Side Stream Cooling Water Treatment 1

[sshep]

I am moving to a plant which suffers from terrible cooling water problems. The source of make-up water is from a waste treatment system and loaded with solids (biological and other), which are further cycled up by the cooling towers. Water is very precious there so no other make-up source is practical.

At present I have no quantitative detail on % solids or their nature. The water is described as being "thick" with solids, and from previous work in units on the same site I have on occassion observed the cooling water to have the color and consistency of chocolate milk- YIKES! I envision some side stream (or feed water) treatment for solids removal. I am seeking recommendations in advance on the type of equipment, packages, and suppliers normally used for such cooling water treatment. Any advice is appreciated.

best wishes,
sshep

 

[ScottyUK]

sshep,

We installed a self-flushing rotary screen filter in the condenser cooling water lines to our steam turbine. In our application we are only concerned with removing solids down to about 5mm diameter because below this level we do not experience tube-blocking problems. Do I sense that your problems are more of a silt-like nature?

If it is of interest, the equipment was built by a French company, Beaudrey & Cie, and has proven very reliable. We installed it ourselves. They are not a large company, but showed great flexibility and worked well with us to customise our equipment. I've just learned while looking for their url that they have a US subsidiary too.

http://www.beaudrey.com/english/indexEn.html

http://www.beaudreyusa.com/

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I don't suffer from insanity. I enjoy it...

 

[cub3bead]

Lots and lots of things to look at besides just the solids.

How much NH3? If you have Cu alloy tubes you can expect alot of issues usnless the NH3 is nitrified or removed otherwise.

How much P? The P and NH3 will feed the bugs that have the nice warm and wet environment of the cooling tower to live in. Left unchecked your fill will have lots of slimey things hanging. Hmm...a giant trickling filter.

Any residual surfactants will cause foaming.

You will need to provide more detail for more complete opinions but you won't likely get a complete design package.

 

[sshep]

When I first made this post I had not been to the site, now I have seen it. Very dark coffee is a more appropriate color description- essentually no light can penetrate even 1cm of water. The solids concentration from evaporation tests are tremendous, but practically no settling is observed in standing liquid. An ammonia smell is present. In a few days I will get a complete analytical report.

In the meantime a rather interesting theory was presented in that some biological solids are healthy for cooling water. The rationalization is that scaling from water hardness will adhere to suspended solids rather than tube walls (all are carbon steel by the way). I am skeptical- any opinion on that?

On the otherhand when I arrived considerable work was under way to hot tap high volume caustic batch injection nozzles in the inlet piping for purposes of improving heat transfer. I would not have bet 2 cents on that and yet when we did the injection today there was an dramatic positive effect. Any suggestions on why that works?

best wishes,
sshep

 

[Yorkman]

The system sounds like its a mess, I don't have much in the way of advice. Most of the filtration systems that I've seen use a large amout of water as they cycle and flush the solids down the drain. With your water issues or lack of quality water as it were, I'm not sure these type of systems would be of benefit. As far as the caustic injection the only thing I can think of is that it caused the desolved solids to drop out of suspension, where they dropped to, your guess is as good as mine but I bet sooner or later you'll find out!!

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[bimr]

"In the meantime a rather interesting theory was presented in that some biological solids are healthy for cooling water. The rationalization is that scaling from water hardness will adhere to suspended solids rather than tube walls (all are carbon steel by the way). I am skeptical- any opinion on that?"

Pure nonsense is my opinion.

"On the otherhand when I arrived considerable work was under way to hot tap high volume caustic batch injection nozzles in the inlet piping for purposes of improving heat transfer. I would not have bet 2 cents on that and yet when we did the injection today there was an dramatic positive effect. Any suggestions on why that works?"

It is a well known phenomena in the water treatment business. A change in the composition of the water will frequently shell off the old scale right down to the bare metal. Don't worry however, the scale will quickly reform.

 

[EdStainless]

You will get you basic water chemistry data, then you can make real decisions.

The bio-solids theory would not be too far off, if you had huge volumes of sediment to deal with.
Actually the particulate (non-disolved solids) are of little concern to me.
You need to focus on scaling, pH and biocide are where I would start. You may need to knock the solids down in order to control biological growth, since that may be what is feeding it.
You also need a good inventory of what metals are in the systems that use this water. Much copper an brass? What about carbon steel? stainless (check clorides).
I have seen similar plants, but in there case the incoming grey water was very much dead. Still lots of organic content, but no biological activity.

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Rust never sleeps
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http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[JimCasey]

It sounds like yo're on "Dune". Is there ANY possibility of getting the plant to spring for a still to purify the water? I have in mind the military reduced pressure types frequently used on ships to provide fresh water. Reduced-pressure lets them operate at lower temperatures on waste heat. Aqua-Chem is one manufacturer that comes to mind. This stuff sounds WAY too contaminated for an RO Unit to work-besides an RO unit generally disposes of 75% of its source water anyway-so you'd "still" need a still to reclaim that.