North Europe’s largest biofilter test facility inaugurated

’Mini-wetland with biofilter pilot and test facility’: That is quite a mouthful, but it describes something quite special, that was inaugurated at Gyldenholm Manor on the island of Zealand on June 14, 2018. It is no less than North Europe’s largest test facility of its kind, which one of the vice-chairmen of the Danish Agriculture and Food Council, Torben Hansen, cut the ribbon to. This took place in the presence of approximately 90 participants, including people from the authorities, advisory sector, commercial companies, agricultural organisations, agricultural schools and the research world.

The test facility has three basins with wood chips that contribute to removing nutrients from drain water from a 120 ha catchment area. Five basins would be sufficient to remove nutrients from all of the drain water from the 120 ha. Photo: Janne Hansen

It was yet another dry and windy day in the weeks-long drought, but despite this, the participants were satisfied, because now there even more knowledge in an important area will be forthcoming. The facility will be used for both research and testing with the aim of improving the efficiency of nitrogen reduction and phosphorous retention so that these drain water nutrients do not end up in the aquatic environment. Researchers will also use the facility to investigate how any potential negative side effects can be minimised. 

Aarhus University, at the request of the Ministry of Food and the Environment, is responsible for the studies in a project, to which the ministry has granted an extra 15 million DKK. All told, the university is using 31 million DKK on studies regarding mini-wetlands. The present project, led by Senior Researcher Finn Plauborg at the Department of Agroecology, Aarhus University, is a collaboration between the Department of Agroecology and the Department of Bioscience.        

Steward of the Manor Gyldenholm, Herluf Pilgaard-Sørensen, said that he thinks it is exciting to be part of the project and that he is very interested in the figures that it will produce. Photo: Janne Hansen

Collective measures must be tested thoroughly

In order to avoid nutrient emissions from agriculture to the aquatic environment, it is necessary to use a range of measures. Some of these, for example catch crops, are used in the cultivated fields, but there is also a need for collective measures outside the cultivated land. However, more knowledge is necessary about potential collective measures outside the cultivated fields. Mini-wetland facilities are one of the possibilities.  

The new test facility will help researchers and agriculture to shed light on whether it is an efficient and economical way to remove nutrients from field drain water, so they do not reach the aquatic environment.

- Regular mini-wetlands are now approved as a measure to which you can apply for subsidies, but they require more land to remove the nutrients from drain water than a constructed wetland with biofilter. The latter only needs to take up one quarter of a hectare to remove nutrients from drain water from 100 hectares, said Finn Plauborg at the inauguration. He added:   

- Before we researchers can permit ourselves to recommend the ministry that a mini-wetland facility can be considered a viable collective measure, we need more research-based figures that demonstrate the efficiency, costs and durability of the facility under various geographical, hydraulic and weather conditions.

More research facilities underway

The facility at Gyldenholm Manor is the first in the project. There are three basins with wood chips to remove nutrients from drain water from 120 hectares – although not from all the drain water because that would require five basins and for financial reasons the project has only established three. 

Water flow is measured on a continual basis and data are sent electronically directly from the field to the researchers. Water samples are taken regularly, and they are analysed for a series of substances, including nitrogen and phosphorous. The preliminary figures indicate that the facility removes about 80 percent of the nutrients from the drain water from the 120 hectares catchment area.

The representative for Danish agriculture was quite satisfied. 

- We need to get drain measures on board, and I am pleased that visible results are forthcoming. We need many more tools and smart solutions to meet the challenges outside the cultivated fields. We cannot live with more restrictions in our cultivated fields, said the Danish Agriculture and Food Council vice-chairman, Torben Hansen, just before he cut the green ribbon and inaugurated the new, large constructed mini-wetland with biofilter test facility.  

Facilities will also be established in Spjald, Vindum, Haderslev, at Hofmansgave on North Funen, and in Ringe, so the researchers can carry out studies under various physical conditions. In addition, a semi-field test facility will be established at AU Foulum, where the efficiency of various kinds of wood chips and the possibility of including microorganisms to improve nitrogen reduction during the winter months will be investigated.