Challenges in building stormwater systems nowadays

Ebba Waernbaum, can you tell us about yourself?

I work at VA SYD, which is the utility for five municipalities in the south of Sweden. I work with strategic questions concerning stormwater, and especially on stormwater treatment.

How extensive is the area you work on?

It’s five municipalities, each one also has cities, like Malmö. In all of these we deliver drinking water, manage both wastewater and stormwater and we have a big system with wastewater plants, waterworks, and an extensive pipe system. 

What are some of the main challenges you face with regard to water management?

It would be good to visualise how big our system is. As well as the plants and pipes previously mentioned, we have a pipe system hidden underground which, because it is out of sight, it can be hard to grasp its actual size. It has 5,600 kilometres of pipes in our actual system, which is long enough to get to India. 

The system is huge, and this is key to understanding the four major challenges we face. The first is that much of the system was built during the fifties and sixties, so it’s getting old. On top of that, over the same period, the population in two of the cities, Mälmö and Lund, has doubled. So, the system needs to be upgraded whilst simultaneously continuing to function as it should. That means still delivering drinking water and managing wastewater.

Can you explain a little about the process involved when planning a water management project? 

We need to get involved early in the process, and we need to think, plan smart and think strategically about these questions. When I started working at VA SYD, we didn’t talk much about stormwater treatment. The focus was mostly on detaining stormwater. We only talked about stormwater treatment  when we were building new areas. But we have been on a journey over a number of years, and this journey has taught us three lessons. 

Firstly, we need to think about which problem we are trying to solve. Secondly, we’ve seen that when it comes to pollution loads, in the future most will come from existing areas and not new areas. The third lesson is that VA SYD’s part of the system, large solutions are more cost effective. 

As you mention, parts of the water system may be seventy years old. How big an impact does this have on the affected areas?

In the city we have existing areas, and we have new areas we are going to build. When we compare the pollution loads from existing areas with new areas it shows that ninety percent of the pollution will come from existing areas. This was an eye opener, because we had been focusing on new areas. Consequently, we made an action plan for existing areas. 

What is the strategic view when you are planning water infrastructure for a new area?

You could say that stormwater brings two types of problem. One is the risk of flooding, and the other is pollution. With regard to the risk of flooding, we have a pipe system that the stormwater runoff is drained into. When we build new areas we build new pipelines, but they go to our existing pipe system. 

As the city grows, we reach the maximum capacity and from that point the water needs to be detained in certain places. When it comes to stormwater, the problem is the risk of pollution in the water retention areas. Stormwater treatment is intended to protect the recipient where the water is retained. This treatment can be at several places in the system, as long as it is before the water reaches the recipient. 

How do you decide which water solution you will use?

First we need to consider if we have a risk of flooding, or if we need to treat stormwater. If we need to do both, then the systems can be combined in the same facility. The geography we are dealing with differs widely, but if you look at our pipe system, you could say that it looks like a tree. The leaves are the private property, the small and larger pipes are the branches which lead to the main pipelines which are the tree trunk. This then leads to the recipients. Stormwater treatment can be used at all levels in the system.  Of course, each solution has to be tailored to the city. 

When you talk about water pollution treatment, what processes do you mean?

We have just started stormwater treatment using ponds and wetlands. We want to develop a treatment toolbox, which can deal with all the different situations and locations in our system. For example, solutions in a dense area like a city centre need to be space effective and easy to maintain. 

Is it challenging to treat water from industrial activity?

The ponds and wetlands can treat water with different pollutants like phosphorus or heavy metals. When we have more dissolved pollutants, some of those can also be treated. The challenge is in a densely packed area, like in Malmo, because it’s hard to find places, areas, to place these treatments. 

 We’re now working on a research project where we look at different techniques for treating stormwater, both close to property and in larger areas. The project is called Eyeswim which works together with different municipalities and research institutions. So hopefully in the future, we will have more solutions for our toolbox. 

In these more densely populated areas, we might need ‘hidden solutions’. What kind of challenges do they bring?

First of all, the infrastructure needs to be renewed. The city keeps on growing, and the system needs to grow accordingly. The consequence is that there will need to be big investments. We have estimated 50-60 billion Swedish Kr by 2050. As well as this financial consideration, there is also a ‘people’ consideration. Therefore, the work has to be prioritised. Do the right thing, at the right place, at the right time.

If we look to the future, how prepared do you feel we are for the water management challenges that are coming?

We have the problem of the old infrastructure that needs to be renewed. We also have newer types of problem from climate changes, its impacts and also the new environmental restrictions we will need to address. We haven’t figured out all of the answers yet, but we’re working on it. 

In Sweden, when it comes to stormwater quality, we have the European Water Framework Directive and the environmental standards. One risk to reaching these goals is the stormwater, because it has pollutants. But stormwater isn’t the only source of these pollutants, and even by doing everything that we can to achieve these goals, it won’t be enough. These problems cannot be solved by one party alone. We can take responsibility for our part but we can’t do it alone.

On a national level, however, There are several investigations underway examining the legislation and the possibility of imposing requirements. However, I wish we could do more. It’s a slow process that requires effort from many different parties. 

Yes. One part is the legislation, and the other part is that everyone takes their own responsibility for their actions. For example, don’t wash your car in the street, so that the water doesn’t go into the stormwater. And don’t throw garbage into the pipe system. 

The real solution would be to stop the pollution at its source, then we wouldn’t need to treat the water at all. But that isn’t currently the situation and we, as a utility, don’t have the power to reduce the pollution going into out stormwater system.  

Do all citizens living in urban areas need to be aware, and educate our children to be aware of water management issues? 

Of course. If you throw something into our stormwater, and that goes into the pipe system, eventually it goes into the ocean, a place where you might like to go and swim one day. The European Water Directive’s whole purpose is to protect the water so that we have water of sufficient quality and quantity for future generations. However, it is also for our generation. 

Regarding the 2027 European Water Directive goals, how are we doing?