Full‐Scale Implementation of Second‐Stage Contactors for Manganese Removal

Abstract

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.

Self-forming dynamic membrane filtration for drinking water treatment

“…Because the oxidation reaction of Fe(II) is much faster than that of NOM-chlorine reaction, this situation contributes to the control of DBP formation. Similar relationship was shown for manganese (Bazilio et al 2016). Therefore, NOM requires a comprehensive evaluation to select proper treatment alternatives by taking into account water characterization.…”

Influence of manganese oxide‐coated granular media on disinfection byproduct formation

“…The second‐stage contactors (SSCs) are designed for Mn(II) removal only, providing MnOx‐coated surfaces after particle removal by anthracite‐sand first‐stage DM filtration (Figure 2). The majority of Mn(II) removal occurs across the SSCs at Lantern Hill WTP, after nearly complete iron removal and 1–2 mg/L of TOC removal across the DM filters (see Bazilio et al, 2016). The objective of pre‐filter chlorination at Lantern Hill is for Fe(II) oxidation only with a goal of no free chlorine residual entering the DM filters.…”

“…Schematic of the Lantern Hill WTP (Bazilio et al, 2016). kMnO 4 , potassium permanganate; NaOCl, sodium hypochlorite; NaOH, sodium hydroxide…”

“…The 700 gpm (1 mgd) AWC Lantern Hill WTP (Stonington, CT) treats groundwater in a two-stage direct filtration treatment train. The groundwater has 1.5-2.5 mg-Fe/L, 0.15-0.25 mg-Mn/L, 3-4 mg/L TOC, and an average pH of 6.5 (Bazilio et al, 2016). The second-stage contactors (SSCs) are designed for Mn(II) removal only, providing MnOx-coated surfaces after particle removal by anthracite-sand first-stage DM filtration (Figure 2).…”

“…deep bed of coarse ($2 mm) MnOx-coated ceramic media. (Bazilio et al, 2016). kMnO 4 , potassium permanganate; NaOCl, sodium hypochlorite; NaOH, sodium hydroxide…”