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The amount of mercury measured in sewage sludge in the Seattle South Treatment Plant has been decreasing since 2000. The average concentration of mercury in biosolids has reduced by nearly 70% since measurements began.
Mercury levels in this King County treatment plant hovered around 2.5 parts per million (ppm) of mercury through the end of the last decade. King County began outreach efforts in 2002 - 2003, and the strongest reduction appears in 2003 – 2004, after mercury-reduction efforts began. Levels have receded steadily ever since.
Mercury in Sewage Sludge/ Biosolids
Biosolids as an Indicator of the Effectiveness of Mercury Reduction Programs
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