Selective　adsorption　of　arsenic　in　co-existing　oxyanions　competition　systems　remains　a　significant　challenge　in　water　treatment　due　to　the　limitations　of　adsorbent　materials　that　often　overlook　competitive　adsorption,　resulting　in　an　overestimation　of　their　actual　purification　potential　for　target　contaminants.　In　this　study,　a　novel　hydrogel　bead　adsorbent,　composed　of　water　treatment　residuals　(WTRs)　and　chitosan　(Chi),　was　developed　to　selectively　remove　arsenic,　while　minimizing　the　interference　from　phosphate,　which　is　the　strongest　and　most　representative　competitor　in　multi-oxyanion　systems.　The　WTRs-Chi　beads　(WCB)　adsorbents　were　optimized　by　adjusting　the　ratios　of　WTRs:Chi,　with　characterization　results　indicating　that　increased　WTR　doping　improved　the　degree　of　crosslinking　and　the　formation　of　bidentate　complexes　with　enhanced　electrostatic　selectivity.　Importantly,　the　co-existence　of　phosphate　had　minimal　adverse　effects　on　arsenic　removal　compared　to　other　reported　adsorbents.　The　maximum　adsorption　capacity　for　As　(V)　in　the　binary　system　was　34.12　mg/g,　and　the　adsorption　behavior　was　fitted　well　by　the　pseudo-second-order　kinetic　model　and　the　extended　Langmuir　isotherm　model.　The　experimental　results,　supported　by　X-ray　photoelectron　spectroscopy　analysis　(XPS),　revealed　that　both　As　(V)　and　P　(V)　adsorption　in　the　single　system　were　driven　by　electrostatic　attraction　and　ligand　exchange.　However,　in　the　binary　system,　the　inhibition　of　P　(V)　adsorption　was　attributed　to　competitive　desorption　caused　by　electrostatic　repulsion,　which　hindered　the　formation　of　inner-sphere　complexes.　This　study　provides　a　practical　approach　for　developing　selective　adsorbents　to　address　arsenic　contamination　in　complex　water　environments　and　promotes　the　recycling　of　municipal　solid　waste.