What’s All This Copper Everyone’s Always Talking About? - Part 2
May 24, 2012 | by: Jeff Coyne, EIT
If you are reading this blog, it’s likely that you are having some issues with copper either in your water utility, wastewater utility, or both. The most common copper concerns on the potable water side are probably pin holes leaks and lead & copper rule (LCR) compliance; while the most common copper issue on the wastewater side (at least here in Virginia) is compliance with discharge permits requiring (what seem like) exceedingly low copper concentrations in wastewater treatment plant (WWTP) effluent (the lowest effluent limit I’ve seen in Virginia is 3.6 μg/L total copper). And while addressing these issues (on the potable water and the wastewater side) may require a multifaceted systematic approach covering multiple disciplines, they are all connected by a common root cause: corrosion in the potable water system*.
Copper pipe corrosion has a number of important and potentially detrimental ramifications. Widespread pinhole leaks in home plumbing systems lead to wasted water and energy. Additionally, elevated levels of copper in potable water and WWTP effluent may have potentially significant effects on public health and the environment. Perhaps an equally pressing issue (especially in these fiscally difficult times) is the added financial burden of addressing copper corrosion in order to comply with the LCR, WWTP discharge permits, etc.
In order to have a more well-rounded discussion on copper corrosion, a better general understanding of copper itself may be beneficial (or at the very least somewhat interesting).
Copper, which must be mined from the earth, is most abundant in Chile (followed by the U.S., Indonesia, Peru, etc.). While copper’s relevance in the water and wastewater industry is the focus of this blog series, the industry which utilizes the most copper is the electrical industry (via manufacturing of wire, electromagnets, circuit boards, etc.).
Copper is commonly used as a pipe material in the water industry for a number of reasons. Several natural properties of copper metal make it desirable for applications in household plumbing systems:
1) Biocidal: copper is somewhat antimicrobial and may inactivate some potentially detrimental organisms.
2) Ease of use: copper is strong, light weight, and relatively easy to work with and install.
3) Corrosion resistance: although the focus of this blog is copper corrosion, copper pipe is relatively corrosion resistant compared to other metals in potable water applications.
It seems counterintuitive that we are discussing corrosion issues of a pipe material that is touted as being inherently corrosion resistant. I’ll try to elucidate this paradox by covering some of the mechanisms of copper corrosion in the next blog post entitled: Where did all that copper come from?
* Although corrosion may be the most common cause of elevated copper concentrations, other major sources do exist. For example, on the potable water side: some ground or surface waters may have naturally high levels of copper or may be contaminated by polluted water with elevated copper levels originating from industry, mining operations, etc. Additionally, on the wastewater side: some sewer collection systems may have elevated levels of copper due to industrial discharges into sanitary sewers, localized use of copper based root killers, etc. For more information, see an article entitled Copper in the Urban Water Cycle by Nicolle Boulay and Marc Edwards (Critical Reviews in Environmental Science and Technology. V. 30, No. 3, 297-326 (2000)).