Challenges of Brominated Disinfection By-Products and Options for Stage 2 DBP Compliance

Authors:

  • David S. Briley PE, Cory Hopkins PE, Erik Rosenfeldt PhD, PE - Hazen and Sawyer

Bromide levels have been increasing in some water supplies throughout the Carolinas as well as other parts of the country. Bromide sources range from coal-fired electrical generation plants to other industrial sources. Bromide is not a regulated parameter, so rarely are discharge limits established for these sources. Bromide presents several unique challenges for Stage 2 Disinfectants/Disinfection ByProducts Compliance. Bromide gets incorporated into total trihalomethanes (TTHMs) first by chlorine oxidizing bromide to hypobromous acid. Hypobromous acid is a stronger halogen substitution agent than hypochlorous acid. When significant levels of bromide are present in the raw water, TTHM speciation shifts more towards the brominated species. Brominated species have higher molecular weight, so the mass concentration of TTHMs can increase even if molar concentrations are similar. Also, TTHM formation occurs at a more rapid rate in the presence of hypobromous acid.

Several case studies will be presented for water systems facing increasing bromide levels in their source water. These systems represent a wide range in treatment processes and disinfection techniques (ozone, free chlorine, and chloramines).

One unique approach to DBP compliance uses post-treatment aeration at the water treatment plant as well as tanks in the distribution system. Case studies for water systems that implemented aeration will be presented, including:

1. The evaluation approach utilized to ascertain potential benefits of aeration and select where to aerate within the water system.

2. Review of current trends in aeration system technology

3. Performance data from operating aeration systems installed in clearwells at the WTP as well as aeration systems installed in elevated tanks.

4. Comparison of capital and operation and maintenance costs for various technologies and approaches to aeration.

For more information, please contact the author at dbriley@hazenandsawyer.com.

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Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.

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