The Situation

Biosolids are generated at municipal wastewater treatment facilities all across the US, and are the solids fraction left over after microbial degradation and treatment. Biosolids are highly organic and contain many constituents found in the wastewater stream, including unabsorbed nutrients and pharmaceuticals that pass through the human gut, trace metals from the municipal piping infrastructure, and other materials that enter the sewer system. 

The US Environmental Protection Agency (EPA) governs biosolids land application and the environment from adverse pollutants found in biosolids is governed by a risk-based assessment. Risk is based on whether pollutants can harm humans or the environment, forms of exposure to the pollutants, and what happens after exposure to both an individual and a population.