Purifying and reusing processed water from construction sites

When we expand and rebuild Sweden's infrastructure, blasting, drilling and digging for new tunnels is part of the process. In comparison with road, bridge or railway projects tunnel construction uses large volumes of process water. Therese Rönnkvist Mickelson, Head of Sustainability at Implenia Sweden, talks about how we ensure sustainable and efficient water treatment using different technologies suitable for each project.

Building and civil engineering projects can result in large amounts of contaminated or pH-increased water from the production that usually needs to be purified before it is released into the waste water system or to a water recipient. Water purification has therefore become a significant environmental issue in the construction industry and at Implenia.

«In our purification processes we recirculate as much water as possible.»

Therese Rönnkvist Mickelson
Head of Sustainability, Implenia Sweden

“Water is a natural resource that is used over and over again. We rely on water and therefore, it is important that we protect the earth's water resources and purify our water from the construction industry. We also believe that it is important to contribute to reduced water consumption and in our purification processes we therefore recirculate as much water as possible,” says Therese Rönnkvist Mickelson.

Suitable purification technology chosen for each project

At Implenia Sweden, the water purification technology is selected for each individual project and is thus adapted to the degree of pollution that the water from the project is assumed to carry.

“The quality of the process water is analyzed and investigated already in the tender phase. Later during the construction period, however, unforeseen events may occur, which means that the water treatment plant of the project needs to be supplemented and adjusted - for example with extra containers for sedimentation or extra filtration for metals”, Therese Rönnkvist Mickelson explains.

Increased demands

According to Therese, the demands on water purification are increasing all the time both from the clients and from the authorities, which means that Implenia attaches great importance to keeping up with technological developments. In this way, the company ensures that it is always at the forefront when it comes to water purification.

Water purification installation at Project E4 Stockholm Bypass: Since construction projects often have limited establishment areas and water purification often requires large areas, the space for water purification can be a big challenge

“We work actively to find alternative efficient methods for cleaning the water from our construction sites. Above all, we are investigating methods for even better purification of metals and nitrogen. For example, we have used biological treatment of water with some success to reduce the nitrogen content where the nitrogen is converted into nitrogen gas and water. At the same time, we have succeeded in reducing the chromium and zinc content to very low levels with chitosan flocculation.”

Operating in dense urban environments

Talking about the major challenges the team faces, Therese explains: “We use large volumes of water within our projects, above all when we drill and blast for tunnels. The water is pumped from the tunnel or shaft pits and collected in large containers. At the same time, our projects are almost exclusively located in dense urban “

A strong commitment to sustainability

Construction companies can contribute a lot in the areas of environment, economy and society. But this also brings with it a great responsibility. Implenia takes this responsibility seriously and considers the issue of sustainability in all these dimensions when developing, planning and building.

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“Here we believe that collaborations and feedback of experience between different practitioners are a prerequisite for finding solutions for a better and more efficient purification. The business therefore has collaborations with specialists in water treatment in several of its projects in order to be able to evaluate which technology is best suited. We have also looked into how the mining industry handles its process water - and can thus learn from them.”