Interplay of water temperature and fouling during ceramic ultrafiltration for drinking water production

Abstract

Ceramic ultrafiltration (UF) is an emerging technology for drinking water production, but the interplay and influence of water temperature on fouling is lacking. This research investigates temperatures from 5 to 35 °C and explored the fouling impacts of humic, protein, and polysaccharide substances on a ceramic UF membrane. Water temperature not only affected water viscosity but also altered the fouling behavior of organics. At 5 °C, while approximately 50 % of the change in the unified membrane fouling index (UMFI) was attributed to the change in water viscosity the remaining 50 % was due to change in organic fouling behavior. Conversely, at 35 °C, the overall UMFI decreased relative to the 20 °C standard, of which 36–53 % of the decrease was associated with changes in fouling behavior. Constant flux blocking models determined that standard pore blocking dominated the first filtration cycle for all temperature cases, suggesting that material accumulation inside the pores was responsible for fouling during the initial stages of filtration. The standard blocking continued throughout filtration for 20 and 35 °C suggesting that fouling was mostly reversible. In contrast, at 5 °C condition, fouling transitioned to intermediate blocking, suggesting deposition inside the pores causing irreversible fouling. UMFI and carbon analysis showed lower backwash and chemical cleaning efficiencies at the 5 °C condition indicating higher irreversible fouling mass, while better cleaning was observed at the warmer water temperatures. The exacerbated fouling at low temperatures demonstrates that changes in membrane backwash and chemical cleaning should be implemented under fluctuating water temperature conditions.