The
AlgaeWatch On-Line Fluorometer as Used by the Santa Clara Valley Water
District in California
The AlgaeWatch
On-Line Fluorometer provides a continual indication of the algal
biomass in water, thus allowing for the early detection of algal blooms,
detection of nuisance species, and a measure of daily and seasonal
fluctuations in the algal community. The Santa Clara Valley Water
District (SCVWD) has been using the AlgaeWatch system since 2005 and
presently owns multiple instruments installed at various reservoirs
and treatment plants. Grab samples from the facilities are taken periodically
and sent to the in-house laboratory for algal speciation and algal
count measurements. The AlgaeWatch used at the Penitencia Water Treatment
Plant (PWTP) measures the relative Chlorophyll a content of
the pre-treated water which is received mainly from the Sacramento-San
Joaquin Delta via the South Bay Aqueduct (SBA). This facility can
treat up to 40 million gallons of water per day and measures other
water quality parameters such as turbidity and pH at the pre-treatment
sampling point.
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| The Turner
Designs AlgaeWatch installed at the pre-treatment sampling point.
The AlgaeWatch is typically cleaned and calibrated twice per month. |
Water treatment
tanks (flocculation basins) at the Santa Clara Valley Water District
Penitencia facility. |
The PWTP is a conventional water treatment
plant with coagulation, flocculation, sedimentation, ozonation, and
filtration processes. Pre-treated water is first injected with coagulant
chemicals and then mixed with flocculator paddles to turn undesirable
particles in the water into bigger denser flocs; which settles away
in the sedimentation basins. In the final stage, filters composed
of granular activated carbon and sand remove the remaining particles
in the 'settled' water. A high chlorophyll a measurement by
the AlgaeWatch can be an indication that an algal bloom is occurring
along the SBA. As a result, the filters may be taking on an increased
load during an algal bloom and have to be washed more often.
Many thanks to Lotina Nishijima and Karla
Guevarra and the Santa Clara Valley Water District for their contributions
to this article. Information on the Santa Clara Valley Water District
can be found at http://www.valleywater.org.
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