Wastewater treatment plants and disposal applications: Niksar Municipality example

The aim of this study is to determine the technical and environmental suitability of the stabilized sewage sludge obtained from the Niksar Wastewater Treatment Plant in the Niksar district of Tokat province, and to evaluate safe disposal or recovery options. Analyses conducted on the stabilized sludge sample included parameters such as heavy metals (Pb, Cd, Cr, Cu, Ni, Zn, Hg), organic pollutants (PAH, PCB, PCDD/F), pH, moisture content, dry matter, organic matter, nitrogen, phosphorus, and E. coli, in accordance with the "Regulation on the Control of Sewage Sludge for Use on Soil" (2010). The results showed that the sludge does not pose an environmental risk in terms of heavy metals and organic pollutants, although the E. coli level was slightly above the permissible limit, indicating the need for additional stabilization. According to the evaluation carried out in line with Annex 3/B of the Waste Management Regulation, the physicochemical properties and heavy metal levels of the stabilized sludge were found to be below the limits for non-hazardous waste (Class II), although it did not qualify as inert waste. In toxicity tests, the fish bioassay (ZSF = 8) showed no toxic effect, while in the Daphnia magna test, toxic effects were observed at 100%, 50%, and 25% eluat concentrations, as all individuals were inhibited (immobile); however, at 12.5% and lower diluted solutions, no toxic effect was detected since all individuals remained mobile. Furthermore, within the framework of the Regulation on Landfilling of Waste, it was determined that the sludge could be disposed of in a Class II landfill or evaluated through alternative recovery processes.In conclusion, it has been determined that stabilized sewage sludge can be safely managed in terms of environmental and human health, and it can be integrated into sustainable and environmentally friendly disposal or recovery options. In conclusion, it has been determined that stabilized sewage sludge can be managed in a manner that is safe for both the environment and human health, and can be incorporated into sustainable and eco-friendly disposal or recovery practices."