×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

BFW Water treatment pH control

BFW Water treatment pH control

BFW Water treatment pH control

(OP)
i'm having difficult control with my water  treatment unit. u see the make up water pH for the BFW is control by an ion exchanged bed and the pH is off scale (it supposed to be 7-9 not 5.6). so any suggestion?

RE: BFW Water treatment pH control

Regretfully I do not quite understand the term "make up water pH for the BFW" but if you treat your water with an ion exchange bed it will absorb most of the non water ions. Consequently the pH of water treated by ion exchange should be near 7. Due to absorbtion of CO2 which is a weak acid the pH is shifted to  5,6.
It is possible as well that the very low conductivity of water, treated by ion exchange (about 0.5 microS/cm), your pH meter and the electrode chain cannot detect a reproducible signal on the input of the instrument amplifier. Just to check: to increase the conductivity dissolve a minute amount of KCl in your sample- it will not change the pH and make a reading.
There is another possible reason for erroneous readings (-if we assume that you calibrate your pH meter with a buffer solution before measurements and you have removed the protective cover from the electrodes ) and it has to do with the basic pH measurement circuit design: in some cases the imput impedance of the glass electrode pin is really very high, in the order of 10^12ohms, but not of the reference electrode that could be in some designs about few kohms.If this is your case then the reference electrode is not on the same potential as the entire equipment earth or ground potential, which is considered zero.You can check it easily: if your pH meter chain works fine in a completely electricaly isolated glass beaker on a dry desk(plywood, ceramics..but not on stainless steel!)then you have prooved it.You should go step by step and be aware that industrial pH measurement is not very easy because you work in a terrible electro smog surrounding,with a relatively low signal (abot 100 mV)and at extremly high impedance and sometimes with nonconductive liquids.
m777182

RE: BFW Water treatment pH control

(OP)
but i think the water still contain dissolved CO2 eventhough it already degassified. and i wonder how to increase degassification of CO2without deteriorating the ion resin's power to exchange ion (because it can only work to 45oC)

RE: BFW Water treatment pH control

Do you have a deaerator prior to the BFP's?  Most DA's guarantee zero CO2 effluent

RE: BFW Water treatment pH control

Your trouble does not seem to be a pH meter.Did you titrate your water on indicator color change? Maybe this would be a simple step to eliminate one possible source of your problem.
m777182

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources