BROMIDE REMOVAL IN SOURCE WATER BY ELECTROLYSIS – APROCESS FOR REDUCTION OF DBPs IN DRINKING WATER

摘要

Brominated THM specie is seventy five percent of the four regulated TTHM and hasrnsignificantly greater implications, especially DCBM, as drinking water contaminant thanrnchlorinated THM regarding human health. Of the four individual trihalomethanes, only highrnDCBM exposure was associated with spontaneous abortion both alone and after adjustment forrnthe other THMs [1]. This project explored the use of electrolysis with silver electrodes, coated Tirnelectrodes (DSA)* and combination of both to remove bromide from California SWP at PalmdalernWater District Treatment Plant, CA, USA. Herbert Henry Dow used electrolysis coupled with airrnstripping of brine that has high proportion of bromide to manufacture bromine [2]. In surfacernwater treatment, bromide occurs at very low levels and may form very low levels ofrnhypobromous acid (HOBr), hypobromic acid (HBr) and hypobromite (Obr-) ions duringrnelectrolysis especially if the energy provided is below the ionization energy for bromide. Thesernbyproducts are difficult to remove by air or gas stripping and make bromine available to formrnTTHM downstream. With silver electrodes at ambient temperature, silver ions released from thernanode immediately bond directly with all halogens to various degrees depending on theirrnconcentrations, current applied, contact time, and electrode spacing. Minimal amount of oxyhalidesrnare formed and power requirement is low. Varying current density and bromidernconcentration, positioning the electrolytic cell before coagulation and after sedimentation, andrnchanging electrode combinations (Silver/Silver, DSA/DSA, and Silver/DSA as cathode/anodernrespectively), bromide removal was achieved to varying degrees. This process in combinationrnwith enhanced coagulation can be used to substantially extend the life of biologically active GACrnfilter and ensure compliance with the USEPA Stage 2 DBPR, LRAA of 80μg/L TTHM.