The use of Mg(OH)2 will increase the amount of metal removal. The main
reason for adding mag hydroxide is for the electrolytic transfer for
metal removal. If you use only the Mag hydroxide exclusively, you are
adding more than you need. If you use a combination of lime with the
Mag. Hydroxide, you will get the removal you need, the pH control that
is desired, and a reduction in cost.
Dave Creager
Chemist
----------
From: [log in to unmask]
To: [log in to unmask]
Cc: Technet; [log in to unmask]; [log in to unmask]
Subject: Re[2]: Mag. hydroxide & DTC in waste water
Date: Monday, April 28, 1997 8:42AM
In general I would agree with Mr. Miller. We switched to Mg
hydroxide
on all our batch treatment processes here. It is MUCH more cost
effective that sodium hydroxide simply due to its alkaline content
pound-for-pound. Magnesium hydroxide improves solids settling.
You
do not have to worry about over shooting pH either which can happen
very easily with sodium hydroxide if it is being added manually.
We continue to use sodium hydroxide in our continuous waste water
treatment system because of the ease of use issues mentioned below
as
well as kinetics. Magnesium takes longer to react because it is in
a
solid slurry and as the dissolved OH is consumed additional
particles
of MgOH must dissolve. We had to purchase a special mixing drum
pump
tube from Lutz that allows us to mix the slurry before we pump it
for
use in a batch treatment procedure.
Michael Holan
Process Engineer
Continental Circuits Corp. of Texas
______________________________ Reply Separator
_________________________________
Subject: Re: Mag. hydroxide & DTC in waste water
Author: "Richard R. Miller" <[log in to unmask]> at INTERNET
Date: 4/25/97 12:11 AM
Mg hydroxide is primarily utilized to increase "weight" to the solids
formed,
thereby improving the settling characteristics of "over-loaded" systems.
There are products on the market that combine Mg with DTC, or other
heavy
ions,
to achieve this same affect.
A more cost effective, and easier approach, would be to utilize
"solids-recycling" from your sludge holding tank to your primary
reaction
tank.
This will provide, the "weight", to improve your settling, as well as,
reduce
your DTC, flocculant, and alkalinity requirements by 20-50%. Also, this
will
allow you to use sodium hydroxide, in place of, Mg, or Ca Hydroxide
(cost/ease
of use savings).
Rick Miller
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