USA, Environmental Protection Agency EPA, Conditioning of fly ash with sulfur trioxide and ammonia, 1975-08, p. 2 ([Internet, 2025-09-19](https://nepis.epa.gov/Exe/ZyPDF.cgi/9101K2Y2.PDF?Dockey=9101K2Y2.PDF))
The management and disposal of excess sludge are emerging issues owing to the high costs associated with treatment. In this study, the viability of a modified bentonite was investigated as a conditioning agent for the stabilisation of heavy metals (i.e., Cu, Zn, Cr, Pb, and Cd) and the retention of nutrient species (i.e., total nitrogen (TN), total phosphorus (TP), available nitrogen (available N), and Olsen-phosphorus (Olsen-P)) in sewage sludge for agricultural use.