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RO Membranes Cleaning

02/04/2013 12:08 PM

WHICH CHEMICAL BEST FOR BIO FOULED MEMBRANS OF HYDRONAUTICS SWC5. WE ARE TRIED BOTH alkali and acid cleanig we cant get atleast 10 percet imprvement.plz give a best way for cleaning chemical to me

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#1

Re: RO MEMBRANES CLEANING

02/04/2013 12:15 PM
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#2
In reply to #1

Re: RO MEMBRANES CLEANING

02/04/2013 12:20 PM

If that fails try this: Clear the aera first.

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#3

Re: RO Membranes Cleaning

02/04/2013 1:08 PM

Talk to a professional, such as ECOLAB.

For one thing, you do not have enough information and is not taking it seriously or looking for cheap shortcuts and your membrane will fail prematurely.

An example, some cleaning solutions have a polymer molecule in them to encapsulate the dirt and removes it..... its true, and a saleman will tell you so.......

Works great in some process systems, but in a membrane system, For one thing a polymer molecule is a large molecule, which is difficult to pass through a membrane, and the worst part is a polymer molecule could react with other agents such as chlorides and set up within the membrane. Your Flux will never improve, and the only resolve is new membranes.

I hope this helps.

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#4

Re: RO Membranes Cleaning

02/04/2013 6:24 PM

Go here: Membrane Element SWC5-LD - Hydranautics

At the bottom of the page you will find their contact information, including an e-mail address. Contact them.

Or, do they want to sell you a cleaner?

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#5

Re: RO Membranes Cleaning

02/04/2013 11:16 PM

Refer the O& M manual. Consult the supplier for frequency and actual procedure for membrane cleaning. Install antscalant dosing system as an integral part of the system and install automatic control to reduce human errors.

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#6

Re: RO Membranes Cleaning

02/05/2013 3:25 AM

It's quite amazing the percentage of posts these days where the answer lies in contacting the equipment manufacturer by telephone.

"Oh, no. Not another one", or something similar.

If that fails, try semtex.

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#7

Re: RO Membranes Cleaning

02/05/2013 10:23 AM

I would like to help you, but there is such a paucity of information initially provided.

(1) how much increase in net driving pressure did you experience?

(2) how much increase in differential pressure per vessel was noted?

(3) how much increase in salt passage was observed?

In cleaning: which cleaner did you use first? and why? what is the feedwater quality? i.e. - brackish or seawater? if brackish, well water or lake or river source?

what kind(s) of pretreatment exists before the RO inlet?

All types of questions like this will make a difference in the approach. But in general, it is best to contact the company that sold you the equipment, and contact your service representative for any dispersant you purchased to help reduce fouling/scaling of the membranes. And always make sure your procedures are accepted by the OEM, unless you wish to void their warranty (if that matters to you).

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#8
In reply to #7

Re: RO Membranes Cleaning

02/05/2013 11:51 AM

I agree with James S. Bio is notoriously difficult to remove, then comes back quickly unless you address the root cause.

The questions asked are valid and important. respond with answers if you need further assistance.

Some tips that you may find useful.

1. Effect of pH - pH must be high enough to have good effect. Check the specification of the membrane. Take the pH to just below the specification.

Unless absolutely necessary, don't use acid (low pH) as this will cause the bio to become stuck to the membrane spacer. Always use high pH first, until this has no more effect.

usually bio is a combination of biofouling and some suspended solids fouling. it may be necessary to use a low pH cleaning solution to remove the non-bio fouling, but alwasy use this after using high pH.

Oxalic Acid is an exception. Can have very good results with biological fouling.

2. Effect of Temperature. Reaction rate doubles every 10degC. Always heat the cleaning solution to just below the temperature limitation of the membrane (typically 40degC). I use 35degC temperature for CIP solution.

3. Effect of the CIP formulation - pH & Temp are important, also important are the other components of the CIP solution. Consider adding detergents, surfactants, chelating agents into the mix. Plenty of info online about this.

4. Effect of time - this typcially takes hours, don't think this will be done in 15 minutes. It won't. Typically I will spend all day to do a full clean on a plant. Then soak it over night, and the next day as well.

5. CIP solution flowrate (or velocity). 10 m3/hr per 8" vessel. pressure must be maintained less than 50PSI. The flowrate can by slightly slower for acid CIP, but for high pH faster the better.

6. Salt - after high pH clean soak in 100,000 mg/L NaCL solution for as long as possible. has good results for long term management.

There are other silver bullets in development, there has been very good research done in the last few years. But products are not yet on the market (still at patent stage).

Once you have the RO performance back, after sucessful CIP, there is large amount of effort required to prevent re-occurance. You must address the root cause of the problem, which is very complex. Also sugest regular treatment with DBNPA is similar (DBNPA cannot be used for drinking water systems).

Hope this helps.

Anthony

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