Drinking Water Chlorination

First Nations Infrastructure Conference

February 5, 2014 Marion Axmith Canadian Chlorine Chemistry Council (C4) Mary Ostrowski American Chemistry Council (ACC)

•  Over 100 years ago, chlorine was first used to reduce waterborne disease outbreaks in the U.S.

•  A bold step at the time due to aversion to chemicals or ‘chemophobia’

•  “Chlorine” is derived from the Greek word “chloros” meaning green

Chemophobia

“Chemophobia, the fear of chemicals, was prevalent at the

turn of the 20th century & continues to be an issue”

“Chemophobia almost derailed the use of chemical disinfectants then & it often dominates discussion of

drinking water safety today”

Michael J. McGuire

The Chlorine Revolution: Water Disinfection and the Fight to Save Lives

Protecting

Public Health •  Dr. Leal, physician - breaking sewer pipe-water pipe “death spiral”

•  “Death spiral” – wastewater disposed of in same body of water used for drinking water perpetuated waterborne disease

Improving Water Quality •  Jersey City Legal challenge

over water quality

•  Dr. Leal & George Warren Fuller constructed the first water chlorination system

Illness & Death

Rates Plummeted

•  Leal & Fuller presented results at 1909 American Water Works Association meeting

•  Jersey City death rates from typhoid fever fell from 20 per 100,000 in 1905 to single digits by 1920

Drinking Water Chlorination

“For more than a century, the safety of Canadian drinking water supplies has been greatly improved by the addition of chlorine.”

Health Canada

It’s Your Health: Drinking Water Chlorination, 2006

Drinking Water Chlorination

is One of the Most

Significant Public Health Improvements

in History

(Data from U.S. Centers for Disease Control &

Prevention, Summary of Notifiable Diseases, 1997)

Chlorine-Based Drinking Water Disinfectants   Elemental chlorine

(Cl2 gas)

  Sodium hypochlorite (NaOCl liquid solution)

  Calcium hypochlorite (Ca(OCl)2 solid)

 On-site generation of sodium hypochlorite (NaOCl liquid solution)

Water Treatment

Steps

(Image from U.S. Environmental

Protection Agency website)

Q: Why Treat Drinking Water?

A: The

Invisible Threats!

Salmonella  typhi  

Vibrio  cholerae  

E.  coli  

The Concept of

“Free Chlorine”

 Elemental chlorine and the hypochlorites form “free chlorine” in water

 Hypochlorous acid (HOCl) and hypochlorite ion (OCl-)

 pH determines which form dominates

 Hypochlorous acid best penetrates pathogens

Chlorine Provides

Long-Lasting Protection

Against Waterborne

Germs

  Chlorine residual helps prevent microbial re-growth in the

distribution system

Chlorination Does More

Than Destroy Waterborne

Germs

Potent germicide

  Destroys most bacteria, viruses and parasites

Taste and odor control

  Oxidizes disagreeable algae secretions, sulfides and reduces odors from decaying organic matter

Biological growth control

  Eliminates slime bacteria, molds and algae that grow in reservoirs, water mains and storage tanks

Chlorination Does More

Than Destroy Waterborne

Germs

Chemical control

  Removes hydrogen sulfide, ammonia, iron and manganese from raw water

Suitable for a wide range of water quality

Easily monitored and controlled

Cost-effective

Disinfection By-Products

or “DBPs”

•  Chlorine reacts with natural organic matter

•  DBPs are associated with most disinfectants

•  Chlorinated DBPs are the most well-studied

•  Reduced by removing natural organic matter before chlorination

Comparing Chlorine-Based

Disinfection Methods

Elemental Chlorine   Lowest cost of chlorine forms

  Unlimited shelf-life

  Hazardous gas

  Requires special handling and operator training

  Transported and stored as a liquefied gas under pressure

  Facilities use 100 or 150 lb cylinders or one-ton containers

  Large systems use railroad tank cars or tanker trucks

Sodium Hypochlorite

(bleach) o  Higher chemical cost than elemental chlorine

o  Limited shelf-life

o  Less hazardous than elemental chlorine

o  Easier to handle but more difficult to store

o  Fewer training requirements and regulations

o  Higher shipment volume than elemental chlorine

Calcium Hypochlorite o  Higher cost than elemental chlorine

o  Long shelf-life

o  Dry chemical

o  Fire or explosive hazard if handled improperly

o  More stable than sodium hypochlorite

o  Precipitated solids formed in solution could complicate chemical feeding

o  Fewer training requirements and regulations than elemental chlorine

o  Typically used in small facilities

Chlorine-Based Drinking Water Disinfectants

 Chloramine (NH2Cl, liquid)  Chlorine Dioxide (ClO2 gas, generated onsite)

Chloramines   Formed by combining chlorine and ammonia in specific ratios

  Requires shipping/handling ammonia and chlorinating compounds

  Weak primary disinfectant; well-suited as a secondary disinfectant

  Reduced formation of DBPs

  Very stable residual

  Good control of coliform bacteria and biofilm growth

  Lower taste and odor than free chlorine

  Must be removed for kidney dialysis

  Must be removed for aquarium water

Chlorine Dioxide   Dissolved gas generated onsite from mixing

sodium chlorite and elemental chlorine in solution

  High operating cost

  Strong disinfectant

  Effective against Cryptosporidium and Giardia

  Does not form chlorinated DBPs

  Very volatile residual

  Treats some taste and odor problems

  Requires on-site generation equipment

  Requires high-level technical competence

From  Hubbs,  S.,  “Disinfec4on  Source  Water  Quality  Drives  Treatment  Selec4on,”  Opflow,  April  2013.  

Comparing Disinfectants: Including Energy Efficiency and Greenhouse Gas Emissions

Chlorine: A Public Health Chemistry for

100 Years and Running…

  Most water systems use some type of chlorine-based process

  No “one size fits all”

  Every water system is unique

  Industry is committed to safe, sustainable use of chlorine-based disinfectants

We Welcome Your Inquiries!

Marion Axmith ⎜416.456.4619

Canadian Chlorine Chemistry Council www.cfour.org

Mary Ostrowski ⎜202.249.6705

American Chemistry Council www.americanchemistry.com/chlorine

The Chlorine Institute ⎜703.894.4140 www.cl2.org