The surface flow wetland consists of a series of 10 ponds covering an area of 8 ha, holding up to 52,200 m3 of water. An aerial photo of the wetland system can be found on the Eniro (2012) website. The GPS coordinates are; N 59.21436, 12.862 E15.21166, 12.699. The depth of the ponds is on average 0.4–0.6 m with the exception for the 1st pond which has a depth of 1 m. The wetland is intermittently loaded, in most cases when the leachate ammonium nitrogen concentration is below 100 mg/l (Supplementary information Table 1). In 2005, three sediment traps were constructed at the inlet of pond 1. In pond 1, sediment was also excavated during late 2007 and the pond was divided into two ponds with an overflow. Further information on the design, operation and performance of the wetland can be found in Waara et al. (2008)