Manganese (Mn) in drinking water can cause aesthetic and operational problems. Mn removal is necessary and often has major implications for treatment train design. This review provides an introduction to Mn occurrence and summarizes historic and recent research on removal mechanisms practiced in drinking water treatment. Manganese is removed by physical, chemical, and biological processes or by a combination of these methods. Although physical and chemical removal processes have been studied for decades, knowledge gaps still exist. The discovery of undesirable by-products when certain oxidants are used in treatment has impacted physical-chemical Mn removal methods. Understanding of the microorganisms present in systems that practice biological Mn removal has increased in the last decade as molecular methods have become more sophisticated, resulting in increasing use of biofiltration for Mn removal. The choice of Mn removal method is very much impacted by overall water chemistry and co-contaminants and must be integrated into the overall water treatment facility design and operation.

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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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