Control of seasonal organic contaminants in water sources for drinking water production has traditionally relied on adsorption processes by using Powdered Activated Carbon or time-based replacement of Granular Activated Carbon filters. With the aim to determine whether full-scale biologically-active filters are capable of controlling the spike of atrazine in source waters heavily impacted by agricultural run-off, two GAC filters were monitored for 15 months. During this period, one filter aged from zero to 14 months old (new filter), and the second one from 24 to 39 months old (spent filter). A LC/QTOF methodology, utilizing an integrated scientific information system, was applied to monitor atrazine in raw water and well as individual filter influents and effluents. An automatic post-data acquisition metabolite identification workflow was established to identify potential transformation products of atrazine resulting from biological activity. This workflow was validated by spiking QA/QC samples with suspected transformation products (i.e., hydroxylatrazine, desethylatrazine, desisopropylatrazine, desethylhydroxyatrazine). In the spent filter, atrazine removal during the planting seasons decreased from 60% to 20% (filter two to three years in operation). An increase in atrazine concentration was continuously observed in the effluent during the baseline season (in between planting seasons 2015 and 2016). All the validated transformation products with the exception of hydroxyatrazine were found to also increase in this effluent during the baseline period, suggesting that desorption from media or biological transformation could be occurring in the biofilter. In contrast, the new filter presented a steady decline in the removal of atrazine during the 15 months monitoring (100% to 45%) as well as for the other compounds currently identified. Additional results from the investigation of the presence of other transformation products and further differences in the quality of the filter effluents, based on multivariate statistical analysis, will be discussed in the presentation.

When does a GAC filter become a biofilter for removing seasonal trace organics? Application of LC/QTOF analysis to evaluate (bio-)filter performance

253rd National Meeting (2017)

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