Filters set to improve aquatic environment

Scientists will be giving nature a helping hand by developing filters in the landscape. The filters will primarily curb the emission of nutrients to the aquatic environment and thus give a better balance between agriculture, environment and nature.

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Increasing food and energy requirements, adaptation to climate change, and impact on nature and environment are tough challenges facing modern agriculture today. Some of these apparently opposing challenges can be addressed by establishing nutrient filters in the landscape.

A new strategic research project on the development of filter technologies to reduce nutrient concentrations in drainage water is being launched by scientists from the Faculty of Agricultural Sciences and the National Environmental Research Institute at Aarhus University, as well as the Faculty of Life Sciences and the Institute of Food and Resource Economics at the University of Copenhagen.

THE SUPREME-TECH PROJCT WILL DEVELOP AND OPTIMISE DRAINAGE AND LANDSCAPE FILTERS DESIGNED TO REMOVE NUTRIENTS, PARTLY THROUGH THE CREATION OF REACTIVE FILTER ZONES HERE IN THE FORM OF MINI WETLAND AREAS. PHOTO: TORBJÖRN DAVIDSSON

Natural processes optimised

The idea basically consists of optimising nature s own remediating processes. In nature, soil and plants will filter out nutrients before they end up in watercourses and lakes, but with the increasing nutrient load from agriculture it has been difficult for nature to keep up.

– It is a huge challenge for agriculture to combine the increasing need for food production and biomass for energy purposes with the increasing requirement for protection of the aquatic environment and natural resources. There is particularly a challenge in reducing the phosphorus load, explains senior scientist Charlotte Kjærgaard from the Department of Agroecology and Environment at the Faculty of Agricultural Sciences, Aarhus University.

– Drains and ditches that directly connect fields to the aquatic environment are important transport pathways for especially phosphorus. However, to date there are no effective remedies that restrict phosphorus losses in drainage waters, says Charlotte Kjærgaard. Climate changes also play a part. In Denmark we can expect more extreme rainfall and thus a higher risk that nutrients leach. In  combination with a higher water temperature this will make lakes more vulnerable.

Filters in the landscape

The SupremTech project will help to reconcile intensive agriculture with good surface water quality. The initiative focuses on severing the short cut between field and water body. This is done by implementing drainage filters that are designed to retain phosphorus and to convert nitrate into gaseous nitrogen. In contrast to natural wetland areas that are typically confined to wider river valleys, the SUPREME filters will operate further up in the stream network and closer to the actual source areas of nutrient losses.

The scientists will develop and examine various concepts for drainage filters, including different types of small constructed wetlands, as well as filter systems adapted to drainage wells. The concept is that environmentally friendly industrial waste products may be used as effective filter bed materials.

– Our particular focus is on new filtration mechanisms and filter materials that can remove phosphorus at actual drainage water concentrations and very varying flow conditions, explains Charlotte Kjærgaard. A side benefit is that phosphorus, which is a globally limited resource, can be recycled. The project will therefore examine the use of the phosphorus-saturated filters as an agricultural soil improver. The multifunctional landscape

– The many challenges and interests relating to agriculture and environment emphasize the need for a determined and concerted effort. Drainage filters can be an important tool for farmers and environmental managers to reduce the nutrient load to the aquatic environment and can become important landscape buffers for nutrients in a changing climate, points out Charlotte Kjærgaard.

– The small constructed wetlands can be of particular value in the landscape in their capacity as green corridors and contributors to a richer biodiversity. Retaining/recapturing nutrients closer to their source areas on agricultural land will also reduce the pressure and thus increase the protection of the nature in the river valleys.

The five-year research project Sustainable Phosphorus Remediation and Recycling Technologies in the Landscape (SUPREME-TECH) is financed by the Danish Council for Strategic Research. In addition to the partners mentioned above under the leadership of professor Hans Christian Bruun Hansen from the Faculty of Life Sciences, University of Copenhagen and senior scientist Charlotte Kjaergaard from the Faculty of Agricultural Sciences, Aarhus University, the project also includes the Danish Agricultural Advisory Service, the consulting engineers Orbicon, a number of Danish and international companies, and university partners from Agroscope Reckenholz Tänikon Research Station (Switzerland), Alterra Wageningen (The Netherlands), Linköping University (Sweden), Oklahoma State University (USA) and University of Natural Resources and Applied Life Sciences (Austria).