[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[APD] RE: RO Units and carbon filtration

Wright Huntley wrote:

  "... the RO unit has essentially no ability to block small molecules, like
ammonium and chlorine."

I don't believe the above statement is correct. Given the correct conditions
of high pressure, correct temperature and pH, and fairly low TDS of the
supply water, and RO unit can remove everything but the wet from water. Each
of these parameters has a direct effect on both the quantity and quality of
the product water. A RO unit operated under optimum conditions can filter
out almost everything in the water supply.

There are two types of membranes commonly in use today, Thin Film Composite
(a synthetic), and Cellulose TriAcetate (organic in nature). Carbon filters
are required on RO units with TFC membranes because the chlorine (and maybe
some other substances as well) will degrade the membrane. On the other hand,
those with CTA membranes require exposure to low concentration of chlorine
or some other disinfectant to prevent the growth of bacteria that foul the
membrane. TFC is generally preferred over CTA due to its longevity and

For those of us concerned about the quantity of waste water generated by RO
units, a two stage system can be employed. The product from the first
membrane is fed into the second membrane. The reject water from the second
membrane is pumped back to the inlet of the first membrane. Some systems use
three membranes, two as first stage and one as second. This configuration
yields very high flow rates and exceptional water quality. I have operated a
RO unit using this design that made 35,000 gallons of 5 mmoh RO water daily
for use in a boiler feedwater system. Of course, that unit would not fit
under the kitchen sink. That unit would not even fit in my kitchen. The
membrane cases were each 20 feet long and 10-inches in diameter. The reject
water was not wasted, but was used in the plant's cooling tower.

  Douglas Guynn, in West Texas, where drinkable water is a valued commodity,
and every drop of rain is a precious gift from God.

Douglas Guynn
        d.guynn at sbcglobal.net

Not everyone who says to Me, 'Lord, Lord,' will enter the kingdom of heaven;
but he who does the will of My Father who is in heaven. Matt 7:21
Aquatic-Plants mailing list
Aquatic-Plants at actwin_com