Acid Wash Instuctions

[backyardsugarer]

Could someone please post good instructions for acid washing membranes. I have a waterguys 2500 RO and one of the membranes really needs a good acid washing. I have everything from leader to do it and now I have the time so I want to get that membrane cleaned then stored. Thanks.

Chris

[DrTimPerkins]

Could someone please post good instructions for acid washing membranes. I have a waterguys 2500 RO and one of the membranes really needs a good acid washing.

Your FIRST source of information should always be the manufacturer of the RO system you are using. If you change the membrane from what was supplied, you should consult both the RO manufacturer AND the membrane manufacturer. Different systems have different ways of doing things and different pH specifications. What works on one system may not work on another, and doing the wrong thing could result in damage to the RO system, the membrane, your product, or to YOU.

In NY, there are now specific NYDEC procedures in place which need to be followed to first neutralize and then dispose of (discharge) RO wash water. Not following these instructions could result in some fairly unpleasant consequences for maple producers.

[Bucket Head]

Alright, seeing nobody else has, I'll jump in first. Dr. Tim, what are these discharge procedures? Are you familiar with them? How new are these requirements? What are we supposed to do with the water? This is the first time I've heard of it. Where would this be covered on the DEC website, if it is covered there? Thanks for the 'heads up' on this one.

To all- I would have thought the state Association would have mentioned this to everyone. Did they and I missed it somehow? If so, when and where was it mentioned?

Steve

[DrTimPerkins]

I expect it will be communicated to producers through the NY producers association and through the equipment manufacturers and dealers. In essence, as long as producers follow the recommended procedures, they will fall under a "blanket" permit for discharge of the wash and rinse water. If they do not, they will be required to get an individual discharge permit....and you don't want to go down that road.

[Brian Ryther]

At the Catskill Maple Producers Meeting this past Wednesday Hellen Thomas from the NYSMPA did mention this topic. She eluded to the practice of adding citric acid to the wash water before putting it down the drain. She did not give details if this was the requirement or sudgested practice. If it is the requirement I do not feel that it is that bad of a procedure. Just add a little lemon juce to your wash water before it goes down the drain.

[maple flats]

According to an article in the NY Farm Bureau newspaper that arrived today you can dump permeate any place in the environment. The wash water must be brought to a PH of 7 by adding citric acid (lemon juice or other) before dumping it. I saw nothing addressing where you can and can't dump. I'll try to find out if there are limitations where it can be dumped.

[Bucket Head]

A NYSMPA rep. "eluded to" and did'nt say wether it was required or suggested? And Dave gets more info on the issue from a newspaper? Thats interesting.

Thanks Tim, Brian and Dave for the information. Like I said, I had no idea there was an issue with RO wash water. No other states have an issue with wash water, just New york? Thats interesting too. More permit and/or fine possibilities for revenue generating here in the good ole' empire state.

Anyway, I agree that adding a little lemon juice is'nt that big of deal.

Steve

[DrTimPerkins]

The wash water must be brought to a PH of 7 by adding citric acid (lemon juice or other) before dumping it.

I believe that in the case of some ROs, the wash water will circulate back through the membrane before being discharged. In that case, it is probably best to use citric acid (which is approved for membrane use and typically available through your maple equipment dealer) to neutralize the wash water. Citric acid shouldn't harm most membranes (check your specifics with your manufacturer and supplier though). If you use lemon juice, you could end up cycling it though your membrane(s). Lemon juice has a LOT more stuff in it than simply citric acid, in particular, lots of strong flavor compounds. In short...I doubt anyone would like to make syrup that tastes like lemons.

[Maple Hobo]

If your washing with an acid, wouldn't it need an alkaline to newtralize it, not more acid?
I didn't think the "acid" wash was an alkaline?
Guess I need to get a PH kit next season and see what our is?

[DrTimPerkins]

Usually, RO "Soap" (which is a real misnomer) used to wash membranes is a strong alkaline material (a high pH material, essentially sodium hydroxide or lye), which is buffered to the right pH for your particular membrane. This is why you need to use the right wash material for your membrane. An "acid wash" (low pH material, citric acid typically) is less frequently used for most membranes, unless they are very dirty and cannot be brought back into proper operation by the "soap" wash. You probably only want to do an acid wash on the recommendation of your equipment dealer/manufacturer. In that case the acid can "sometimes" clean out remaining residues, and can "tighten" the membranes (if you're lucky) if they begin passing too much sugar. Using too high or too low a pH material can destroy your membranes. Also, most membranes are sensitive to chlorine (don't use municipal tap water to wash or rinse membranes), and sometimes to other things as well. Because of that, DON'T use hydrochloric acid or muriatic acid in your RO to neutralize the "soap" or to acid wash...it will probably destroy your membrane.

First and foremost in protecting your membranes....use a good sap filter BEFORE the RO inlet and change it frequently.

So IF you wash with membrane "soap" (an alkaline, caustic) it would require neutralizing the wash water with an acid (typically citric acid, NOT lemon juice or hydrochloric acid or muriatic acid or any other acid). In that case, running the wash water through your membrane to a drain wouldn't be an issue, as you would be using two things the membranes can tolerate.

Copious rinsing after any type of "wash" is required.

Again, the BEST thing to do is to check with your specific maple dealer/supplier for instructions and materials that are SPECIFIC to your RO machine and your membrane. Using the same thing your friend does can result in a very costly lesson if the RO/membrane system and the wash materials are incompatible.

Finally....yes, a way to measure pH is a good idea if you have an RO.

[Maple Hobo]

Ah.. Thank you for the clarification.
I was confused by the thread starting as an acid wash question and then people saying you need to add citric acid to dispose of it.

So if your supposed to rinse using 500 gallons of water/filtrate... does the regulation require you to hold the 500 gallons of water in order to treat it too after your wash/rinse? Its bad enough having to hold that much filtrate for the rinse. If you need 2 500 gallon tanks to rinse I think its going to be a pain in the butt.

[DrTimPerkins]

No, once the wash water is neutralized and disposed of, it is followed by a permeate rinse. You do not need to hold the permeate rinse water (you aren't going to do anything to neutralize it, so it can go down the drain immediately).

[Brent]

I believe it was on the DOW web site that they explained that the alkaline wash was to remove the bio-film that fouls the membranes fast and that the acid was was to remove mineral deposits. When you send a membrane back to the factory for professional cleaning, they do repeated alkaline/rinse/acid/rinse cycles until the membrane performs close to new spec.

It seems that most membranes need the alkaline "wash" after 4 or so hours ( your mileage may differ ). An acid was in normally only need at the end of the season, if at all.

On the legality issue. I am sure there are very simple polution regulations about dumping acid or alkaline solutions ... regardless if it is an industrial process, a farm milking operation or your maple syrup operation. They don't need a new reg just for us.
If it's not neutralized it is poluting.

[sapman]

So in essence, we will be doing a short acid wash (or acid rinse, as the case may be) every time we wash our membranes? I thought acid wasn't the best thing to put through a membrane very often, so I've only used it at end of season typically.

[DrTimPerkins]

So in essence, we will be doing a short acid wash (or acid rinse, as the case may be) every time we wash our membranes?

No, that isn't the case. The acid is neutralizing the alkaline material (soap) to a neutral pH within the wash tank. So in essence, you're running water, with some minerals/salts, through the membrane at the end. Definitely NOT an acid wash.

[sapman]

Oh yeah, makes sense now. Didn't think of it that way.

Thanks much!

[802maple]

If you have your wash tank set up right ,you should be able to neutralize with lemon juice, as that water when rinsing doesn't go back thru the machine anyway. Because your incoming water is coming from your rinse tank. I would neutralize the water in the wash tank and then the rinse water would go into the wash tank and out the overflow until you were done.

If your water you are using to do your acid wash isn't free of iron and other minerals you will be doing a wash for not anyway as you will most likely end up destroying your membrane with this water.