Copper and Molybdenum Source Tracking

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City of Prince George

Limits on trace element concentrations in biosolids, including copper and molybdenum, help ensure the suitability of biosolids for beneficial use in land application.  With many years of experience in managing biosolids and working with biosolids generators, SYLVIS helped the City of Prince George identify inputs of copper and molybdenum to the local wastewater system to aid in improvements in biosolids quality and suitability for land application.

The Organic Matter Recycling Regulation in British Columbia limits the concentration of key trace elements in biosolids destined for application to land.  The City of Prince George measured increases in copper and molybdenum concentrations in their biosolids that could impact their ongoing successful biosolids land application program.  Locating the sources of these elements at the level of the wastewater system was initiated to allow for measures to reduce these inputs and improve biosolids quality.

Already at work in the operational aspects of biosolids land application in the region, SYLVIS was retained by the City of Prince George to investigate copper and molybdenum inputs to the wastewater system.  These sources could be due to a variety of inputs to the system, with different timings and locations of “hot spots” across the city sewer system.

SYLVIS reviewed the City’s wastewater system layout and designed a phased series of wastewater sampling events to locate inputs of copper and molybdenum reaching the wastewater treatment plant.  SYLVIS also interviewed many potential dischargers within the city to assess the prevalence of certain likely input activities

SYLVIS was able to identify a small number of probable sources of these elements to the final biosolids production process.  Future regulation, outreach, and changes to wastewater treatment processes should ensure that trace elements are kept well below regulatory limits and allow the City’s successful management program to continue.