Land application of municipal biosolids: managing the fate and transport of contaminants of emerging concern

Abstract

Municipal biosolids provide organic matter to soil, and nutrients essential for crop growth. Some contaminants of standing and emerging concern such as pharmaceutical and personal care products (PPCPs), hormones, brominated flame retardants, and highly persistent perfluoroalkyl acids are not fully removed in the waste treatment process; and thus, they are often found in resultant biosolids applied to land. This paper provides an overview of selected research led by Agriculture and Agri-Food Canada on monitoring and predicting the fate and transport of these noted contaminants in field soil-hydrological environments following land applications of dewatered and liquid municipal biosolids. Different land application practices were examined in the context of their potential to reduce environmental exposure. Field studies of liquid/slurry municipal biosolids demonstrated that in macroporous soils contaminants of all types can rapidly reach shallow groundwater and tile drainage systems. Nevertheless, loads of contaminants in subsurface (tile) drainage can be significantly reduced if an aeration-based pre-tillage is employed. For dewatered municipal biosolids, directly injecting biosolids into subsoil had an indifferent effect upon water contamination, when compared with traditional surface application methods. For very high single applications of dewatered municipal biosolids to land, compounds such as the antifungal miconazole, the PBDE congener BDE 209, and perfluorooctanoic acids, for example, can persist in biosolid aggregates. Yet, for modestly macroporous soils, most of these compounds will not enter critical subsurface water receptors.