Membranes
The most popular membrane material is Thin Film Composite (TFC). This material is NOT chlorine tolerant, but they can handle bacteria attack. There are Cellulose Triacetate (CTA) that are chlorine tolerant, but bacteria will destroy a CTA membrane. Also, CTA rejection rates are no where as good as TFC rejection rates. In ultra-pure water you will find TFC membrane much more commonly used, they just need to be preceded by a carbon.
Also membranes are funny, not funny haha. They are made in lots. Two different membranes in a lot can/will perform differently. This is the nature of membrane technology.
The 3 main factors affecting an individually membranes performance are;
1. Pressure (YOU NEED A GAUGE) the first question we ask when a system is not working properly is "what is the pressure?" If that can not be answered, I really can not help much. I need to know what the pressure was when it was operating and any changes, gradual or rapid. Folks are amazed when they add a booster pump. The unit increases the volume of production water, water quality improves and there is a reduction in waste water, in other words MUCH BETTER EFFECINCY. We use DOW FILMTEC Membranes, the gallon out put is rated at 40 PSI. Most cheaper membranes are rated at 60 PSI. So it is important to understand the specs when comparing membranes. The RO systems you purchase are normally limited to 80 PSI. You can experience component failure at higher pressures, check with your equipment manufacturer before going wild with pressure. Your membrane can handle it, but that maybe the only part of your system that can.
2. Temperature; I have seen some very good experiments on Canadian Reef Boards; the ambient water temps are lower there. With minimal adjustments to temp
:idea: NEVER EXCEED 80 degrees F :idea: You can also see amazing results. Not quite as dramatic as pressure, but amazing none the less.
3. Water Quality; the membrane is designed to reject approximately 95% of incoming Total Dissolved Solids (TDS) this is done by splitting the incoming stream. 3 to 4 times the product water goes to waste. This can not be changed with any type of long term success. There are adjustable flow restrictors that tighten up the amount of waste water produced.
Example; the membrane initially sees the incoming TDS (let say) 200ppm, this work fine for awhile (lets say 1 month). Then due to the lack of flushing (the waste stream) there is a build up on the membrane. Now the membrane “sees†the higher TDS. The membrane is operating properly it is rejecting 95% of the TDS it “sees†BUT the TDS is now 2500ppm, due to the build up. We do call the water we send to drain the waste water, but more properly it should be called CONCENTRATE. Although it is sent to drain, it is VERY important to the process. Now in situations where sending water to the drain is undesirable, this practice is used. You will be replacing membrane every 6 months or so.
This should have gone under carbon; But its here;
At this point we should address carbon changes; some carbons claim 2,500 of water @ .5 ppm chlorine. That is just too simple. Today you measure your total chlorine of the in coming tap water and it is 0.25ppm. Tonight while you sleep the local water keepers disinfect the water line, you wake up and your bathroom smells like the YMCA. You are now a 3ppm total chlorine.
If you make 2 to 5 gallons per day, change your carbon every 6 months If you make 5 to 10 gallons per day, every 3 months 10 gallons and up change your carbon every month
I am talking averages; EXAMPLE you fill your 40 gallon storage tank 1 time per week, that only in the 2 to 5 gallon range or carbon change every 6 months
Now, only you know how bad you chlorine/chloramine is. Slugs aimed to disinfect water supply lines are less detectable with chloramine. Use your judgment or add a test port.
in and out of the system. What this means in terms of top off water.
