Do biosolids contain heavy metals and toxics?
Biosolids that are created in wastewater collection facilities usually contain low levels of heavy metals. Due to the implementation of industrial pretreatment programs at most municipal collection plants, metal concentrations in the resulting biosolids have decreased dramatically in the last two decades. The metals that do exist in biosolids after treatment are usually measurable, but these concentrations are at levels far below state and federal standards. Many of the trace metals that exist (nickel, iron, selenium, and zinc) are micronutrients that are required for healthy animals and plants. Laboratory research has also showed that organic compounds that result from pesticides and polychlorinated biphenyls (PCBs) are usually present in very low concentrations or are undetectable. Only biosolids that meet certain regulatory criteria are permitted for land application.
