Environmental Impacts Associated with the Land Application of Municipal Biosolids

Municipal biosolids (MBs) contain fecal contaminants making them a potential non-point source contributor to water quality degradation. Ontario regulations classify MBs as being CP1/CM1 or CP2/CM2 based on pathogen/metal loads. The transfer of nutrients, metals and bacteria through soils and leachate were monitored over time following land application of MBs. A significant increase in nitrate and total-P in leachate was observed in plots receiving MBs suggesting impact to surface water. Host-specific Bacteroides spp. markers were detected up to one month in soils receiving CP2 MBs, but not in leachate, suggesting their use in source tracking is better suited to recent pollution events or following surface runoff. Illumina sequencing analysis of the MBs plasmid metagenome identified various antibiotic resistance genes and mobile genetic elements highlighting the need for future research to focus on the ability of resistant genes to be transferred between environmental bacteria following the land application of MBs.