Membrane Cleaning - Field Expedient?

[Off Trail]

I'm pretty sure after debug testing that we have biological contamination in our Spectra watermaker membrane.

Spectra specifies only their proprietary cleaners to avoid damaging any of the seals in the Clark pump. But, I've got none onboard (an oversight not to be repeated!) and am currently in the Exumas with limited resupply options.

Is there any alternative cleaner that would help, or do I need to get something shipped from the states?

[Sailmonkey]

You could remove the membrane from the housing and use whatever cleaner you can source locally in a PVC tube.

Get a pvc tube, blank cap and a threaded cap, shove the membrane in with your cleaning soup, thread in the cap and sit in the cockpit rocking the tube while drinking a beer.

[DefinitelyMe]

This is the link from spectras website for the msds for their alkaline cleaning compound, which is the one you want for biofouling (the other type of fouling is scale, which is dealt with with an acid). Looks like it's basically 20-30% sodium percarbonate. pH about 10.5. I think any weak alkali would do the trick. But then it's not my water maker. :-)

https://www.google.com/url?sa=t&sour...d1Jwbi1SBeHg0T

[Tellie]

How have you determined that the membrane is bio-fouled? What are the symptoms that lead you to this conclusion? This is critical before cleaning and determining that this is the actual problem you are having and not some other part of the system. Many times people mistakenly misdiagnose an issue which is not hard to do and Spectras can be a bit tricky at first to pin down the exact cause of the problem you are having. If it is truly only bio-fouling then just replace the membrane. Cleaning a boat based watermaker membrane is usually a waste of time. Maybe 1 or 2 out of ten will clean and even if they do they are usually on their last leg and will need replacing sooner than later.

[Woodland Hills]

Originally Posted by Tellie

How have you determined that the membrane is bio-fouled? What are the symptoms that lead you to this conclusion? This is critical before cleaning and determining that this is the actual problem you are having and not some other part of the system. Many times people mistakenly misdiagnose an issue which is not hard to do and Spectras can be a bit tricky at first to pin down the exact cause of the problem you are having. If it is truly only bio-fouling then just replace the membrane. Cleaning a boat based watermaker membrane is usually a waste of time. Maybe 1 or 2 out of ten will clean and even if they do they are usually on their last leg and will need replacing sooner than later.

The OP is in the Exumas where water costs $.35 or more per gallon. He NEEDS to get this back into service if at all possible. If there is a chance that a good cleaning and descaling will work for a couple of months then it is worth trying. A new membrane is at least two weeks from delivery.........

[Off Trail]

Originally Posted by Tellie

How have you determined that the membrane is bio-fouled? What are the symptoms that lead you to this conclusion? This is critical before cleaning and determining that this is the actual problem you are having and not some other part of the system. Many times people mistakenly misdiagnose an issue which is not hard to do and Spectras can be a bit tricky at first to pin down the exact cause of the problem you are having. If it is truly only bio-fouling then just replace the membrane. Cleaning a boat based watermaker membrane is usually a waste of time. Maybe 1 or 2 out of ten will clean and even if they do they are usually on their last leg and will need replacing sooner than later.

Thanks for weighing in JT!

Ok so it's a cape horn... salinity has been creeping up 500, 650, 800.

1.We get bio smell in the product water for the first few minutes after startup despite careful flushing the day before.

2. Clean pre filter and strainer did not help.

3. Flow test pump A 1.6 gpm, pump B 1.52 gpm, both 2.6 gpm. Product flow pump A 8.9%, pump B 9%, both 9.2%.

4. Unit is pretty new (<2 years) though in daily use, clark pump pressure 96 psi and symmetric between the two sides.

I would be happy if we could get back down to 500-600 ppm until we get back to the US in July.

Dan

[Tellie]

Originally Posted by Off Trail

Thanks for weighing in JT!

Ok so it's a cape horn... salinity has been creeping up 500, 650, 800.

1.We get bio smell in the product water for the first few minutes after startup despite careful flushing the day before.

2. Clean pre filter and strainer did not help.

3. Flow test pump A 1.6 gpm, pump B 1.52 gpm, both 2.6 gpm. Product flow pump A 8.9%, pump B 9%, both 9.2%.

4. Unit is pretty new (<2 years) though in daily use, clark pump pressure 96 psi and symmetric between the two sides.

I would be happy if we could get back down to 500-600 ppm until we get back to the US in July.

Dan

The sulfer smell is the problem we need to address. Are you turning the yellow handle to "OFF" when flushing? Also, I'd like you to take a PPM reading with your hand held TDS meter of the brine discharge at about 15 seconds before the end of your normal flush (after the system is saturated with salt water by running) and let me know what the PPMs are. One last test as well, I want you to run each pump individually while watching the pressure gauge. Then kink off the brine discharge hose like you would a garden hose. The pressures on the gauge should climb to around 125psi within a 1.5 second. record each pump individually like this and let me know what you find. A bio fouled membrane will usually create more feed pump pressures than 92psi. Creeping salinity is usually more a sign of bad pressures so we want to eliminate this first before attempting any cleaning. Call me if you need more help. If need be, we have plenty of membranes in the shop.

[Off Trail]

After pump testing and a call with Tellie / JT at Halden Marine Service, it does appear that the membrane may be skunked. Lacking the proper cleaner (and with a low probability of lasting success as Tellie mentioned above) he mentioned flushing/washing with hot soapy water.

Spectra has a tech note describing this for dirty membranes so I followed their procedure.

So now after "cleaning" and flushing we've gone from 800-850 ppm to 620-650. Not great but a definite improvement that, if it holds, will keep us limping along until we can properly replace the membrane.

Thanks Tellie for your help!

Dan