The Santa Clara Valley Water District (SCVWD) receives approximately 150,000 acre-feet
of water per year from the Central Valley Project through the San Felipe Division
Unit of the San Luis Reservoir. When water levels in the San Luis Reservoir fall below
300,000 acre-feet, algae-rich waters in the upper 20 to 30 feet of the reservoir can be
drawn into the intakes. In the future, the San Luis Reservoir may be drawn down below
the "low point" as much as 50 percent of the time due to proposed CALFED changes in
water management. These conditions can cause taste, odor and filter clogging problems
for SCVWD as well as line and emitter clogging problems for San Felipe agricultural
customers using drip irrigation systems.
In order to better quantify the treatment and supply problems associated with reservoir
drawdown to "low point" conditions, SCVWD conducted a pilot study of the impacts of
high algae feedwater on flocculation, sedimentation, ozonation, and filtration
processes. The pilot study included collection of algae from the reservoir surface water
during the peak algae growth season. This collection allowed for testing of feedwaters
with high algae concentrations (on order of 5,000 to 10,000 cells per mL and up to 1,000
fluorescence Rhod-equivalents). Blue-green algae (i.e. Aphanizomenon, Microcystis,
Anabaena) are the dominant species in the San Luis Reservoir.
Two pilot treatment trains were run side-by-side to compare water treatment
performances for: algae-laden surface water collected from the top 3 ft., containing algae concentrations
that may be anticipated under "low point" conditions; and,
intake water withdrawn from the reservoir bottom, representing current withdrawal
practices from San Luis reservoir.
Side-by-side pilot testing of these two waters allowed evaluation of treatment
performances including: filter clogging, filter run length, headloss development, unit
filter run volume (UFRV), filtered water turbidity, filtered water particle counts, water
production capabilities, taste and odor control, and impact on intermediate ozonation.
Pilot-scale evaluation compared filtration performance for the two water sources and two
different filter media designs: anthracite and sand dual-media design; and, granular
activated carbon.
This paper focuses on the pilot study results that demonstrate and correlate the impact of
various algae count feedwaters with shorter filter runs. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 800 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 15 |
| Published : | 06/15/2003 |
