Waste water ratio as far as i know is not determined by air pressure, every ro i know runs at about 1:3 rejection rate meaning 1 part permeate to 3 parts concentrate.
In my observations, When the tank is empty and beginning to fill, I get about three drops of concentrate for every drop of permeate. As the tank fills, it increases to about 5 drops and then before the system shuts down, I see a steady stream of concentrate water. I pull the line to the tank and the concentrate returns to about three drops, again. It is not a scientific examination but a pretty clear observation. My conclusion was that as pressure increases against the membrane there is a ratio change from permeate production and concentrate going to the drain.
Yes Ro membranes can be run at all kinds of diffrent ratio, you can run no rejection whatsoever if you wanted to.
By completely stopping/plugging the drain flow? Naturally, that can't be recommended as it would defeat the purpose of an RO.
In all RO's that we sell rejection ratio is is a figure of drain flow restriction combined with pressure. As the RO fills up the tank, pressure diffrence between the tank and incoming water begins to equalize slowly closing off the membrane valve that controls flow to the membrane. If the pressure in the tank drops the mebrane opens up flow again and the ro begins to make water.
So as the tank fills the flow rate of permeate production drops eventually shutting down completely, right?
the wow design must have backpressure on the membrane, unless the water creating the mechanical pressure to push out permeate trough the fawcett magically disapears when the RO makes water.
Not really magically at all. The patented valve releases it faster than incoming water. I think it creates a small negative pressure allowing incoming water not only to have no back pressure but 'invites' water to enter the membrane.
You say 35-45 gallons per day, the literature says it has a 50GPD membrane I wonder what temperature water with how much tds and what the Ph of your water is?
I couldn't find anywhere in the literature where it states it has 50gpd membrane. If you have different information, please let me know. It does say it has a 50gpd capacity. I assumed that means a system capacity not that of the membrane. The rounding of numbers like that, though, I find are estimates (why not 48.6 or 53.2?) and should not be taken as definitive. Incoming pressure, temperature and TDS, among other factors, affect water production of any RO system. My estimates of 35-45gpd coming from installing one and judging by how long it takes to fill and shut off. Again, external factors can great allow for differences. Just my personal observations.
the pile of ruptured pressure tanks at my shop would tend to argue with the remote posibilty of contamination.
I, too, have a "small" pile of failed bladders from air-charged tanks. I never denied the possibility of contamination. As of yet, I have heard of no WOW barriers failing in that regard. This doesn't exclude the possibilities but in my persoanl experience, I haven't seen one yet.
don't get me wrong I like the idea of the wow design, but I would never say it is better then an aircharged tank.
I appreciate your experience and stated opinions. No problem. I have gone that route and now have switched for many reasons including what I feel as advantages of WOW tank approach to RO systems. I think the next best approach is atmospheric tank designs when space is available and demand is required. The WOW tank designs do have a few handicaps but not really a hinderance, yet.
