This study examines the effectiveness of Modified Drinking Water Treatment Residue (MDWTR) in removing Microcystis aeruginosa, as well as its collaborative action with Poly aluminium Chloride (PAC) for effective contaminant removal. In addition, the phosphorus adsorption capacities of MDWTR samples with differing particle sizes are evaluated. The results indicate that MDWTR alone has a positive effect on Microcystis aeruginosa removal, with S-type MDWTR(<90µm.) exhibiting the highest removal efficiency. Moreover, when combined with PAC, MDWTR's removal efficiency is significantly enhanced, further validating its efficacy. The analysis of isotherms provides strong evidence for the substantial adsorption capacities of MDWTR samples, with various MDWTR types exhibiting distinct affinities. These results demonstrate MDWTR's potential as adsorbent, Microcystis aeruginosa removing and emphasise its versatility in water treatment applications.