Batch Test to Evaluate Microbial Disinfectant Decay...

During 2020 - 2021, when there was less going on than normal, myself and the research group at the University of Waterloo where I did my Master's studies took the time to finally get a draft manuscript that had been sitting on the back burner for a while ready for publication. Now that that has happened, here is a link to that paper.

Title: Batch test to evaluate microbial disinfectant decay and the onset of nitrification

By: Daniel B. Scott;Michele I. Van Dyke;William B. Anderson;Patrick W. King;Peter M. Huck

Journal: Journal of Water Supply: Research and Technology-Aqua

(The paper is open access so you don't need a subscription to read it)


A batch test procedure was investigated to provide insight into the microbial contribution to disinfectant decay in drinking water distribution systems using chloramines. A modified method for determining the critical threshold residual (CTR), the intersection point on a semi-log plot between first-order total chlorine fitted decay curves before and after the breakpoint, was developed. Unlike the CTR as originally defined, initial sample conditions were retained rather than artificially raising the monochloramine concentrations. The CTR calculated with this modified method can more easily be applied to distribution system scenarios. In addition, four types of decay curves were identified and could distinguish differences in the microbial contribution to disinfectant residual decay. This study revealed that chloramine decay batch tests should be evaluated based on decay curve type, decay rates, and the CTR value, in addition to the microbial decay factor, which has been used alone in previous studies. The batch test approach and evaluation criteria established here can be used to predict conditions favorable for rapid chloramine decay and nitrification, and that monitoring and control strategies should be implemented.

Keywords: chloramine, chlorine residual, critical threshold residual, decay curve, microbial decay factor, nitrification

Here are some links to previous posts on my blog that may be of interest:

  • Regarding my Master's thesis
  • Announcing a previous journal article published from that work
  • A case study related to my current job that I presented a few years ago is mentioned and linked at the bottom of this post
  • Revisiting some work I did as a summer student that was included in a conference presentation (related)
  • An R script for the most probable number (MPN) analytical parameter

Aside from the above publication announcement, I also wanted to briefly mention that I recently had the chance to visit Pt. Pelee National Park. It's a place I've wanted to go for quite some time, and it worked out that I had a free evening when I was in southwestern Ontario earlier this month. I hiked a couple of short trails: the marsh boardwalk (pictured below) and Shuster.

Marsh Boardwalk at Pt. Pelee
Point Pelee juts out into Lake Erie. The image on the left is from a model of the Great Lakes in a park in Sarnia, Ontario, and the image on the right is one I took from a flight (Omaha to Newark, I believe) in 2018.