Others coupounds

Heavy metals :

Biosolids also contain heavy metals in very small quantities.
Heavy metals are naturally present in soil. Their concentration depends on the bedrock on which the soil was formed, also known as the natural background.
Heavy metals in soils can also come from atmospheric deposition, manure, slurry, fertilizer or Biosolids spreadings. To avoid unacceptable risk to public health, European member states have set up legal threshold values for different metals in sludge as well as in soils. Most of the time, the amount of heavy metals in the Biosolids spread on land are dramatically below regulatory thresholds.

Furthermore, some metals such as copper and zinc are essential for plant growth.

Quality of sewage sludge (on dry solids) recycled to agriculture (2006) (CEC, personnel communication 2009) from the Environmental, economic and social impacts of the use of sewage sludge on land - Draft Summary Report 1 "Assessment of Existing Knowledge"

Organic compounds:

Biosolids may contain traces of organic compounds. As for heavy metals, limit values have been defined by some European member state to ensure the safety of sludge land application.

Pathogens:

Due to their origin, pathogens are present in the Biosolids. The experience gained though years of practice shows that a properly mastered treatment and a regulated use of Biosolids greatly reduce the risk they pose to human and animal health.

SYPREA, the French association for sludge landspreading, has conducted in 2008 a risk assessment study to determine the exposure to pathogens of the employees in charge of landspreading operations.