The chemistry behind the Flint Water Crisis: Corrosion of pipes, erosion of trust
By George Lane
When Flint, Michigan changed its water supply in 2014, it initiated a cascade of chemical reactions inside decades-old water pipes that caused Lead to leach into its drinking water, triggering a major public health crisis. When Flint used its own river as a water supply, drinking water contained a staggering 13,200 parts per billion (ppb) Lead, almost 900 times higher than the 15 ppb regulatory limit set by the Environmental Protection Agency (EPA). Some water samples exceeded the EPA criteria for Lead concentration in hazardous waste, 5,000 ppb.
Although Lead pipes have been used for water distribution for over two thousand years beginning with the Romans, the use of Lead pipes carrying water in the United States on a major scale began in the late 1800s, particularly in larger urban cities. By 1900, more than 70% of cities with populations greater than 30,000 used Lead-lined pipes for drinking water.
The use of Lead pipes to carry drinking water was recognized as a cause of Lead poisoning by the late 1800s in the United States. In 1890 the Massachusetts State Board of Health advised the state’s cities and towns to avoid using Lead pipes to transport drinking water. By the 1920s, many cities and towns were prohibiting or restricting their use. To combat this trend, the Lead industry carried out an effective campaign to promote the use of Lead pipes, affecting public health and delaying the replacement of Lead water pipes.
Normally water managers add chemicals to water, such as orthophosphates, to prevent corrosion. Orthophosphates bond with Lead in pipes, creating a protective coating between Lead and water. When that shield is intact, corrosive chemicals like Dissolved Oxygen (DO) can’t interact with the Lead; however, orthophosphates have to be added continually or the barrier breaks down. If the barrier does break down, DO combines with Lead atoms, oxidizing them. Oxygen takes electrons from Lead, grabs its Hydrogen protons, turning into water, and allows Lead to leach into drinking water. Once oxidized, Lead dissolves into the water instead of sticking to the pipe.
Flint’s water treatment plant did not add orthophosphates, allowing the pipes to corrode, and Lead quickly contaminated the drinking water. Additionally, Flint River water had high levels of chlorides, which accelerate corrosion. There were two other sources of chloride: Ferric chloride used in Chlorine disinfection of water and road salt applied during tough Michigan winters. Switching from Detroit’s Lake Huron to Flint River water created a perfect storm for Lead leaching into Flint drinking water.
A complex brew of acids, salts, Chlorine and many other chemicals were involved in oxidizing Flint’s metal pipes and releasing Lead. High levels of Lead in Flint drinking water weren’t reported to the public for 18 months; however, the corrosion happened quickly, especially in the warmer summer months. Without effective treatment to control corrosion, Flint’s water leached high levels of Lead from the city’s pipes into city drinking water. Following the switch, E. coli bacteria was also found in the water.
To combat E. coli, extra Chlorine was added as a disinfectant to remove it. Ferric chloride was also added as a coagulant to remove organic matter from the water, initiating a domino effect of chemical causes and effects. Flint’s water quality problems were also caused by corrosion in both the Lead and Iron pipes that distribute water. When city residents began using the Flint River as its water source, the water’s ability to corrode those pipes wasn’t adequately controlled. This led to high Lead levels, rust-colored tap water, and the growth of pathogenic microbes.
When Flint changed its water supply, the city didn’t adequately control corrosion. Flint isn’t the only city susceptible to these problems. The pipes in its old distribution system had seen the same water for decades, similar to many other cities. Switching water supplies changed the chemistry of the water flowing through those pipes.
When a switch like this happens, the chemistry in the water system moves toward a new equilibrium. In Flint the change was catastrophic. Flint was getting its water from the Detroit Water & Sewerage Department, which would draw water from Lake Huron and then treat it before sending it to Flint.
To lower the city’s water costs, in 2013 Flint officials decided to take water from another source which was building its own pipeline from the lake. Shortly after that, Detroit told Flint it would terminate their original long-term water agreement within a year and offered to negotiate a new, short-term agreement. Flint declined the offer. While waiting for the new pipeline to be finished, Flint began taking water from the Flint River and treating it at the city plant.
Problems with the city’s tap water started the summer after the switch in 2014. First, residents noticed foul-tasting, reddish water coming out of their taps. In August, the city issued alerts about E-coli contamination and told people to boil the water before using it. A General Motors plant in Flint stopped using the water because it was corroding steel parts.
In early 2015 Lead reached Flint’s University of Michigan campus. Researchers sampled water from 252 Flint homes and reported the results (www.flintwaterstudy.org). Hurley Children’s Hospital in Flint released data showing that since the water change, the number of Flint children with elevated levels of lead in their blood had increased from 2.4% to 4.9%.
Lead is neurotoxic, causing behavioral problems and decreased intelligence. The Blood Brain Barrier limits the passage of ions, but because it has not formed in children, they can absorb from 40% to 50% of water-soluble Lead compared with 3% to 10% for adults.
So why did the switch to Flint’s river water cause this catastrophe? As water travels through the miles of pipes in a city’s distribution system, molecules of contaminants in the water react with the pipes themselves, acting as a geochemical reactor. There are miles and miles of pipes, some Iron, some Copper, some Lead, that got corroded. Corrosion occurs when oxidants, such as DO or Chlorine, react with elemental metals in the pipes.
Cities no longer install lead pipes. But older cities such as Flint still rely on them, usually as water mains in the street to a home’s water meter. Because of Lead pipes, some states regulate the corrosivity of water to deposit a protective coating on the pipes. A 1990 report from the American Water Works Association estimated there are over 3 million Lead-lined pipes transporting drinking water in the Northeastern U.S. alone. According to EPA, nationwide over 10 million American homes and buildings receive water from Lead-lined pipes.
So why is Lead used in water pipes? The answer can be found literally thousands of years ago in the first “plumbing” systems, named for the word “Lead” in Latin, “plumbum”. Tap water in ancient Rome had 100 times more Lead than local spring waters. Lead piping was used because of its unique ability to resist pinhole leaks while still malleable enough to be formed into shapes that deliver water. Lead was used in many other common products, such as Tetra Ethyl Lead in gasoline and Lead-based paint, until scientific advancements in the 20th century demonstrated its toxicity. With passage of the Safe Drinking Water Act Amendments of 1986, installation of Lead water pipes was finally prohibited nationwide.
Today utilities treat their water to maintain a mineral crust on the inside surfaces of their pipes. This so-called “passivation layer” protects the pipes’ metal from oxidants in the water. The coatings consist of insoluble oxidized metal compounds produced as the pipe slowly corrodes.
If the water chemistry isn’t optimized, the passivation layer may dissolve and allow mineral particles to flake off of the pipe’s crust. This exposes bare metal, allowing the Iron, Lead, or Copper to oxidize and leach into the water. Flint water chemistry was not optimized to control corrosion. Most importantly, the treated Flint River water lacked one chemical that the treated Detroit water had: Phosphate. Cities such as Detroit add orthophosphates to their water as part of their corrosion control plans because of the formation of Lead phosphates, which are largely insoluble and add to the passivation layer.
The entire Flint water crisis could have been avoided if the city had added orthophosphates, commercially available chemicals, used in Detroit. After just five weeks in the Flint water, the pipes leached 16 times as much Lead as those in the Detroit water, demonstrating just how corrosive the treated Flint water was. But orthophosphates aren’t the only corrosion solution. Some water utilities treat water so it has a high pH, a high alkalinity. These conditions decrease the solubility of Lead carbonates, which also contribute to the pipe’s protective mineral layer.
The pH drop over time indicates that plant operators in Flint didn’t have a target pH as part of a corrosion plan. Water utilities usually find a pH that’s optimal for preventing corrosion in their system. For example, in Boston, another city with old Lead pipes, average water pH held steady around 9.6 in 2015, according to reports from the Massachusetts Water Resources Authority.
Problems with Flint’s pipes started quickly. The rust color and bad taste of the water coming out of residents’ taps in the summer of 2014 was a sign that the passivation layer on was dissolving into the water. Iron corrosion also encourages the growth of pathogens in the distribution system. As the mineral layer in iron pipes falls off, it exposes bare iron that can reduce free Chlorine added to the water as a pathogen-killing disinfectant. One home with Lead levels almost 900 times higher than the EPA limit had no detectable Chlorine levels over 18 days of monitoring.
Although Flint has switched back to the Detroit water, it may take years for pipes to regain their passivation layers for corrosion to slow to normal levels, and for Lead concentrations to drop back into an acceptable range. However Joel Beauvais, Deputy Assistant Administrator of EPA's Office of Water, emphasizes “EPA’s position is there is no safe level of lead exposure.” While the drinking water crisis has focused on Flint, almost 2,000 additional water systems in all 50 states have shown excessive levels of Lead contamination over the past four years.
The lesson from Flint is to continually monitor water chemistry, especially when switching water supplies. Water utility officials were already collecting all the data they needed, pH, alkalinity, chloride levels, to determine if the water was too corrosive. The message is to consider the connections between the stability of the water infrastructure and the chemistry of the water flowing through that infrastructure. That will inevitably control the water quality at the tap.
By not adding a corrosion inhibitor, Flint expected to save about $140 per day. But the human costs of the errors made in Flint will reverberate through the community forever and their magnitude will dwarf the original planned savings. According to Flint Mayor Karen Weaver, replacement of Flint’s Lead water lines is now estimated to cost up to $1.5 billion.
On December 20, 2016, Michigan's Attorney General announced felony charges against two former Flint emergency managers and two other former city officials linked to the city's disastrous decision to switch water sources, which resulted in widespread and dangerous Lead contamination of Flint drinking water. These latest charges bring the total number of people charged to thirteen.
On December 30, the Louisiana Department of Health and Human Resources (DHHR) reported unsafe levels of Lead in the drinking water in over 20% of the homes and businesses of St. Joseph, a rural city in North Louisiana. Dr. Jimmy Guidry, Louisiana DHHR Director, warned citizens saying “The message to the folks who live there is not to drink the water.”
George Lane, a resident of Baton Rouge, Louisiana, has 25 years of experience in the development of chemical security systems, conducting research as a NASA Fellow at the Stennis Space Center and as a NASA Fellow. Lane was air quality SME for the University of California at Berkeley Center for Catastrophe Risk Management during the BP Oil Spill. He is currently Chemical Security SME for the Naval Post Graduate School Maritime Interdiction in the Center for Network Innovation and Experimentation.