Ferric Chloride Water Treatment

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Joshua Kogan

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Hey all, I just created another WRE PM problem.  You have to know how to work with basic water treatment chemical reactions in order to ace the PM portion.  I feel that many study programs cheat their students by offering tricks and tables; however, the PE problem developers are normally one step ahead of the study program providers -- learn to work with the equations! 

A 40MGD water treatment plant employs ferric chloride as a coagulant at a dosage of 20ppm in which hydrated lime is used as the source of alkalinity.  The ferric chloride stock solution is delivered at 60% strength and contains a specific gravity of 1.551.  Calculate the discharge rate of the ferric chloride pump (gpm), and the lime feeder setting (lb/hour).

a) 0.20, 190.5

b) 0.50, 182.5

c) 0.60, 182.5

d) 0.80, 190.5

Check out the solution here: http://wrecrossfit.com/post/137896529681/example-problem-6-a-40mgd-water-treatment-plant

Please let me know what you think about the question!

 
Last edited by a moderator:
Need to work on this one !!! I've worked with ferric sulfate at a drill mud dewatering facility that I managed for 2 years.

 
That is "Marcellus"

Sorry for the typo

Could not figure out how to edit. I was educated in the 80s. I will be the old guy in the PE exam !!!!

 
Hey all, I just created another WRE PM problem.  You have to know how to work with basic water treatment chemical reactions in order to ace the PM portion.  I feel that many study programs cheat their students by offering tricks and tables; however, the PE problem developers are normally one step ahead of the study program providers -- learn to work with the equations! 

A 40MGD water treatment plant employs ferric chloride as a coagulant at a dosage of 20ppm in which hydrated lime is used as the source of alkalinity.  The ferric chloride stock solution is delivered at 60% strength and contains a specific gravity of 1.551.  Calculate the discharge rate of the ferric chloride pump (gpm), and the lime feeder setting (lb/hour).

a) 0.20, 190.5

b) 0.50, 182.5

c) 0.60, 182.5

d) 0.80, 190.5

Check out the solution here: http://wrecrossfit.com/post/137896529681/example-problem-6-a-40mgd-water-treatment-plant

Please let me know what you think about the question!
I had two different mistakes, but figured out the coagulant feed rate at 0.556 gal/min. So I chose C. If this were an exam question, you would only have to solve for one parameter because each of the four answer choices are unique. Thank you for the information, as I now will know how to approach the alkalinity side of the question. It looks like you will be selling PM exam questions at some point. Please keep me updated.

Loren Salsman  

 

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