Effect of ozone on the combination performance of ceramic membrane ultrafiltration-biological activated carbon filtration

Abstract

Two combination processes, including ozonation-ceramic membrane-biological activated carbon (BAC) (process I) and ceramic membrane-BAC (process II), were tested to treat polluted raw water. The performance was evaluated with the removal efficiencies of turbidity, ammonium and organic matters in a scale of 3 L/d. The effects of ozone on membrane flux and BAC were also considered. More than 96% of turbidity was removed by both combination processes either with or without ozone addition. The ammonium that can be removed by both processes was limited to 1.0~2.0 mg/L. Increasing the dissolved oxygen to 30.0 mg/L can lead to a complete removal of ammonium with the concentration as high as 5.5 mg/L. The average removal efficiencies of the total organic carbon (TOC) and ultraviolet absorbance at 254 nm were 48.3% and 51.8% for process I without ozone addition, 51.1% and 48.2% for process II when ozone dosage was 2.0 mg/L. Ozonation had no effect on turbidity removal, while it resulted in the changes of organic molecular structure at an ozone dosage of 2.0 mg/L and this helped alleviate the membrane fouling. Membrane flux in process I increased by 25%~30% compared with that in process II with no ozone addition. However, residual ozone may affect the microbial activities in the BAC, which impacted the removals of organic matter and ammonia negatively.