(GP/GT) for Additional Water Supply in the Lower Rio Grande

APPENDIX G
4 DEC 1993
TO:
MR. KLEBER DENNY
Terra Associates, Inc.
Houston, Texas
FM: EUGENE R. REAHL
Ionics, Inc.
5455 Garden Grove Blvd
Suite 321
Westminster, CA 92683
cc: EPG, JWArnold,
R. Johnson, £ile
tel: 713-993-0333
£ax: 713-993-0743
tel: 714-893-1545
£ax: 714-892-1592
SUB:
PRELIMINARY EDR / RO COSTS & PERFORMANCE STUDY
REF:
State o£ Texas Water Development Board Grant
Ionics M-10 (TX)
Reviewed your water data £or GROUP 1 thru GROUP 4 conditions. We
used the "mean" water analysis £or each group for the EDR vs RO comparisons.
We also used the range o£ feedwater pH's £or each group
and then took the average (high + low) / 2 plus about 20% £or our
calculations. We used 24 degrees C as the £eed temp in all cases.
(1) Per our discussion, rough data indicates GROUP 1 thru GROUP
4 waters contain levels o£ Boron (above 1.4 ppm) which will cause severe
problems £or £ruits, plants, and other growing things. Although
Bo causes problems £or plants, you and I can drink same up to 45 ppm
with no problem!! EDR does not remove boron at normal pH. RO requires
elevated pH, as well, £or e££ective reduction. As discussed,
we've ignored boron removal in this study. Keep in mind though, i£
Bo reduction is required, both EDR and RO could reduce same by having
the £eed water pH raised to 8.5 - 9.5. This requires a presoftening
system installation (either lime or lime-soda clarification or softening
RO membranes) - so that 2nd phase EDR or RO system will not
su££er catastrophic membrane scaling due to high pH.
(2) Since you asked £or high water recovery to minimize brine
disposal via injection wells - this was our overriding objective in
the study. The RO design pushed water recovery to a limit of 180 to
~ ppm Si02 in the brine £or GROUP 1 thru GROUP 3. For GROUP 4 (be­
.use Si02 is low), we used 85% as a normal upper limit. Due to the
level o£ Calcium and Bicarbonate in the "mean" water analysis £or
each GROUP, RO requires the £eeding of sulfuric acid to £eedwater in
each case, to control the level of CaC03 scaling in RO brine.