Treatment of log yard run-off in an infiltration wetland

To protect timber stored for industrial use, sprinkling is often used in the Nordic countries to minimise fungal and insect attack and drying of timber. Log yard run-off from timber sprinkling can be harmful for the water recipient due to i.e. eutrophication and oxygen depletion. A wetland system for treatment of log yard run-off is being evaluated in central Sweden. To examine the potential purification capacity of a sloping couch grass field, log yard run-off was applied to the field through a sprinkling system. Despite high irrigation intensities, up to 66 mm/d, no surface flow occurred; instead the field functioned as an infiltration wetland. Water samples were taken from groundwater pipes in the field during four summer seasons (May to September, 2002-2005) and analysed for Total Organic Carbon (TOC), phosphorus (P), nitrogen (N), and phenols to evaluate the purification capacity of the infiltration wetland. Results from 2002 to 2004 were compared with results from 2005 when the irrigation intensity was considerably lowered. Overall, the results showed good purification capacity even if the sustainability of the system was uncertain considering the limited plant uptake of P. The reduced hydraulic load did not increase the purification