AWWA ACE63032

Compliance needs for the Stage-2 Disinfection Byproducts (DBPs) rule isprompting many water treatment utilities to explore additional DBP precursorremoval beyond enhanced coagulation. The use of biologically active granular activated carbon (GAC) filtersis now becoming popular as an effective means of lowering DBP levels. Tominimize DBP levels by biologically active GAC filter, many water treatmentfacilities are now abandoning the practice of pre-chlorination. Two large watertreatment utilities, one located in Texas and the other located in Arizona, haveimplemented or will soon be implementing such practices.Elimination of pre-chlorination, however, causes iron/manganese (Fe/Mn), ifpresent in source water, to remain in soluble form (due to non-oxidation) passingthrough filtration processes. Upon chlorination of post-filtered water and/orinadequate mixing during caustic addition have caused dissolved Fe/Mn toprecipitate causing yellow or reddish coloration, staining submerged surfacesand/or increasing the turbidity in the finished water. To avoid these waterqualities related issues several treatment strategies were investigated in benchand full-scale settings for these two utilities. Proposed strategies included apreliminary assessment of the fate and transport of Fe/Mn from raw to finishedwater and evaluation of conventional (chlorine, permanganate) and alternative(chlorine dioxide) oxidants to minimize Fe/Mn related issues for the finishedwater. Includes figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2006

Number of Pages:

18

File Size:

1 file , 380 KB