Chlorine residuals in Flint: Continued improvements

Flint residents have been asking, “Since the automated flushing stopped in November, have chlorine levels dropped because the water is not moving through the system as quickly?” 

The expectation is “No.”  Cold weather improves nearly all aspects of water quality, because lower temperatures reduce corrosion rates, slow bacteria growth, and stabilize chlorine disinfectant levels in water. On the basis of our experience with dozens of water systems in cold northern states, chlorine residuals tend to be highest in the winter and bacteria levels lowest.

To examine this question for Flint we provide two datasets.

The first is my own chlorine data collected at 3 am from my home away from home in Flint (i.e., LeeAnne Walters’ house).  Yes, I also take baths in Flint water while I am there — thankfully I have never had a problem with the rashes that afflict some residents. This house has one of the worst problems getting a chlorine residual that I have ever seen.  In summer 2015 to spring 2016, we could not get any detectable chlorine in this house, even if I ran the water continuously (Figure 1).  But in August 2016 (with flushing), or January 18, 2017 (without flushing), chlorine levels were in a satisfactory range, especially considering that the data is from a 3 am sample.  In our experience, 3 am is the worst case because that is the time of least water use across a city. This house had an automated flusher right next to it in August 2016, so it would be expected to show amongst the greatest differences with and without flushing.

Figure 1. Free chlorine at Flint house at 3 am. (Note: For the Feb 2016, chlorine was non-detectable at both midnight and 6 am, and was therefore assumed to be zero at 3 am).

Heterotrophic aerobic bacteria levels have also plummeted at this house.  The recent levels in August 2016 and January 2017 were undetectable to ≈ 500 cfu/mL, compared to the very high levels we found in August 2015 of ≈ 500,000 cfu/mL or moderately high levels in February 2016 of ≈ 7,000 cfu/mL.

The second set of data was collected by EPA from all of their standard distribution system monitoring sites located around Flint, and they were kind enough to share it with me. I made a histogram graph (Figure 2) to compare a hot month (Aug 2016) with the automated flushing on (red line) versus early December 2016 after flushing had been turned off for several weeks.  Put simply, the recent data from December shows much higher chlorine without flushing, compared to chlorine residual data from August with automated flushing. The average chlorine has increased from 0.83 mg/L in August 2016 (with automated flushing) to 1.3 mg/L in December 2016 (without automated flushing). The key reason is that temperature dropped from 23 down to 12° C.  Because temperatures have been getting even colder since,  things should continue to improve.


Figure 2. Free chlorine monitoring data from the Flint water system in August 2016 (n = 161) with automated flushing, compared to December 2016 (Dec 1-20) when automated flushing was turned off (n = 54). Chlorine levels are much higher in cold weather, even when automated flushing is turned off.

The EPA and the State will keep monitoring the situation closely. Bacteria levels were dramatically improved in Summer 2016 versus Summer 2015 based on our monitoring. If automated flushing is adopted again in summer 2017, even more improvements in chlorine and bacteria levels are possible.

In Flint MI and elsewhere, the “good news” that higher chlorine brings in terms of controlling potentially harmful bacteria, also brings “bad news” in the form of aesthetic problems.  Chlorine can irritate skin and smells like….well, chlorine. Given the trends in data above, Flint residents now perceive that chlorine levels are higher than they have been historically. That is not just a perception– that is a reality.  In general, chlorine in Flint, has historically been lower than is desired, and also lower than is common in many other cities. Now that chlorine levels are returning to levels considered normal and desirable for bacteria control, Flint residents are noting the change.

What can be done to reduce the irritation due to chlorine, which is one of the most common consumer complaints about drinking water nationally? The state provided lead filters do remove chlorine taste from the water which is used for cooking or drinking. If the chlorine is causing irritation in the shower, inexpensive shower filters do exist that can help although we do not officially recommend such filters, because they could potentially grow some harmful bacteria in a shower device designed to create aerosols that could increase human health risks. We consider purchase of such shower filters to be a personal choice.  Whole house filters can also remove chlorine, but this potentially allows harmful bacteria to grow throughout the entire volume of the building plumbing system.

Primary Author: Dr. Marc Edwards

Acknowledgements: Siddhartha Roy

Reflections on the Flint Water Heater Sampling Trip (June 2016)

For two weeks at the end of June, the Flint Water Study Team led a sampling effort which included a 14 person “sampling team,” which traveled to Flint, MI to collect samples, and an 8 person “lab team,” that stayed behind to process the samples. The purpose of this study was to look for the presence of Legionella bacteria in the homes of Flint residents – especially in the water heaters and hot water taps – located near the McLaren and Hurley Hospitals. We also wanted to determine if a simple water heater flushing protocol could be used to improve hot water quality. During the effort we sampled kitchen and bathroom taps, water heater drain valves, and cold flushed water from the distribution system at a total of 32 homes.

When the students were not knee deep in sampling, they got a chance to explore the Flint community. One of the community helpers with Orchard Children Services, Mr. Ronnie Russel, took the team to Bertson Field House to get a great lesson on Flint history from Mr. Bryant “BB” Nolden, a community hero. The team watched the weekly community baseball game, along with some delicious barbeque chicken and popsicles (thanks Mr. Ronnie). The students appreciated the good people, food, and music in preparation for another week of sampling.

Although sampling is over, the residents, plumbers, and volunteers we were able to connect with will never be forgotten. We would like to give a big thanks to all of the homeowners who volunteered in this effort. We’d also like to thank all the volunteers from Orchard Children Services and the plumbers who helped us every step along the way. This study could not have been conducted without them. Finally, we have to give a huge thank you to MDEQ for helping us with scheduling and for providing residents with answers to any questions they had.

We’re working on getting this data processed right now, and will post a summary as soon as we have it. Stay tuned!

Primary Author: Taylor N. Bradley

Acknowledgements: William Rhoads

Round III of Flint Lead-in-Water Testing Schedule (July 11-19 2016)

We are excited that testing begins on Monday, July 11th. Here is our testing schedule:

Week of July 11th

Woodside 1309 E. Court St.

Monday, Wednesday and Friday // 5-7 pm
Tuesday and Thursday // 11am-1pm

Saints of God Church 2200 Forest Hill Ave.

Monday, Wednesday, Friday // 11am-1pm
Tuesday and Thursday // 5-7pm

Week of July 18th

Woodside 1309 E. Court St.

Monday //11am-1pm
Tuesday // 5-7pm

Saints of God Church 2200 Forest Hill Ave.

Monday // 5-7pm
Tuesday // 11am-1pm

The last date for test kits to be turned in is July 19th. If you need a pick up or have any questions, please call LeeAnne Walters on 616-212-6233.

We want to give a big thank you to Woodside Church and Saints of God Church for donating space to us again for this round of testing.

Round III of Flint Lead-in-Water Testing (July 2016) Announcement

Hi Everyone!

We are getting ready to start the third round of Virginia Tech testing for Flint citizens who participated in the previous two rounds. The testing dates are July 11th through July 19th. We will post an update next week with the times and places for kit pick up. If you need to schedule for a kit drop off please email me at (or on Facebook). As a thank you for your participation and helping us gather this valuable data from the same homes sampled in August 2015 and March 2016, again Marc Edwards is giving $20.00 cash once your kit is returned during the dates listed above. We are so excited to be doing this again! Thank you again for your participation, and thanks to the EPA for providing us funding to re-sample and see the status of lead in Flint water!

— Lee

See more info on this effort here.