Application of downflow floating medium flocculator/prefilter (DFF) - coarse sand filter (CSF) in nutrient removal

In this study, the applicability and the advantages of the downflow floating medium filter (DFF) in wastewater treatment were examined. The experimental results indicated that the DFF with in-line flocculation addition is a good pretreatment unit to reduce phosphorus load (up to 80-89% removal). The DFF also resulted in uniform filterable-flocs of 32-42 µm throughout the filter run. Thus it can also successfully be used as a flocculator. The backwashing of floating medium was achieved with a small quantity of water and at low backwash velocity. The introduction of floating medium filter bed on top of a coarse sand filter unit (CSF) increased the filter run time and removal efficiency (more than 87 and 94% of NH₃-N and T-P removal respectively), particularly at a low filtration rate (5 m³/m².h).