Water quality and filter performance of nutrient-, oxidant- and media-enhanced drinking water biofilters

Abstract

Nutrient, oxidant and media enhancement strategies were applied to pilot-scale biofilters with the objective of enhancing biodegradation to improve effluent water quality (e.g., TOC, DOC, SUVA, THMfp, HAAfp) and filter performance (e.g., effluent turbidity and head loss). While some statistically significant (α = 0.05) differences in DOC removal and DBPfp were identified as a result of specific enhancement strategies, enhancement strategies did not result in improvements in water quality (as measured by TOC, DOC, SUVA and DBPfp) that could be considered of practical operational importance. Water quality improvements were either operationally inconsistent, small in magnitude and/or within the deviation that would be expected from the biofilters when operated under equivalent ambient (i.e., not enhanced) conditions. With respect to filter performance, enhancement strategies also occasionally resulted in a statistically significant difference in effluent turbidity and head loss. However, when identified, statistically significant mean differences in effluent turbidity were deemed not meaningful given the instrument accuracy (i.e., ±0.02 NTU), the relatively small magnitude of the mean differences, or the magnitude of the mean difference observed between biofilters operated under equivalent ambient conditions. With respect to head loss, statistically significant mean differences in head loss that were also considered meaningful given the magnitude of the deviation between ambient biofilters and the accuracy of the pressure transmitters, were largely consistent with the literature; however, the magnitude of the mean differences that showed improvement to head loss were small (10–18 cm), and likely would not be sufficient to substantially extended filter run times to have any practical operational importance.