Optimization of sludge recirculation for sustainable water treatment at Ait Massoud dam Morocco

Abstract Treatment plants play a crucial role in producing drinking water, but managing the sludge produced is a major challenge. This study aims to investigate the effect of sludge recirculation on the coagulation-flocculation treatment of water from the Ait Massoud dam. The aim is twofold: to optimize reagent doses in order to reduce treatment costs, and to limit environmental impact by reusing the sludge produced. The results showed that sludge can be used effectively as a flocculant, enabling the polyelectrolyte dose to be reduced from 0.3 to 0.1 mg/L while maintaining the same treatment performance. As a coagulant, sludge also enabled better removal of turbidity and oxidizable matter, while reducing the dose of aluminum sulfate to 30 mg/L. A techno-economic analysis revealed that applying this method on the scale of the plant (6 000 m 3 /h) would result in daily savings of around 3,715 euros, while reducing the disposal of almost 7,200 m 3 /day of sludge, thus helping to reduce the environmental footprint. Although promising, this approach needs to be validated on a larger scale and over the long term, particularly given the variability of raw water characteristics.