Effectiveness of Tank Aeration for Stage 2 DBP Compliance

Authors:

  • David S. Briley PE, Allison Reinert, Erik Rosenfeldt PhD, PE - Hazen and Sawyer
  • Tiffanie Hawley - Cape Fear Public Utility Authority

Aeration is gaining interest as lower cost alternative for Stage 2 DBP Rule compliance as compared to other compliance strategies. This method utilizes gas transfer principals to physically strip volatile THMs from finished drinking water and achieve reductions of 25 – 45 percent.

But, aeration is certainly not a panacea. One critical consideration for implementation of aeration is where to locate aeration treatment; at the water treatment plant, in tanks in the distribution system, or both.

Aeration at the water treatment plant provides for TTHM reductions throughout the distribution system but, the size of the aeration system is larger, which affects capital and operating costs. Tank aeration systems in the distribution system can be more cost-effective since the systems are treating a smaller flow. However, aeration in a distribution system tank does not necessarily correspond with significant THM reductions at all Stage 2 monitoring locations.

By carefully considering system hydraulics aided by a calibrated distribution system model, along with a firm understanding of THM formation kinetics and the benefits and limitations of in-tank aeration for THM stripping, a methodology for evaluating the true impact of these technologies as Stage 2 DBP Rule compliance strategies has been developed.

Several case studies will be presented for water systems that have implemented post-treatment aeration. The case studies will present:

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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