of phosphorus will be cut from an already low level by around 35 percent. Bravida is happy to invest in projects that bring ecological benefits to both society and the environment. 

Building in efficiency to protect the climate
In this project, Bravida has more of an active construction role than an advisory one, but this does not prevent Peter Johansson and his team from coming up with suggestions on how to further optimise the facility in terms of climate-related aspects. One of their proposals involves manufacturing ventilation ducts on site down in the rock.

“Instead of shipping in long ventilation ducts, which just contain air, on lorries across the country, we suggested that they could be manufactured on site. We are already doing this in another project at the bus terminal in Slussen, and this is a big plus from a climate perspective,” says Peter Johansson. 

Facts about the project
What it involves: Updating the Henriksdal wastewater treatment plant in Stockholm
Client: Veidekke
Bravida’s assignment: Installation of heating, plumbing and support systems for the treatment plant’s processes and ventilation systems in rock rooms and technical spaces.
Schedule: Start in autumn 2024, completion at the end of 2027.
Number of employees from Bravida: Approximately 47 employees will be involved