Published 8 May 2024 at 15.48
Domestic. A new thesis shows an inexpensive way to purify wastewater.
– I was surprised that we achieved such high water quality with a relatively simple and short purification process, says researcher Maria Takman.
< h2>Share the article
TwittraShare
Wastewater is currently only cleaned enough to protect the environment in which it is released. Most commonly, it is sent into the sea, lakes or rivers.
But instead, it could be further purified so that it can be watered with – and even drunk, according to researchers.
– It is actually a much more expensive option to desalinate seawater, because the salt ions are so small and difficult to filter out. The molecules in wastewater are larger. Therefore, it is relevant to start seeing wastewater as a resource, says Maria Takman, who recently completed her PhD in water supply and wastewater technology at LTH, Lund University.
Toilet water is not usually reused in Sweden – so far. Other, drier, countries sometimes do it. But according to Maria Takman, the knowledge of how effective different methods are is still limited.
The EU will soon come up with a new sewage directive. According to it, the reuse of waste water must be promoted and large treatment plants must clean away organic micro-pollution, for example pharmaceuticals.
The most common technique for producing drinking water from wastewater is reverse osmosis, which can be likened to a tight filter. According to Maria Takman, it is expensive and energy-intensive.
Just outside Kivik there is a treatment plant where she, together with Österlen VA, is evaluating another, significantly cheaper method, or rather a combination of methods: First, the wastewater is purified with a membrane bioreactor (MBR ) followed by granulated activated carbon (GAK), and as a final step the water has been disinfected with ultraviolet light in a lab at Lund University.
– In two scientific publications, I have analyzed what was left of hundreds of chemicals and microorganisms, such as drugs, metals and bacteria. My results show that we removed almost all of the harmful substances we analyzed. Simplistically, you can say that activated carbon removes chemicals while UV light neutralizes microbes.
– This shows that a treatment plant that is only intended to clean wastewater could actually meet all limit values for drinking water quality with the help of a relatively simple extra process.
An exception was nitrate, but according to Maria Takman, this is unproblematic because it is easy to clean from wastewater, which is done at larger sewage treatment plants, which the treatment plant in Kivik is not.
< p>The levels of pharmaceuticals were also low.
– But since there are no limit values for pharmaceuticals, which occur in higher concentrations in wastewater compared to groundwater and lake water, we cannot say for sure how low the concentrations need to be. Unfortunately, we did not have the opportunity to analyze viruses.