Retention of organic Fe-P-colloids from peat mining water in an overland flow wetland treatment system in northern Finland

Abstract

The importance of dissolved organic matter (DOM) for the organic, Fe and P reductions achieved in an overland flow area (OFA) was estimated and the changes in the nature of DOM studied by gel filtration at a site in northern Finland. In the OFAs peat mining water is purified conducting it across a natural mire of a given size. DOM plays an important role in the transport and reduction of organic matter, Fe and P in OFAs. The retention of Fe in filtrates, dissolved organic P and to some extent also DOM in the OFA under low flow conditions in summer is probably promoted by the high Fe content of the highest apparent molecular (HAMW) weight DOM in the peat mining water. On the other hand, the originally low Fe content of the DOM in the HAMW fraction may be one reason for the generally low reductions in these water quality parameters achieved during flood periods.