<p>Granular filtration systems are often used for onsite treatment of greywater. In this study, sand filters modified with the introduction of aluminium-based water treatment sludge were used for treating greywater. Using real greywater, the performance of the modified filters was compared with that of a sand filter in long-term study spanning 73&#xa0;days. The performance was evaluated in terms of the removal of organic matter, nutrients, solids and faecal coliforms with modified filters operated at different hydraulic loading rates (HLR). Results of the study shows that the modification improved the performance of the filters in terms of chemical oxygen demand (COD), phosphate and faecal coliform removals. Best removals were obtained at the lowest HLR used (9 m³/m²/day). At this HLR, the mean turbidity, COD, PO₄³⁻-P and faecal coliform removals were 91, 54, 65 and 99.5%, respectively for this filter which were significantly higher than those observed for the sand filter (89, 39, 32 and 76.9% respectively). The study thus revealed the potential of water treatment sludge for improving the performance of sand filters treating greywater.</p> Graphical Abstract <p></p>