"Sodium really has no
redeeming value in the environment outside of saltwater or brackish water
ecosystems. If alternatives to sodium chloride for water treatment can be
developed, they should be used. Potassium chloride is a logical choice to
reduce sodium discharge from water softening systems, to provide additional
potassium in human diets, and to serve as a nutrient source for plants."
From "Potassium Chloride: Alternative Regenerant for
Softening Water" by Dr. Kim Polizotto and Dr. Charles Harms
If you are concerned about water
softening brine and its possible effects on your septic system (and the
environment), an alternative chemical can be used. Potassium chloride is as
effective as sodium chloride for water softening in both residential and
commercial processes. Plus, using potassium chloride has several benefits: it
reduces the amount of sodium in drinking water; the treated water contributes
potassium to people’s diets; and it eliminates the addition of sodium from
water softeners into a household’s septic system tank and drainfield.
Potassium chloride works exactly
the same way that sodium does in the water softening process. The mineral tank
is flushed with potassium (instead of sodium) from the brine tank to coat the
resin beads. With its positive electrical charge, the potassium clings to the
negatively charged resin beads in the tank. As hard water passes through the
softener’s mineral tank, the calcium and magnesium in the water change places
with the potassium on the beads.
The treated water now has a small
amount of potassium in it. The mineral tank will eventually need to be
regenerated when most of the potassium adhering to the resin beads has been
exchanged for the calcium and magnesium carried in the water.
The regeneration process flushes
the mineral tank with a potassium chloride solution that drives the calcium and
magnesium minerals off the resin beads. The excess potassium, calcium, and
magnesium-rich water in the tank is then discharged into the home’s drain pipes
and into the septic system. The
regeneration brine mixes with the standing water in the tank, then eventually
flows into the system’s drainfield. Potassium is an essential mineral for
plants; whereas, sodium can damage plant tissues. Because sodium is replaced by
potassium, this diluted wastewater is beneficial to a grass covered drain
field.
Wastewater from water softeners
that use potassium chloride in their regeneration brine can be recycled to
irrigate agricultural land. An article titled “Potassium Chloride ...
Alternative Regenerant for Softening Water,” written by Dr.Kim Polizotto and
Dr.Charles Harms for the Potash and Phosphate Institute’s Better Crops with
Plant Food (Fall 1993), suggests using potassium in water softening units and
then recycling the diluted wastewater as an alternative to disposing of it.
Polizotto and Harms mention that
several cities in California, Florida, and Michigan have called upon the water
softener industry to help reduce sodium and chloride discharge into municipal
sewage treatment facilities. Reduction of these chemicals is necessary to meet
discharge standards set to decrease groundwater pollution in those communities.
These researchers also tell of
other towns that want to develop secondary markets for their wastewater, such
as selling it to farmers for irrigation purposes. Because sodium may harm some
plants’ growth, wastewater from treatment plants might not be marketable if
sodium chloride is the predominant salt used for water conditioning in the
community.
Cost may be the only drawback in
switching from the standard sodium chloride used in most water softeners to
potassium chloride. Both can be found in most retail home improvement centers,
but the potassium chloride can cost up to twice as much (even more on the West
Coast) as the sodium chloride. The average price of sodium chloride (in the
East) is around $4 for a 40 pound bag, and potassium chloride costs
approximately $9 for 40 pounds. However, consumer group studies show that, for
many potential users, the health and environmental benefits of potassium
chloride outweigh the price difference.
National Small Flows
Clearinghouse (NSFC)
The NSFC offers a variety of technical assistance and free and low-cost
information and materials about wastewater technologies for small communities.
Just a few of the NSFC’s many resources and services are mentioned in this
newsletter. Call the NSFC at (800) 624-8301 or (304) 293-4191 or visit our Web
site at http://www.nsfc.wvu.edu/ for
more information.