AWWA WQTC58901

For many utilities the aesthetic problems that accompany elevated manganese levels are of paramount concern. Unsightly deposits and colored water problems cause innumerable complaints in some systems. Such conditions can occur even when manganese levels are below the 0.05 mg/L secondary standard, causing some utilities to set internal goals of 0.015 or 0.02 mg/L. Results from two projects are presented in this paper. In recent years, the Hyde Park Water Treatment Plant has received customer complaints described as "dirty water" or "pinkish water". In addition, dark brown or black deposits have formed on some of the plant equipment and the walls of the clearwell and a dark sediment/film was observed in a storage tank. These complaints and deposits were determined to be caused by manganese passing through the treatment plant after process changes were implemented to reduce disinfection byproduct levels. Upgrades to the Stamford Water Treatment are currently being designed. The raw water supply is a reservoir that undergoes stratification. During the late summer period, elevated manganese levels caused by anoxic conditions in the bottom waters and taste and odor episodes caused by geosmin and MIB are the major treatment concerns. Manganese is controlled by the induced-greensand effect that occurs when chlorine is added prior to anthracite or sand filters. Conversion to GAC filters to control the taste and odor events may inhibit the induced-greensand effect. Manganese control, although not a health issue, is essential for maintaining consumer confidence. The results of this paper will help utilities that experience difficulty in controlling manganese, and also those utilities that are considering treatment changes to reduce DBPs or control taste and odors to do so in a manner that will not compromise manganese removal. Includes tables.