Softening vs pH dosing of cooling towers
Softening vs pH dosing of cooling towers
(OP)
Hi there,
Does anyone know which option is best for the environment
1. Water softening prior to cooling tower through an ion exchange resin which is regenerated, discharging brine to foul sewer Or
2. Acid dosing of cooling towers which should give a reduced bleed off but will introduce acid loading.
Thanks in advance,
Chemicalenvironment
Does anyone know which option is best for the environment
1. Water softening prior to cooling tower through an ion exchange resin which is regenerated, discharging brine to foul sewer Or
2. Acid dosing of cooling towers which should give a reduced bleed off but will introduce acid loading.
Thanks in advance,
Chemicalenvironment





RE: Softening vs pH dosing of cooling towers
As for your question about which is more environmentally benign, probably the sofetining system is. Provided the brine dump is not massive and overwhelms the treatment plant, or upsets the salinity index of the sewers or surface waters.
Hope this helps.
saxon
RE: Softening vs pH dosing of cooling towers
Make up with soft water is generally used where the emphasis is on zero discharge/ reduced blowdown frequency. Make up with softwater enables one to go higher on the cycles of concentration. But it can take water into the corrosive range. It should be noted that some of the commercially available corrosion inhibitors do not work well when the TDS is below 50ppm CaCO3. A proper selection of corrosion inhibitors is required. Moreover softwater CW tends to eat away Zinc from galvanised iron pipes.
The cost of softwater generation/ regeneration waste has to be viewed against the savings in blowdown and increased cycles of concentration (reduced make up.)
Unless one knows the specific water quality and quantities it will be difficult to say cost wise whether soft water make up or traditional treatment ( reduced cycles ) is economical from cost as well as waste water generation point of view.
RE: Softening vs pH dosing of cooling towers
Most of the above comments are untrue.
When treating cooling water for scale reduction, the only items removed by softening are calcium and magnesium, reducing chances of mag silicate, calcium mag silcate, and calcium carbonate. If you remove all calcium, you will actually make the water MORE corrosive.
By feeding acid, you are attempting to keep the LSI (Langelier Saturation Index) at a level below the saturation point for the scales mentioned above. You can definitely keep the pH above the corrosive zone for steel and yellow metals (brass, copper, bronze) without going below 7. If you use acid at pH 7,2-7.6 along with scale inhibitors such as phospate, you can keep the exchangers very clean.
One company that can helpo is GE Betz, or email me and I will get you help.
RE: Softening vs pH dosing of cooling towers
The injection of chemicals (contaminants) is of utmost importance. As an example, biocides, used for cooling water treatment, may make the (concentrated) blowdown unsuitable for reuse. Any procedure that would minimize the need of fresh water make up would be indirectly beneficial to the environment.
Better integration by using, for example, pinch analysis, could reduce discharges where conventional water reduction programs by process changes had already made significant savings.
Comments are invited.
RE: Softening vs pH dosing of cooling towers
I doubt seriously that you can compare both treatmentw, they may be used to solve different problems.
You may use softening to remove Mg/Ca ions but the total ionic load will not change because you will be adding Na ions. You substitute the permanent hardness with temporal hardness. As already mentioned in the other postings when you eliminate all ions you may get a higher corrosivity. You will get deposits only if the conditions are given (concentration, pH, etc.)
By adding Sulfuric acid you may lower the akalinity and also the possibilty of deposits but the amounts are really low (or you will get serious problems) so it probably will not affect the enviroment.
At the end only a comprehensive analysis and chemical treatment program can help you. This requires more than a posting and is where companies like Nalco, Betz, etc. make their business and where you will get qualified help.
Kind regards
RE: Softening vs pH dosing of cooling towers
Check out this link for a report on another alternative that was evaluated recently by our local utility:
http://www.smud.org/education/cat/cat_pdf/PulsePower.pd...
Dean