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How does Coliform get into RO water?

I am working in the mine site and there are various systems for water treatment. We conducted water sampling and sent samples to SGS lab for analysis. Surprisingly when the results came underground RO encountered with coliform contents about 48/500 mls. What could be the source?

Renatus Rwehabura
health graduate - Dar es Salaam, Tanzania
September 22, 2011

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Coliform contamination must be coming either from contaminated pipework within the "clean side" of your RO system, or from leaching of contaminated water into the RO system, although this would normally show up as poor quality water if you do a conductivity test. Coliform is usually a sign of fecal contamination, but not always; it can also be found in the air. I suggest that, to minimise any air contamination, you keep all RO water receptacles and systems covered

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
October 5, 2011

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October 13, 2011

Hi Renatus, If your R.O.system is a ring main system you can put a U.V. lamp in the loop. This is a common method of keeping the bug content down in R.O. systems. if your system is not a ring main design then perhaps you could consider putting loop on the storage tank so that the whole volume passes through the lamp section several times in 24 hrs.
Also periodic flushing of the system with bleach ⇦ bleach/sodium hypochlorite in bulk on eBay or Amazon [affil links] can effect a rapid killing off of a large coliform contamination. You only need about 20 liters of 15% bleach for a system of say 5000 liters capacity.
This will of course mean dumping the contents of the R.O. system afterwards, then flushing until the conductivity goes low again. But as it should be only done say a couple of times a year, or as a last resort it should not be too inconvenient.
best regards and good luck

Mark Lees
- Isle of Man, Great Britain

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October 19, 2011

One of the first questions that will be asked of you is your sampling procedures.
Did you follow guidelines in ISO 19458. Sampling for microbiological analysis.
If the answer is no then the tendency will be to dismiss the results no matter how accurate they are as it is easier to call sampling into question than deal with a potentially difficult problem.

Ciaron Murphy
Aerospace - South Wales, UK

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November 4, 2011

Sir:

I once drank some distilled water to see if it tasted different. I got a terrible throat infection.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA