Using Existing Cascade Tray Aeration Infrastructure to Strip Total Trihalomethanes

Abstract

To assess the efficacy of using falling‐cascade tray aeration to reduce total trihalomethanes (TTHMs) from potable water, a pilot aerator was constructed and operated in a recirculated mode. In addition, a full‐scale water treatment plant and distribution system serving less than 10,000 people were monitored for eight months while operating a falling‐cascade tray aerator with and without recirculation. Pilot results showed that 56.5 μg/L of TTHMs could be reduced to below the detection limit after five passes through the tray aerator. Full‐scale results showed an approximate 40 μg/L TTHM reduction at several monitoring locations. Although pilot and full‐scale results confirmed that recirculation will not significantly impact THM re‐formation postaeration, both pilot and full‐scale monitoring results indicated that recirculated cascade tray aerators could reduce TTHM content to concentrations below regulated levels. The average increase in operating cost, resulting from an increase in electrical power when recirculating water on site, approximated $850/month.