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Estimated reading time: 2 minutes
Much has changed since the Clean Water Act (CWA) was passed in 1972, but not how water quality is regulated. Existing environmental data analyzed with advanced statistical models can bring CWA regulatory compliance into the 21st century. With global warming, and societal concerns about sustainability, modernizing regulatory compliance benefits everyone.
The use of maximum concentration limits (MCLs) on individual chemical ions or collections such as total dissolved solids (TDS) applied to all water bodies regardless of type or geographic location is similar to the way medicine was practiced centuries ago when we did not understand human physiology and variability.
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MCLs have three critical shortcomings: geochemical constituents are predominantly compounds, not ions; there is no context to separate natural variability from anthropogenic effects; and there is no ecological cause-and-effect inkage between a specific concentration and the status of a beneficial use at a defined location and time.
Consider calcium. It is present as calcium carbonate, calcium sulfate, and other compounds. Calcium carbonate forms shells of fresh water mussels and snails as long as the pH is between 7.0 and 8.4. Below pH 6.8 calcium carbonate dissociates and the mollusks die. Knowing calcium ion concentrations without he context of pH, hardness (alkalinity), and other variables reveals nothing about the state of the aquatic ecosystem.
Avoiding environmental issues is critical to permitted operations.
This work was originally published on the Applied Ecosystem Services, LLC web site at https://www.appl-ecosys.com/blog/maximum-concentration-limites/
It is offered under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license. In short, you may copy and redistribute the material in any medium or format as long as you credit Dr. Richard Shepard as the author. You may not use the material for commercial purposes, and you may not distribute modified versions.
