AWWA JAW57437

A high manganese (Mn) concentration in sourcewater is a common problem faced by water utilities.Utilities often remove this Mn by oxidationof the manganous ion (Mn2+) to manganese oxide(MnO2(s)) using an oxidant, such as chlorine dioxide(ClO2). Excess MnO2(s) may remain in the water aftertreatment, causing brown staining on plumbing fixturesand laundry. Many water utilities experience Mnproblems from effluent concentrations as low as 20ug/L, leading some utilities to strive for finished waterMn2+ concentrations <10 ug/L. Most studies reportedin the literature have not fully explored oxidation oflow initial Mn2+ concentrations (60-200 ug/L) and thedose requirements of the primary oxidants, ClO2,potassium permanganate (KMnO4), and ozone (O3).The overall objective of this study was to evaluate theseoxidants for the oxidation of low initial Mn2+ concentrationsto Mn2+ <10 ug/L. Bench-scale experimentswere performed by applying different doses of eachoxidant to a raw surface water and measuring Mn2+residuals over time.The study found that it was more difficult to removeMn when the initial concentration was low, regardless ofthe oxidant used. ClO2, however, consistently producedfinal Mn2+ to <10 ug/L, generally within 60-120 s. Alloxidants produced final Mn2+ <10 ug/L when the initialMn2+ concentration was high (1,000 ug/L). The conclusionsindicate that ClO2 may be a viable treatment alternativefor water utilities wishing to reduce Mn concentrationsin finished water to <10 ug/L. Includes 17 references, table, figures.

Product Details

Edition:

Vol. 95 - No. 1

Published:

01/01/2003

Number of Pages:

11

File Size:

1 file , 260 KB