AWWA WQTC62505

AWWA WQTC62505 Bromide Removal In Source Water by Electrolysis - A Process for Reduction of DBPs in Drinking Water
Conference Proceeding by American Water Works Association, 11/01/2005

Labisi, Bo; Sutherland, Justin

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Brominated trihalomethane (THM) specie is seventy-five percent of the four regulated total trihalomethane (TTHM) and hassignificantly greater implications, especially DCBM, as drinking water contaminant thanchlorinated THM regarding human health. Of the four individual trihalomethanes, only highDCBM exposure was associated with spontaneous abortion both alone and after adjustment forthe other THMs. This project explored the use of electrolysis with silver electrodes, coated Tielectrodes (dimensionally stable anode) and a combination of both to remove bromide from California SWP at PalmdaleWater District Treatment Plant, California. Herbert Henry Dow used electrolysis coupled with airstripping of brine that has high proportion of bromide to manufacture bromine. In surfacewater treatment, bromide occurs at very low levels and may form very low levels ofhypobromous acid (HOBr), hypobromic acid (HBr) and hypobromite (OBr-) ions duringelectrolysis especially if the energy provided is below the ionization energy for bromide. Thesebyproducts are difficult to remove by air or gas stripping and make bromine available to form TTHM downstream. With silver electrodes at ambient temperature, silver ions released from theanode immediately bond directly with all halogens to various degrees depending on theirconcentrations, current applied, contact time, and electrode spacing. Minimal amount of oxy-halides are formed and power requirement is low. Varying current density and bromideconcentration, positioning the electrolytic cell before coagulation and after sedimentation, andchanging electrode combinations (Silver/Silver, DSA/DSA, and Silver/DSA as cathode/anoderespectively), bromide removal was achieved to varying degrees. This process in combinationwith enhanced coagulation can be used to substantially extend the life of biologically active granular activated carbon (GAC)filter and ensure compliance with the US Environmental Protection Agency Stage 2 DBPR, LRAA of 80g/L TTHM. Includes 11 references, tables, figures.