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Abstract

The improper management of sewage sludge poses a significant global risk to environmental and public health. In this study, the valorization of sludge as an organic fertilizer for lettuce cultivation was evaluated, offering a sustainable waste-to-resource solution. Sludge from two wastewater treatment plants (Mazouna and El Kerma) were collected between 2019 and 2021. Comprehensive physicochemical analysis was conducted to determine its nutrient value and contaminant levels. In addition, the efficacy and safety of the fertilizer were assessed by measuring lettuce growth and the bioaccumulation of heavy metals in plant tissues. The analyzed sludge, with an organic matter content of 9.91%–83% and dry matter content of 31%–77%, is considered a suitable soil amendment to improve structure and water retention.  The levels of organic and metallic micro-pollutants were trace and below regulatory (AFNOR) thresholds.  Results showed that sludge application can enhance plant dry biomass in the leaves and roofs. Although sludge can increase plant’s uptake of heavy metals, leading to accumulation in aerial tissues, all concentrations remained within safe regulatory limits. These promising results advocate for the agricultural valorization of sewage sludge to improve yields. Integrating this practice into a circular bio-economy can reduce waste volume and mitigate environmental impact.

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