Full Description

Effective residuals management is becoming critical as water utilities are implementingtreatment techniques for complying with US Environmental Protection Agency's (USEPA) Maximum Contaminant Level of 10 g/L.This project, funded by AwwaRF, researched bench- and pilot-scale approaches for minimizingresiduals from arsenic absorption technologies such as granular ferric hydroxide (GFH) orBayoxide E-33 absorbers that are used with arsenic-containing groundwater. These strategieswere centered on diminishing backwash volumes from such iron-based sorbents by eitheremploying a prefiltration device to lower the backwash frequency or by treating the backwash toallow for it to be recycled, thus reducing the residual volume requiring disposal. Prefiltrationdevices included cartridge filters or sand columns to remove particles that would have otherwisebeen retained on the absorbers and hence would have triggered a backwash sequence to alleviatethe headloss. Benchscale tests showed that coagulation/sedimentation and bag filtration werevery effective in removing the arsenic detected in the spent backwash, because arsenic remainedattached to the settled or filtered particles. Pilot test results showed that for the prefiltrationtechnique a significantly lower filtration rate than suggested by the benchscale tests would beneeded. Additionally, pilot test results implied that spent backwash treatment bycoagulation/sedimentation would be the preferred method, because the possible carryover ofiron-based media particles during backwash would otherwise quickly saturate cartridge filters. Includes reference, tables, figures.

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Edition: Vol. - No. Published: 11/15/2004 Number of Pages: 16File Size: 1 file , 660 KB