Treatment performance comparison between regular O(3)–BAC and O(3)–BAC with rear sand filtration: verification in a full-scale study

BACKGROUND: To improve the microbial safety of drinking water, an arrangement of O(3)–BAC with rear sand filtration (O(3)–BAC–sand) has been proposed. In this study, efforts were devoted to evaluate the benefits and drawbacks of O(3)–BAC–sand in a full-scale water treatment plant. The performance of the two configurations was compared in terms of particles, turbidity, COD(Mn) and typical odorants and pesticides. RESULTS: The O(3)–BAC–sand yielded lower turbidity but higher COD(Mn) (by approximately 7%) in the finished water than regular O(3)–BAC (sand–O(3)–BAC). Both systems removed odors in raw water; however, sand–O(3)–BAC was more effective on septic and musty odorants. The total pesticide removals by sand–O(3)–BAC and O(3)–BAC–sand were 78% and 72%, respectively; though the latter had shorter activated carbon durable years. CONCLUSION: The re-location of the sand filter would sacrifice the BAC efficiency in removals of organic matter and micropollutants. This tradeoff is a result of the loss of the particulate organic matter removal by sand filters, because locating the sand filter behind BAC causes particle load increase on BAC; some measures of enhanced coagulation should be suggested to improve the turbidity and particle removal. The study will be helpful for improvement of the O(3)–BAC process in drinking water treatment.