Cooling Tower Blowdowns and Treatment

Difficult!

Dosing chemicals are particularly effective at disabling biology, as required in a well-run cooling tower, so as to minimise the possibility of air-borne problems, like http://en.wikipedia.org/wiki/Legionella_pneumophila among others.

Ozone would be classed as a dosing chemical.

Some additives would be prohibited in a pharmaceutical works.

Suspended matter is best removed by filtration; strainers around the circulating pumps are probably best for large items, like bits of wood, leaves, feathers, guano, cardboard, plastic bags, spanners, etc. A well-run cooling tower's water circuit would have low turbidity and small quantities of low-size suspended solids are not normally much of a problem.

Total dissolved solids [TDS] is another matter. Whether one doses or not, water in its purest form is lost from the circuit by evaporation; that is how a cooling tower works. Make-up water has dissolved solids, and as evaporation takes place the concentration of these will rise. At some point the TDS concentration approaches an operating limit, measurable by the conductivity of the water, at which point blowdown is unavoidable. The reason is that with rising TDS and no blowdown, solids will begin to precipitate out both on the tower packing and also the heat exchange surfaces that it is feeding, reducing the effectiveness of the cooling circuit. With blowdown one also loses the biological protection effect of any dosing chemical so one needs to add more. Some additives have the property of keeping precipitating species in suspension, thereby enabling the TDS setpoint to be raised and a reduction in the frequency of blowdown, which can be economically attractive.

Operating a cooling tower is a potentially hazardous operation that needs to be well-managed to be both safe and lawful. Experimental work with a live system is not recommended. One option, if perhaps the expertise might be lacking in-house, is to contract-out the chemical dosing. Many companies can supply this service in all parts of the world and some research is needed to determine locally the best one for the particular application. Payback for this can be expressed in terms of reduced maintenance costs and greater equipment availability, both of the tower circuit and the equipment it feeds.

I have seen towers erode quite quickly without proper chemical/bio treatment. There are several companies I am aware of that make alternative treatment equipment. when I installed my last tower 'ahem' replaced my last tower, I did extensive research into these methods. My conclusion was (two years ago) that these technologies were still in the infant stages. A cost/value comparison made my decision. Still dosing, and don't want to be a guinea pig. I do however feel that a 'greener' approach is in our near future.

http://www.evapco.com/media/pdf/water-treatment.pdf

Check out www.heislergreen.com. They just came out with a complete line of GREEN cooling water treatment products. They can use a GREEN chemical combination, or include new technologies for mechanical systems that modify the crystalline structure of CaCO3. If you want green, this is the way to go. The chemicals are also capable of running a tower at high cycles, and even zero blowdown and zero liquid discharge.

Off-line "Electro Coagulation" is what you are looking for.

Chemical Dosing builds up and up to dangerous proportions.

Google -and ask a few vendors for quotes.

If you want an inexpensive DIY solution ,Yours Truly can help implement that.

• Where is your Cooler located.
• What is the total water in circulation
• pH presently.
• ANY relevant plant layout limitation?
• Cost /Budget limitation

Check out EVAPCO Pulse Pure System. www.evapco.com We have had success with this system.

Using it or selling it?

It is an interesting question. Chemical treatment is best answer for high TDS system since it is specifically designed to take care of individual constituent in water.

You have not mentioned using RO water for make-up. We have tried it in our cooling tower for yeast fermentation and it worked well. You start with very low TDS and feed with a low TDS as well and you reduce overall water consumption.

RO permeate has so little dissolved species present that any contaminant is going to have a greater effect than it would using town mains.

Returned steam condensate that is rejected on the basis of conductivity is another option.

Provided the water is buffered for pH both should work well. In both cases the treatment regime will change in comparison with using town mains, and the treatment company may be displeased, as less chemical will be needed and their income may drop.

A technique called 'seed slurry crystalization' has been used with good success at nuclear power plant in Arizona where recycled municiple waste water in the source for cooling water. There are 2 different potential problems in any evaporative cooling tower--biological growth (slimes,algae,etc) and mineral deposits -scale. All must be properly managed to avoid corrosion under deposits and capacity degredation. Get site/tower specific advice from your local water treating experts (Nalco is one) There are NO general solutions as the chemistry can be very specific.

Just stumbled upon this discussion, I know its late, but the problem with magnetic pulsing on the outside of PVC piping is that the heat from the electromagnet hetas up the PVC pipe. Scale builds up on heated surfaces first. These two points leads to scale forming on the inside of the device section leading to loss of efficacy.

This problem is the same one that plagues the Dolphin system as well.

Go to www.eh2o.com (manufacturer) to look at the system eH2O manufactures. It directly fires the pulse charge into the water rather that into an electromagnetic coil around the water.

Also, this system is the only one I know of that is 100% chemical free (not even iodine) for its entire lifetime. Not biocides or inhibitors ever.

You can go to www.ifacilitation.com if you want to send me comments or if you're interested in getting one of these. I can hook you up with a distributor (of which I'm not).

Saving the planet one BTU at a time.

Wayne