OPERATIONS
HRD’s schematic for the San Jose Water Company’s
new membrane treatment plant with coagulation,
flocculation and sedimentation pre-treatment.
www.ca-nv-awwa.org 17
San Jose Water Company Builds
Country’s Largest PES Membrane
Filtration Plant By Francois Rodigari and Richard Stratton
A design-build contract upgrades a 46 year-old direct
filtration treatment plant to membrane filtration.
DRIVEN BY THE NEED TO modern-ize
a plant commissioned in 1970 and
built for a million dollars (a bargain
even in 1970 dollars) the San Jose Water
Company (SJWC) committed to upgrading
its Montevina direct filtration water treat-ment
plant in the Santa Cruz Mountains to
a membrane filtration plant equipped with
a full-fledged pre-treatment suite of coag-ulation,
flocculation, and sedimentation.
While the direct filtration plant’s
simplicity ensured its capacity to treat
water with no major upgrades and minimal
maintenance over the past 46 years,
compliance with the Interim Enhanced
Surface Water Treatment Rule (1988)
restricted treatment to raw water with
turbidities of less than 15 nephelometric
turbidity units (NTU). Because of limited
water storage in SJWC’s watershed, this
treatment limitation technology resulted
in lower water production than could be
possible if the plant were able to treat water
during storms when turbidities can routinely
reach 100 NTU for up to 24 hours. Although
the original plant was nominally a 30 million
gallon a day (MGD) facility, historically a
supply of raw water with a turbidity of less
than 15 NTU has not been available.
SJWC recognized that to maximize the
use of its available water resources, it had
to build a new plant. It commissioned
Kennedy/Jenks Consultants to perform
a review of its existing facilities, the
characteristics of the source water
available to the plant, and existing plant
performance, and make recommendations
on improvements that would make it
possible to treat available water during
storm runoffs. Based on the Kennedy/
Jenks recommendations, SJWC requested
authorization from the California Public
Utility Commission (CPUC) to upgrade the
Montevina plant to membrane filtration.
The CPUC authorization was granted in
2013 and proposals were solicited from
three design-build firms. A Professional
Service Agreement was executed with
HDR, Inc. in April 2014. The contractor for
the project is HDR Constructors, Inc.
SJWC’s decision to adopt a progressive
design-build process streamlined design
and construction, making it possible
to proceed from signed contract to
construction in 16 months. During that
time, the project progressed from a 30
percent design to bidding by subcontractors
(based on a 60 percent design) to HDR’s
submission of a Guaranteed Maximum
Price (GMP) for the project (within the
$48 million original target) to initiation of
construction in August 2015.
The plant was shut down for construction
from August 2015 through December 2015
and again in July 2016 and will remain
offline through the expected completion of
the project in 2017. The shutdown periods
were chosen to minimize water production
losses by treating the available stored water
and runoff between the months of January
and June and to replenish storage during
wet weather.
The design-build process made it
possible for SJWC and HDR to collaborate
on membrane selection, perform a proof of
performance for the membranes selected,
and make several design changes as
SJWC better understood the operational
implications of the evolving design prior to
agreement on a GMP. Changes incorporated
prior to HDR’s arriving at a GMP included:
1) development of sufficient administrative
capacity to manage the upgraded plant
and the watershed in space that resulted
from moving the operations control
room from the old operations building to
the new membrane building, including
space for an analytical laboratory, and 2)
redesigning the solids handling facility to
provide the ability to handle peak solids
production during wet weather without
storage or the need to arrange for multiple
dewatered sludge pickups on any given day.
Additional improvements included security
improvements, the ability to fully remotely
control the operation and access to the
solids handling facility, and repurposing
of the old lagoons to serve as emergency
storage for settling basins sludge in the
event of equipment failure or sustained raw
water turbidities in excess of 100 NTU.
Based on an analysis by HDR and a suc-cessful
proof of performance test conducted
in the SJWC’s watershed in Fall 2014, the
SJWC/HDR design-build team unanimous-ly
selected BASF/inge ultrafiltration mem-branes.
The multibore® inside-out design of
the membranes, made of polyether sulfone
(PES), offers the advantage of being robust
and the guarantee to experience zero to
very low breakage under projected normal
operating conditions. Each membrane fiber
bundle is made of seven bores with a diam-eter
of 0.9 millimeter and a filtration layer
pore size between 10 and 20 nanometers. A
surrounding highly porous foam layer sup-ports
and protects the fibers. The hydrophilic
characteristic of the membranes translates
into lower transmembrane pressures and
lower filtration energy costs compared with
other membranes.
The design-build process afforded SJWC
the ability to build what will be the largest
PES membrane filtration plant in the U.S.,
but it was the extraordinary dedication of
the SJWC and HDR staff and their ability
to cooperate under the pressures of tight
deadlines and budgets that have made it
possible. The plant upgrade is being fi-nanced
with SJWC equity and short-term
debt, which will be refinanced with long
term debt to be repaid over 30 years. S
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