[Methylated]

I make biodiesel, methyl esters of fatty acids. The process generates waste water containing 3-5% methanol as well as about 1% methyl esters and soap. The fatty acids and methyl esters can be released by the addition of acid. That leaves salt and methanol in the water.

I want to "neutralize" the methanol into a non-toxic substance. Is there something cheap that can be added to this methylated water that will destroy the methanol and not leave toxic waste behind? As an example, what would be the effectiveness of using UV radiation to break down the methanol like occurs naturally in the atmosphere?

If this is not an appropriate question for this forum, please excuse and advise where it would be appropriate.

[Arkcon]

I make biodiesel, methyl esters of fatty acids. The process generates waste water containing 3-5% methanol as well as about 1% methyl esters and soap. The fatty acids and methyl esters can be released by the addition of acid. That leaves salt and methanol in the water.

Cool.

I want to "neutralize" the methanol into a non-toxic substance. Is there something cheap that can be added to this methylated water that will destroy the methanol and not leave toxic waste behind?

No

As an example, what would be the effectiveness of using UV radiation to break down the methanol like occurs naturally in the atmosphere?

Minumal.  Methanol is a small molecule, it doesn't work as much of an "antenna" to catch UV radiation.  Furthermore, hydrocarbons in the atmosphere react slowly, and they are more dispersed than your methanol in water.  Reclaim your reactant by distillation, perhaps freeze distillation.

If this is not an appropriate question for this forum, please excuse and advise where it would be appropriate.

Plenty of people would like a cheap, quick, flawless way to remove methanol from a solution -- these people usually want to bootleg denatured alcohol into drinkable ethanol.  Methanol was chosen for this purpose precisely because it was hard to do.  The topic of detoxifying methanol is not one to shout from the rooftops.

[ARGOS++]

Dear Methylated;

In case your wastewater has to pass a “Waste Water Treatment Plant”:   ─   Don’t fear!

The bacteria therein are crazy for Methanol. In some such plants they add Methanol to get better “Clarification Results” of other Toxics.

Good Luck!
                    ARGOS⁺⁺

[Methylated]

Argos,

I wish it were that simple. The water will be discharged into a stream. Federal and state laws severely limit BOD content for water discharged into a stream.

Arkcon,

I am not trying to separate ethanol from methanol. If there were any other alcohols in the water, I would want them destroyed as well.

Distillation is too energy intensive.

What about spraying the water into an ozone rich atmosphere?

Methylated

[ARGOS++]

Dear Methylated;

Of course, directly discharging to a Stream generates a Lot more troubles.

Unfortunately I believe that the ozone method will even be very cost and energy intensive, because almost all other toxic may consume the ozone before the Methanol.

Let’s anyway hope I may be wrong.

Could it be that you produces in batches and keeping the waste back in a collector to discharge it continuously below the BOD limit? That’s maybe the cheapest.

Good Luck!
                    ARGOS⁺⁺

[Methylated]

First, Thanks you guys for answering.

I can process the BOD down to "irrigation" quality water, but not to "stream discharge" quality by breaking down the soaps and settling.  It fails on both BOD and salinity.

What about bubbling O2 through the water? (other than the huge risk of BOOM)

What about esterification into something that does not dissolve in water? Small amounts of water inhibits esterification with fatty acids. 

Finally, what about zeolites or molecular sieves?

[sjh9]

zeolites no, molecular sieves no (analogous).   most will take on water before methanol.  Certain carbon products perhaps.. Are you making methyl esters from triglycerides?  If so then you have glycerol to deal with as well.  If you are converting fatty acids directly to methyl esters then you may want to use an excess of the fatty acids to consume almost all of your methanol. 

[Methylated]

Thank you every one for responding. I was hoping there was some obscure chemistry that someone might know that would do the job.

Here is what I'm doing. After making the methyl esters the raw glycerin settles and is drained. The biodiesel is then washed with water to remove the soap and methanol. The water is passed slowly through hydrated CaSO4 which causes the soaps to exchange their K ion for the CA ion.  The new soaps are not water soluble and float between the water and the oil. This is passed through a grease trap to capture the soaps and oils. Once through the grease trap the water contains Potassium Sulphate and Methanol. Potassium sulphate will mostly precipitate out leaving the methanol and trace salts.

So Aside from removing the methanol before washing, I'm stuck with water containing high enough concentrations of methanol to prevent discharging into a stream due to BOD.

[Arkcon]

Thank you every one for responding. I was hoping there was some obscure chemistry that someone might know that would do the job.

'Fraid not.  Like I said methanol is a small molecule, chosen in part for it's toxicity.

So Aside from removing the methanol before washing, I'm stuck with water containing high enough concentrations of methanol to prevent discharging into a stream due to BOD.

You haven't mentioned your scale.  Are you a hobbyist working outside of your garage/shed/barn on a small farm?  In which case, you might just leave it open, and let the methanol evaporate, if you can keep animals and children away from it. 

If you generating gallons of the stuff, well, welcome to the wonderful world of fuel refining.  You'll have to drum, secure, inventory, and contract for the disposal of your toxic waste.  You'll pass the charge on down to the end user -- who will gripe, file nasty editorials, and generally treat you like foreign and domestic petroleum producers.

If you're somewhere in the middle, you'll have to see which is for you.  Though I think distillation, at least to concentrate waste and produce a greater volume of easier to dispose of water waste, is the answer.

[Methylated]

We're on the smaller end of the scale. More farmer/hobbyist than anything.

I guess I'll focus more on removing the methanol before we wash.

Methylated

[AWK]

Methanol can be easily distilled off from water
(boilng point about 65 C) and recycled to esterification since it do not form an azeotrope with water and can be obtained nearly anhydrous this way.

[Arkcon]

Like AWK says, distill it.  You're a fuel producer, burn some of your fuel to reclaim your waste, again, just like the petroleum refineries do.  If that cuts into your yield, well, maybe you have to rethink the feasibility?

[dlzc]

Arkcon,

I am not trying to separate ethanol from methanol. If there were any other alcohols in the water, I would want them destroyed as well.

Distillation is too energy intensive.

What about spraying the water into an ozone rich atmosphere?

Ozone and water alone are not enough to help.  It would take advanced oxidation (ozone-or-H2O2, TiO2, and UV).  Even more expensive.

If biology likes this stuff, you probably could aerate it and blow it through carbon, which would become a substrate for "bugs" that would consume this down to nothing.

How much water per day do you produce?