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Active Contributor

Join Date: May 2014
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Zero Effluent from Plant

10/06/2014 10:32 AM

Many industries are faced with Zero Effluent stipulation by regulatory agencies.The one which drastically reduces the quantity, is by converting all dissolved solids to Sodium Salt in Softner, then Passing through Ultra-filtration and multiple RO. The Reject water has high solid content but not enough to precipitate out. If the dissolved salt is Sodium Sulfate , what is economical way to get the liquid evaporated? Solar ponds takes large area. Sodium Sulfate recovery plant is expensive. Flue gas of 500 Deg C is available to heat the liquid to around 80 degree. Can passing repeatedly by pumping via atmospheric type cooling tower, precipitate out the solids? The resultant paste can be disposed off after pressing in filter press, to authorized solid waste dump area. Kindly share your experiences or some innovative ideas.

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Guru

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#1

Re: Zero Effluent from Plant

10/06/2014 12:30 PM
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Guru

Join Date: Apr 2014
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#2

Re: Zero Effluent from Plant

10/06/2014 7:21 PM

Do what Vermont does: in winter they make snow with the effluent. Even their very posh ski resorts do this and no one's the wiser.

In other words, Vermont is where the affluent meet the effluent.

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Active Contributor

Join Date: Sep 2014
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#3

Re: Zero Effluent from Plant

10/06/2014 10:36 PM

Hello;

Take a look at this company: CINC Industries

They have a long history of solid/liquid separation. You might remember them

from the BP Oil Spill a few years ago.

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Guru

Join Date: Jul 2007
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#4

Re: Zero Effluent from Plant

10/07/2014 3:40 AM

No-one wants sodium sulphate.

The solution to pollution is dilution.

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Guru
Engineering Fields - Instrumentation Engineering - EE from the the Wilds of Pa.

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#5
In reply to #4

Re: Zero Effluent from Plant

10/07/2014 8:20 AM

Uhhhh....NO. In the USA, EPA is wise to that move. Can't do it.

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Guru

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#6
In reply to #5

Re: Zero Effluent from Plant

10/08/2014 1:20 AM

Yes, probably best to let the EPA and their off-the-books operatives do it directly themselves. They know where all the best dump sites are, anyway. You realise of course that the EPA are also in the business of selling the 'right to pollute', and to the highest bidders? How do you think some of these big polluters stay in business? Somebody is allowing it - and at a price.

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Guru

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#7

Re: Zero Effluent from Plant

10/08/2014 4:37 PM

There is a new technology coming down the pipes to take industrial wastewater from boilers and cooling towers, and clean it up to a re-usable state. The only by-product is going to be solids, which might substitute for aggregate in road building.

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Active Contributor

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#8
In reply to #7

Re: Zero Effluent from Plant

10/09/2014 2:13 AM

Can you elaborate the technology. Currently the Treated Effluent has about 3500mg/liter Calcium Sulfate, we pass it through Softner, to convert it to Sodium Sulfate, then we pass it through ultra filteration , before passing it through two stage RO plant. We have a resultant water 5 KL per day,with about 30000mg/liter of Sodium sulfate, whose saturation point is close to 140K mg/liter. instead of evaporating in a furnace, we are thinking, to heat up to 80 degree and pass it through cooling tower , till it reaches close to saturation point. then leave the water to cool, at some point the solids will crystalize out. Before attempting this, we wanted expert opinion.

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Guru

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#9
In reply to #8

Re: Zero Effluent from Plant

10/09/2014 4:26 AM

Hello ranabir chakraborty,

Just curious, but what measures are you considering should the ambient air-temperature drop and your solution crystallises within the cooling-tower piping? Seems to me that such a situation could happen easily enough whilst getting very expensive very quickly?

Once the solution begins to crystallise in the pipes - even if it were to start in just one spot - it's all downhill from there. Once the flow slows and comes to a halt because crystals are blocking the pipe, the rest of the solution in the pipe will cool to supersaturation, crystallise and there goes your pipe; all of it - and your profits with it.

I would definitely explore other means of cooling your solution, preferably by doing the cooling outside of any piping. What of using a 'curtain' of fine spray, for example, where the droplets of solution cool in free-fall, becoming supersaturated en route to the bottom and crystallising there on some sort of carrier which can removed for post processing? Make the carrier itself out of the same material and you can process the whole thing in one shot.

A heated, near-saturated solution running through piping inside a cooling tower is asking for trouble. Think of other approaches. The basic idea is sound, but don't depend on that solution not crystallising where you can least afford it to - and it will crystallise at some point, say, if outside temps plummet overnight and nobody is minding the temps.

Pipes are bad news in general where heated, near-saturated solutions are concerned. You may end up replacing it all. Find another approach. As some piping will be necessary no matter what approach you take, make sure it's heated and provide an automatic mechanism to drain the pipes quickly should flow stop for any reason.

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#10
In reply to #9

Re: Zero Effluent from Plant

10/11/2014 1:50 AM

Let me clarify further. The place is in India, with summer temp of 45 Degree C and winter day time 15 degree C. Use of Natural draft Cooling tower means.It is free fall from spray nozzles to the sump. No pipes/no trays, no plastic bundles. The Sump is to be maintained at about 80/90 Degree C. Pump will spray the water from sump to spray nozzles and back again. When the concentration is close to saturation point, heating will be stopped. The water then cools at night, to atmospheric temp. The solids should separate and we tap out the clean water. The solids would be manually collected to a a drying pit , before packing them in gunny bags for disposal to Govt. authorized dumping facility nearby. Can this be done or feasible ?

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Guru

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#11
In reply to #8

Re: Zero Effluent from Plant

10/13/2014 4:17 PM

There are crystallizer plants out there that do something like what you have proposed to sodium sulfate, just make sure it is sodium sulfate, and by analysis you are near the detection limits for calcium and magnesium, etc. Once you do that, you could even use solar brine pond trick to provide enough energy to operate a vapor compression cycle - crystallizer combination plant, to produce salable sodium sulfate, and reasonably high quality condensate. At the 30,000 mg/L mark, your waste water from RO is probably past the useful point of further recovery by seawater RO membranes, but you should still check that out as a possible pre-concentration step.

The technology I was referring to is just past research phase, is highly confidential, and has only just entered first pilot-plant phase within the last 30 days. It does not remove all of the TDS, but can approximate the incoming quality of the water being used in a cooling tower, with no hardness, and nearly complete removal of silica. Patents are held on the technology, and after the first commercial run on it, I plan with the patent holder's permission to further discuss major breakthrough on this blog.

Any water technology that will deliver ZLD with low-tech, no membranes, etc. is a major deal.

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Crabtree (1); europium mkII (3); James Stewart (2); KeithMorin (1); Phys (1); ranabir chakraborty (2); SolarEagle (1)

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