[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Questions regarding some PHREEQC output




I am writing this time regarding PHREEQC rather than PHRQPITZ
> 1.  I have a data set for injection well disposal.  Two aqueous streams
are mixed together and then injected.  In the attached file,
CoolingTowerMixA.out, the calculated errors for solution 2 are rather
large, >20%.  Does a calculated error this large suggest problems?

It's not great. Calcium and alkalinity errors will naturally affect the
SI(calcite) more than errors in sodium and chloride. A beneficial factor,
the SI's are log quantities, so 20% error in calcium translates to about .1
in SI(calcite) (log10(1.2)). However, a .2 error in pH translates to .2
error in SI(calcite).

> I am particularly concerned with the high calculated pH value.  Were this
to be
significantly in error all of the calculated saturation indices would be in
question.

I think the pH is probably about right if the water were to completely
equilibrate with air. You can check, but I don't think the calculated pH is
very sensitive to the analytical data for the initial solution.

> 2. later on in the process I will be equilibrating the mixed stream with
the
existing groundwater, which has a TDS of 34,000 mg/L with chloride 18,000
mg/L and sodium of 11,000 mg/L. Will PHREEQC handle this groundwater?  As
opposed to PHRQPITZ?

The ionic strength is a little high. I'd probably do a little checking with
PHRQPITZ, but I think because it is a sodium chloride dominated water,
PHREEQC and PHRQPITZ will be pretty similar. Also, if you are mixing the
waters, the resulting water will tend to have a lower ionic strength.

> Without documentation for PHRQPITZ PHREEQC is proving a lot easier to
deal with.

I can send the documentation for PHRQPITZ if you forward your address.

David

David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225




Project Home Page
Complete Water Resources Division Software
USGS Home Page
Water Resources Division Home Page
NRP Home Page
Help Page
USGS Privacy Statement       

Please note that some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. 


The URL of this page is: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/mail/msg00286.html
Email:dlpark@usgs.gov
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 2128 since Jan 22, 1998.