Soil amendments using poplar woodchips: an effective strategy for the removal of wastewater-originated contaminants?

Vegetation filters, a nature based wastewater purification technology, have been reported as a feasible solution for small municipalities and scattered populations with limited access to sewage networks. However even when such a technology is properly planned, the leaching of contaminants through the unsaturated zone may occur. The amendment of soil with a readily-labile source of carbon is supposed to ameliorate the removal of contaminants by stimulating microbial activity and enhancing sorption processes. In this study, leaching column experiments were carried out to explore if the addition of woodchips to soil could be a feasible strategy to be integrated in a vegetation filter. The soil was collected from an operating vegetation filter treating wastewater that originates from an office building. The column influent solution was synthetized simulating the real wastewater. The infiltration through the column was monitored by tensiometers. Daily effluent samples were collected and analyzed for NT, PT, COD, EC, pH and redox potential. Preliminary results suggest that soil amendments with woodchips enhance the elimination of wastewater-originated contaminants. In particular, NT was highly removed in the column containing woodchips. Elution of organic carbon as a consequence of woodchips degradation may represent a concern when this material is used with high organic carbon wastewater.