Potential priority pollutants in sewage sludge

Sewage sludge has been used as fertilizer for agricultural land over a long time. This is part of a sustainable practice utilizing and recycling the macronutrients back to land. During the last decades, questions have been raised concerning the risks related to heavy metals and xenobiotic organic compounds (XOCs) present in the sludge. Application on land used for agriculture is, therefore, not socially acceptable in some countries, e.g., Sweden. In this study, literature reviews showed that 541 XOCs potentially could be present in sewage sludge due to their presence in e.g. construction materials, pharmaceuticals, personal care products etc. 192 compounds have been quantified in sewage sludge, which indicate that, although many XOCs have been measured in sludge, there are potentially a vast number of compounds present that have not been analyzed for yet. In a hazard identification of the quantified compounds using their inherent properties and environmental fate it was shown that 99 XOCs could be classified as being hazardous with regard to the solid phase and 23 were found to be priority pollutants in the subsequent hazard assessment. The final selected priority pollutants can act as indicators when assessing sludge quality. They were compared with European legislations and discussed in regard for pointing out the need for mitigation such as substitution. Furthermore, the potential need for implementation of sludge treatment trains in order to meet the society's needs was addressed.