On-line citywater alkalinity measurement

[ajw160]

Hello All:

Has anyone here had any successful dealings with Hach's APA 6000 meters? The problem we're having is that the automated readings are not even close to the manual testing. Perhaps a specific backround interference is affecting one test but not the other (methyl purple and N50 as standard)?

Thanks, any ideas would be great,

Drew

 

[bimr]

Have you tried using a pH meter instead? You probably are aware that pH correlates to alkalinity. pH is probably easier to measure online because all that you need is a probe.

 

[ajw160]

Thanks for the reply. Yep, Alk is related to pH and we're monitoring that too (it's for a beverage manufacturer). The log makes it difficult to get the precision that is needed.

That said, I've run-across problems with the same brand of controller and apparently often-times the widely accepted calibration "standard" is not a standard at all--simply widely accepted. Just thought I'd check on here first, no use reinventing the wheel if anyone had direct experience making these controllers work.

 

[bimr]

ajw160,

There are lots of online instruments available, but usually there is so much maintenance required that the equipment is usually ignored. Ultimately the equipment goes into disrepair.

Why are you concerned with the alkalinity and the precision? Are you doing any water treatment? I vaguely recall a standard beverage water treatment process using lime softening, which would of course control the alkalinity.

 

[ajw160]

Yes, cold lime softening is being used. But per regulation, city water quality needs to be continuously verified and recorded.

All maintenance on the meter is current and has been performed to specs. My current guess is that an unknown interference is present in too high quantities that is fouling-up one of the tests. Just a guess at this point though; thought I'd check on here first before burning a lot of time figuring out exactly what is going-on, on the off-chance that someone had already fought this battle.