Kamloops turns to low-pressure membranes for water safety
By Brian Comerford and
Troy LaPlante
ZeeWeed membranes are immersed directly into the process tanks at the River Street Water Treatment Plant and are capable of producing up to 160
MLD of potable water for the community.
The waters of the North and
South Thompson Rivers that
meet in Kamloops, British
Columbia, have long influenced
settlement in this growing city.
Surrounded by sprawling arid grasslands
and rolling mountains, the confluence
of the rivers has drawn people
to its banks ever since the native, seminomadic
Secwepemc people gathered
there to trade goods and enjoy the pristine
waters. The native fur trade
attracted the first European settlers to
this area and the gold rush of the 1850s
brought the railway, which facilitated
the rapid expansion of the city.
For generations, the river has
always provided aboriginals and the
early settlers with an abundance of
pure, safe drinking water. As the trading
post became a settlement, and the
settlement grew to be a city, the river
began to show signs of decline, and
many residents became concerned
about the river’s water quality.
In the early 1940s the City of
Kamloops began chlorinating the municipal
water supply to reduce the risk of illness
from water-borne pathogens. Until
recently, pre-screening and chlorination
were the only treatments that the City
provided for the drinking water supply.
However, as the population of the City
and the surrounding area continues to
grow, the increasing activities along the
watershed are adversely affecting the
river water quality. Forestry, agriculture,
mining, recreation, construction, and
transportation are all producing an
increase in the sediment and pollutants
from point and non-point sources that
are entering the river.
Springtime turbidity spikes
Today, this city of 82,000 is most
aware of these problems in the spring,
when silted debris washes down the
river, causing turbidity spikes in the
range of 30 to 50 NTU, but these can
go as high as 500 NTU. Although the
problem is short lived, lasting only a
week or two during the peak spring
runoff period, the existing chlorination
system cannot remove the suspended
solids from the water.
In addition to increasing the chlorination
levels to combat the rising turbidity,
the City also advises residents
to boil water for additional protection
whenever turbidity rises above 5 NTU.
But troubling outbreaks of water-borne
illnesses in nearby communities left
many Kamloops residents wondering
if they are at risk of a similar occurrence.
Committee looks for solutions
In 1997, the City formed the
Committee on Drinking Water Quality
to specifically address the water quality
issue. During the Committee’s
review process the Thompson Health
Region applied new conditions to the
City’s operating permit for potable
water production. The changes
required the City to reduce potable
water turbidity to below 1 NTU 95 percent
of the time, eliminate at least 99.9
percent of Giardia and Cryptosporidium,
and maintain trihalomethane
concentrations below 100 µg/l.
The Committee continued with
developing strategies to ensure compliance
with the new operating conditions
and issued a final report in
January 2000. Several options were
examined by the Committee that
included improvements to the watershed
to reduce pollutants and sediment
in the river, development of alternative
water sources from the Clearwater
River or a new groundwater source,
purchasing water from a neighboring
aboriginal band, and the construction
of a new water treatment plant.
The Community Advisory Committee
recommended that a new water
treatment plant would be the best solution
for Kamloops to ensure a stable,
long-term, high quality water supply.
The Committee also recommended
that membrane filtration should be further
investigated as an option to a conventional,
sand filtration plant.
Pilot studies of four leading membrane
systems were conducted during
2000, and the results were presented to
city council in May 2001. The results
showed that membrane filtration could
provide higher quality water to the
City, and was easier to operate than a
conventional sand filtration plant. The
study also showed that the capital cost
of constructing a new membrane filtration
water treatment plant would be
about the same as that of a conventional
plant.
Membranes selected
In September 2001 the Kamloops
city council selected membrane technology
as the best solution for the new
plant, and a year later, in September
2002, awarded ZENON Environmental
Inc. with the contract to supply
immersed, low-pressure ultrafiltration
membranes for the project. ZENON
was selected over three other membrane suppliers after a detailed review
process which, in addition to the pilot
testing, also included company experience
and qualifications, product quality,
and project lifecycle costs.
Construction of the new $48.5 million
River Street Water Treatment
Plant (WTP) began in April 2003 and
the plant is expected to be fully operational
by the end of 2004. When completed,
the plant will be Canada’s
largest low-pressure, enhanced coagulation
membrane water treatment plant
and will be capable of supplying up to
160 MLD (42.3 MGD) of clean drinking
water to the community, regardless
of the turbidity in the raw river water.
How the plant works
The City’s new membrane ultrafiltration
WTP will pump water from the
South Thompson River to a low lift
pumping station for screening and
coagulant addition to aid in the
removal of total organic carbon (TOC).
The removal of TOC minimizes the
formation of any chlorination byproducts
such as trihalomethane which are
suspected carcinogens. Six flocculation
tanks will mix the incoming water
for several minutes to facilitate floc
formation and then release it to the
membrane process tanks.
The flocculated water will flow by
gravity to the membrane process
trains. The plant is equipped with 12
process trains; however, water production
is handled by 11 trains to enable
one train to be removed from production
for maintenance cleaning.
ZeeWeed® membrane cassettes are
immersed directly into the process
tanks. Thousands of membrane fibers
hang loosely in each membrane cassette
and a slight vacuum is applied to the
end of each membrane fiber to draw
water through microscopic pores and
into the hollow fibers. With a nominal
pore size of 0.04 µm, the membranes
form a physical barrier to suspended
solids and provide greater than 4-log
removal of pathogens such as Giardia
and Cryptosporidium. Rejected particles
remain in the process tank.
The River Street Water Treatment
plant incorporates a two-stage filtration
process that enhances the recovery of
potable water from the river. This second
stage has six trains of ZeeWeed UF
membranes and can treat up to 12.5
MLD (3.3 MGD) of reject water from
the first stage. Any reject water from
the secondary stage will be returned to
the headworks of the plant and mixed
with the incoming raw water for further
processing. This configuration enables
the plant to recover 99 percent of
potable water from the river and also
substantially reduces the cost of raw
water pumping and the waste stream to
the sewer system. In the final step,
chlorine will be added as a disinfectant,
prior to releasing the water to the
municipal distribution system.
Future expansion
The River Street WTP has been
constructed with community growth in
mind and, when required, additional
membrane cassettes can be added to
the process tanks to increase capacity
to a total of 200 MLD (52.8 MGD).
Each process train currently holds six
membrane cassettes, but space is provided
for eight cassettes, enabling
water production capacity to be
increased incrementally as necessary.
Leadership in sustainable design
In addition to providing a safe drinking water supply, the new water
treatment plant will demonstrate the
City’s leadership in water conservation
and environmental stewardship. The
facility was designed and constructed
according to Leadership in Energy and
Environmental Design (LEED) criteria
to reduce the environmental impact of
the construction and operation of the
plant. The building meets the silver certification
level of the LEED program
and is currently the only accredited silver
LEED water plant in Canada.
Responsible land use is achieved by
constructing the new plant on a brownfield
site with 45 percent of the site to
be restored to wetlands or planted
areas. Fossil fuel consumption is
reduced by using high efficiency lights
and natural light wherever possible, as
well as designing the HVAC system to
reject heat during the warmer months
into the incoming raw water and eliminating
the need to use cooling towers.
Water is conserved by low flow
plumbing fixtures and rainwater collection
for non-potable uses. A green
roof will reduce run off and absorb
heat while overflow from the roof and
the porous pavement of the parking lot
will be redirected to a constructed wetlands.
Grey water from the plant
processes will provide irrigation to city
parks and an adjacent sports field.
Even the building itself incorporates
recycled materials in the concrete, aluminum,
insulation, and drywall, just to
name a few.
Brian Comerford is Utilities Manager,
City of Kamloops and
Troy LaPlante,
M.Sc, P.Eng., is Project Manager –
Municipal Systems, ZENON
Environmental Inc.
Contact: bcomerford@kamloops.ca.
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