Description

Removal of elevated levels of Mn in drinking water supplies to address aesthetic concerns (staining of laundry and fixtures, discoloration of water) is an ongoing challenge for water suppliers. Earlier AwwaRF studies documented several aspects of the process of removing Mn via sorption to Mn-oxide surfaces on standard granular filter media and subsequent oxidation. This project expanded knowledge of factors affecting this process and examined alternate operation strategies via laboratory and full-scale experiments. The overall goal of this project was to increase knowledge of the control of manganese (Mn) by adsorption to oxide surfaces.
Project objectives included (1) characterizing the nature and Mn uptake capacity of various types of granular media from full-scale plants, (2) evaluating media regeneration requirements, (3) studying impacts of operational variables on Mn removal, (4) conducting case studies of Mn control, and (5) providing guidance to utilities regarding use of oxide-coated media for Mn control.
The research approach consisted of seven tasks: (1) laboratory characterization of media samples from full-scale plants for levels of metal oxide coating, Mn uptake capacity, size, and surface area and microscopic analysis for some samples; (2) laboratory assessment of intermittent and continuous media regeneration; (3) laboratory scale column investigation of operational and water quality variable impacts on Mn uptake; (4) full-scale case studies involving collection of the media samples for Tasks 1 to 3 and documentation of full-scale practice and the results of certain field-scale trials of changed treatment practice; (5) field and laboratory investigation of the impact of pre-filter chlorination on subsequent disinfection by-product (DBP) formation; (6) laboratory and pilot-scale investigation of post-filter contactors; and (7) preparation of guidance for engineers and utilities.