Recycling treated wastewater for agricultural use

On the island of Bornholm, treated municipal wastewater from a wastewater treatment plant is purified using a slow sand filter (SSF) to make it suitable for the irrigation of agricultural land. An important component of this long-established filtration technology is what is referred to as a “biofilm”, a biological layer in the sand filter that contributes significantly to the reduction of microorganisms and the improvement of water quality. This layer must be removed, and the filter cleaned on a regular basis.

In certain terrains, the SSF does not require a pumping mechanism, which makes it an energy-efficient solution. In addition, the water can be distributed to neighbouring farms using simple, inexpensive plastic pipes.

• Type of pilot measure: Real-world testing
• Location: Svaneke, Bornholm island (Denmark)
• Water source: Treated municipal wastewater
• Type of treatment: Slow sand filter (SSF)
• Target water quality: Quality class D according to Directive (EU) 2020/741
• Utilisation: Irrigation of agricultural land in the immediate vicinity of the WWTP
• Return to natural cycle: Infiltration
• Responsible: BEOF – Bornholm’s Energy & Utility Co. A/S
• Operational & open for visitors: Since September 2024

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