Alternative Secondary Disinfectants: Advantages and Disadvantages

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Alternative Secondary Disinfectants Advantages
and Disadvantages

• Jeffrey K. Griffiths, MD MPHTM
• Associate Professor, Tufts University
• Member, Science Advisory Board, US EPA

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How can Pathogens get into our drinking water? 1.
Failure of treatment (no killing of
pathogens!) 2. Leaky pipes, joints, etc. 3.
Cross-connections e.g. sewer line close to
water line, sewage seeps into soil and then into
water pipe 4. Storage tanks with a route for
contamination (no roof) 5. Contaminated
equipment/materials used during repair 6.
Intentional introduction (bioterrorism)
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Re-growth of Bacteria Accidental
Cross-Contamination
Raw Water Treated Water Distributed Water
Additional of Residual Disinfectant
Raw Water Treated Water Distributed Water
Remains safe to drink
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Residual Disinfectant Concentration Minimums

• Chloramine report total chlorine residuals
  need 0.5 mg/L
• Minimum free chlorine residual of 0.2 mg/L
• Allow at least 30 minutes of contact time between
  the chlorine and water to allow adequate time for
  disinfection

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Surface Water Treatment Rule 1989

• Maximum Contaminant Level Goals of zero for
  viruses, Legionella bacteria, and Giardia
  parasites.
• Practically speaking, goal is to kill 99.9 of
  Giardia, and 99.99 of viruses.

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Disinfection byproducts

• 1971 Bellar discovers that chloroform absent in
  the Ohio River, yet was present in drinking
  water. This was some of the first evidence that
  chlorinating water led to the development of
  disinfection products that can affect
  reproduction, fetal development in pregnant
  women, and are carcinogens (Cotruvo 1981).
• Factors include the type of disinfectant, the
  dose, and the disinfection residual. The reaction
  time, temperature, and pH affect disinfection

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What affects production of DBPs?

• If reaction time is short higher
  trihalomethanes and halogenic acetic acids (HAAs)
  may be formed.
• At higher temperatures (summer), reactions occur
  more quickly, and a higher concentration of
  chlorine is needed for disinfection, and thus
  there are more disinfection byproducts

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More about DBPs

• The levels of disinfection byproducts are often
  higher in the distribution pipes than at the
  drinking water treatment plant.
• Trihalomethanes include trichloromethane
  (chloroform), brominedichloromethane (1 bromine,
  2 chlorines), dibromochloro-methane (2 and 1) and
  tribromomethane
• Dibromochloro gt bromoform gt chloroform gt
  bromodichloromethane for cancer risks

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Free Chlorine to kill 99.99 of viruses, Need a
contact time of 50 minmg/L
Chloramines to kill 99.99 of viruses, Need a
contact time of 10,000 minmg/L
Chlorine Dioxide to kill 99.99 of viruses,
Need a contact time of 150 minmg/L
Potassium permanganate and ozone with hydrogen
peroxide, Copper combined with hydrogen
peroxide Silver and hydrogen peroxide Anodic
oxidation
???
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Free Chlorine to kill 99.99 of viruses, Need a
contact time of 50 minmg/L Form worrisome
DBPs Inexpensive
Chloramines to kill 99.99 of viruses, Need a
contact time of 10,000 minmg/L No
trihalomethanes formed at correct pH Better
killing of bacteria in biofilms than Chlorine
Chlorine Dioxide to kill 99.99 of viruses,
Need a contact time of 150 minmg/L
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What is an ideal residual disinfectant? Summary -
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• Protects against contamination
• Can indicate when there is a problem in the
  distribution network by being chemically altered,
  rather than consumed
• Controls biofilms slimy layers inside water
  pipes where bacteria such as Legionella
  (Legionnaires disease agent) can hide

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What is an ideal residual disinfectant? Chemistry
2

• Easily measured (so you know what you are doing)
• Generates minimal or no DBPs
• Lasts a long time in the pipes
• Does not react with the pipes or their linings
• Can tell if contamination has happened as agent
  chemically altered, not consumed)

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What is an ideal residual disinfectant? Physical
Properties 2

• Dissolves in water easily
• Safe to generate, safe to transport, safe to
  store, and safe to put into the water (note in
  Iraq, chlorine tanks being used as explosive
  devices)
• Cost-effective

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What is an ideal residual disinfectant? Activity
against Pathogens Properties 3

• Kills bacteria, protozoa, viruses, algae, fungi
• Kills the above when they are floating in water,
  and when hiding on particles
• Does all of the above at concentrations that are
  safe for people to drink

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What is an ideal residual disinfectant? Aesthetic
Properties 4

• Kills pathogens without creating tastes and odors
  that people find objectionable
• If too much is put in, the overfeed can be
  detected by taste, odor, or color changes

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What Rules Guide Residual Disinfectants? Why? 1

• Surface Water Treatment Rule 1990 have to
  maintain a detectable disinfectant residual in gt
  95 of samples (or heterotrophic bacteria lt
  500/ml) e.g. kills bacteria and viruses
  consistently
• Total Coliform Rule 1990 disinfectant listed as
  a Best Available Technology for compliance with
  maximum coliform contaminant levels

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What Rules Guide Residual Disinfectants? Why? 2

• Disinfection Byproducts Rule (Stage 1)
  established maximum levels for chlorine,
  chloramine, and chlorine dioxide, and the maximum
  contaminant levels for THMs was decreased from
  0.10 mg/L to 0.08 mg/L, set new maxs for
  haloacetic acids, chlorite, and bromate to
  control risks.
• Levels of DBPs, residual disinfectants monitored
  at same sites as for coliforms

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What Rules Guide Residual Disinfectants? Why? 3

• Disinfection Byproducts Rule (Stage 2)
  compliance determined on location specific
  running annual averages and not generic running
  averages
• Stage 1 and Stage 2 rule exist because there is a
  evolving body of knowledge that high levels of
  disinfection byproducts can cause cancer and
  reproductive effects in lab animals and in people.

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More on bad effects of DBPs

• Very good evidence for bladder cancer resulting
  from DBPs 3-10,000 cases per year in the US
  14 all cases in Canada
• Very suspicious for a relationship to adverse
  reproductive effects Stillbirths, Low Birth
  Weight and Very Low Birth Weight Babies, specific
  defects such as ones related to the nervous
  system and the cardiac system. Hundreds of
  scientific studies done led to rule changes.

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Chlorine

• Free chlorine reacts with natural organic matter
  and bromide to form halogenated compounds, such
  as THM, HAAs, and chlorophenols posing health
  risks.
• Also forms non-halogenated compounds, such as
  aldehydes, carboxylic acids, ketones, and
  alcohols
• DBPs generally increase in concentration over
  time in the distribution system

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Chloramines 1

• Formed by chlorine ammonia
• Initially used to control taste and odor
• More stable than chlorine in distribution system
  more effective in controlling bacteria as more
  stable.
• Not as effective as chlorine for primary
  disinfection as requires more contact time.
• Widely used in 1930s and 1940s ammonia shortage
  in WW II led to decreased usage Boston has used
  since 1932.

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Chloramines 2
Chlorine plus ammonia chloramines Monochloramine
NH2Cl if pH 7.5 9 Predominant form if ratio of
chlorine to ammonia 51 or less utilities keep
in range of 31 51 Other potential products
of chlorine plus ammonia Dichloramine
NHCl2 Trichloramines NCl3 (volatile) These form
when chlorine to ammonia ratio Increases, or if
pH is lower
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Nitrite (NO2-) and Nitrate (NO3-)

• Nitrite - Often seen w/ ammonia decomposition,
  e.g. plants, manure, sewage curing meats
• Nitrate fertilizer, decomposition as above
• If ingested at high levels, binds to hemoglobin
  and reduces oxygen carriage especially for
  babies, pregnant women
• 10 ppm nitrate, 1 ppm nitrite, combined 10 are
  maximum contaminant levels
• ? Combine with amines/amides to form nitrosamines
  unclear if this happens, but noted

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Hydrazine N2H4

• A probable human carcinogen levels of 10
  nanograms/L are linked to a one in a million risk
  of cancer.
• No mention but one in the literature of hydrazine
  formation as a by-product of chloramination
• No detectable formation (lt 5 ng/L) under typical
  conditions for chloramination

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Chlorine Dioxide

• Strong disinfectant
• Not a long-lasting residual disinfectant
• When it breaks down, forms chlorite (70), a
  regulated DBP, and (less) chlorate and chloride
  (30)
• In water, exists as a dissolved gas between pH 2
  and 10

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Considerations -

• Chlorine cheap, widely used, clearly linked to
  human cancer and to adverse reproductive outcomes
  (stillbirths, miscarriages) and bad fetal
  development outcomes. Easy to target for
  bioterrorism.
• Chloramines excellent potential to decrease
  known problems relating to the above. Bit more
  expensive. Better than chlorine in controlling
  biofilms

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What are we to make of

• Reports of rashes and respiratory difficulties
  relating to chloramines
• In the published literature, this has been
  related to low pH conditions and excessive use of
  chloramines which favor the production of
  trichloramines.
• Lack of well done, prospective, studies to
  examine this issue.
• Historical experience of cities using chloramines
  for 75 years (Boston) without these health effects

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6 year old boy developed coughing, shortness of
breath, required treatment for allergies Motel
had 26 safety violations, including cloudy
water, free chlorine levels half of the Minimum
required (0.8 ppm, chloramine levels 8 times the
maximum, and pH of 3.95. Likely formation of the
trichloramines led to lung and eye irritation
fans were not operating and very poor
ventilation. Similar to 2 outbreaks in Illinois
in 2004.
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Lead

• Chloramines alter water chemistry
• When used in systems with lead pipes, fixtures,
  or solder, may increase the levels of lead in
  water other agents such as coagulants and
  fluoridation may remove scales of lead dioxide
  built up during chlorine use.
• Managed by use of anti-corrosion agents
• Monitor by checking lead levels in water,
  especially older housing stock.

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Questions?