Deposition of manganese in a drinking water distribution system

Abstract

The deposition of manganese in a water distribution system with manganese-related "dirty water" problems was studied over a 1-year period. Four monitoring laboratories with Robbins biofilm sampling devices fitted to the water mains were used to correlate the relationship among manganese deposition, the level of manganese in the water, and the chlorination conditions. Manganese deposition occurred by both chemical and microbial processes. Chemical deposition occurred when Mn(II) not removed during water treatment penetrated the filters and entered the distribution system, where it was oxidized by chlorine and chlorine dioxide used for disinfection. Microbial deposition occurred in areas with insufficient chlorination to control the growth of manganese-depositing biofilm. At 0.05 mg of Mn(II) per liter, the chemical deposition rate was much greater than microbial deposition. Significant deposition occurred at 0.03 mg of manganese per liter, and dirty water complaints were not eliminated until manganese levels were continuously <0.02 mg/liter and chlorination levels were >0.2 mg/liter. A guideline level of 0.01 mg of manganese per liter is recommended.

Evaluation of loose deposits in distribution systems through: unidirectional flushing

“…The second important component found in deposits is organic matter representing 14-24%. Once again, these values were similar to values published elsewhere, which vary from 10% (Zacheus et al, 2001) to 23% (Sly et al, 1990). The organic matter most likely originates from the adsorption of dissolved organic matter escaping the water treatment plants.…”

“…According to Smith et al (1996), the principal form of corrosion deposits is goethite (␣-FeOOH). The iron fraction of deposits from the study sites were in the same range as concentrations found in the literature, which vary from 23% (Sly et al, 1990) to 76% (Gauthier et al, 1996).…”

Diverse manganese(II)‐oxidizing bacteria are prevalent in drinking water systems

“…In this study, we isolated Mn(II)-oxidizing bacteria from a conventional DW system and showed that some of the taxonomic groups are novel and some are abundant in communities of bacteria within a DW system. Although previous studies have isolated Mn(II)-oxidizing bacteria from DW systems (Schweisfurth, 1973;Sly et al, 1988;Sly et al, 1990;Cerrato et al, 2010), they have not reported that such bacteria can be abundant members of DW bacterial communities. These results contrast those of other environments where bacterial Mn(II) oxidation is prevalent but cultured Mn(II)-oxidizing bacteria were at such low abundance that they remained undetected with culture-independent methods (Dick and Tebo, 2010).…”

Assessing taste and visual perception of Mn(II) and Mn(IV)

“…This early standard suggested that manganese in drinking water be limited to 0.05 mg/L, which was a compromise between difficulty of manganese removal and the concentration likely to be tolerated by consumers, i.e., 0.01–0.02 mg/L (USDHEW, 1962). Consumer complaints have also been associated with 0.02–0.03 mg/L manganese, leading to recommendation of lower guidelines for manganese in finished waters (Kohl & Medlar, 2007; Sly et al, 1990).…”