Ch 17. Water, pollution and its prevention

Chapter 17
What is water pollution
Water pollution can be defined as
"the presence of a substance in the
environment that because of its chemical
composition or quantity, prevents the
functioning of natural processes and
produces undesirable environmental and
(human) health effects."
Categories of Water Pollutants
Main groups of water pollutants
Rapidly degradable (non-persistent)
Slowly degradable (persistent)
Water Pollutants: sources
a. Non-point-source
agricultural runoff,
b. Point-source
discharges from
factories, sewage
systems, power
underground coal
mines, oil wells.
Strategies to bring water pollution
under control:
Reduce or
remove the
Treat the water
to remove
pollutants or
convert them to
harmless forms.
Water pollutants: types
a. Pathogens
b. Organic wastes
c. Chemical pollutants
d. Sediments
e. Nutrients
agents that
sickness and
Come from
from humans
and other
animals that
are infected
Infectious Agent
•Typhoid fever
•Salmonella typhi (bacterium)
Vibrio cholerae (bacterium)
•Salmonella sp. (bacteria)
•Echerichia coli,
•Campylobacter sp. (bacteria)
•Cryptosporidium pavum (protozoan)
•Infectious hepatitis
•Hepatitis A virus
•Shigella sp. (bacteria)
•Entamoeba histolytica (protozoan)
•Giardia intestinales (protozoan)
•Numerous parasitic
•(Roundworms, flatworms)
Public heath
Before mid 1800s: epidemics were common in cities
(typhoid fever, cholera)
After: connection between disease and sewagecarried pathogens
Today: public health measures
 Purification and disinfection of public water supplies with
chlorine and other agents
 Sanitary collection and treatment of sewage wastes
 Maintenance of sanitary standards in all facilities in which
food is processed or prepared for public consumption
 Public education in personal and domestic hygiene
Sanitation = good medicine
Good health is a result of the prevention of disease
through public-health measures
Population in areas where here is little or no sewage
treatment are extremely vulnerable to deadly
Organic wastes
Includes leaves, grass clippings, trash, etc.
Enter water as a consequence of runoff or excessive
aquatic plant growth
As bacteria and detritus feeders decompose organic
matter, they consume dissolved oxygen (DO) in
BOD (biochemical oxygen demand): measures the
amount of organic material in water in terms of how
much oxygen will be required to break it down.
 Fishes and shellfish are killed below a DO of 2 to 3 ppm
 A BOD value for raw sewage is around 250 ppm
Chemical pollutants
Inorganic chemicals: include heavy
metals (lead, mercury, cadmium, nickel,
etc), acids from mine drainage and acid
precipitation, and road salts.
Organic chemicals: include petroleum
products, pesticides, industrial
chemicals (PolyChorinated Biphenyls,
cleaning solvents and detergents)
Erosion from farmlands, deforested slopes,
overgrazed rangelands, construction sites,
mining sites, stream banks and roads increase
the load of sediments.
Inorganic chemicals carried in solution in
all bodies of water are classified as
 Include phosphorus and nitrogen
 Stimulate undesirable plant growth in
the bodies of water.
 Sources include sewage outfalls,
agricultural runoff, lawns and gardens,
golf courses and storm drains.
Water quality standards
National Recommended Water Quality
Criteria (EPA) provides standards for
assessing water pollution.
Lists 158 chemicals and substances as
criteria pollutants and recommends
concentrations for fresh water, salt water
and human consumption
Water quality standards
 Criteria maximum concentration (CMC):
highest single concentration beyond which
environmental impacts may be expected
 Criterion continuous concentration (CCC):
highest sustained concentration beyond
which undesirable impacts may be expected
 Drinking water standards and health
advisories: enforceable under the authority
of the Safe Drinking Water Act (SDWA)
○ Maximum Contaminant levels (MCLs)
Arsenic as a example:
Listed as a human carcinogen
 CMC and CCC values are 340 and 150
g/L for freshwater bodies, and 69 and
36 g/L for saltbodies.
 Drinking water MCL concentration is 10
Other applications to the water
quality criteria
National pollution discharge elimination
system program (NPDES): addresses
point-source pollution and issues
permits to regulate discharges from
industrial sources.
Total maximum daily load
program(TMDL): evaluates all sources
of pollutants entering a body of water,
especially non-point sources
Types of aquatic plants
 Submerged aquatic vegetation (SAV)
 Emergent vegetation
Phytoplankton (algae, protists, cyanobacteria)
What is an oligo-trophic body of
Oligotrophic = low in nutrients
What is a Eutrophic Body of
Eutrophic = well nourished
How do you create a Eutrophic
Body of Water?
1. Nutrient enrichment,
natural or cultural
2. Increased
phytoplankton growth
resulting in increased
3. Loss of sunlight, food
and habitat
4. Depletion of dissolved
oxygen from
decomposition of
phytoplankton by
How to Stop Eutrophication
Attack the symptoms:
 Chemical treatments (with herbicides)
 Aeration
 Harvest aquatic weeds
 Draw water down
How to Stop Eutrophication
Attack the root cause:
 Control point-source pollutants
○ Ban the sale of phosphate detergents
○ Regulate the maximum alowable level of
○ NPDES permits
How to Stop Eutrophication
Attack the root cause:
 Control non-point-source pollutants
○ EPA regulations through the TMDL program
○ Identify pollutants
○ Estimate pollution comming from all sources
○ Estimate the ability of the body of water to
assimilate pollutants
○ Determine the maximum allowable pollution load
○ Allocate the allowable level of pollution among the
different sources
How to Stop Eutrophication
Attack the root cause:
 Best management practices (BMPs)
○ Practices used to minimize erosion, runoff and
○ Methods of soil conservation
When washings from animal facilities are
flushed directly into natural waterways, they
contribute significantly to eutrophication. This
may be avoided by collecting the flushings in
ponds from which both the water and the
nutrients may be recycled.
How to Stop Eutrophication
Attack the root cause:
 Recovery
○ Government practices for the management of
○ Lake washington
History of sewage treatment
Late 1800s: human excrement was disposed in the
outdoor privy
Louis Pasteur and other scientists showed that sewage
borne bacteria were responsible for many infectious
Human wastes started to be disposed through drain
The flush toilet was introduced
Water became unfit to swim in because of sewage
1900: Sewage treatment systems were developed
What is in Raw Sewage
1. Debris and grit: plastic bags, coarse sand, gravel
2. Particulate organic matter: fecal matter, food wastes,
garbage, toilet paper
3. Colloidal and dissolved organic matter: urine, soaps,
detergents and cleaning agents.
4. Dissolved inorganic matter: nitrogen, phosphorus, and
other nutrients
5. Pathogens: bacteria, protozoa, virus
6. Heavy metals, pesticides, and various other toxic
How Do We Remove These
Substances from the Water?
Preliminary Treatment - debris and grit
removed by a bar screen and grit chamber
How Do We Remove These
Substances from the Water?
Primary Treatment - particulate organic
matter removed by primary clarifiers
How Do We Remove These
Substances from the Water?
Secondary Treatments - colloidal and
dissolved inorganic matter removed by
trickling filter systems or activated sludge
How Do We Remove These
Substances from the Water?
Biological Nutrient Removal - dissolved inorganic matter removed
by bacterial denitrification and bacterial uptake of phosphorus
a. Can also be done inorganically by using chemical processes
·Lime causes phosphate to precipitate as insoluble calcium
·Ferric chloride causes phosphate to precipitate as insoluble ferric
b. Removal of the dissolved inorganic matter is not standard
treatment though it is becoming more common
Final Clarification and Disinfection
Meant to eliminate pathogens
 Disinfecting agents
 chlorine gas
 Sodium hypochlorite (chlorox)
 Ozone gas
 Ultraviolet light
BOD values are 10 to 20 ppm (200 ppm
in the incoming sewage)
Many cities are still operating with lower
quality treatments or with no treatment
at all.
Treatment of sludge
Raw sludge
 Most is disposed in landfills with no previous
 It is considered a biologically hazardous
 It is a nutrient-rich organic material with
potential to be used as organic fertilizer
 Methods for treating sludge include:
○ Anaerobic digestion
○ Composting
○ Pasteurization
Anaerobic digestion
Raw sludge is put into large
airtight tanks (sludge
Anaerobic bacteria break
down the organic matter
End products include carbon
dioxide, methane and water
Treated sludge is called
Dewatered it becomes a
sludge cake
Raw sludge is mixed with wood chips
 Placed in piles that allow air circulation
 Aerobic bacteria and other decomposers
break down organic material to rich
humus-like material
The sludge cake is put through ovens to
be pasteurized
 The product is dry, odorless organic
Alternative Treatment Systems
On site wastewater
treatment systems
Using effluents for
Reconstructed wetland
Public Policy
EPA is responsible for overseeing water
 Depends on laws passed by Congress
 Clean water act (CWA) of 1972
○ Required permits for all point source
discharges of pollutants
 Clean water state revolving fund program
○ Gives funds to local governments to build
treatment facilities
Problems and progress
 Non point source
Construction of new
wastewater treatment
Storm water discharges
Sewer overflows
Wetlands protection
Animal feeding
 The number of people
served by adequate
sewage has increased
 Soil erosion has been
 Two-thirds of the nation’s
waterways are safe for
fishing and swimming
 Many rivers have been
cleaned up and restored

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