Efficiency of a DAF System in Removing Organic Matter and Lipid Compounds from Municipal Effluent

Oil and grease (O&G) pollution in municipal effluents represents a critical environmental challenge. This study contributes a novel experimental assessment of how pressure and recirculation time influence oxygen transfer, microbubble generation, and pollutant removal in a pilot-scale DAF system, providing new insights into process optimization for municipal wastewater treatment. This study evaluated the efficiency of a DAF system in removing organic pollutants and solids from municipal effluent by varying gauge pressure (1–5 bar) and recirculation time (1–20 min). The initial concentrations present in the effluent were 800 mg/L total solids (TS), 590 mg/L total suspended solids (TSS), 450 mg/L oil and grease (O&G), 360 mg/L biochemical oxygen demand (BOD5), and 710 mg/L chemical oxygen demand (COD). The concentration of dissolved air (interpreted as dissolved oxygen supersaturation) reached 102.3 mg/L and removal efficiencies of 84.4% for O&G, 88.9% for BOD5, 88.7% for COD, and 85% for TSS were achieved, while pH and dissolved solids (DS) remained stable. The saturation factor (f = 0.8) confirmed efficient oxygen-liquid transfer, attributed to the use of Raschig rings in the absorption column. The significance of this work lies in demonstrating that operating conditions directly enhance oxygen dissolution and flotation performance, highlighting an optimization pathway rarely reported for municipal effluents. The results demonstrate that DAF is a robust, stable, and energy-efficient technology capable of effectively removing organic and lipid loads from municipal effluent, providing a sustainable alternative for the pretreatment and reuse of urban wastewater.