Water scarcity is an increasingly critical global issue, particularly in arid regions like Morocco. Innovative approaches, such as the use of alternative water sources like landfill leachate, offer promising solutions. In this study, phosphate washing sludge was used to treat landfill leachate with the aim of producing irrigation-quality water and recovering nitrogen from the resulting sediment. A total of 40 L of raw leachate was treated with three concentrations of phosphate washing sludge (25%, 37%, and 50%). This volume was processed at the laboratory scale as a proof of concept for potential larger-scale applications. After 24 to 36 h of mixing and agitation, the mixture underwent sedimentation, yielding clear supernatants and nitrogen-rich sludge pellets. These pellets showed a significant increase in organic matter content, from 6.4% to 13.5%, representing an enhancement of 110.9%, thus demonstrating partial leachate depollution and organic matter enrichment. Microbiological analyses revealed a 98.9% reduction in fecal streptococci. The supernatants met irrigation water standards in terms of pH and electrical conductivity, and phytotoxicity tests on maize seeds confirmed their suitability for irrigation. Additionally, the recovered nitrogen-rich sediment presents a valuable input for composting and soil amendment.