Application of used wetland filter media in agriculture - control of heavy metal contents and faecal contamination

Concentrations of heavy metals, bacteriophages and thermotolerant coliform bacteria (TCB) were investigated in light weight aggregate (LWA) filter media collected form four horizontal subsurface flow constructed wetlands in Norway. Comparison of heavy metal contents in these filters did not show any values exceeding the maximum allowable concentrations in organic materials, e.g. sewage sludge, used on cultivated areas (in accordance to Norwegian regulations). Also numbers of thermotolerant coliform bacteria did not exceed the number of 2500 TCB per gram of dry substance (TS), which is limited in such kinds of materials. Bacterial viruses were not detected in filter media.