Removal of trace metals from municipal sewage sludge: a review
Sewage sludge is a by-product of wastewater treatment. Sewage sludge is a desirable material for application in agriculture production as a fertilizer or soil conditioner, as it is characterized by a high content of organic matter and nutrients such as nitrogen, phosphorus and potassium. However, sewage sludge tends to concentrate trace metals, organic pollutants and pathogenic organisms due to the initial pollutant load of the treated wastewater and the treatment processes. Although various chemical methods can be used to remove trace metals from sewage sludge, the use of microbes is considered a more cost-effective and environmentally friendly approach compared to chemical treatments. This review examines the risks of trace metals in the application of sewage sludge and demonstrates the efficiency of their removal using physical, chemical and biological methods.