Fensholt Field Case 2A full-scale experimental drainage P-filter system was established at the Fensholt catchment and near the town of Odder, Denmark. The system is fed with tile drainage water from an arable field of ca. 25 ha with loamy soils that had developed on Weichselian glacial till. The filter system is dimensioned to handle only part of the drainage water (8.3% of the drainage runoff in the first half of 2020).
The filter system consists of the following main units:
- a pump feeding drainage water from the collector drain into the filter system at flow rates of typically 1 – 1.5 l/s.
- a WaterCare A/S DPF sediment filter of 1000 l capacity which has the function of retaining small particles and thus particulate P.
- KrohneTM electromagnetic flowmeter that measures the actual amount of water transported through the WaterCare A/S sediment filter unit.
- a flow divider for directing ca. 10% of the incoming drainage water to the reactive filter for dissolved P.
- a CGK group BV filter box containing 50 kg of iron coated sand (ICS).
- a flow meter at the outlet of the filter box.
Three ISCO™ samplers for continuous automated water collection are positioned at the inlet (ISCO1), between the sediment and reactive filter (ISCO2) and at the outlet (ISCO3). Total P (TP), total dissolved P (TDP), turbidity, pH and EC are measured in the lab on time proportional samples.