Delineating multi-phase performance of ozone-enhanced ceramic filter–microfiltration system for treating polluted surface water

Abstract

Pre-ozonation may affect microorganisms in the biofilter and impact the removals of organics and nutrients. This study investigated the effect of pre-ozonation on biofilter-membrane filtration for removing organic matter and subsequent membrane fouling to treat polluted surface water. To mimic seasonal variation on water quality, one-year experiments were divided into five phases, having different organic loadings. A ceramic bead was used as the media in the packed-bed filter. The ozone-treated system achieved the maximum total organic carbon (TOC) removal by 53 ± 7 %, greater than without ozone for the initial TOC of 15–20 mg/L. The effect of pre-ozonation on the removal of organics was more pronounced during the first month (phase I), but gradually diminished in time, probably due to developing refined bioactivities in the media filter. Pre-ozonation substantially reduced the suspended aerobic bacteria count, but thereafter, 4-fold increase in the bacterial count was observed in the ceramic-media filter. The system without pre-ozonation suffered from a rapid increase (ca. 20 kPa within 14 days) in the transmembrane pressure, which required chemical cleaning. Contrarily, pre-ozonation offered relatively stable filtration until 300 days. The difference is attributable to eliminating cake resistance, which is composed primarily of aromatic proteins, by pre-ozonation.