SWT Water Treatment Tips
Field Notes by Rusty Waters
“Unscientific notes from a collection of the greatest minds in water quality improvement.”
Potential Dead Zones in Pressure Filter Tanks and What Causes It

I'd like to tell you a little bit about “Dead Zones.” No, not some teenage zombie movie, but those pesky areas of your media bed that don't seem to do much of anything. Ideally, every bit of a media bed will be used to its fullest, providing optimum flow-thru and maximum treatment. But sometimes this doesn't happen and you end up with those dreaded dead zones. To help you out, I've created the following diagram. It shows you the areas that dead zones most commonly appear in a media bed (Zones A – D) and lists the most likely causes. So the next time you are sizing a water treatment system, consider these causes, and then you too can stay away from... The DEAD ZONES!
Zone A     Zone A
1. Too much or too little underbedding
2. Hub set too high off bottom of tank
3. Insufficient backwash
Zone B   Zone B
1. Laterals not fully extended
2. Too much slot area in center of tank
3. Flow rate too slow
4. Insufficient backwash
5. Channeling because of bed lock-up
Zone C   Zone C
1. No upper diffuser
2. Flow rate too slow
3. Too much slot area in center of tank
    (upper and/or lower screens)
Zone D   Zone D
1. All of the above in abundance.
  Dead zone areas in typical water treatment vessel
If you have an unscientific idea that you would like to share with your fellow water quality improvement professionals, by all means let us hear it so we can pass the information along. Design by experience and evolution can be more reliable than what the eggheads can do in the lab or on a computer. We here at SWT believe that knowledge is meant to be shared. We do not presume to know more than our customers, and we really enjoy the exchange of ideas. You may e-mail your idea(s) to us at fieldnotes@swtwater.com.
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996 Bluff City Boulevard
Elgin, IL 60120 USA
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E-mail: info@swtwater.com

Last Updated: June 13, 2018