Water quality has been in the news lately. Flint, Michigan. Sebring, Ohio… situations where water has eaten away at pipes to deliver both lead and water to homes and communities. So how does water become corrosive? To understand how water can “attack” pipes and corrode surfaces, three examples of water chemistry help us make sense of water quality in the news.
- Rust. Making car owners everywhere cringe. You may know that the ingredients for rust are just iron and water and air. Oxygen slowly weakens the bonds between metal molecules and, over time, will form an oxide which makes the rusty color. Water is the vehicle, the junction, that oxygen needs to take an electron from the iron molecule to form the orange and crumbly oxide. Like a mutual friend who introduces two people, water can facilitate the interactions between different compounds. “Hey, I just met you but this chemistry we share sure is attractive!” Water does that for oxygen and iron.
My car, my beautiful car, shows the beginning of a rust patch. Iron rust can be accelerated by chloride, a major component of road salts in northeast Ohio.
- Acid mine drainage.In this instance, water picks up harsh compounds and carries them.Minerals and metals that have not seen the light of day in thousands of years are exposed to wind and water in many mining practices.Water dissolves heavy metals such as aluminum (Al3+), zinc (Zn2+), and manganese (Mn2+). Sometimes mineral deposits contain sulfides which, in the presence of water and oxygen, can react to form sulfuric acid (H2SO4). Water absorbs and the noxious properties of sulfuric acid and heavy metals, and carries those downhill, which wreaks biological havoc and damages the waterway for many years. Water can carry compounds harsh compounds and deliver them elsewhere.
Acidic water pours over and dissolves minerals that have been unearthed in the metal and coal mining process. Photo courtesy of NASA.
We know that water can introduce two reactants to form something new: rust, as an example. And we know water can dissolve and deliver compounds such as sulfuric acid to new locations. We will apply both lesson in the third example.
- Lead, dissolved in water, from pipes and solders.The primary source of lead in water comes from the use of lead pipes and lead solder (50/50, tin/lead). The Environmental Protection Agency banned the use of these heavy lead service lines in 1986, but some still exist. You may have guessed where some are located.
Water from the Flint River in Michigan was corroding pipes. It may contain low pH, similar to acid mine drainage. It may contain dissolved solids that aggressively corrode iron and lead, such as salts and sulfates. It needed to be treated with a corrosion inhibitor and yet it was not. Corrosion inhibitors are chemical agents that balance acidity (calcium hydroxide), stabilize pipes (sodium fluorosilicate)
Water quality is something we should all be familiar with, I think. Rust, acid mine drainage, and the water crises in places like Flint, MI and Sebring, OH provide examples to understand water chemistry and quality. In Cleveland, we have a reliable supply of not-so-corrosive water from Lake Erie. It is not to be taken for granted. Its long-term sustainability will be the responsibility of our community in Northeast Ohio and the Great Lakes Watershed as a whole. Through collaboration and meaningful investments, who knows, we will be in the news for excellent water quality.
Warman encourages you to visit the Watershed Stewardship Center in Parma where you can dive into water quality education and learn about the living creatures that depend on clean, healthy waterways.