Transcript Drinking water contaminants

Water Quality
Monroe L. Weber-Shirk
School of Civil and
Environmental Engineering
Water Quality
History of our understanding of waterborne
disease
Brief history of water treatment
Drinking Water Standards: how do we
decide what is allowed in the water we
drink?
Germ theory
 Pasteur (1822-1895)
 Proved that microorganisms cause fermentation and
disease
 Lister (1827-1912)
 Founder of antiseptic medicine and a pioneer in
preventive medicine
 Koch (1843-1910)
 One of the founders of the science of bacteriology
 Discovered the tubercle bacillus (1882) and the cholera
bacillus (1883)
The Flush Toilet’s Connection to
Disease
In the early 1800s new flush toilets and
sewers carried the waste directly into rivers
and streams
London drained its raw sewage into and
withdrew its drinking water from the
Thames River, both without any treatment.
Several of the drinking water intakes were
below sewage outfalls!
Southwark and Vauxhall Water
Company
 In 1850, the microbiologist Arthur Hassall wrote of the
River Thames water they were using,"...a portion of the
inhabitants of the metropolis are made to consume, in
some form or another, a portion of their own excrement,
and moreover, to pay for the privilege."
 Next Cartoon presents John Edwards, owner of the
Southwark Water Company, posing as Neptune
("Sovereign of the Scented Streams"). He is seen crowned
with a chamber-pot, seated on a stool on top of a cesspool
which doubles as the water-intake for the Southwark Water
Company customers in south London.
Southwark and Vauxhall Water
Company
Courtesy of the National
Library of Medicine
Drinking Water Treatment and
Germ Theory
 1829: First sand filter used to treat some of
London's drinking water
 1850: John Snow established the link between
drinking water (from a contaminated well) and
Cholera
 1872: Poughkeepsie, NY installs first filter in US
 1885: Sand filters are shown to remove bacteria
 1892: Cholera outbreak in Hamburg, Germany
1892 Cholera outbreak in
Hamburg Germany
Altona's water
intake and
filter beds
Altona
Hamburg
Hamburg's sewer outfalls
Hamburg's water intake
Elbe River
 Large outbreak of Cholera in Hamburg
 17,000 cases; 8,600 deaths
 Very few cases in neighborhoods served by Altona's
filtered water supply
 Hamburg's sewers were upstream from Altona's intake!
Altona vs. Hamburg: Cholera Cases
Cholera cases
Cases in Altona acquired in Hamburg
Received water from Altona
Conclusions
Altona
Cholera was waterborne
Slow sand filtration
may have protected
Altona
Hamburg
Disease Definitions
Pathogen: an agent that causes infection in a
living host. It acts as a parasite within the
host or host cells and disrupts normal
physiological activities
Infection: growth of a disease-producing
organism within the host
Virulence: ability of the pathogen to inflict
damage on the host
Epidemic
An occurrence of disease that is temporarily
of high prevalence
An epidemic occurring over a wide
geographical area is called a pandemic
Epidemics require
an infected host
_________________________
a number of non-infected potential hosts
__________________________
a mechanism of pathogen transfer
__________________________
Waterborne Threats to Human
Health
 Infectious diseases
 caused by viruses, bacteria, protozoa (pathogens)
 Noninfectious diseases
 _____:
acute caused by short term exposure to harmful
chemicals
 _______:
chronic caused by long term exposure to harmful
chemicals
 low levels of exposure to certain chemicals over a long period
of time may cause cancer, liver and kidney damage, or central
nervous system damage
Pathogens: Protozoa
Organism
Disease
Information
Giardia lamblia
Giardiasis
FDA
Entamoeba histolytica Amebiasis
FDA
Cryptosporidium parvum cryptosporidiosis
FDA
Cyclospora cayetanensis
FDA
Pathogens: Bacteria
Organism
Vibrio cholerae
Shigella spp.
Salmonella typhi
Disease Information
Cholera
FDA
Shigellosis
FDA
Typhoid
FDA
Enterotoxigenic Escherichia coli Gastroenteritis FDA
Pathogens: Viruses
Organism
Disease
Information
Hepatitis A virus
Hepatitis
FDA
Hepatitis E virus
Hepatitis E
FDA
Norwalk virus viral gastroenteritis FDA
Propose a Drinking Water
Standard
 You have been granted the authority to regulate
drinking water quality. Create a standard for the
concentrations of disease-causing organisms in
drinking water.
 In the absence of technological/economic
constraints,
 Which pathogens would you regulate?
 What concentration would you choose?
 Given technological and economic constraints
how might you change your regulation?
Setting the standards
Optimal Pathogen Exposure
 Should we be exposed to small doses of pathogens
so we build up our resistance?
 How could we build pathogen exposure into our
daily lives?
 Potential application
 Common cold (continues to mutate)
 Norwalk virus (Immunity, however, is not permanent
and reinfection can occur after 2 years)
 HIV (no immunity)
Typhoid mortality rate
(per 100,000)
Philadelphia Typhoid
100
Typhoid
Filtration
Chlorination
10
1
0.1
1900
1910
1920
Year
1930
1940
Optimal Pathogen Dose?
Safe Drinking Water Act (1974)
 Specific standards for drinking water
 primary (__________)
mandatory
 secondary (__________
suggested upper limits for non-health
related parameters)
 Applicable to all water supplies serving more than
25 people or having 15 or more service
connections
 Enforced by U.S. Environmental Protection
Agency
Primary Standards: (Health)
Inorganic chemicals (units of mg/L)
Contaminant
Antimony
Arsenic
Asbestos (fiber >10 micrometers)
Barium
Beryllium
Cadmium
Chromium (total)
Copper
Cyanide (as free cyanide)
Fluoride
Lead
Inorganic Mercury
Nitrate (measured as Nitrogen)
Nitrite (measured as Nitrogen)
Selenium
Thallium
U.S. EPA
0.006
0.01
7 MFL
2
0.004
0.005
0.1
Action Level=1.3; TT8
0.2
4.0
Action Level=0.015; TT8
0.002
10
1
0.05
0.002
A Few Organic Chemicals
(units of mg/L) see the complete list!
Contaminant
MCLG
MCL
Acrylamide
Alachlor
Atrazine
Benzene
1-1-Dichloroethylene
Dioxin (2,3,7,8-TCDD)
zero
zero
0.003
zero
0.007
zero
TT7
0.002
0.003
0.005
0.007
0.00000003
Epichlorohydrin
Ethylbenzene
Ethelyne dibromide
Lindane
Polychlorinated biphenyls (PCBs)
Tetrachloroethylene
Toluene
Total Trihalomethanes (TTHMs)
Trichloroethylene
Vinyl chloride
Xylenes (total)
zero
0.7
zero
0.0002
zero
zero
1
none5
zero
zero
10
TT7
0.7
0.00005
0.0002
0.0005
0.005
1
0.10
0.005
0.002
10
Secondary Standards:
Aesthetics
Contaminant
Aluminum
Chloride
Color
Copper
Corrosivity
Fluoride
Foaming agents
Iron
Manganese
Odor (Threshold Odor Number)
pH
Silver
Sulfate
Total dissolved solids
Zinc
U.S. EPA, 1993
0.5-0.2 mg/L
250 mg/L
15 color units
1.0 mg/L
Noncorrosive
2.0 mg/L
0.5 mg/L
0.3 mg/L
0.05 mg/L
3 TON
6.5-8.5
0.1 mg/L
250 mg/L
500 mg/L
5.0 mg/L
WHO, 1984
0.2 mg/L
250 mg/L
15 color units
1.0 mg/L
0.3 mg/L
0.1 mg/L
6.5-8.5
400 mg/L
1000 mg/L
5.0 mg/L
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How do they determine MCLGs?
 Determine NOAEL (No Observed Adverse
Effect Level) by experimental data on humans or
animals
 Divide NOAEL by uncertainty factor (UF)
 UF = 10 when good data on humans available
 UF = 100 when good data on animals available
 UF = 1000 when no good data available
 To get reference dose
 Determine drinking water equivalent level
Setting the Standards (NonCarcinogens)
 For chemicals that can cause adverse non-cancer
health effects, the MCLG is based on the reference
dose.
 A reference dose (RFD) is an estimate of the
amount of a chemical that a person can be exposed
to on a daily basis that is not anticipated to cause
adverse health effects over a person's ________.
lifetime
 In RFD calculations, sensitive subgroups are
included, and uncertainty may span an order of
magnitude.
MCLG Calculations
reference dose
adult body weight
(70 kg)
daily water consumption
(2 liters)
RFD
M
Q
Drinking Water
Equivalent Level
DWEL
Maximum Contaminant
Level Goal
MCLG
mg O
L
M
Nkg day P
Q
kg
L O
L
M
day P
N
Q
RFD M
mg O
L
DWEL 
M
P
Q
NL Q
RFD M
mg O
L
MCLG 0.2 
M
P
Q
NL Q
Example MCLG: Lindane
50 mg/lifetime (exposure over 70 years)
mg O
L
RFD = ________
30x10-6
M
P
kg

day
N Q
Estimate the MCLG
RFD M
MCLG 0.2 
Q
mg
30 10
70kg
kg day
MCLG 0.2 
L
2
day
mg
MCLG=______
0.0002 L

6
L
O
M
NP
Q
Primary Standards : (Health)
Related to Microorganisms
Contaminant
MCLG MCL
Cryptosporidium
zero
TT3
Giardia lamblia
zero
TT3
Cause disease
Legionella
zero
TT3
Viruses (enteric)
zero
TT3
Heterotrophic plate count N/A
TT3
Total Coliforms
zero
5.0%4 Indicators
Turbidity
N/A
TT3 Interferes with
disinfection
Microbial Contaminants
 For microbial contaminants that may present
public health risk, the MCLG is set at zero
because ingesting one protozoa, virus, or
bacterium may cause adverse health effects.
 EPA is conducting studies to determine whether
there is a safe level above zero for some microbial
contaminants.
 The MCL is set as close to the MCLG as feasible,
(the level that may be achieved with the use of the
best available technology, treatment techniques,
and other means which EPA finds are available),
taking cost into consideration.
Treatment Technique (TT)
 When there isn’t an economical and technically
feasible method to measure a contaminant, a
Treatment Technique is set rather than an MCL.
 A treatment technique is an enforceable procedure
or level of technological performance which
public water systems must follow to ensure
control of a contaminant.
 Surface Water Treatment Rule (disinfection and
filtration)
 Lead and Copper Rule (optimized corrosion control).
Indicator Organisms
Impractical to detect, differentiate, or
enumerate all of the pathogenic organisms
that may be present in water
Pathogenic organisms share a common fecal
origin
therefore limit fecal contamination of water
need a measure of fecal contamination
Ideal Indicator Organism
Be present when pathogens are
Not reproduce in the environment
Survive at similar rate to pathogens
Correlate quantitatively with pathogens
Be present in greater numbers than
pathogens
Be easily, accurately and quickly detected
Fecal Contamination Indicator:
Coliform Bacteria
Normally are not pathogenic
Always present in the intestinal tract of
humans and excreted in very large numbers
with human waste
Easier to test for the presence of coliforms
rather than for specific types of pathogens
Are used as indicator organisms for
measuring the biological quality of water
Indicator Organism Failure
Relative viability of pathogens and indicator
organisms
Some pathogens survive for a longer time in the
environment (raw water concentrations are different)
 Effect of treatment processes
Some pathogens are resistant to chlorine
Testing for Coliform Bacteria:
Presence/Absence Tests
 Colisure allows testing for coliform bacteria
and/or E. coli in 24 - 28 hours.
 The detection limit of ColiSure is 1 colony
forming unit (CFU) of coliform bacteria or E.
coli per 100 mL of medium.
 If coliform bacteria are present, the medium
changes color from yellow to a distinct red or
magenta.
 If E. coli are present, the medium will emit a
bright blue fluorescence when subjected to a
long wave (366 nm) ultraviolet (UV) light.
Testing for Coliform Bacteria:
Membrane Filtration
Membrane filter
0.45 μm pores
47 mm in diameter
Filter 100 mL of
water to be tested
through the
membrane filter
Membrane Filtration
Petri dish with
sterile absorbent
nutrient pad
Add 2 mL of mendo broth
(selective
media)
Place membrane
filter in the petri
dish on top of
the nutrient pad
Membrane Filtration:
Incubation and Results
 Incubate for 24 hours at
35°C
 Coliform bacteria grow
into colonies with a
green metallic sheen
 Non-coliform bacteria
may grow into red
colonies
 Coliform concentration
is __________________
8 coliform/100 mL
2
1
5
3
7
4
6
8
Turbidity
 A measure of the scattering of light by particles in
a suspension
 A turbid water sample appears cloudy or “dirty”
 High turbidity is the result of lots of light
scattering caused by the particles in suspension
 Measured in NTU (Nephelometric Turbidity
Units)
cloud
Turbidity Measurements
lens
90° detector
lamp
180° detector
sample cell
170° detector
LED
Turbidity Sensors
(approximate turbidity measurement)
sample cell
90° Detector Output?
90° detector
25
90°
1.2
180°
20
90°/180°
15
180° detector
1
0.8
0.6
10
0.4
5
0.2
0
0
0
100
200
300
400
Turbidity (NTU)
500
600
90°/180°
Detector output (Volts)
1.4
Coagulant Dose
How will you determine coagulant dose for
your water treatment plant?
What will you monitor to decide if
coagulant dose should be increased or
decreased?
Why is it hard to use feedback (data from a
sensor) to set the coagulant dose?
Summary
The causes of waterborne disease have been
identified
Indicator organisms are used to measure the
extent of fecal contamination
Standards for microbiological and chemical
contaminants have been set by US EPA
Waterborne disease continues to be a
significant public health concern especially
for the poorest 2 billion