my concern here is though our RO permeate conductivity is < 20, and the AAMI results are coming back good and at 75% recovery rate, I surely can sleep better! Thanks Florian!
<???>
Posted
What is your feed conductivity/rejection rate?
<Tech>
Posted
Feed conductivity averages 148 ppm and % rejection is 97%
To validate your conductivity limit you should document what the conductivity was when the sample was taken. Also, were any of impurities in your analysis close to the AAMI limit.
The AAMI analysis only validates that the conductivity when the sample was taken is acceptable. If the conductivity was 15 when the sample was taken and today your RO is running at 12, you can be pretty sure you are making good water. If your conductivity today is at 20, then you don't know if your water meets AAMI. You should resample. You should take your AAMI sample when your RO is performing its worst (before chemical cleaning or before replacing membranes). If you change the membranes, you should resample to validate the new membranes.
The Water Guy - Florian Services
Posts: 354 | Location: Chicago | Registered: 24 January 2005
You're numbers seem skewed. It's not adding up like it should.
With a feed conductivity of 148 ppm and a % rejection of 97, your permeate conductivity should be about 4 ppm. If you use the 20 ppm you first said was your permeate conductivity, with a feed conductivity of 148 ppm, your % rejection is actually about 86%.
Are you sure the conductivity probes on the RO are calibrated correctly? I'd definitely look into that. Additionally, I'm not sure what RO you're running, but typically I don't see them run at a 75% recovery rate. Usually, that will foul out the membranes rather quickly. I try to aim for anywhere between 50-65%.
Feel free to correct me if I'm wrong with any of this, Florian. I know you're the Guru!
<San Augustine>
Posted
Just to make sure you have the right equation- Feed (minus) Perm. (Divided) by Feed.
