Steps to Correctly Select Water Treatment Systems

Good job Mr. Buecker! You and I both know that emerging tech in the field of water treatment will advance cooling systems far beyond what we thought were possible at all 10 or 20 years ago! Not only that, finally someone has put forth a more sane way to estimate particulate emissions from cooling towers, and big shocker, it is way less than the old, factored approach should in EPA-42.

Unfortunately, as everyone can easily understand, taking a cooling system from 3-4 cycles of concentration to zero liquid discharge will reduce waste-water, and save chemicals costs (or should by design do so), but it cannot reduce evaporation cost of makeup water, or the pressure to reduce water consumption even further. Utilizing treated effluent has been a valuable way to deal with this, and progress has this near perfection at this time, but it does (I am sure we agree on this point) requires substantial upstream treatment to condition the water against slime-forming organisms, and scale tendency.

Even though there is at least one cooling tower OEM that offers condensate recovery from the cooling tower plume, this does not come without its own energy penalty, since nothing is "free".

Thank you, Mr. Stewart. Your note brings up several good points. First, as once-through cooling continues to be eliminated due to 316a and 316b regulations, many new plants are adopting cooling towers as the core technology for condenser and heat exchanger cooling. However, cooling towers obviously convert a large and steady stream of liquid water to vapor, which escapes to the atmosphere, thus increasing water consumption. And, you mentioned something that people often forget, cooling towers are a source of air emissions, which may have to be controlled or may place limits on the cooling tower cycles of concentration. Another item I often see in the water treatment portion of proposals that cross my desk is a blind call for perhaps 10 or even 15 cycles of concentration without due consideration given to the raw water quality and the effects such high COC would have on emissions. If one examines a chart of blowdown (BD) vs. COC, where a general calculation is BD = Evaporation/(COC-1), it is easy to see that the gains in blowdown conservation greatly diminish as COC climbs above a range of 6 to 8. Thanks again, Brad Buecker.

This is all true, and later with permissions, I will share newer insight on the PM10 and PM2.5 particulate calculations. Basically, the new thinking is that cooling tower flow and fan air flow really does not exert enough shear force to produce as large a fraction of droplets leading to PM10 as originally thought, not only that, but PM2.5 is practically out of the question. Going even further, suppose a droplet that at 3 CoC would produce a 10 micrometer sized particle. How can one take the same droplet at 10 CoC, and cram all that salt into a 10 micrometer diameter particle?

That is apparently what EPA expects us to believe?