Simple steps to sustainable water: How treated wastewater can meet drinking standards
As extreme weather, droughts and water scarcity become more common, we need more ways to ensure access to clean water. New research by PhD student Maria Takman shows how wastewater in Kivik has been treated to near drinking water quality.
“I was surprised that we achieved such high quality with a relatively simple and short treatment process. This type of wastewater reuse could become an important resource in the future,” she says.
Maria Takman is a PhD student in the Agenda 2030 Graduate School and also belongs to the Department of Process and Life Science Engineering. On 26 April, she defended her thesis 'From removal of organic micropollutants to municipal wastewater reuse – technological and social perspectives'. In her research, she has studied a new treatment plant at Kivik in Österlen, where wastewater is treated using membranes, known as ultrafilters, and granulated activated carbon, known as GAC filters. The aim is to be able to reuse the wastewater, which is not normally done at conventional treatment plants in Sweden.
The result of the first stage was that the water reached irrigation quality. This is about the same quality as the water in lakes such as Vänern, Vättern and Mälaren.
To further reduce the bacterial content of the water, she had it disinfected with ultraviolet light. This paid off - the water samples from Kivik now reached drinking water quality in terms of microbial levels. Maria Takman sent the samples for more detailed chemical analysis, looking at about a hundred different bacteria and chemicals. The results were still better than expected.
Treated wastewater during water shortage
"The water sample from Kivik met drinking water standards for all parameters except nitrate. And nitrate could easily have been removed in an extra step. This shows that a treatment plant that is only designed to treat wastewater can actually achieve drinking water quality with a relatively simple extra process. Even though we analyzed this many different concentrations, we are still a bit unsure about when it is actually a safe drinking water, since we for example have not analyzed viruses, and limits on pharmaceuticals are lacking in the drinking water criteria. But these compounds can be present at higher concentrations in wastewater compared to if the source is groundwater or lake water," she says.
Areas such as Österlen, the Bjäre peninsula and Gotland already experience water shortages during the summer months. In the future, climate change is expected to bring more droughts, more extreme weather and lower groundwater and lake levels. This is where the research can be useful.
"If we want to maintain the society we have today, including agriculture, it is good if we can reuse wastewater as an additional resource. It can also contribute by being more energy efficient compared to for example desalination of sea water, and some crops may not need to be irrigated with ultra-pure water."
Comparing attitudes to wastewater and desalinated seawater
In addition to the research on wastewater in Kivik, Maria Takman has also studied the discussion around new methods of producing drinking water. On Gotland and Öland, seawater desalination is used as a complementary means of producing drinking water. When Maria Takman examined the media image and interviewed involved residents on the islands, there was a clear difference in how the method was received.
"On Gotland, desalination was by some people linked to mining on the island and was sometimes seen as a negative, unnatural, technical solution. Such controversies were not seen on Öland. We also investigated the discussion around drinking water from treated wastewater. Surprisingly, it was well received – people in general did not seem to find it disgusting or dangerous."
The interview study demonstrated the importance of the local context in gaining acceptance of new water sources. This part of the doctoral thesis inspired Maria Takman in the interdisciplinary research school Agenda 2030.
"I wouldn't have done the interview study without the graduate school; I would probably mostly have measured bacteria and chemicals. I have really learnt a lot about research outside the natural sciences. In the beginning I sometimes felt that we hardly understood each other in the graduate school, but now we can communicate and the interdisciplinary part is developing the research!"
After her dissertation, Maria Takman will take up a position at Himmerfjärdsverket in Stockholm, where she will work as a process engineer.
Maria Takman's thesis 'From removal of organic micropollutants to municipal wastewater reuse – technological and social perspectives' - portal.research.lu.se
Article in Swedish about Maria's research "Snart dricker du kanske renat avloppsvatten" - lu.se
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