There has been a lot of finger pointing and hand wringing
over last week’s spill of Crude MCHM and the shutdown of the water facility in
Charleston, WV. While we are a long way from knowing all of the facts we
probably know enough to describe what we would have liked to have happened in
this situation.
To do this we will look at consequence and work back
upstream (just a minor pun here) to the source of the problem and see what
could have been done (in a perfect world) to prevent this problem from
happening.
Prevent Crude MCHM
from Entering Drinking Water System
The proximate cause of the shutdown of the municipal water
system was that it had been come contaminated with Crude MCHM that entered the
system through the river water intake. If that intake of contaminated water had
been prevented there would have been no major news story and no significant
discomfort to the people of the area.
Water Treatment
The whole point of having a water treatment plant is to take
in contaminated water and make it clean. If we could just drink the river water
without processing we could save lots of money. But, almost by definition,
river water is contaminated with stuff and the treatment plant removes that
stuff. The plant is designed to remove a specific range of stuff that is
expected to come down the river, typically the standard animal and plant
material (and their normal waste and decay products) that are found in and around rivers.
That treatment process in Charleston did not remove Crude MCHM from the
water. There are probably thousands of chemicals that it would not have removed
from the water. But, systems to remove everything from the water (okay, no
system removes all contaminants from the water, but we are really talking about
safe levels of contaminants here) are very expensive to construct and maintain.
So you design a treatment system that will remove the chemicals that you
reasonably expect to see in the water supply that you will be treating.
Water Testing
The second way that you prevent unwanted chemicals from
getting into your drinking water is to stop taking in water when something is
present that the treatment system cannot remove. There have been a number of
news stories about communities downstream of Charleston that will be shutting
down their intakes as the Crude MCHM approaches their water intakes. These
communities have an advantage over Charleston; everybody and their grandmother
has told them that the Crude MCHM is on the way. Nobody told the water
treatment folks in Charleston.
If you don’t get told in advance of a contamination stream
that you can’t clean up, you have to rely on inlet water testing to identify
such contaminants. This requires two things; first a list of chemicals of
concern and second a method to test for them. Now there is something like
80,000 registered chemicals in production/use in the United States (that is a
number I have seen tossed around, it is probably not accurate but it is in the
right ballpark for this discussion). It is unlikely that any treatment facility
knows exactly which of those it can and cannot remove from the water, but again
it is unlikely that all of those will head towards your water treatment
facility.
Even if you did know (highly unlikely) there are not
standard and accepted test methods for detecting each of those chemicals in
trace amounts in water. For a very large percentage of them, there is not even
a standard for determining what is an acceptable safe level.
The best that you can hope for as a treatment facility
operator is to know what could be headed your way and be able to test for that.
That means you have to know what is routinely found upstream of your facility,
both at fixed facilities and in transportation.
But even then it is not necessarily possible to continuously
test for all of those chemicals. Some tests are so complex and time consuming
that they consume resources that would make a water system too expensive to
operate if testing were done on a continuous or even routine basis. Those tests
you only want to run if you have a reason to suspect that that particular
contaminant is heading your way. So you have to know about spills and accidents
upstream, the sooner the better.
The Perfect World
Solution
Okay, for this point in the discussion what would be the
perfect solution to the problems that we have identified to this point? Here is
a nice start; each water treatment plant would:
• Understand the limits of its treatment
process, particularly what chemicals (and at what concentrations) that it
cannot remove from the water;
• Know which of those chemicals are
found upstream of the treatment plant both at fixed sites and in
transportation;
• Know what the safe levels are for
those chemicals in the drinking water;
• Have water testing capabilities
in place to test incoming water, down to below the safe drinking limits, for
those chemicals routinely expected to be found upstream that cannot be removed
from water by the current treatment process;
• Have, for those tests that it
could not afford to continuously do, a method for determining when that
chemical was introduced into the water upstream of the facility so that it
could begin testing as the chemical approached the facility.
Obviously, we want to keep these chemicals out of the water
in the first place, but we have to recognize that we do not live in perfect
world and accidents will happen. Since those accidents are beyond the control
of the water treatment facility owners the solutions noted above really should
be in place to provide perfectly safe drinking water.
I’ll discuss in later posts what can be done in a perfect
world to prevent those chemicals from getting into the water in the first
place.
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