www.ca-nv-awwa.org 31
Figure 2. Results of CVWD’s bench test with 0.75 mg/L stannous chloride, 5 minute reduction and 1.0
mg/L residual chlorine pre-filter oxidation
ed in Figure 1 show that this process effec-tively
removed from 68 to 83 percent of the
chromium in CVWD’s well water samples,
which is enough for CVWD to meet Cali-fornia’s
new MCL. CVWD’s initial results
did vary from Dr. Seidel’s findings, howev-er,
and this led CVWD’s research team to
develop a modified treatment process that
incorporates the addition of chlorine before
the filtration step to improve particle re-moval
(Figure 2). The team named this pro-cess
Oxidized Stannous Chloride Assisted
Reduction (OSCAR).
Based on these new findings, CVWD
suspended work just days before mobi-lizing
to construct its shovel-ready $228
million ion exchange treatment project.
One month later, CVWD initiated work
to pilot test OSCAR. The potential bene-fits
of the alternative process warranted
this significant course change. It would fit
on small well sites, use low profile equip-ment,
and would not require large main-tenance
trucks, important advantages that
minimize neighborhood impacts. The ap-parent
selective nature of OSCAR and the
low chemical dosages used is expected to
generate about one-tenth the waste of the
ion exchange CVWD had initially select-ed,
which is better for the environment.
OSCAR would be simple to construct and
operate and does not require advanced wa-ter
treatment operator certification, which
is important for small water systems. Ear-ly
estimates indicate capital costs could be
as much as half of the original project, and
operation and maintenance costs could
be about one-third of the ion exchange
treatment option. If pilot tests confirm the
bench-scale results, CVWD expects treat-ment
systems to be operational sooner than
the ion exchange treatment option, even
with the added time to pilot test and design
facilities for the alternative process.
CVWD’s Board of Directors unani-mously
approved taking time to evaluate
this alternative treatment process, which
may prove to be better for the communi-ty,
better for the environment, and better
for CVWD’s ratepayers. If California reg-ulators
provided reasonable compliance
periods, proactive water agencies like
CVWD would not be penalized, using
valuable resources pursuing technologies
available when MCLs are adopted only
to find that these technologies may be ob-solete
before they are installed due to the
technology advancements that typically
follow newly adopted MCLs. Congress
knew this in 1996 when it decided it was
important to provide water agencies ad-equate
time to evaluate and implement
treatment technologies needed to meet
new drinking water regulations. Let’s
hope that in future drinking water reg-ulations
California regulators heed the
call for compliance periods that avoid un-achievable
compliance dates. Reasonable
compliance periods promote the treat-ment
technology innovations needed for
water agencies to select and implement
the best and most cost-effective treat-ment
technology to meet new drinking
water regulations. S
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