During the construction of the West Link some of the existing properties along the current railroad line will be demolished or rebuilt, and electrical wiring will be reconstructed. The Swedish Transport Administration also builds a new electrical substation for the train traffic at Olskroken.

At the same time, PEAB, which is one of the leading construction companies in the project at Olskroken, explores new technologies for managing and treating storm water in the construction area. In November 2016, a preliminary study was commenced at Olskroken.

– We have considered different methods and techniques, but are in need of a simple solution that doesn’t need large amounts of project space and is easy to integrate into our production. Therefore, the choice of using Swedish Hydro Solutions’s unique water treatment technology was made, a choice that the Swedish Transport Administration also endorse, said Margaretha Ringström, block manager of Time Critical Works at Peab.

A challenge to manage incoming storm water

The first challenge in the project was to handle the large volumes of storm water collected in the construction area. During periods of heavy rain, both the ground at the construction site, as well as excavated shafts, can be filled with large amounts of storm water, which then will create a bottleneck in the treatments systems that handle the storm water.

– Usually we fill an entire sedimentation container with storm water in one day. But If It rains a lot, that volume will increase quickly. That is why we need to have water treatment equipment that is able to manage the rapid changes in the volume of water.

Furthermore, the treatment system need to be easy enough to operate that one of our coworker are able to handle the whole treatment process, says Margaretha Ringström.

The next challenge in the project is to reduce the contamination that is present in the incoming storm-water at the site. Lead, arsenic, copper and mercury are some of the heavy metals that are both naturally occurring in the soil, and they also exist as residues in the surrounding ground because of earlier industrial activities at the site.

Suspended particles in the storm water, such as soil and clay, as well as various types of organic compounds also contribute to the problem with storm water contamination.

Storm water from construction zones with a lot of concrete often has a particularly high pH value. Peab’s supervisor Jon Göthlund has therefore in cooperation with Swedish Hydro Solutions developed a solution to that problem.

With this method, the incoming storm water is carried through a specially designed dosage cylinder where carbon dioxide is added in to the water stream, and this solution reduce the pH from 13 to 7. This is a solution that Swedish Hydro Solutions often applied during projects in the United States, but it is a relatively new method in Sweden.

In order to rationalize the water treatment process at Olskroken, the water treatment system from Swedish Hydro Solutions has been placed into a mobile trailer. This generates a system that is both mobile and furthermore it reduces the amount of space needed for the equipment at the project site.

With the encouraging test results from the beginning of the year, Peab increases the volume of water treatment at the location and extended the test period throughout 2017.

– Usually our staff will spend many working hours managing storm water treatment during a construction project. But with Swedish Hydro Solutions treatment technology, a single person can easily handle it – without it interfering with the rest of the day-to-day responsibilities, says Margaretha Ringström.

And she is particularly pleased that the process can take place without the need to add any hazardous chemicals.

– At a time like this, environmental awareness is very important not least because it’s about cleaning water that’s already polluted. And it feels good that we can clean it in as environmentally friendly manner as possible. says Margaretha Ringström.

Using the Swedish Hydro Solutions chitosan-based technology, the treated storm water is so clean that it can be released in to the local storm water system. If the entire test period is successful, other participants is also looking into examine the chitosan based technique offered by Swedish Hydro Solutions.

– We have had visits from NCC who are interested in how to handle water volumes in tunnels and shaft around the central station. These are places where you really do not want water standing, says Margaretha Ringström.