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End Of Semester Final Exam Question – All or Nothing

December 24, 2018

Water Supply

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“A perchlorate is the name for a chemical compound containing the perchlorate ion, ClO− ₄. The majority of perchlorates are produced commercially. Perchlorate salts are mainly used for propellants, exploiting properties as powerful oxidizing agents…”Wikipedia

Final Exam Question (All or Nothing):

99. Can Perchlorate ClO4 be generated BY YOUR MUNICIPAL DRINKING WATER SYSTEM INFRASTRUCTURE (ie. Tanks and Piping)?



Chemistry Professor’s Response:

[A. NO] “Perchlorate can’t come from infrastructure such as pipes, so if it’s found in drinking water, “it would have to be from the source water,” Vengosh said.”

Chemical Engineer Response (me): 

[B. YES] “Perchlorate is generated from the electrolysis of chlorides in water.  It can be generated by low voltages (typically ~ 4-6V DC) triggering electrical currents within an aqueous solution containing water and dissolved chlorine, hypochlorite, chlorate, etc. ,  Electrolysis can be triggered by impressed current cathodic protection (ICCP) systems within municipal water storage tanks and piping and most likely piping systems that are poorly grounded or with an electrical current running through them.



Electrochemical production of perchlorate within a public water distribution system has been shown previously. “In this detailed incident, perchlorate (ClO4) was detected in the distribution system of Levelland, Texas, and was eventually isolated to one elevated storage tank. Theoretical considerations supported the production of ClO4 by an electrochemical process within the tank. ClO4 was produced (64–113 μg/L in 338 h) in laboratory experiments that simulated the cathodic protection system in place in the storage tank. Because cathodic protection systems are widely used, this research confirms a potentially troubling mechanism of ClO4 generation.

You choose the correct answer, your children’s health may depend upon it.




From → Biology, Geophysics

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