Risk of Heavy Metals Transport and Remobilisation by Water Transfer Project: Case of Beni-Haroun Project, Algeria

This study examines the environmental risks associated with the transport and remobilization of heavy metals due to inter-basin water transfer, focusing on the Beni-Haroun to Timgad Dam project in Algeria. Sequential extraction and aqua regia digestion were utilized to evaluate the concentrations and speciation of iron, nickel, and lead in water and decanter sludge before and after water transfer. The results revealed substantial changes: iron levels increased significantly in sludge, rising from approximately 3559.95 mg/kg to a range of 40 765.33–67 262.26 mg/kg after transfer, primarily due to hydroxide precipitation under neutral to slightly alkaline pH conditions. Nickel concentrations in water rose sharply from 81 × 10–5 to 0.263 mg/L in the decanter water and from undetectable levels to 0.206 mg/L in the filtered water, which is attributed to redissolution mechanisms under altered pH conditions. Lead concentrations, while undetectable in the water samples, increased in sludge, peaking at 250 mg/kg, which was due to its precipitation as lead sulphate. These findings underscore the ecological risks posed by water transfer projects, emphasizing the need for sustainable strategies and rigorous monitoring to mitigate heavy metal remobilization impacts on water quality.