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Old 08-08-2012, 11:45 PM   #11
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Yes, your first filter would be the 5 micron (go after the big particles first) and if fouled with iron hydroxide it could be gray though it is usually a really disgusting brown. Manganese hydroxide tends to be the same ugly brown. How does the 1u filter look?

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Old 08-08-2012, 11:51 PM   #12
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I cant see the 1u as the first ones in a transparent enclosure(5u) but the others are in white plastic. Can this 'fouling' actually affect the output of the RO unit. I dont have much of an understanding of the science behind them but it appears to me that they are filters based on physically blocking particulates so I dont understand how anything other than RO water could make it out the output? I would have thought a buildup in the 5u or 1u would just result in a reduced throughput?

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L

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Old 08-08-2012, 11:58 PM   #13
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Yes, that's the main effect. As a filter fouls the pressure drop across it increases for a given flow. For a fixed source pressure the flow rate will decrease but there will still be more of a pressure drop across it i.e. of the total mains pressure proportionally more will appear across the fouled filter and proportionally less across the RO membrane. Membrane flow is thus decreased. As the pressure across the membrane approaches the osmotic pressure of the water the flow slows to a trickle.

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Old 10-19-2013, 11:02 AM   #14
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The most common cause of off flavor/odor in RO water is a post-membrane "taste and odor" filter that is past its useful life and needs to be replaced. They are very inexpensive and easy to replace.

If CO2 really is your issue, rather than boiling the water, you ca remove the CO2 @ less cost by simply aerating the RO water.

Russ

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Old 10-19-2013, 11:04 AM   #15
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Quote:
Originally Posted by Larso View Post
I would have thought a buildup in the 5u or 1u would just result in a reduced throughput?

Thanks

L
As prefilters clog and rob pressure from the RO membrane, the membrane performance (how well it cleans the water, a.k.a. rejection rate) drops. In residential systems, the drop is severe at the lower end of the pressure range (e.g., less than 40 psi).

Russ
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Old 10-19-2013, 04:08 PM   #16
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I recently had a client that had to toss out several thousand gallons of beer that was too acidic. Their water supply has a significant dissolved CO2 content and that gas passes easily through a RO system into the product water. This brewery had recently made a change that prevented the treated RO water to vent off the CO2 and it stayed in the brewing liquor. The result was a bunch of tart beers. They installed an air stripping tower to pass the treated water through. The tower helps get that excess CO2 out of the treated water. This is a common step for water utilities that use RO treatment.

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Old 10-19-2013, 04:19 PM   #17
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Something doesn't compute here. If the water came out of the RO system under pressure and were kept under pressure then the CO2 would stay in solution but as soon as it was splashed into the mash tun or piped into the mash tun, stirred and heated the CO2 would escape. I can see how this (stripping) would be important for a utility where the entrained CO2 has no opportunity to escape. The pH would stay low and the possibility of corrosion would be increased. But in a brewery? Must be something involved I don't understand.

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Old 10-20-2013, 01:41 AM   #18
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The water is stored in a separate unpressurized tank. Treated water is transferred to the HLT for the brew day. They formerly had a vent in the HLT and they capped that vent. It was that point that they started to incur the low pH in their mash.

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