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7/31/2019 North Battle Ford General
1/20
Requirements to produce high
quality water
Stephen Stanley, Ph.D., P.Eng.
EPCOR Water Services
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Capable Plant Model
High Quality Treated Water
Operation (process control)
Capable Plant
Administration Design Maintenance
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Capable Plant
A capable plant means if it is managed,
operated and maintained properly, the plant
has the required infrastructure to meet allrequirements
Criteria for capable plant largely dependent
on regulation
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Capable Plant
Requirements constantly changing as new
information becomes available
turbidity requirements have gone from 5 NTUto 1 NTU to 0.5 NTU and now proposed to go
to 0.3 NTU
Requirements for a capable plant alsodependent on raw water source
ground water - disinfection
surface waters - filtration and disinfection
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Capable Plant - Giardia Example
Raw Water
Giarida Levels
Recommended Log
Reduction
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Capable Plant
Multi-barrier Approach
Water treatment uses the concept of multi-
barriers to meet treatment requirements
a number of treatment processes which are eachbarriers for contaminants
Giardia example for 4 log removal
Clarification 0.5 log removalFiltration 2.0 log removal
Disinfection 1.5 log removal
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Capable Plant - Cryptosporidium
One of the greatest challenges facing the
water industry
Regulations just starting (US EPA and
Canada)
Resistant to chlorine (loss of major barrier)
For conventional treatment must rely on
particle removal
UV and ozone disinfection effective
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Capable Plant - Regulation
Regulations generally based on the concept
of reducing the risk associated with water to
an acceptable levelother factors include available technology and
economics
Poorer standards result in greater risk thatpublic health can compromised
typically event related (when plant challenged)
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Capable Plant - Summary
Requirements of a capable plant dependent
on regulation
Also dependent on raw water source
Capability of plant restricted to design flow
rates
A capable plant only provides the ability to
produce high quality water if proper
administration, maintenance and operational
systems are in place
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Adminstration
Relates to having administrative policies,
and staffing and funding requirements
needed to produce high quality water
Requires a commitment from senior
administration to produce high quality water
Needs quality assurance and quality controlprograms to ensure high quality water
Must ensure adequate staffing and funding
are available
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Design
Design of a treatment facility must not only
meet requirements for the capable plant but
must also consider operational andmaintenance realities
Design should also consider technical
expertise required
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Maintenance
To make a capable plant sustainable, regular
maintenance must occur
Maintenance activities must consider
operational constraints and must be planned
accordingly
For critical systems redundancy may berequired
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Operations - Process Control
Water treatment of surface waters,
especially those treating river waters is a
very dynamic process raw water quality may vary from a turbidity of
1 NTU to over 1000 NTU
water demand may vary by 3 times Treatment plants must constantly vary
operating conditions (chemical doses,
flows, etc.)
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Operations - Process Control
For process control require:
a measure of the state of the system
comparison of the current state to the desiredstate
an action (for example a change in chemical
dose) to return the system to the desired state
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Challenges in Process Control
Multiple and conflicting objectives
water quantity vs. water quality
disinfection vs. disinfection by-products
Multiple operating parameters
must simultaneously adjust more than one
chemical dose and operating conditions
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Challenges in Process Control
Long residence time in plant
if treated water turbidity increases and requires
change in coagulant dose at front of plant, canhave 3 to 5 hours of water in the plant that must
pass through before change will be noticed
requires intermediate assessment of treatment
process
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Challenges in Process Control
No standard methods to determine proper
chemical dosing
must rely heavily on operator experience
must ensure available tools are being used (jar
tests)
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Operations - Process Control
Upsets can occur in water treatment
Must have clearly defined emergency
response plans
Should have programs such as a boiled
water notice in place
Can not wait for illness
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Production of High Quality
Water
Requires not only a capable plant but proper
administration, design, maintenance and
operations Failure in any of these areas significantly
increases the risk to public health
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The Challenge
Requirements for the production of high
quality of water is largely independent of
the size of the community The complexity of the treatment system is
largely dependent on the quality of the raw
water The challenge is implementing the
requirements in smaller communities