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

Jeff Oxenford

(720) 353-4242

joxenford@comcast.net

Thank you!