Sweden trailblazes zero pollution wastewater treatment
By 2040, all water released into the environment, from treatment plants serving 100,000 people or more, must be free of pharmaceuticals, pesticides, antibiotics, manufacturing chemicals and other harmful substances.
That is the European Commission's new zero pollution proposal for cleaner water, and requires stricter laws for Europe's tens of thousands of wastewater treatment plants (WwTPs). It also applies to smaller plants at environmentally sensitive sites.
Two plants that already meet the new strict requirements can be found in southern Sweden, in the villages of Degeberga and Kivik in the county of Skåne. Some 12 years ago, local fishermen in Kivik raised the alarm about foul-smelling water, dead birds, and sore, fungal-infested fish and the situation prompted the authorities to take action.
The Swedish Agency for Marine & Water Management cited a cocktail of harmful substances as one of several possible explanations, and it was established that the existing WwTPs could not remove micropollutants, even at low levels. It was even a problem to measure samples reliably.
“We were able to start mapping the emissions of micropollutants in Skåne in 2016," said Ola Svahn, a researcher in environmental analytical chemistry at Kristianstad University. "Ongoing projects have led to the region being the most mapped in the country today,”
The measured emissions of micropollutants from WwTPs, and receiving water around Skåne county showed that traditional treatment plants are not built for the chemical profiles of today's wastewaters, due to changes in society and lifestyles. The two WWTPs in Degeberga and Kivik have since been upgraded and are the first of their kind.
They both have a fourth treatment step consisting of pretreatment with sand filters and granular activated carbon (GAC), complementing the three traditional mechanical, biological, and chemical stages. Granular activated carbon is made from raw organic materials, such as coconut shells or coal, which are high in carbon.
Heat is used to activate the surface area of the carbon and the activated carbon removes certain chemicals from the water passing through a GAC filter by trapping them. The research shows that this fourth treatment step removes most harmful substances that would previously have traveled straight through the system.
When Ola Svahn started researching water purification with GAC ten years ago, the technology was considered complicated to operate, expensive and inefficient, and the carbon had too short a lifespan. A lot has happened in a decade, and Svahn has shown that the GAC technology is cheaper and more efficient than previously thought.
“It has been critical to develop and evaluate the technology on a large scale, together with the industry and the treatment plant's operating staff,” says Ola Svahn. “Then we are out in reality and have real conditions to develop, research and measure.”
The WwTP in Degeberga became Sweden's first full-scale treatment plant equipped with GAC, and it has been in operation for three years with the same filter. A sand filter is used before the GAC filter, to protect the active carbon from clogging.
“We are only at the beginning of the research on granular activated carbon," says Svahn. "I think we will be able to refine and develop new carbon materials."
Under the EC's proposal, the degree of purification of water leaving WwTPs must be at least 80% on a selected number of micropollutants. The fourth purification step at Degeberga WwTP is at 84% after almost three years of operatoin. However, several of the selected pollutants have a significantly higher degree of purification than that.
Diclofenac, the active substance in the painkiller Voltaren, which is quite an elusive substance, is now at 98%, and the researchers say the work has only just begun on developing new carbon materials to make the processes even more efficient. They see PFAS substances - complex manufactured chemicals that are used in lots of everyday products - as an area of particular focus.
“We are only at the beginning of the research on granular activated carbon," says Svahn. "I think we will be able to refine and develop new carbon materials – new adsorbents so that the carbon becomes even more efficient.
"We see the need, not least in our work with PFAS, which adsorbs relatively poorly to activated carbon. In the future, filter materials will be tailored depending on the substances that need to be removed.
"Furthermore, by combining these different filters, we can achieve even better levels of purification, to the benefit of both the environment and human health.”
The GAC technology has been evaluated and the levels of micropollution in the Skåne waterways have been mapped through various projects. The sampling area have extended via international projects in Denmark, Poland, Germany and Lithuania.
"Here are successful examples of how the research is put into practice through full-scale treatment plants that are now in use with treatment technology for micropollution. We need this knowledge.”
Recently, a delegation from Latvia and Lithuania visited Sweden to take a closer look at the upgraded WwTPs in Skåne.
“Sweden has a lot to share," says Sergej Suzdalev from the Marine Research Institute of Klaipeda University in Lithuania. "Here are successful examples of how the research is put into practice through full-scale treatment plants that are now in use with treatment technology for micropollution.
"In the Baltics, we need this knowledge about how cooperation between different decision-making authorities, researchers, and other interest groups works.”