The use of post‐filtration contactors for the removal of manganese (Mn) in the dissolved, reduced form (Mn2+ or Mn(II)) by sorption to manganese oxide–coated granular media and catalytic oxidation by free chlorine was implemented at the Lantern Hill Water Treatment Plant in Stonington, Conn., in order to lower disinfection by‐product (DBP) formation while effectively controlling metals. The second‐stage contactors (SSCs) successfully removed Mn at hydraulic loading rates of up to 10 gpm/ft2 with little head loss accumulation and effluent Mn concentrations typically ⩽0.01 mg/L. A mass balance showed similar masses of Mn removed from the water by the SSCs and in the backwash waste (total difference of <10%) during the study period. DBP concentrations were lower than historical concentrations for the plant, with average plant effluent total trihalomethane and five haloacetic acid concentrations of 30 µg/L each. Other treatment goals (e.g., turbidity, iron removal, free chlorine residual) were also successfully achieved.

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The objective of this study was to determine the influence of manganese oxide (MnOx) coated granular media on disinfection byproduct (DBP) formation for dissolved manganese (Mn(II)) and natural organic matter (NOM) concentrations typical in drinking water treatment (DWT). Instantaneous and 24‐h haloacetic acid and total trihalomethane concentrations of influent and effluent samples from two DWT plants, one using MnOx‐coated dual media (DM) filters and the other using second‐stage contactors for Mn(II) sorption by coarse MnOx‐coated ceramic media after DM filtration, were examined. Results showed that interaction with MnOx‐coated surfaces did not increase measured DBP concentrations. Observed increases in 24‐h DBP concentrations for the surface water plant were attributed to filter‐associated NOM, and not the MnOx coating. The findings of this study indicate that a second‐stage contactor – with MnOx‐coated media utilized for Mn(II) removal after a particle removal filter – does not increase DBP formation under typical treatment conditions.