Physical Water Treatment

[mauricestoker]

I've started on design for chiller plant replacement and minor expansion, to include the cooling towers, control and water treatment. One of the questions that has come up from the customer is water treatment, and usage of physical water treatment as opposed to chemical. Water savings/sewer bill, and reduction of admin for tracking and spill protection, life cycle cost, Legionella are all legitimate concerns.

I'm curious as to other's experience with non-chemical water treatment. I've been looking at various methods, reading the ASHRAE, PIER, DOE, CTI and contacting friends that manage plants. Web literature from vendors runs from conflicting to bizarre.

Anyone care to share their experience or preferences for chem and non-chem water treatment for towers? Posted here as I am an energy engineer. No CaCO3 or white rust problems, no plated or packed bundles, but interested in other opinions as I have only used one PWT method before, it was not a good thing, and do not want to go into that area with all negative bias.

 

[mbeychok]

mauricestoker:

You have lost me! Most large evaporative industrial cooling water towers require pH control and anti-scaling chemical treating, corrosion inhibiting chemicals, algaecides and biocides. I just don't see how you can control scaling, control corrosion,or prevent growth of algaecides and bacteria without using chemicals.

You would have to use essentially distilled water to avoid scaling , stainless steel to avoid corrosion, and perhaps radiation to control algaecide and bacteria ... and the cost would probably be totally unacceptable.

Perhaps my problem is that you haven't told us the size of your cooling towers. Maybe in very small sizes, physical methods might be feasible ... but I'm not sure of that. I am also not sure if you consider radiation to be a "physical" treatment.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[dcasto]

here is one

http://intevras.com/evras.html

 

[mbeychok]

dcasto, I can see how the Intevras sysytem will certainly help clean up the cooling tower draw-off (blowdown) ... but I fail to see how that helps with preventing scaling, corrosion, algae and bacteria growth in the circulating cooling water piping and the heat exchanger tubes in all of the water cooled heat exhangers served by the cooling water.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[mauricestoker]

There are scores of non-chemical cooling tower water treatment companies, ASHRAE has publshed recomendations on physical water treatment (RP-1155) and I'm trying to find their publication on biocidal effectives. VRTX technologies and the Dolphin (Clearwater Springs) are both endorsed by California Energy Commission. EnviroTower would be another option, but with a price tag.

I'm looking at about 6300 gpm.

No problems with the current system, which is chemical. I've had no problems with chemical treatment. I've been speaking with friends that run larger plants, 15-20,000 gpm, who have tried physical water treatment, and none have been endorsed (though one friend at a large plant is going to the Dolphin, and he has concerns). I prefer chemical just like I prefer Tranes, but that doesn't mean R-123 is best. Just looking for a different perspective.

 

[RossABQ]

I've run into this too, and as you say, some large gov't organizations have "endorsed" them. After much investigation, I've concluded the organizations endorsing them (save ASHRAE) don't care at all if the systems really work, as long as they get rid of "nasty, hazardous" chemicals. None of the regulators will be chipping in for a new chiller bundle or CT basin if they don't work. The one vendor I spoke to who appeared to be honest said they would not recommend their system unless their chemical analysis of the make-up water indicated a probable success story, but who knows?

The science appears to be sound, within limits, but no users I polled seemed resoundingly positive about them.

 

[mauricestoker]

Thank you, Ross. That's how I feel, too, but was concerned that maybe I was missing something over the last 30 years. I'd rather have nasty chemicals than a packed bundle.

 

[SailorNuke]

Have you thought of going to a new type of tower technology that uses a closed loop and reduces water consumption by 95 to 98%. With this type of tower one only needs to treat for a closed loop and reduces chemical and water usage. The Italians have been making this for about 15-20 years and have recently brought it to the US. They have been mostly using them in the plastics industry.

 

[RossABQ]

Sailor,
If the ambients are moderate, they work OK, but any of them that require external (to the tubes) spray water to meet spec on hot days are to be avoided IMO.

Overall, cost killed them on my project; 3x the first cost for equal performance (same ambients, same condenser water range and temps). You can buy a lot of water for that kind of money (in most places).

 

[cdxx139]

One word of caution. Have the water tested by the local non-chemical water treatment rep. I specified and designed for the Evapco non-chemical water treatment system along with a new cooling tower. It was a LEED building, and it didn't get us a LEED point, but assisted in getting some of the points.

The rep told me they tested water in the area before, so he didn't need to do an actual testing. When it came time to build, and they did the actual test, it turned out the water content was not right for their system, and it was abandoned for a chemical system.

These non-chemical treatment systems for cooling towers bond with certain minerals in the makeup water to "pull" the scaling etc out of the water. So if your water is not dirty enough, it cant bond to it, and is ineffective. (I am oversimplifying this, because I don't recall all the details, and haven't done one since).



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