Reducing contaminants in a jar with water:

Originally posted by sonhouse
Interesting. The DI piping is all teflon with just the occasional glass flow tube like I said. Are you saying the algae built up inside teflon? If so, what acid did he use? I would think that would be a major repair because you would have a major DI water line flush to do. Do you remember how many gallons it took to do that? Our DI water tank is a teflon tu ...[text shortened]... te, do mean from say 7 to 7.2 or were they really nuts like 4 to 15?

What lab do you work at?

Our piping is also teflon, but the algae built up along joins in the pipeline. I'm not sure what nutrients the algae had there, but there they grew. It's possible the joins aren't sealed properly, but I can remember the old lab-tech not finding anything wrong with the seal on the joins.

As for quantity, I don't think that was a problem, the DI unit feeds a small diamond research laboratory. Its about 75litres in capacity and the piping runs maybe 30metres. He used a dilute HF solution to kill the algae. I doubt he used it often, or we would have seen damage to the DI system (HF = bad). The pH would fluctuate between about 4 and 6.5. It was the occasions when the pH was around 4 that people really took notice.

We never used to mind the algae much, it used to burn off during sintering. The pH was more of an issue.

Originally posted by Igloo
Our piping is also teflon, but the algae built up along joins in the pipeline. I'm not sure what nutrients the algae had there, but there they grew. It's possible the joins aren't sealed properly, but I can remember the old lab-tech not finding anything wrong with the seal on the joins.

As for quantity, I don't think that was a problem, the DI unit feeds a ...[text shortened]... d to mind the algae much, it used to burn off during sintering. The pH was more of an issue.

I think algae will grow where there is a discontinuity in the liquid flow, so small vortices would allow for algae to stay put and grab on to a surface. So weak HF. The PH meters we work with are electrodes covered with a sub micron layer of glass that allows some ionic movement so if the expected PH is say 6 and you get a jump to 4 the meter head will have more ions trapped and therefore a longer time to settle down after flushing.

Do you used PH calibrating fluid to check if the meter is accurate? We have 3 separate fluids you immerse the meter head into and see how close it comes. If not, you do a calibration. If it can't calibrate correctly, you replace the head, a fair expense. I think around 1000 bucks. You also cannot have those sensors exposed to air for long either, somehow the ions crossing the barrier gets filled with contamination and sustained rinsing in DI water, for instance, does not get the head back in shape.