Evaporation Pond with Surface Aerators

Use a method that will create millions of tiny droplets. This will greatly increase the evaporation rate. Try using compressed air injected into upward spraying water jets with a venturi or duckbill nozzle at the end.

Hello FerdiH,

Try this search page:

http://www.google.com/search?hl=en&q=calculate+evaporation+of+an+evaporation+pond+equipped+with+surface+aerators&btnG=Search

Hope you find what you want. Let us know how you get on please, OK?

Take care...........................

Babybear,

I did it before submitting my request. Most of the information is commercial. I did find a document that I think could be of use although it is on activated sludge systems.

http://web.cecs.pdx.edu/~scott/waer_77_05_25_makinia.pdf

I also contacted some of the suppliers but the response seems to be poor.

Thanks for your suggestion.

Hello FerdiH,

Before you go spraying that stuff into the air, you might better calculate the effect of said stuff on the down wind community. I frankly am totally lost as to how the industry was able to get permits to enlarge the facility with out having resolved this issue in the first place. These kinds of industries are strictly regulated by the EPA in most jurisdictions, that is in the good ole U.S. of A.

Further spraying to evaporate the liquid will only serve to concentrate the stuff that remains, like heavy metals etc.. What will happen if your retention pond floods and over runs it's retaining structure, and does this pond have a liner in it to prevent the effluent from entering the ground water. It sounds to me like a little bit of piss poor planning from the "git go".

My suggestion is to buy more land and in large the pond to accommodate the additional liquid, and forget about the band aid approach, there seems to be too many liabilities in doing a half ass job in an already screwed up manner.

TMF

Hello FerdiH again, Regarding "constrictive input, I submit."

I live in Florida where phosphate fertilizer is mined in massive quantities. Retention ponds abound everywhere, and the banking for said ponds rival the huge mounds seen in many landfills that have been closed. Unfortunately this liquid is very expensive to treat and absolutely cannot be released into the local streams and rivers. HOWEVER: That being said, not a year passes that a spill from one of these retention ponds doesn't occur. Those responsible are fined heavily, but always blame it on conditions beyond their control, like too much rain, etc. THAT doesn't save the fish and wildlife that die as the result of this very toxic soup. The mining began long ago before restrictions to cause the industry to properly deal with this liquid waste existed. These companies made hundreds of millions of dollars in profits and now the public is stuck with all of these left over problems. Sure these companies are fined for their spills but that dose not replace the wild life nor does it reduce the risk. Consider this constructive input.

If the effluent you are spraying into the air gives off an undesirable smell, said smell will only be carried by the prevailing winds across the neighboring community. Strong enough winds might also carry tiny droplets containing carcinagens further than one may assume. The liability goes up. This Mfg. should be restricted from exceeding the amount of waste that this pond was intended to retain until a realistic , not band aid solution can be found, and if that means cutting back production, so be it. This Enterprise now finds itself with this problem because it attempted to increase production on the cheap and now finds that "CHEAP" has become very expensive. Consider this constructive input.

I have had to construct many detention and retention ponding areas of assorted depths, sizes, and configurations. Some required dewatering as much as 15 acres to a depth of ten ft. with the suitable fill being reused to raise a rim around the area and where not suitible removed from the site and replaced with that which is acceptable. I have constructed lined land fills along with unlined land fills that were intended only for acceptable construction debrie. Consider my experience.

I well realize the liability for failure to get it right the first time. Clearly your effort is a time sensitive one, and time and space doesn't permit you to explain the entire subject in full, so there is always something missing, like what exactly is the complete chemical make-up of this effluent how far does the prevailing wind carry any offensive smell at this time and just how much more of this smell and potentially harmful by-product will be released into the atmosphere. Consider this constructive input.

Remember for every attempt to find and install the least expensive solution to a problem, the contract to resolve this matter will be let to the lowest bidder. Consider this a possible problem.

AND: when it fails to perform up to the Engineers assumptions, the Engineer points the finger at the Contractor and the Contractor denies any responsibility and the matter now becomes a law suit that is generally resolved through mediation as continuing the argument just eats up any possible profit with Lawyer fees and Court costs. Consider this constructive input.

Therefore from a very experienced, now retired Contractor, please consider that from experience, I too am well qualified to speak to this issue. As for relaxing, don't bet on it, you already are looking for the cheap fix, to gain the contract, to fix the problem. It is simply the nature of the business.

Exposing what is likely the real issue is always

TooMuchFun

I am a CE in California, we have done similar preliminary design work for recycled agricultural drainage water concentrates, which contain arsenic and selenium as well as many salts. There are a number of companies you can contact redgarding such sprayers to improve evaporation rates by spraying over the ponds. There is substantial documentation and research available through universities such as Fresno State and Cal Poly of the spreading rate of solids from evaporative sprays, and there are recommendations for the clear space for this drift and wells as barrier facilities such as halophytic trees. Many of these facilitiess are actually overseen by state agencies, not federal oversight (except in Oklahoma). Compliance is not only achievable, it is a practice to evaporative spray to concentrate waste ponds, across the US. Your state oversight agency may want you to demonstrate the applicability, as it has been approved in California in the past I would think pretty much any other state will accept those approvals to demonstrate acceptability. However, The improvement in evaporation is only on the order of about 3 times over the long term, or less, and such spray evapaorators must be shut down during high wind conditions (the critical wind speed depends on how much land is set aside down wind). Also, you may be further limited if the waste water contains semi volitile or liquid wastes such as H2SO4, as they can be aerosolized and drift much further then the heavier solids like salt. You should really contact a engineering company familiar with this process. I know the former Boyle Engineering (now AECOM) in California has dealt with a number of such projects for major water districts, drainage district and various chemical companies.

Hello CE from California, I have family members living in your State and I also lived there for a little while. I found cost affordable ways to work within the rules of the Tahoe Regional Planning Agency for several clients.

I gave you a good answer for your comments and others should also,

TooMuchFun

If there is no footprint available for the expansion of the pond, and the only purpose of the pond is to dewater the effluent (why this is needed would be of great interest, as dilute effluents are usually more benign than concentrated ones), then another process unit option to consider is the membrane bioreactor. These are widely used where land values are high and a lot of processing capacity is needed in a small place.

Try talking to a few multinational effluent treatment equipment suppliers.

"Fertilizer Plant" covers a multitude of potential effluents.

Is this being used like the tailings dam in a mine? In that case you want to contain the material and will eventually bury it, so you need to dewater.

Assuming the tailings dam scenario, you could do the same as we did on a gold mine - pump through a pipe with a lot of slots cut in it so it sprays the effluent into the air.

The one I did I cut sufficient slots so that the total area of slots was the same as the cross section of the pipe. It looked funny with a collection of fan shaped sprays into the air going to steadily diminishing heights as it progressed along the pipe. Of course, if I'd calculated the changing pressure drop along the pipe I could have used less slots and made it more uniform, but it really wasn't worth the bother.

Our mine was part of a large cattle station, so more land would not have been a problem.

You mention you can't expand the pond, so you probably have neighbours too close to risk overspray reaching them. In that case, there are numerous makers of surface aerators as used for sewage treatment. These are usually paddles that agitate the surface, increasing the area of effluent exposed to the air. They have the advantage of virtually no overspray and needing little power for the aeration increase achieved. Any number of commercial makers can help you.

Fertilizer effluent can be very acid and have numerous nasties in it. When you talk to an aerator manufacturer, be sure to give him an analysis of your effluent. You don't want to install the thing and have it rotted out in a few weeks or even days.

On our mine we had a pump taking water from the leach pond and mixing it with lime to neutralize it. The impeller on our first (cast iron) pump lasted about 24 hours!

Sceptic,

Thanks for your response. Did you quantify the additional evaporation resulting from spraying? How did you calculate it?

We had a similar problem in our tailings dam in that we reused the water in the process (didn't want to waste the cyanide in it) but rains were increasing the level and our new dam wasn't ready yet.

I didn't calculate the evaporation rate. If it wasn't enough, the system used was so cheap and quick to install, we could simply duplicate as often as we thought necessary. We also had spare diesel driven pumps galore as we used to heap leach and were now open cut mining, grinding and using a conventional processing plant. The old leach pumps were unused and still available. We also had heaps of spare HDPE pipe around, so this setup cost practically nothing. You probably don't have the same luxury.

In fact, not long after we installed it, the rains stopped, and the pressure to reduce the water was off. A couple of months later, the new dam was ready and the 2 dams gave us much more flexibility.

Our situation was different to yours in that we had so much heavy earthmoving equipment available for the open cut mine, that large scale earthworks were quite cheap.

In your case, if overspray is no problem, the simple spray line is quick, cheap and easy. If 1 line is not enough, add more.

You could calculate evaporation by assuming a drop size, estimating how high it goes in the air and hence the residence time, then calculate evaporation from the increased surface area due to the drops and their exposure time to the air. There will also be an additional effect due the agitation of the water surface when the drops fall back in, but I would be inclined to treat this as a bonus and not bother taking it into account.

It is probably not worth the time to calculate the evaporation for this system.

If overspray is a problem, and you need to use a proprietary aerator, the manufacturer can do the estimates for you.

Please keep everyone posted on the outcome.

Good luck

FROM JOHN WEAR, TRIDENT ENVIRONMENTAL SERVICES & TECHNOLOGIES

Regarding the need for increased efficiency in the subject pond:

Design of most aerators, of the type you probably have, does not focus upon the need for large volumes of the smallest sub-surface bubbles possible. A surface air screw, pulling the pond effluent down a shaft with "shearing blades" and forcing the effluent into dispersion by a specially designed impeller which can force the smaller bubbles at least 90 feet surrounding, might increase the efficiency 2X or more. JW

Hello Guest, It would be nice if we knew just who we were responding to, but however;

It seems apparent to this by stander that any action that can create a flow of the existing pond water also disturbs the settled undesirables, that is particulates, fine enough to flow through the system and said particulates could be carried off site by prevailing winds. The OP has yet to identify the chemical content contained in this solution, yet has stated that it must remain on site. If heavy metals are also included within this solution then spraying said solution into the air even higher and with jets producing a finer spray only increases the possibility of not being able to control just where this effluent will land. I must remind you that this retention pond is too small for the quantity now being introduced there, and the OP has stated that there is no room to enlarge.

Actually I would like to be informed of the restrictions to the enlargement, If it is a river or other body of water that cannot be moved that is understandable, but if it is residential or commercially used property, they should buy it, rather than incur any further liability.

TMF

Can someone please show me the solar evaporation calculations, for use here.

thanks,

Chris

Our problem at the gold mine was cyanide for some 6 months after deposition, but long term it was potential leaching of heavy metals and oxidization of sulphides to generate acid runoff. The solution was to dewater the finally filled tailings dam, then cover with a clay layer to isolate the contaminants from the environment. I forget how deep we had to bury them.

The final barrier was better than the isolation of the minerals before they were mined.

It strikes me we have a similar case here. It also sounds as though something needs to be in place fairly soon.

If the area permits it, spraying into the air to increase evaporation is the simplest, cheapest and least likely solution to go wrong.

If there is likely to be a problem with airborne overspray, sewage type aerators can significantly increase evaporation by forcing bubbles of air through the effluent, significantly increasing the surface area and hence evaporation.

I admit this is not the normal use to which these aerators are put, but it should work with no overspray, although, depending on the effluent, it may cause significant smell in the area.

Simplest solutions are frequently the best.

Let me know if you are still looking for information concerning this. Also where do you get your surface pond aerators?

Let me know if you still need information on this. By the way where do you get your surface aerators.

http://www.livingwateraeration.com/