New approach gives nature a boost in wastewater treatment
In Finland, it is easy to take clean water for granted. This is because there is infrastructure, regulations and technology in place to make sure water is safe to use. However, there is new pressure for wastewater utilities to improve their treatment systems in the next decade to make water even more free of chemicals and micropollutants, says Senior Research Fellow Elisangela Heiderscheidt.
“For Finnish people, it is hard to think about not being able to use lake water or not having a safe drinking source. It’s difficult to imagine an environment that could make you very ill, but this is reality in many parts of the world. It’s clear that we need to do more to protect our water and nature at large, and this motivates me to do my research,” Heiderscheidt says.
Heiderscheidt’s research focuses on water and wastewater treatment systems and processes. She is a proponent of nature-based solutions, which means taking a naturally occurring process and boosting it to be more efficient and scalable to large communities.
Currently, she is running an innovative project at the University of Oulu with the support of the Kvantum Institute, where she and her team, including doctoral researcher Laura Tarvainen, are testing the use of electroconductive material as filter and substrate media in constructed wetlands instead of sand or gravel to remove pollutants from wastewater. The HyMETland project (Hybrid Microbial Electrochemical Technology Constructed Wetlands) is the first of its kind in Finland, and it is based on the findings of the iMETLAND Horizon 2020 project.
In nature, water quality is improved by naturally occurring processes. Any hole in the ground that is filled with water will offer the opportunity for plants to grow. Plants will uptake nutrients like nitrogen, and sand or gravel in the bottom of the basin will filter out particles. Constructed wetlands have been used for centuries to treat municipal wastewater, especially in Southern countries as the warmer the climate, the more efficient the treatment processes become. Heiderscheidt is looking to make the processes more efficient and applicable to colder climates, such as Finland.
“We try to create a system that boosts the natural processes, for example by giving nature more time and opportunity to do its business. At the same time, these new solutions should be completely or mostly passive, low-maintenance treatment systems, as well as sustainable,” Heiderscheidt explains.
Treating water more efficiently and more naturally
Nature-based solutions have numerous benefits as they are based on low-cost and low-maintenance processes, but they can’t compete in efficiency with centralised wastewater treatment plants that use chemicals and other advanced technology to remove pollutants. Further research is needed to be able to offer more sustainable but at the same time more efficient solutions. For example, an efficiently constructed wetland to treat wastewater at scale currently needs an impractically large land area: you need 4 square meters of wetland surface area per person to treat municipal wastewater. This is one of the issues Heiderscheidt is planning to tackle with her research.
Substantial research is being carried out around the world to develop innovative and high-tech solutions for wastewater management and it is focusing on emerging contaminants, resource recovery and energy harvesting from wastewater. Heiderscheidt and her research team are also conducting research in those veins, but she says it is critical to work on the development of sustainable nature-based solutions alternatives.
“The development of the constructed wetland technology via the application of, or the combination with, microbial fuel cell technology principles can be a game changer in this aspect,” Heiderscheidt explains.
While most studies investigating the combination of these two technologies have focused on the possibility of energy recovery from wastewater, so far this is not feasible at scale due to many issues, not least of which are financial, as electroconductive materials can be expensive.
“The research on this technology has run into problems, sure, but one of the things that has emerged is that the microbes that grow on the electrodes in these trials can degrade wastewater faster. So, what if we think about sustainable, low-maintenance sanitation solutions? Instead of having a couple of electrodes connected by a circuit to harvest energy, could we replace the whole media with electroconductive media, like graphite or coke?” This, Heiderscheidt says, is the “one million liters of clean water question.”
According to Heiderscheidt, the first reports from studies using coke as an alternative to sand or gravel in constructed wetlands were very promising and this kind of hybrid approach could prove to be the catalyst for a sustainable wastewater management future.
“It appears that the degradation is much better in microbial electrochemical-constructed wetlands. It also seems to work better the more load you put into the system, the more you stress it. This combination of low and high-tech approaches leads to faster degradation of pollutants. And if the process is faster, you don’t need as much surface land area for the wetlands,” Heiderscheidt says.
Indeed, she says that the process appears to be four times more efficient in terms of land area used per person, cutting down the necessary surface area from 4 square meters to one square meter, or even less.
“By using a high-tech approach, you can optimise a system that is centuries old and something no one thought could be improved upon,” Heiderscheidt explains.
This type of system would be applicable in a small community, but using graphite is not sustainable nor is it cheap. Heiderscheidt’s collaborators at Aarhus University started to look at other, more inexpensive materials to bring the cost down, being that sanitation cannot be expensive to everyone. They started testing other materials with lower conductivity compared with coke and significantly lower compared with graphite, and the results improved, surprisingly.
“Now, why is that? The consensus currently is that while the electrical conductivity of the material used is a factor, it is not the main one as previously thought. Other things like the surface of the material and how well it interacts with the biofilm play important roles. To that end, we have started to test biochar produced from waste biomass, locally produced, which has some conductive properties. And the preliminary results show that we are on the right path,” Heiderscheidt says.
“The next ten years will be a lot of fun”
The next stage for Heiderscheidt and her team is to look at how well the system works in a cold climate, such as Finland. They will conduct real-world, long-term, large-scale tests under Finnish conditions and see how the system works outdoors with fluctuating temperatures and precipitation, rain and snow.
Heiderscheidt says that now is a crucial moment for water and wastewater management in Finland. EU drinking water regulations were revised in 2020 and urban wastewater regulations were updated in late 2024. This puts a lot of pressure on utilities.
“In regard to wastewater treatment, they have 5-10 years to update their treatment systems to comply with regulations, to monitor pollutants more closely, to remove more nitrogen and micropollutants like pharmaceuticals. The system needs to be more efficient, work towards carbon neutrality and so on. The next ten years are going to be a lot of fun,” Heiderscheidt says.
The many aspects involved in treating water and managing wastewater are very complex. The goal is to reduce the pollution that reaches our waters, lakes and rivers and seas and to produce clean and safe drinking water for all. But there is no one answer, no single system or process that could answer all the issues in all the use cases even in Finland. For Heiderscheidt, it is important to strive toward a world where we can have a good quality of life and make the smallest possible impact on the environment.
“It’s a complicated situation and I don’t like not knowing the answers. This is why I surround myself with specialists like microbiologists, material specialists, chemists and so on in a very multidisciplinary approach. I believe we can live well and give nature time to recover, and that these things are not mutually exclusive,” Heiderscheidt says.
Elisangela Heiderscheidt's researcher profile
The list of the Kvantum Institute's Emerging projects 2023-2026
Story and photos: Janne-Pekka Manninen