Incorporating DAF Into Flocculation Process to Enhance Particle Removal During Intermittent Events

ABSTRACT This study compared a standard Direct Filtration process (DF STD ) with a similar process that incorporated dissolved air flotation into a flocculation basin (DF DAF ) to mitigate the effect of particle loading events on filter run time and water quality. Pilot tests evaluated coagulant (0–20 mg/L as FeCl 3 ) and cationic polymer (0–1 mg/L) dosing under varied influent turbidity conditions (0.5–20 NTU) at a fixed DAF recycle ratio (9.5%–10%) and hydraulic loading rate 2.2–2.4 gpm/ft 2 (5.4–5.8 m/h). With an influent turbidity of 20 NTU, DF DAF consistently extended filter run times (48–55 h) compared to DF STD (< 18 h), while meeting filter effluent water quality goals. Polymer addition during DF DAF resulted in a thicker sludge blanket, enhanced solids removal (NTU, Fe, and TSS), organics removal meeting enhanced coagulation requirements (TOC and UV 254 ), and floc/particle accumulation in the upper filter layers rather than throughout the media. Continued development could prove the DF DAF process as feasible for full‐scale implementation.