drinking water

Why is it possible that Flint River water cannot be treated to meet Federal Standards?

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The key problem is that water from the Flint River is highly corrosive to iron and lead, and, unfortunately, these pipe materials are widely used throughout Flint. Herein, we discuss the higher corrosivity of Flint River water to iron, and the associated problem maintaining chlorine disinfectant in the system.

Why is Flint River water more corrosive compared to Detroit water? Flint River water has about 8 times more chloride (Cl–) in it than Detroit water. Chloride is generally considered to be very corrosive to iron. For instance, chloride present in road salts applied in the winter causes iron in cars and bridges to rust. Detroit also adds a corrosion inhibitor chemical (orthophosphate) to their water that helps to reduce corrosion of metals such as iron and lead. So, current Flint water is not only more corrosive, but there is also no corrosion inhibitor present.

Iron corrosion can cause a serious problem for meeting Federal standards using Flint River Water, because iron corrosion consumes chlorine. Chlorine is added to the water to prevent growth of microorganisms that cause disease, and maintaining a chlorine residual is the best way to protect public health against human pathogens.

To illustrate how iron corrosion is problematic for maintaining a chlorine residual, we collected a sample of Flint water. We put some of that sample into a clean glass container, and some more of it into an identical container with a piece of iron to simulate the effect of water on iron pipes in Flint. We then measured the decay of chlorine over time (Figure 1). The initial level of chlorine was 1.15 milligrams per liter (mg/L), and it stayed pretty high when it was in a glass container. It only dropped to 0.95 mg/L over 12 hours (blue line). Thus, if Flint had a glass (or plastic or concrete) pipe system, chlorine would stay high as it was transported to homes. But when we did the same test with iron present, the chlorine dropped faster due to the corrosion, and was all gone after only 12 hours (red line). After 6 days of doing the test, the chlorine dropped even faster, and was below the minimum required chlorine residual of 0.2 mg/L in just about 1 hour in our test system (green line). The key point is that Flint River water is corroding iron pipes, and that will cause the chlorine to disappear very quickly.

Figure 1: Decaying of free chlorine in Flint River water with and without iron
Figure 1: Decaying of free chlorine in Flint River water with and without iron

When we did the exact same test using water from Detroit (collected on the outskirts of Flint), the chlorine in the container without the iron stayed high at about 0.6 mg/L over a 12 hour test (blue line below). When iron was present, chlorine dropped, but much slower than in the Flint River water (red line and green line). Ironically, Detroit water started with only about 60% of the chlorine initially present in Flint water, but ended up with much more chlorine after 12 hours because there was less iron corrosion. What is more, comparing Day 1 to Day 6, Flint water ate up more chlorine the longer the test was run, whereas Detroit water ate up less chlorine the longer the test was run.

Figure 2: Decaying of free chlorine in Detroit water with and without iron

Figure 3 shows a picture of Flint water and Detroit water after reacting in the glass containers described after the first 5 days of the test. This also illustrates why residents have been complaining of “red” or discolored water after the switch to the Flint River source.

Figure 3: Higher release of iron is evident in the Flint water glass reactor containing iron than that of Detroit water
Figure 3: Higher release of iron is evident in the Flint water glass reactor containing iron than that with Detroit water

At present, as a rough estimate which we will elaborate on later, it looks like Detroit water is about 5 times less corrosive to iron pipe than Flint River water. This also probably means that the iron pipes in the city of Flint system will fail 5 times faster using the Flint River water rather than the Detroit water. In fact, this is probably already occurring as evidenced by increased rates of water main leaks and breaks. While an economic analysis cannot yet be done based on our limited data, it is possible (and even likely) that the economic damage to the Flint pipe system due to corrosion is going to cost the city tens of millions of dollars more in pipe repair costs in the coming years compared to what they would have paid if they had stayed on Detroit water.

Conclusion: The high rates of iron corrosion from using Flint River water as a drinking water source are damaging the Flint distribution system. The corrosion is also causing chlorine to disappear quickly, which may make it more likely for harmful bacteria to grow in the water. Furthermore, it is possible that with the existing unlined iron pipe system in Flint, and the relatively low water demand (due to declining population, loss of GM – which used a lot of water – as a water customer, and high rates), that it will very difficult to meet Federal standards for minimum chlorine levels no matter what is done to treat the water.

Primary Author: Dr. Marc A. Edwards

Acknowledgements: Siddhartha Roy

Opportunistic Pathogens (OPs): #1 cause of waterborne diseases in the United States

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We have long known about the dangers associated with waterborne pathogens. Fecal contamination of drinking water sources can lead to gastrointestinal illness and deaths caused by a variety of waterborne pathogens. We control for these risks by 1) selecting clean water sources for treatment, 2) treating the water to remove particles and bacteria by filters, and 3) disinfecting water with chlorine. Treatment plants have to prove they are meeting very high standards in protecting the public from this danger, by frequently measuring filter efficiency and chlorine levels at the treatment plant. In addition, utilities also have to double-check their control of this threat, by sampling their water pipelines for indicator bacteria which are present at very high concentrations in feces, such as coliforms and E. coli, and also maintaining significant levels of chlorine as water is transported to homes.

In recent decades, we have also come to recognize that fecal contamination is not the only source of waterborne pathogens in our drinking water. These other bacteria do not come from fecal contamination, but rather they grow in pipes and homes themselves, and are commonly referred to as Opportunistic Pathogens, or OPs for short. The presence of OPs in drinking water is a danger that is not directly addressed by existing Federal Regulations, despite the fact that an OP, Legionella pneumophila is now known to be the most frequently reported causative agent of waterborne disease outbreaks (and deaths) in the United States.

The impacts that OPs can have on human health are numerous, and they generally do not come from drinking the water. For example, Legionella pneumophila (the bacterium which causes Legionnaire’s disease) and Mycobacterium avium live in pipes, and human exposure occurs when consumers breath tiny water droplets in the air from showers or washing hands. Staphylococcus aureus can lead to skin infections when it contacts open cuts or existing irritations. Pseudomonas aeruginosa can lead to a variety of infections: lung and blood stream infections, skin irritations, and infections of the eye or ear.

Legionella bacteria (Image courtesy: CDC)
Legionella bacteria (Image courtesy: CDC)

Most OPs are not regulated or routinely measured in drinking water. Legionella is only regulated in water as it leaves the treatment plant, which is the location that is least likely to have high levels of Legionella, and the regulation does not do enough for public health protection. However, the conditions which are associated with a typical building’s plumbing, can create ideal conditions for these bacteria to take hold, such as warm water, so Legionella can be present at very high levels in homes even when it is not detected at the treatment plant.

Residents of Flint have also reported many symptoms (see, here, here and here) which are consistent with those associated with some infections caused by waterborne OPs, such as skin irritations. However, it is unclear whether OPs may be contributing to this problem due to a lack of water testing, and difficulties in linking human health problems to water exposure. There is some indication that in March 2015, the Health Department was exploring possible links between drinking water and cases of Legionnaire’s disease in Genesse County.

Additional water testing targeting OPs, particularly of samples collected at the point of use within homes, could offer valuable information regarding the microbial water quality of the drinking water available to residents of Flint.

Primary Author: Emily Garner

Acknowledgements: Dr. Marc Edwards, Dr. Brandi Clark and William Rhoads

The Unintended Consequences of migrating to Flint River water

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The City of Flint had been purchasing drinking water from neighboring Detroit for almost half a century. With rising water costs rooted in an acute fiscal crisis, the city’s Emergency Manager decided to stop this practice. Instead, the city decided to treat the nearby Flint River for potable use beginning April 30 of last year (2014). This was a temporary move until Genesse County (where Flint is located) and other Michigan counties finished building a ‘Karegnondi Water Authority (KWA) pipeline in 2016. The Flint River basin has suffered from poor water quality for a number of years and the water is difficult to treat. The most recent consumer confidence report further acknowledges that on a scale of 1-7, with 7 being most at risk for contamination, the Flint River is a 7.

Immediately following the switch, consumers started noticing a drastic reduction in tap water quality. Initially it was taste and odor problems. Flint residents have described their water to be blue, yellowish, and even sewerage-like, with unpleasant odors. Discolored water caused by metallic rust, released from unlined cast-iron pipes or iron service lines carrying the water with increasing corrosion occurring along their lengths. Microorganisms like sulfate-reducing bacteria living in the rusty pipes can produce the smell of rotten eggs (i.e. hydrogen sulfide) and render the water acidic.

Figure 2: Exemplary pictures looking into Flint drinking water pipes, showing different kinds of iron corrosion and rust (Photo: Min Tang and Kelsey Pieper)
Figure 1: Exemplary pictures looking into Flint drinking water pipes, showing different kinds of iron corrosion and rust (Photo: Min Tang and Kelsey Pieper)

There were also health concerns associated with multiple violations of the National Primary Drinking Water Regulations, most notably due to Coliform bacteria and Total Trihalomethanes (TTHMs). High levels of coliforms indicate likely fecal (i.e., sewage, poop) contamination of the potable water supply. The Flint River has significant sewage input, and if the treatment plant does not completely remove the bacteria and other dangers posed by the sewage, high coliforms and public health risks can result. The TTHMs are formed when naturally occurring organic compounds (i.e., decaying leaves and grass and plants) present in the water react with the free chlorine, which is added to destroy the fecal bacteria that may be present in the Flint River water (see Dr. Joan B. Rose’s guide to TTHMs in Flint Water). High TTHM levels are a health concern and are suspected to cause a wide array of health problems with long term exposure.

There are also serious concerns with high levels of lead leaching in the water from lead pipes that connect homes to the cities water mains via the service line connection, and also from lead plumbing (i.e., lead solder, leaded brass). See Figure 3 for a detailed schematic. Lead is the best-known neurotoxin and can cause severe learning, neurological and developmental disabilities in both fetuses and children under the age of seven. A Flint household with lead levels measured at 397 parts per billion or ppb by the city (the action level from the EPA is 15 ppb) had a child with increased blood lead level after the switch to Flint water. The high blood lead in the child is even more disconcerting given that the family was not directly drinking Flint water, and the harm therefore arose from either back contact (or indirect ingestion — incidentally consuming water while bathing or from washing dishes, for instance)  or consumption of highly filtered water (two filters were in use). Flint River is very corrosive for iron and lead materials, compared to the water previously purchased from Detroit. Orthophosphates that are commonly added to corrosive waters to minimize lead leaching from aged water distribution pipes made of or containing lead, but water from the Flint River is so corrosive that use of orthophosphate might not provide the normal benefits and might actually make things worse.

Figure 1: Potential Sources of Lead Contamination in tap water of homes, schools and other buildings (Triantafyllidou 2011)
Figure 2: Potential Sources of Lead Contamination in tap water of homes, schools and other buildings (Triantafyllidou 2011)

Clearly, the dramatically increased corrosivity of the Flint River water versus previously purchased from Detroit, and the relatively high contamination of the water from Flint River, has created significant challenges for the Flint Water Department and the City to address. It is possible, that no matter how competent and effectively this source is treated, that Federal Regulations for bacteria, chlorine levels, lead and TTHMs considering Flint’s old water pipe system cannot be met. This issue will be a key subject of our research.

Primary Authors: Ni Zhu and Siddhartha Roy

Acknowledgements: Dr. Marc Edwards, Dr. Brandi Clark, William Rhoads