Solar Evaporation Ponds
Solar Evaporation Ponds
(OP)
I am looking for design information to size and build a Solar evaporation pond for cooling tower and boiler blowdown water. I am in colorado and here they are called impoundments. I need to know the typical type of liner system and how to figure out the evaporation rate per sq ft in the summer and winter to have a shot at sizing this thing. Thanks for any input you have. Google was not much help this time.
Regards
StoneCold
Regards
StoneCold





RE: Solar Evaporation Ponds
as for the liner, just make sure it is waterproof, there are many out there.
Colorado.... Doesn't it freeze there on winter?
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RE: Solar Evaporation Ponds
RE: Solar Evaporation Ponds
The liners (yes you have to have two) must be selected for their specific performance in contact with the fluids you are evaporating, and the design of the leak-detection system between the liners is a week's work.
Design of inlet facilities is another couple of weeks.
Finally, you have to work out your strategy for mucking the solids from the pond (not a trivial task, do you shut down the facility while removing the accumulated solids, or do you build your pond with sections to allow it to stay in service while solids are removed and liners replaced?)
I'm working on permitting a pond in New Mexico, and the first step in the permitting process (the regs allow 60 days) is now in its 10th month.
Oh, by the way, if your "impoundment" has over a certain number of acre-ft of water and/or if your largest wall is over a certain height then the pond suddenly must be permitted both by the state and by the Corps of Engineers. Have you thought about how to keep migrating birds off the pond?
I have a rule of thumb for your--hire someone who know what they're doing before you get into deep trouble.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: Solar Evaporation Ponds
I am always in deep trouble! But you may be right that I need some help on this. I seem to have trouble getting constulants to do anything helpful for me. By the time I have answered all there questions I could have just done the work but that is another topic.
I just want to kick around the basics to see if it will fly, and to see how big it is. My other alternative is to concentrate my water in a brine type evaporator and truck it off. That ain't cheap!.
Regards
RE: Solar Evaporation Ponds
I hear that from clients all the time. Evaporation ponds seem to be one of those things that come into the category "the definition of 'easy' is 'someone else has to do it'". These things just look to be far too simple to be as difficult as they end up being. Engineers tend to want to either leave them earthen or make them into plants. None of the big firms ever builds a second one so they never get really good at it.
I did a talk on getting rid of produced water at the Four Corners Oil & Gas show in 2006 and the PowerPoint handouts are at http://ww
David
RE: Solar Evaporation Ponds
RE: Solar Evaporation Ponds
RE: Solar Evaporation Ponds
David
RE: Solar Evaporation Ponds
Great job in explaining that a task that appears simple is far from that.
Pan evaporation rates are widely used to estimate evap pond sizes but you can run into some serious problems when the salinity in the pond gets high. Hydrate formation tends to hinder evaporation much like the bird netting and wind fences. In desert climates like NM and CO designing for an evaporation rate much higher than an average annual loading of 2 gpm/acre is asking for problems.
The problem with mucking out the ponds is what to do with the accumulated salt. The high sodium content will limit where you can place it as it will readily leach. I have always felt it was better to design and permit the site as a landfill and when the pond filled up with salt, close and cap it.
RE: Solar Evaporation Ponds
We are looking at the pond as an option to mechanical evaporation using steam or natural gas. They are all cheaper than trucking it off but I am not sure that the pond beats the evaporators by much when you consider the cost of construction and mucking out the solids later.
Thanks
StoneCold
RE: Solar Evaporation Ponds
It is very possible that pond muck will be classified as "dirt" and can be disposed of anywhere that you can get rid of dirt. In a chemical plant you'll certainly be required to test it for various nasty chemicals and NORM, but if it passes those tests then it can go to a landfill in most states.
Liners have a finite life, so it is prudent to design a pond such that you approach maximum solids around the same time as the liner integrity becomes suspect (I generally use 10-15 years).
The evaporator vs. pond decision is really a CapEx vs OpEx analysis. The pond is all Capital and the evaporator is minimal capital and a ton of operating expense. As natural gas prices go up, the balance shifts significantly towards ponds.
David
RE: Solar Evaporation Ponds
I agree that there will be salts, they will pile up but I think that biological will pile up faster. Just my gut feeling on that.
You are right about the CapEx vs OpEx on the evaporator. But since the plant is in northern colorado I have to take into account the fact that I am not going to get much evaporation from November to the end of Feb. So then I end up with the situation where 8 months of evaporation has to balance 12 months of water in. I am not sure I have enough open area dirt to make that happen.
Thanks
Brad
RE: Solar Evaporation Ponds
There is no reason that a properly designed facility wouldn't work year round.
David
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: Solar Evaporation Ponds
RE: Solar Evaporation Ponds
David
RE: Solar Evaporation Ponds
Looks like a very challenging problem you have there. Just the reason I started engineering!
From the discussions so far it sounds like most of the issues are being uncovered. I was dealing recently with a evap pond that had silted with acidic/metalurgical waste muck! The issue was no one had thought about how to remove muck from the pond. As you have already identified the need to remove the solids why not design the pond with solids removal equipment. Just throwing ideas up, an interesting application for an Archemedies screw was on a Pulp mill effluent pond to extract sludge from teh bottom of the pond and also served as aeriation to address the high BOD/COD load for the effluent. In your application this splash would assist in evaporation as well as providing a method for sludge/solids removal. Is there any further value for the biological blowdown?
Cheers
Mark Hutton
RE: Solar Evaporation Ponds
Don't forget to report back and let us know how it went!
- leakyseal, former polymer guy, now working wastewater eng
RE: Solar Evaporation Ponds
As far as simply constructing an impoundment and forgetting about all other issues, just be darn sure the impoundment liner, base, walls, etc are designed by an experienced dam designer and not just copied out of a civil engineering text book. These simple objects really can fail .