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Case Study - Arsenic Treatment Technologies
Southern California Water Company's Hollydale
System in Paramount, CA
Background: Water Quality Characteristics
The Southern California Water
Company (SCWC) serves water to the
city of Paramount, California. SCWC's
Hollydale System has more than 1,650
service connections, and uses two
groundwater wells as the system's
sources of supply.
SCWC is conducting arsenic removal
pilot tests at their Hollydale System's
Century well. The Century well, located
in a residential area, has a pumping
capacity of 500-600 gallons per minute
(GPM). It has raw water arsenic
concentrations between 0.015 mg/L
and 0.020 mg/L, manganese
concentrations between of 0.144 mg/L
and 0.180 mg/L, and a pH range of 7.6
to 8.0.
PH
Arsenic (As(V))
Chloride
Fluoride
Iron
Manganese
Silica (as SiO^)
Sulfate
Total Dissolved Solids
7.6-8.0
0.015 - 0.020 mg/L
31 mg/L
0.27 mg/L
0.108 mg/L
0.144 - 0.180 mg/L
20.5 mg/L
60 mg/L
368 mg/L
Galeziewski,T; Castillo, M; Kwart P; Chowdhury Z.
"Evaluation of Iron and Alumina Based Sorbents for Arsenic
Removal Based on Pilot and Full Scale Testing
Pilot Testing
SCWC's Century well site began full-scale pilot testing of adsorption media for the removal of
arsenic in October, 2001. SCWC tested four different proprietary adsorption media:
• Granular ferric hydroxide (GFH);
• Iron coated activated alumina;
• Modified activated alumina; and,
• Activated alumina.1
All of the raw water from the Century well is pre-chlorinated and treated to remove manganese.
During the pilot testing, half the water flowed directly from the manganese treatment system into
the distribution system and the other half was treated by one of the four arsenic removal test media.
The physical plant used for the full-scale testing of 50% of the flow at the SCWC Century well site
Memo written by Kevin Keen an of the Cadmus Group, Inc. based on a site visit to arsenic removal full scale
plant Century well site, SCWC. January 23, 2002.
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was designed to convert to 100% operation. SCWC
designed the site so that the Company could install
an additional four filter vessels once the arsenic
removal media was chosen.
The four arsenic treatment vessels are four feet in
diameter, six feet high, and were operated in
parallel so the influent and effluent of each could
be tested separately. Each vessel contained a pea
gravel filter bed and about 32 - 36 inches of media.
Each was designed to operate at a flow rate of 50
to 70 gpm resulting in five minutes of empty bed
contact time (EBCT), though this varied slightly
from vessel to vessel.
While traditional pressure filter vessels are filled
approximately 2/3 with media to allow for its
expansion during a backwash cycle, SCWC
discovered that backwashing did not appear to be
necessary, nor advantageous with these test media.
It appeared from these tests that the vessels can
operate while filled to near capacity with media,
which would increase operating flow rates and
extend filter operation time between loading and
disposal of media. During pilot testing, all of the
media were assumed to be single-use and
disposable, with no on-site regeneration required.
SCWC planned the pilot testing in two phases. In
the first phase, the raw water pH was not adjusted
and each media was used to exhaustion. In the
second phase of testing, SCWC will adjust the pH
of the raw water and the most promising media, the
GFH, will again be used to exhaustion.
Figure 2: Loading Arsenic Treatment
Media
Figure 3: Arsenic Treatment Media
Conclusions
In the first phase of the pilot tests, SCWC found the GFH medk was the most successful at
removing arsenic and meeting other performance criteria important to the system. Each of the AA
vessels experienced arsenic breakthrough in the effluent well before the GFH vessel. This may be
partially attributable to the influent pH of 7.4 to 7.9 (AA and GFH tend to be more effective at a
lower pH of around 5.5 to 6.0).
The second phase of testing will be conducted on a smaller quantity of the exhausted GFH media
removed from the full scale reaction vessel. SCWC will lower the influent pH to 7.0 for a small-scale
pilot reaction vessel. The pH of a small flow of water that has been pre-chlorinated and treated for
manganese removal will be adjusted by the carefully controlled addition of sulfuric acid. It is
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Figure 4: Century Well Pilot Test Vessels
expected that the performance of the GFH media
will be re-established at the lower pH, allowing the
removal of additional arsenic onto the previously
exhausted media.
One concern associated with use of the GFH
media is that the spent or exhausted media may
need to be treated as hazardous waste, especially
in California.2 If this is the case, the GFH media
can be monitored during use and replaced before
it reaches exhaustion. While close management of
the GFH media may increase overall costs, the
system would not need to pay for hazardous waste
disposal.
The cost of the site improvement package was
approximately $500,000. This included the
manganese treatment system, well pump, office and storage building, and landscaping, as well as the
arsenic pilot testing equipment. It is estimated that each arsenic reaction vessel cost between
California requires the use of the Waste Extraction Test (WET) test to determine if a waste is hazardous. Some
contaminants (including arsenic) are apparently removed more readily by the WET test than by the Toxic Characteristic
Leaching Procedure (TCLP) test used by other States. The spent media containing high levels of arsenic may be more
likely to be considered hazardous in California.
3Dr. Jason Wen, SCWC. "Memo by Kevin Keenan: Site Visit to Arsenic Removal Full
Scale Plant Century Well Site Southern California Water Company (SCWC)." January 23, 2002.
Office of Water (4606M) EPA 816-F-03-014
May 2003 www.epa.gov/safewater
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