Current status of sludge processing and biosolids disposition in Ontario

Sludge processing and biosolids management represent significant ongoing activities for the wastewater treatment industry. Historically, a substantial inventory of sludge processing technologies and operating practices have been developed within regions to manage sludges and produce products that meet disposition requirements. However, access to system-wide information on sludge handling practices that would be of interest to a variety of wastewater industry stakeholders is often not available. As an example, there is little system-wide information available on the types of sludge processing technologies employed and the quantity and quality of biosolids produced at wastewater treatment plants in Ontario. In the present study quantitative data on sludge handling over the period 2014-2016 was gathered for Wastewater treatment plants (WWTPs) with a hydraulic capacity greater than 1000 m3/day. The types of technologies employed were sorted by the design hydraulic capacity (DHC) of the WWTPs. Data on key biosolids properties (i.e. solids content, pathogen indicators, metals, nitrogen and phosphate) were sorted by WWTP DHC and related regulations. Drivers that are expected to impact biosolids handling practices in Ontario in the future are proposed and discussed in context of the current practices.