Common effluent treatment plants (CETPs) produce sludge that contributes to soil and groundwater pollution, posing significant environmental challenges. This study examines the potential of utilizing CETP waste as a partial substitute for fine aggregate in M20 grade concrete to address disposal issues and promote natural resource sustainability. By evaluating the fractional and microstructural properties of concrete with varying CETP sludge replacement percentages (0%, 10%, 20%, 30%, 40%, and 50%), the research assesses compressive, flexural, and split tensile strength, along with durability tests such as dry and wet durability, sulfate resistance, and chloride penetration. Advanced analytical techniques, including significant elements in CETP sludge, were identified using scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy-dispersive x-ray analysis (EDAX). XRD results revealed that CETP sludge contains phases such as alpha-quartz (SiO2) and anorthite (CaAl2Si2O8), which contribute to the compressive strength and chemical stability of the concrete. EDAX analysis of the produced concrete confirmed the presence of these beneficial phases and elements. The presence of alpha-quartz and anorthite phases, as confirmed by EDAX, suggests that the sludge contributes to the formation of a dense and stable microstructure, enhancing the attributes of the concrete. The inclusion of elements like chromium and iron may provide additional benefits such as improved resistance to corrosion and enhanced durability. Mechanical tests showed that a 10% replacement of fine aggregate with CETP sludge optimizes compressive strength, achieving an average of 21.01 N/mm2 after 28 days of curing, compared to 26.58 N/mm2 for conventional concrete. The tensile strength at 10% replacement was 2.40 N/mm2, slightly lower than the 2.90 N/mm2 of the control, and flexural strength for the 10% replacement mix was 1.61 N/mm2 after 28 days, compared to 2.11 N/mm2 for the control. Slump test results indicated good workability, with a slump value of 100 mm for 10% CETP sludge replacement. This study confirms the technical feasibility and economic viability of incorporating CETP sludge into concrete, potentially reducing fine aggregate costs by 10%, supporting the creation of eco-friendly building materials emphasizes the environmental advantages of waste reduction and resource conservation, and aligning with sustainable development goals by providing a viable solution for waste management and sustainable construction practices.