Effect of Media on Biofilter Performance Following Ozonation of Secondary Treated Municipal Wastewater Effluent: Sand vs. GAC

Abstract

Ozone has been shown to be effective in the transformation of several chemicals of emerging concern that escape the wastewater treatment process, but there is concern whether toxic transformation products are formed. Two parallel biofilter columns with granular activated carbon (GAC) and filter sand following a pilot-scale ozone unit to treat secondary treated municipal wastewater were studied. Results show reduced wastewater genotoxicity following ozonation and further reduction following biofiltration. The BAC biofilter outperformed the sand biofilter in terms of reduction in both organics and genotoxicity. Biofilter performance correlated with biological indicators (dissolved oxygen reduction and effluent E. coli counts) but not with ATP bioactivity measurements. Limited bacterial (E. coli) regrowth was observed in treated effluent from both biofilters.

Treatment of Specific NDMA Precursors by Biofiltration

“…TOC removal was low compared with other biofiltration studies involving treated wastewater where removal was >40% (Reaume et al 2015, Farré et al 2011, Reungoat et al 2011), but these studies involved pre‐ozone. TOC removal in this study, under the limiting phosphorus condition, is comparable to biofiltration for drinking water where TOC removals were 6–26% for sand and mixed‐media (anthracite, sand, garnet) biofilters (Zearley & Summers 2012, LeChevallier et al 1992).…”

“…Removal was variable and attributed to both biotransformation and sorption. Ozone‐BAC (O 3 ‐BAC) has also been shown to remove more than 50% of precursors contributing to NDMA chloramine formation potential (Liao et al 2015, Gerrity et al 2014) in addition to removing substantial organic carbon and reducing many trace organics to below detection levels (Reaume et al 2015, Gerrity et al 2014, Reungoat et al 2012, Farré et al 2011, Gerrity et al 2011, Reungoat et al 2011), which is important for water reuse applications. However, the presence of ozone‐reactive NDMA precursors could pose a problem for O 3 ‐BAC.…”

Treatability Studies on the Optimization of Ozone and Carbon Dosages for the Effective Removal of Contaminants from Secondary Treated Effluent

“…Ozonation had a great effect on the operational performance thus resulting in a better reduction. Furthermore, GAC (with an average removal of 96%) performed better than sand filter (with the average removal of 47%) [54]. As predicted, it had a great influence on the reduction of contaminants from the wastewater.…”

Analysis of design criteria for biological post-treatment of ozonated wastewater treatment plant effluent

“…10 and 40%. 6,19,65,68,72,79 Four out of five studies that directly compared non-adsorptive filters and BAC filters found an increased removal efficiency up to twice as high for the latter. 22,68,72,79 No relevant removal of DOC was reported for MBBR.…”