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Solving micro-pollution with innovative biofiltration

Aarhus University (AU) is the coordinating partner for UPWATER’s Danish case study. To preserve important sources of drinking water in the region of Stengaarden in the future, the university is now preparing tests with biofilters and biofilmreactors. ‘We have to remove more than 90 percent of the pollutants to reach healthy drinking level values’, says professor Kai Bester.

The Institute of Environmental Science of Aarhus University is expert in water purification technology, with years of experience in removing organic micro-pollutants from the urban water and waste cycles. In the European project UPWATER, researchers of the university will investigate the use of natural solutions for groundwater pollution. In particular, they will look for solutions that integrate well with the natural landscape.

The university will coordinate activities for the case study of Stengaarden, where an old gravel pit became a dumpsite in the seventies. It is now leaking pesticide residues from industrial production waste into nearby groundwater that provide drinking water. Residues from pesticide production and high levels of iron are among the pollutants detected.

Fertile ground for learning

The grounds of the Stengaarden site require a painstaking water treatment, the Bester explains, and are a fertile test ground for learning and research. ‘Now we would obviously like to do something about the water quality,’ Kai Bester says. The professor for the department for Environmental Science will test Moving Bed Bioreactors (MBBR) and biofilters, both biological methods with a very low energy footprint. Biofilters could in principle even be imbedded in the landscape.

The MBBR’s are an upcoming and innovative technology for micro-pollutant removal. They offer an economically attractive solution for wastewater treatment, when large levels of contaminants need to be removed. In practice, they are also very rugged. The biofilters will function as the second instrument to make sure that removal rates are sound.

Bester and his colleague-researchers will build, test and optimize the biobased systems from the ground up. They will be supported by the Region Sjæland, the local authority that owns the site and is responsible for solving the contamination problem. The support from the authorities are, according to Bester, is to be taken as a sign that they take the issues seriously. The Danish administration also made the site a part of the National Soil and GW protection network and as a part of the Danish Soil Partnership.

Working all year long

Region Sjaeland has been working on the dossier of the Stengaarden dumpsite for six years. Several tests have already been conducted there, although being ‘small and short-term’ according to Bester. ‘These tests gave us the confirmation that the method with biofilters for example is feasible.’ UPWATER will help the research forward, figuring out several outstanding questions.

‘One of the main challenges is to make sure that the biofilters keep working all year long,’ the professor says. During the winter period, surface water will freeze and hinder the filter from working. Another threat comes from levels of iron in the water, that are able to block the filters rapidly when oxidized. Both challenges will be taken on with UPWATER.

As of right now, the MBBR’s need to be shipped to Stengaarden, where they will be placed in containers that are already on site. That will happen in March, together with the biofilter systems. ‘The first couple of steps are taken, but we are not operational yet,’ Bester says.

‘Stengaarden needs to be solved right’

‘We will have a look at how transferrable our results are for other climates. They might be of use in the case studies in Spain or Greece,’ the professor alludes. For his university, the goal is mainly to gain more knowledge about the workings of the innovative MBBR technology and biofiltration systems. ‘We expect to educate our people on the activities and insights of UPWATER, including the involvement of an PhD-student and a post-doctoral researcher.’ Besides the developments in Stengaarden, Bester is interested to follow all activities and insights from Athens and Barcelona.

The UPWATER project should be a clear wake-up call for all those who are in some way responsible for water management and its treatment, according to Bester. ‘The Stengaarden site is political. If it is not solved the right way, the supply of clean drinking water will get critical in many major places. That means shutting down wells that we very much need.’ We can’t do it for the fun of it, he adds. ‘Something is at stake here.’

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