Bromide - An Unsuspected Culprit: Assessing Impacts on Stage 2 DBPR Compliance
- Cory Hopkins - Hazen and Sawyer
As utilities adjust to comply with the Stage 2 Disinfectants/Disinfection Byproduct Rule (DBPR), the impact of brominated species of THMs and HAAs are being scrutinized. In the presence of chlorine, bromide is oxidized to hypobromous acid, a stronger halogen substitution agent than hypochlorous acid. When bromide is present in the raw water at levels as low as 100 ppb, DBP kinetics may become accelerated with a direct incorporation of bromide into DBPs. The bromine atom is significantly heavier than the chlorine atom considering that DBPs are regulated on a mass basis. As a result, this discrepancy can significantly increase the risk of a Stage 2 DBPR violation. Other properties of the DBPs are affected by bromine incorporation as well, including Henry’s Law Constants which govern removal of THMs through air-stripping, a post-treatment technique gaining favor for DBP control. Further, conventional treatment practices implemented at many water treatment facilities do not address bromide removal.
Several utilities have observed elevated levels of bromine in their source waters for a myriad of reasons, including industrial discharges, natural sources, and other unknown inputs. Consequently, these utilities have observed significant related impacts to their DBP concentrations and speciation. One utility evaluated recently came across an anomalous, brief period of high bromide levels with correspondingly high levels of THMs in their distribution system. Follow-up sampling designed to confirm the elevated DBPs found bromide was no longer in the source water with more typical DBP levels. As utilities prepare for Stage 2 DBPR compliance, the impact of bromine species can be exacerbated in certain situations.
This presentation will provide background information regarding formation of brominated DBPs and the potential, associated regulatory compliance challenges. Case studies outlining utility experiences with brominated DBPs and solutions will be provided for understanding and mitigating these associated impacts.
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