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Disinfection Optimization for
Treatment and Distribution
Materials taken from:
Rural Community Assistance Partnership (RCAP)
- Distribution System Water Quality Management
Training Curriculum (funded by EPA)
Colorado Distribution Operator Training Series –
Oxenford Consulting, Rural Community
Assistance Corp, Damon S. Williams Associates
(funded by CDPHE)
Acknowledgements
Be able to discuss regulatory requirements and
partnership goals for disinfection
Be able to identify and describe factors that may
impact disinfectant residual
Be able to apply a strategies for controlling
disinfection residual
Learning objectives
Regulatory requirements and
partnership goals for disinfection
What are the types of disinfection?
Chlorine
Chloramines
Chlorine dioxide
UV (Ultraviolet disinfection)
Ozone
Which disinfectant(s) provide protection in the
distribution system?
Why do water systems disinfect?
Protect the public from waterborne disease
Prevent biofilm buildup in the distribution system
Bacteria (e.g. Total Coliforms)Virus Protozoa
1911- Denver Water disinfected its
drinking water to help prevent
cholera and typhoid
7
Waterborne disease outbreaks still
occur in Colorado
Years Number of
Outbreaks in
Colorado
Number of
Cases of
Illness in
Colorado
1800s – 1964 Unknown Unknown
1965 – 1979 21 6,832
1980 – 1989 49 5,461
1990 – 1999 3 147
2000 – 2010 4 1,416
8
Surface Water Treatment Rules
3-log Giardia removal/inactivation
4-log virus removal/inactivation
Disinfection profiling
0.2 mg/L at entry point to the distribution system
(EPDS)
Groundwater Rule
Minimum at EPDS of 0.2 mg/L
4-log treatment of viruses
Requirements – Water treatment
Continuously maintain CT (meet state
requirements, monitor, report, alarms, SOPs)
Understand chemistry
For chloramines establish a chlorine/ammonia
ratio
Balance disinfection and DBPs
Redundancy
Partnership – Water Treatment
Plant Optimization Self Assessment
Residual concentration cannot be undetectable in
more than 5% of samples within the distribution system,
for two consecutive months
New CDPHE (April 1, 2016)
Undetectable defined as greater than 0.2 mg/L
95% for systems with more >40 samples/month
Not less than one or two samples for <40 samples/month
Requirements - Distribution
System
95% of the distribution system samples should
be:
>0.20 mg/L free chlorine
>0.50 mg/L total chlorine/chloramines
Not undetectable for two consecutive samples at
the same site
Distribution System Partnership
What type residual disinfectant do you use?
Target conc. at EPDS?
Target residual in the DS?
What challenges do you have with
Meeting CDPHE’s new requirements
Meeting partnership goals
Discussion
What can impact residual in the
DS
Chlorine decay
Chlorine degrades in the distribution system
Reaction with natural organic matter (NOM) and/or
pipe materials
Booster chlorination may be needed to maintain an
acceptable chlorine residual
Rapid decay can be an indicator of a distribution
system problem
Water age
The residence time of water in the distribution before reaching the customers
Chlorine Residual
Water Age
Water age
High water age:
Loss of chlorine residual
Increased risk of bacterial regrowth
Increased DBP formation
Higher chance of contamination
AWWA recommends water age of less than 7
days
17
Temperature
The residence time of water in the distribution before reaching the customers
Chlorine Residual
Temperature
Temperature
High water temperature:
Quicker loss of chlorine residual
Faster bacterial regrowth
Higher disinfection byproduct formation
Nitrification
Low water temperature
Chlorine is less effective as a disinfectant
Storage
Increased time in storage, lower chlorine residual
Chlorine Residual
Time in storage
Stratification
Temperature effects
Turnover/ mixing
Contamination
Booster chlorination
Nitrification
Storage – Factors that can
impact disinfectant residual
Cross connections can have a localized effect
on chlorine residual
The presence of a cross connection can be
indicated by localized area of low or no chlorine
residual
Cross connections
Biological growth in the
distribution system will create a
chlorine demand
Biofilms are “self-shielding”
decreasing the chlorine’s
efficacy
If chlorine residual is lost,
biological regrowth may occur
Biological regrowth/ biofilms
Practices for residual control
Maintaining CT - Setting dose, addressing
alarms
Chlorine analyzer – Maintenance, calibration…
Chlorinator operation – Calibration, inspection,
maintenance, redundancy
Safety – Handling, alarms, leaks, response…
SOPs – Water Treatment
Addressing low residual in the distribution
system
Responding to a main break
Nitrification response
Field chlorine analysis procedures
SOPs – Distribution
Disinfection profiling
Quality control charts
Mapping
Data and analysis
Chlorine residual mapping
A temporal and spatial visual record of chlorine
residual
Understand the dynamics of chlorine residual
Seasonal
Operational change
Source water change
Distribution system operation
Chlorine residual mapping
Example: City of Tempe, AZ
Develop a chlorine residual map for the two
scenarios provided and discuss the results.
Activity
Scenario 1
Scenario 2
