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Mercury in Biosolids/Sewage Sludge

Sewage sludge, often called “biosolids,” is dried-out sewage. Biosolids are often incinerated or used as a fertilizer. Either of these processes may release mercury into the environment.

The amount of mercury in biosolids represents the amount of mercury entering the sewage-treatment works. Not all mercury is captured as biosolids, and it cannot be treated, so it can enter our waterways as effluent from treatment plants.  Further, biosolids are often incinerated or applied to land as fertilizer. Either of these methods of disposal may allow mercury to enter the environment.

Recent tests of biosolids show mercury levels in decline.  There is an especially marked decline since focused elimination efforts began with dentists.  Following are links to information on sampling at three statewide facilities. 

• Mercury in Sewage Sludge/ Biosolids, South Seattle
• Mercury in Sewage Sludge/ Biosolids, West Point, Seattle
• Mercury in Sewage Sludge/ Biosolids, Spokane

Related information

Biosolids as an Indicator of the Effectiveness of Mercury Reduction Programs