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

This study compared a standard Direct Filtration process (DFSTD) with a similar process that incorporated dissolved air flotation into a flocculation basin (DFDAF) to mitigate the effect of particle loading events on filter run time and water quality. Pilot tests evaluated coagulant (0–20 mg/L as FeCl3) 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/ft2 (5.4–5.8 m/h). With an influent turbidity of 20 NTU, DFDAF consistently extended filter run times (48–55 h) compared to DFSTD (< 18 h), while meeting filter effluent water quality goals. Polymer addition during DFDAF resulted in a thicker sludge blanket, enhanced solids removal (NTU, Fe, and TSS), organics removal meeting enhanced coagulation requirements (TOC and UV254), and floc/particle accumulation in the upper filter layers rather than throughout the media. Continued development could prove the DFDAF process as feasible for full‐scale implementation.