Frustrating but Fascinating: Treating Inorganic Contaminants in Drinking Water
We all know water is really life itself. Something we often don’t think about, and even take for granted, is the treatment of this indispensable resource. Phil Brandhuber, Ph.D. shares his thoughts and experiences investigating the solutions to some persistent and puzzling water treatment questions.
Like vowels in the alphabet, the names of inorganic containments tend to roll off my tongue: nitrate, manganese, arsenic, and fluoride. My experience with inorganics began almost 20 years ago when my advisor, Professor Gary Amy, asked if I wanted to work on a project to investigate how to treat arsenic (the poison of choice since ancient times) in drinking water using membrane technology. At that point, the only thing I knew about arsenic came from seeing the play “Arsenic and Old Lace.” But in time arsenic and I became “friends,” and this friendship eventually turned into my Ph.D. dissertation. After graduation I was gratified to see my work play a role in the development of EPA’s arsenic rule in 2000.
As a rule inorganic contaminants don’t contain carbon and commonly occur in nature. Contaminants like arsenic, chromium, iron and manganese are widely present on the earth’s surface and naturally end up in our water. Over the years I have learned that treating inorganic contaminants in water can be devilishly difficult. Even the name “inorganic,” is frustrating — defining what they are not — organic.
Not all inorganic contaminants occur naturally, some are the result of pollution. One example is chemical perchlorate, used in some rocket fuels, explosives, and fireworks. Others are a consequence of the interplay of pollution and natural processes. For instance, nitrate is naturally formed by the oxidation of ammonia in fertilizer or leaks from septic systems. In some cases past engineering practices expose us to inorganics, for example through previous decisions regarding which pipe material is used to convey water to the consumer’s tap.
Some inorganics are indisputably harmful to human health. Nitrate and lead present thorny problems for drinking water utilities. Both contaminants are harmful to vulnerable populations, specifically infants and children, and both contaminants are hard to manage. We’re able to effectively remove nitrate from water, but the disposal of the treatment waste stream is technically challenging and expensive.
Lead doesn’t present a treatment issue, since most water sources contain trivial amounts of lead. Instead it is a legacy engineering issue tied to existing distribution system infrastructure. Exposure to lead, released from lead pipes and lead-containing fixtures used in the 20th century is a serious health risk. These pipes and fixtures, sometimes installed 50 to 100 years ago, may leach lead into water at the customer’s tap. Ultimately, removing these sources of lead will eliminate customer exposure; but, this is a vastly expensive undertaking, complicated by the fact that many of the pipes and fixtures are not owned by the utility. They are located on the customer’s property and owned by the customer. Solving the lead problem will challenge utilities for years to come.
In several cases, small amounts of some inorganics are beneficial to human health; while a large amount of the same inorganic is harmful. It is a delicate balancing act. For instance, within a narrow range, fluoride promotes dental health. On the other hand, exposure to too much fluoride can discolor teeth and weaken bones.
Over the years, I’ve developed “friendships” with many inorganics, and have researched the occurrence and treatment of chromium, perchlorate and manganese, as well as working on projects involving inorganics, ranging from the chemical, antimony, to zinc. Along the way, I’ve worked with advanced technologies such as ion exchange and electrodialysis, as well as trying to improve methods for disposing of residuals released from treatment processes.
My current drinking water challenge is collaborating on a project with a Japanese company which has developed a unique ion exchange treatment technology capable of removing arsenic. Working through HDR’s Water Institute, we are evaluating if this new technology can provide value for our clients.
Twenty years of working with inorganics has taught me this about inorganics: Defining and treating inorganics may be frustrating, but working with them is endlessly fascinating.