Engineering students working on sustainability development goals

Picture of five students.
The five students are all in the third semester and in partnership with SAMN Forsyning they have looked closer at how the problem of cotton buds in the wastewater treatment plant in Horsens can be solved.
Clean water and sanitation are one of the UN’s sustainability development goals and are generally high on the climate agenda as they are on the climate and supply engineering educational programme, and in the autumn a group of students set out to solve the well-known problem of cotton buds.

A cotton bud costs only a few cents to buy, but can be expensive for the environment and customers when it ends up in the sewage treatment plant. The EU’s new plastic directive, implemented last year, bans plastic cotton buds in the long term. However, in their end-of-semester project, students from the climate and supply engineering educational programme concluded that cotton buds of, for example, paper or wood can still create problems for wastewater treatment plants. 

The five students are all in the third semester and in partnership with SAMN Forsyning have looked closer at how the problem of cotton buds in the wastewater treatment plant in Horsens can be solved.

For, as researcher and associate professor at VIA University College, Ditte Andreasen Søborg says there are constant problems with cotton buds in the entire wastewater treatment plant system. Both in terms of problems with clogged pumps and the cotton buds reducing the plant’s biogas production.

“There is a financial gain to be won, for instance, in optimising the treatment plant’s biogas production. That could be done, for example, by removing the cotton buds in the fat from the sand and fat trap, so all the fat could be used in production. In fact, the students could see that cotton buds were present in the entire wastewater treatment plant’s system – they even made it all the way to Horsens fjord, where they end up in nature.”

Ready to abandon the project

The group was well underway with the project, when in autumn a large majority of the European Parliament voted in favour of a proposal from the European Commission to ban or restrict the use of plastic disposable products to protect the environment, including cotton buds.

“We were ready to abandon our project, because then the problem was – well – solved,” explains student Eva Christine Nielsen. “We assumed the plastic cotton bud replacements would dissolve sufficiently in the wastewater treatment plant, so they could be caught in the grate of the treatment plant. But, rather than abandoning the project, we decided to test it in a lab experiment.”

The climate and supply engineer educational programme has several well-equipped laboratories with modern analysis equipment, and laboratory tests are an important part of the educational programme. Therefore, with the help of researcher Ditte Andreasen Søborg, the group set up a simple but effective experiment that was to confirm the group’s hypothesis that the problem had been solved – at least in the EU.

A surprising result

To put it mildly, the group was surprised when they saw the outcome of their tests, says student Simon la Cour Petersen:

“We did a lab test to clarify whether cotton buds of a more environmentally-friendly nature decomposed more easily in the wastewater treatment plant. The experiment probably needs to be expanded before we can draw definitive conclusions, but it did actually indicate that cotton buds made of, e.g., paper or wood still create problems.”

With that result, the group decided nevertheless to dive into a solution proposal for Horsens’ wastewater treatment plant. For the educational programme is not only theory; on the contrary, the students always work closely with the supply sector on real and concrete problems and on finding functional solutions.

A relatively simple suggestion

The group was finished in December, and in January they received top grades at their graduation for a well-researched and well-documented project.

“We believe that the problem of cotton buds in Horsens’ wastewater treatment plant can be solved by a relatively simple solution: installing a different type of filter – a so-called drum filter. This would mean that the wastewater treatment plant would be able to use the fat from the sand and fat trap to increase biogas production by 5 % and minimise the pollution from plastic in the treatment plant,” explains Eva Christine Nielsen.

Climate and supply engineers are educated to have an interdisciplinary understanding of how things are connected. This is also how the group chose to work on their solution proposal; thus, they opted to include factors such as finances, maintenance and some of the positive side effects of the solution. For example, a drum filter can also deal with wet wipes, which are another major problem in wastewater treatment plants. Eva and the rest of the group are confident that the relatively simple and profitable solution is interesting to work further on – not just in Horsens, but in wastewater treatment plants around the world.

Not your average student

Ken Trabjerg Pedersen is project manager at SAMN Forsyning and has worked closely with the climate and supply engineering educational programme from the start, including as an internship supervisor.

“The students’ project is a good example of how engineers are educated at VIA with professional skills within exactly what we need. We are a supply company, and we need people who know something about rain and wastewater management,” says Ken Trabjerg Pedersen.

Every student is placed on an internship during their 5th semester, and Ken Trabjerg Pedersen reveals that he was involved in hiring the latest intern from the programme as a permanent student assistant.

“She jumped straight in, solving tasks like an experienced engineer, despite her still having a year of her studies left to complete. They have the skills to take full advantage from the get go,” he concludes.

The EU’s new plastic directive was negotiated between the member states, the European Parliament and the European Commission in December 2018.