Transcript chapter21

Chapter 21
Water Pollution
Core Case Study: Using Nature to
Purify Sewage
 Ecological
wastewater
purification by a living
machine.

Uses the sun and a series
of tanks containing plants,
snails, zooplankton,
crayfish, and fish (that
can be eaten or sold for
bait).
Figure 21-1
WATER POLLUTION: SOURCES,
TYPES, AND EFFECTS
 Point
source: specific location (drain pipes,
ditches, sewer lines)
 Nonpoint source: cannot be traced to a
single site of discharge (atmospheric
deposition, agricultural / industrial /
residential runoff)
Water Quality Factors
 DO
 BOD
 Fecal
coliform 0/100 ml for drinking
water, 200
colonies/100 ml for
swimming
 Chemical analysis
 Indicator species
 Visual analysis
Figure 21-3
Water Pollution Problems in Streams

Oxygen sag curve (5 zones)
 Factors affecting it: volume, temp, flow rate, pH
Figure 21-4
Case Study: India’s Ganges River:
Religion, Poverty, and Health
 Religious
beliefs, cultural traditions, poverty,
and a large population interact to cause
severe pollution of the Ganges River in India.
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Very little of the sewage is treated.
Hindu believe in cremating the dead to free the
soul and throwing the ashes in the holy Ganges.
• Some are too poor to afford the wood to fully cremate.
• Decomposing bodies promote disease and depletes
DO.
POLLUTION OF
FRESHWATER LAKES
 Dilution
of pollutants in lakes is less effective
- Lakes
and reservoirs are often
stratified and undergo little mixing.
- Low flow makes them susceptible
to runoff
- Cultural eutrophication
POLLUTION OF GROUNDWATER
 It
can take hundreds to thousand of years for
contaminated groundwater to cleanse itself of
degradable wastes.
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

Nondegradable wastes (toxic lead, arsenic,
flouride) are there permanently.
Slowly degradable wastes (such as DDT) are
there for decades.
Groundwater has low flow rates, few bacteria, &
cold temps - all slow down recovery time
Avg. recycling time for groundwater = 1400 years
Leaking
tank
Water
table
Groundwater
flow
Free gasoline
dissolves in
Gasoline
leakage plume groundwater
(dissolved
(liquid phase)
phase)
Migrating
vapor phase
Contaminant plume moves
with the groundwater
Water well
Fig. 21-8, p. 502
Case Study: Arsenic in Groundwater a Natural Threat
 Toxic Arsenic
(As) can naturally occur at high
levels in soil and rocks.
 Drilling into aquifers can release As into
drinking water supplies.
 According to WHO, more than 112 million
people are drinking water with As levels 5100 times the 10 ppb standard.

Mostly in Bangladesh, China, and West Bengal,
India.
Solutions
Groundwater Pollution
Prevention
Find substitutes for
toxic chemicals
Keep toxic
chemicals out of
the environment
Install monitoring
wells near landfills
and underground
tanks
Require leak detectors
on underground tanks
Ban hazardous
waste disposal
in landfills and
injection wells
Store harmful liquids in
aboveground tanks with leak
detection and collection
systems
Cleanup
Pump to surface,
clean, and return
to aquifer (very
expensive)
Inject
microorganisms
to clean up
contamination
(less expensive
but still costly)
Pump
nanoparticles of
inorganic
compounds to
remove pollutants
(may be the
cheapest, easiest,
and most effective
method but is still
being developed)
Fig. 21-9, p. 504
OCEAN POLLUTION
 Red
tides
 Dead zones (usually about 61/year)
Figure 21-11
Industry
Nitrogen oxides
from autos and
smokestacks,
toxic chemicals,
and heavy metals
in effluents flow
into bays and
estuaries.
Cities
Toxic metals
and oil from
streets and
parking lots
pollute
waters;
Urban sprawl
Bacteria and
viruses from
sewers and septic
tanks contaminate
shellfish beds
Construction sites
Sediments are washed into
waterways, choking fish and
plants, clouding waters, and
blocking sunlight.
Farms
Runoff of pesticides, manure, and
fertilizers adds toxins and excess
nitrogen and phosphorus.
Closed
shellfish beds
Closed
beach
Toxic sediments
Chemicals and toxic
metals contaminate
shellfish beds, kill
spawning fish, and
accumulate in the
tissues of bottom
feeders.
Oxygen-depleted
zone
Oxygen-depleted zone
Sedimentation and algae
overgrowth reduce sunlight,
kill beneficial sea grasses, use
up oxygen, and degrade habitat.
Red tides
Excess nitrogen causes
explosive growth of
toxicmicroscopic algae,
poisoning fish and
marine mammals.
Healthy zone
Clear, oxygen-rich
waters promote growth
of plankton and sea grasses,
and support Fig.
fish.21-10, p. 505
Oxygen Depletion in the Northern
Gulf of Mexico
 A large
zone of
oxygendepleted water
forms for half of
the year in the
Gulf of Mexico
as a result of
algae blooms.
Figure 21-A
Case Study: The Chesapeake Bay –
An Estuary in Trouble
 Largest
US estuary
 Shallow
 Slow
flushing (1%)
 High phosphates,
nitrates, mercury,
lead
Figure 21-12
OCEAN OIL POLLUTION
 Most
ocean oil pollution comes from human
activities on land.
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
Studies have shown it takes about 3 years for
many forms of marine life to recover from large
amounts of crude oil (oil directly from ground).
Recovery from exposure to refined oil (fuel oil,
gasoline, etc…) can take 10-20 years for marine
life to recover.
OCEAN POLLUTION
CONTRIBUTORS
 Tanker
accidents
 Blowouts
 Pipelines
 Offshore wells
 Runoff
 Dredge spoils
 Sludge
Figure 21-13
Solutions
Coastal Water Pollution
Prevention
Reduce input of toxic pollutants
Cleanup
Improve oil-spill cleanup
capabilities
Separate sewage and storm lines
Ban dumping of wastes and
sewage by maritime and cruise
ships in coastal waters
Ban ocean dumping of sludge and
hazardous dredged material
Sprinkle nanoparticles over an
oil or sewage spill to dissolve
the oil or sewage without
creating harmful by-products
(still under development)
Protect sensitive areas from
development, oil drilling, and
oil shipping
Require at least secondary
treatment of coastal sewage
Regulate coastal development
Recycle used oil
Use wetlands, solar-aquatic,
or other methods to treat sewage
Require double hulls for oil tankers
Fig. 21-14, p. 509
PREVENTING AND REDUCING
SURFACE WATER POLLUTION
 Prevent
runoff
 Buffer zone vegetation
 Reduce erosion
 Clean Water Act - increases
fishable/swimmable lakes, cuts erosion,
increases sewage treatment, decreases
wetland loss
 Water Quality Act - drinking water supplies
Reducing Water Pollution through
Sewage Treatment
 Septic
tanks and various levels of sewage
treatment can reduce point-source water
pollution.
Figure 21-15
Reducing Water Pollution through
Sewage Treatment
 Primary
sewage treatment: a physical
process that uses screens and a grit tank to
remove large floating objects and allows
settling - removes 60% of solids
 Secondary sewage treatment: a biological
process in which aerobic bacteria remove as
much as 90% of dissolved and
biodegradable, oxygen demanding organic
wastes.
Reducing Water Pollution through
Sewage Treatment
 Primary
and Secondary sewage treatment.
Figure 21-16
Reducing Water Pollution through
Sewage Treatment
 Advanced

or tertiary sewage treatment:
Uses series of chemical and physical processes
to remove specific pollutants left (especially
nitrates and phosphates).
 Water
is chlorinated to remove coloration and
to kill disease-carrying bacteria and some
viruses (disinfect).
 Some areas use natural wetlands.
Is Bottled Water the Answer?
 Some
bottled water is not as pure as tap
water and costs much more.
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1.4 million metric tons of plastic bottles are
thrown away.
Fossil fuels are used to make plastic bottles.
• The oil used to produce plastic bottles in the U.S. each
year would fuel 100,000 cars.
Water Laws
 SDWA ‘74
- EPA establishes national
drinking water standards - not on wells
 Water Quality Act ‘65 - established water
quality standards for streams
 Ocean Dumping Act ‘72 - must have permit to
dispose of materials
 Clean Water Act - federal assistance for
sewage treatment, permit to discharge, EPA
sets pollution standards