The role of chloramines in enhancing soluble manganese removal by manganese contactors by W.R. Knocke, A.M. Weber, P.H. Hargette and E. Odom

Abstract

Manganese (Mn) contactors have previously been shown to be quite effective in removing dissolved Mn from drinking water. To date, the contactor media have been regenerated by the application of free chlorine, either continuously in the contactor-applied water or via offline regeneration. This research study was the first to evaluate the potential role of chloramines for the online regeneration of MnOx(s)-coated contactor media. Testing initially at the bench scale and then subsequently over 6 months at the pilot scale demonstrated that chloramines were quite effective at promoting significant media regeneration. Pilot-scale data showed that the presence of chloramines addressed approximately 80% of the media regeneration requirements, allowing for the addition of free chlorine following media backwashing to address the remaining oxidant needs for media regeneration. Hydraulic loading rates of up to 39 m/hr (16 gpm/ft2) could be employed and still produce highly effective Mn removal. The means by which these research results can be applied to other water treatment situations are also discussed.