By Garry Drachenberg, P.Eng.
and Sutha Suthaker, Ph.D., P.Eng.,
Associated Engineering
Recent E-coli and Cryptosporidium
outbreaks in
Canada have focused public
attention on drinking water
quality and water safety. Responding
to public concerns, the community of
Canyon Creek in north central Alberta
embarked on a program to improve
their drinking water quality.
Assisted by consultant, Associated
Engineering, the community adopted
a water treatment upgrade scheme
that optimizes the use of modern
processes and the existing conventional
plant.
The community of Canyon Creek is nestled in the heart
of the Municipal District of Lesser Slave River, a region of
virtually unspoiled land and lakes, and home to abundant
wildlife, fish, and resources. The Municipal District has a
strong economic base comprising farming, forestry, and oil
and gas industries.
In recent years, the community of 1,000 has become a
destination point for fishing enthusiasts, wind surfers,
kayakers, canoeists, and beach lovers. Summer tourism and
community growth have taxed the limits of the existing
water and wastewater infrastructure.
Lesser Slave Lake provides the
water supply for Canyon Creek. As it
is a shallow lake, water quality varies
seasonally, posing treatment challenges.
During the summer, organic
and algae laden water can yield light,
fragile, difficult to settle floc particles.
Plant throughput must be curtailed
during such periods to produce
turbidity compliant water. In the winter,
when anoxic conditions prevail
underneath the ice cover, iron and
manganese can present problems.
The existing facility is a conventional
package treatment plant consisting of a flash mix
tank, three mechanically agitated flocculation tanks, one
clarifier with tube settlers, and a two-compartment filter.
The manufacturer-rated plant capacity is 900 m3/d.
During peak demand periods, operators run the plant 20%
over the rated capacity and 60% over the recommended
throughput for organic laden waters. The capacity shortfall
and inability to consistently meet treated water turbidity
targets drove the decision to investigate upgrade alternatives.
The treatment objectives established for the plant
upgrade were as follows:
Meet current and pending more
stringent Alberta Environment
(AENV) Approval requirements.
The Municipal District also identified
the following considerations for
the upgraded treatment plant:
Operation personnel familiarity and
satisfaction with the existing treatment
process.
Owner and public concern regarding
water-borne disease outbreaks.
Logistical challenges posed by wide
geographic area covered by operational
personnel, i.e., if a quick response
is needed.
Need for treatment process less susceptible
to upset and capable of remote
monitoring.
Exposure to the membrane pilot testing
work undertaken at the Town of
Slave Lake.
Based on a preliminary screening
of technical and qualitative factors,
three options were evaluated to satisfy
the above objectives and considerations:
Option 1 - Expansion via additional
conventional treatment capacity;
Option 2 - Expansion via additional
membrane treatment capacity; and,
Option 3 - A regional water line to
Slave Lake.
Analysis showed that Option 1 had
the lowest capital cost and Option 3,
the highest capital costs. Option 2 -
membrane treatment had the highest
ranking, allowing maximum flexibility
to address both water quality and
capacity issues. Option 2 also met
process and water quality requirements.
Membrane treatment was,
therefore, selected for implementation.
In cooperation with a neighbouring
community, the Town of Slave Lake,
the Municipal District shared in the
membrane treatment pilot testing costs
and pilot testing data. In the fall of
2000, the Town of Slave Lake completed
membrane pilot testing using a proprietary
vendor technology. Pilot testing
validated the suitability of this vendor's
membrane filtration equipment
for the Lesser Slave Lake water source
during the late summer/fall period
when challenging water conditions
were encountered.
To obtain competitive equipment
supply quotations, three additional
vendors were invited to submit letters
of interest for the project, as well as
undertake pilot testing. Pilot testing
was necessary to demonstrate satisfactory
performance and to pre-qualify
vendors for the project. Two vendors
submitted letters of interest and set up
pilot plants. Pilot testing took place
from August to November 2001.
Upon completing pilot testing, vendors
were invited to submit detailed
price proposals for a chemical feed
system, pre-treatment system (enhanced
coagulation capable) and dualtrain
membrane treatment system.
The contract documents also specified
a process warranty for turbidity, particle
counts, total organic carbon (TOC),
net flow rate, and net treated water production
between chemical cleanings of
the membranes. Zenon Environmental
was awarded the equipment supply
contract after a comprehensive evaluation
and formal interviews.
A ZeeWeed membrane module being lifted into place through a roof hatch
The upgraded treatment plant has a
25-year design capacity of 1,879 m3/d,
implemented in two phases.
Phase I involves operating the existing
plant in parallel with the new, 954
m3/d package membrane treatment
plant. The package plant comprises
one dual-train, skid-mounted Zee Weed®
Membrane system, complete with
membrane elements, epoxy-coated,
steel membrane tanks designed for
future membrane expansion, permeate
and back-pulse pumps, membrane air
scour blowers, instruments, programmable
logic controller, and a motor
control centre.
When water demand and/or more
stringent water quality guidelines dictate,
the community will implement
Phase II: converting the existing conventional
plant to a pretreatment unit
and operating the existing plant in
series with the membrane plant. Phase
II capacity expansion of the membrane
process can be accomplished by
removing the existing membrane cassettes,
installing two, higher capacity
cassettes, and replacing the permeate
pumps and blowers. The system design
also allows for operating either the
existing water treatment plant or the
membrane plant on its own.
Blending the old and new treatment
technologies has presented interesting
regulatory challenges. One of the more
interesting regulatory rulings has been
the requirement of different treated
water turbidity limits for the different
processes.
The different limits are based on the
changes proposed by the Federal-
Provincial-Territorial Committee on
Drinking Water (CDW) in conjunction
with Health Canada. The proposed
guideline is technology specific, recognizing
the varying treatment capabilities
of treatment technologies in
reducing turbidities.
The Alberta Environment Approval
for this project, in which multiple turbidity
target requirements have been
set, is the first of its kind in the
Province of Alberta.
As part of the project, the Municipal
District upgraded its SCADA
system, implementing a leading edge,
remote control monitoring and reporting
capability. This initiative recognizes
Alberta Environment¹s intent to
provide web access of drinking water
quality data from all municipalities to
increase consumer confidence in the
quality of drinking water. With
SCADA upgrades, the Municipal
District has the system in place to
enable on-line electronic reporting of
their daily operations.
Garry Drachenberg and Sutha
Suthaker are Senior Water Process
Engineers with Associated Engineering
in Edmonton, Alberta. Contact:
drachenbergg@ae.ca or suthakers@ae.ca.
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