PHYSICOCHEMICAL, ELEMENTAL AND SPECTROSCOPIC CHARACTERIZATION OF SEWAGE SLUDGE FROM THE JIJEL WASTEWATER TREATMENT PLANT (ALGERIA) FOR AGRICULTURAL VALORIZATION

Abstract

Agricultural valorization of sewage sludge represents a sustainable management strategy that contributes to nutrient recycling and soil improvement. However, its safe use requires comprehensive physicochemical and mineralogical characterization. This study aimed to characterize sewage sludge collected from the Jijel Wastewater Treatment Plant (northeastern Algeria) using physicochemical analyses combined with X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS). The sludge exhibited a near-neutral pH (6.76), moderate electrical conductivity (1.77 mS cm⁻ 1 ), high organic matter content (54.11%), and appreciable concentrations of nitrate and phosphorus. XRD analysis identified quartz as the dominant crystalline phase, together with calcite and feldspars. XRF revealed that calcium, silicon, iron, aluminum, phosphorus, and potassium were the predominant elements, whereas Zn, Cu, Cr, Ni, As, and Pb were detected at relatively low concentrations. FTIR confirmed the coexistence of mineral and organic constituents, while SEM observations revealed a heterogeneous and porous microstructure consistent with the EDS elemental composition. The complementary analytical approach demonstrated that the Jijel sewage sludge possesses physicochemical and mineralogical characteristics compatible with agricultural valorization. Nevertheless, its practical use should comply with applicable environmental regulations and be supported by further agronomic and environmental assessments under field conditions.