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

BACKGROUND

To improve the microbial safety of drinking water, an arrangement of O-BAC with rear sand filtration (O-BAC-sand) has been proposed. In this study, efforts were devoted to evaluate the benefits and drawbacks of O-BAC-sand in a full-scale water treatment plant. The performance of the two configurations was compared in terms of particles, turbidity, COD and typical odorants and pesticides.

RESULTS

The O-BAC-sand yielded lower turbidity but higher COD (by approximately 7%) in the finished water than regular O-BAC (sand-O-BAC). Both systems removed odors in raw water; however, sand-O-BAC was more effective on septic and musty odorants. The total pesticide removals by sand-O-BAC and O-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-BAC process in drinking water treatment.