Transcript Miller ch 20 my notes water pollution16th ed

Chapter 20
Water Pollution
Types of Water Pollution
Pathogens
• disease causing agents
– bacteria, viruses, protozoa, parasitic worms
– lack of clean drinking water causes 80% of diseases in
developing countries
– coliform bacteria
WHO recommends 0 colonies/100 ml drinking water
EPA recommends 200 colonies/100ml swimming water
Oxygen Demanding Wastes
• organic waste decomposed by aerobic
bacteria
– can be determined by BOD
– BOD: amount of O2 consumed by decomposers
in 5 days at 20oC
Water
Quality
Do (ppm) at 20˚C
Good
8-9
Slightly
polluted
6.7-8
Moderately
polluted
Heavily
polluted
Gravely
polluted
4.5-6.7
Below 4.5
Below 4
Fig. 19.2, p. 478
Water Soluble Inorganic
Chemicals
• acids, salts, metal compounds, e.g.methyl
mercury
Inorganic Plant Nutrients
• nitrate, phosphate ----> algae bloom --->
oxygen demanding waste
• drinking nitrates lowers oxygen carrying
capacity in blood (blue baby syndrome can
kill unborn and young children)
Organic Chemicals
• Oil, gasoline, pesticides, plastics, antifreeze
Sediment
•
•
•
•
From erosion mostly
Clouds water, blocks photosynthesis
Buries feeding, spawning sites for fish
Clogs shipping lanes, rotors in hydroelectric
dams, reservoirs behind dams
Water Soluble Radioactive Waste
• What? Radioisotopes of iodine, radon,
uranium, cesium, and thorium
• Sources: emitted from nuclear and coalburning power plants, mining, nuclear
weapons production, natural sources
• Health effects: genetic mutations, birth
defects, cancer
Thermal Pollution
• Solubility of O2 down, respiration up, so
less DO
• At startup or shutdown of power plant for
repair, thermal shock
• Some call it thermal enrichment since it
extends fishing season, etc
Genetic Pollution
• Introduced (exotic) species
– Zebra mussel
Detection of Pollutants
• Chemical analysis
• Indicator species (filter feeding mussel:tissues can
be analyzed)
• Computer models (e.g. air pollutants contribute
30% nitrate to Chesapeake bay)
• Point sources
– Controlled in developed, not developing
• Nonpoint sources (runoff)
– Expensive to identify
Pollution of Lakes and Streams
• Cuyahoga and Thames rivers have
recovered
Types of
organisms
Clean Zone
Decomposition
Zone
Septic Zone
Normal clean water organisms
(Trout, perch, bass,
mayfly, stonefly)
Trash fish
(carp, gar,
Leeches)
Fish absent, fungi,
Sludge worms,
bacteria
(anaerobic)
Recovery Zone
Trash fish
(carp, gar,
Leeches)
8 ppm
Clean Zone
Normal clean water organisms
(Trout, perch, bass,
mayfly, stonefly)
8 ppm
Concentration
Dissolved oxygen
Oxygen sag
Biological oxygen
demand
2 ppm
Direction of flow
Point of waste or
heat discharge
Time of distance downstream
Fig. 19.3, p. 479
Problems of Lakes
• Stratified water
– Little vertical mixing so little DO on bottom
• Acid deposition
– Little dilution b/c little mixing
• DDT, PCBs (polychlorinated biphenyls)
– Can be biomagnified
Water
0.000002 ppm
Herring gull
124 ppm
Phytoplankton
0.0025 ppm
Herring gull eggs
124 ppm
Lake trout
4.83 ppm
Zooplankton
0.123 ppm
Rainbow smelt
1.04 ppm
PCBs are
biomagnified
Fig. 19.4, p. 481
Cultural Eutrophication
• Cause-->bloom--> die off-->
aerobic bacteria-->DO down-->
anaerobic bacteria -->hydrogen sulfide gas (toxic)
• Prevention
– Limit phosphate (detergent)
– Advanced waste water treatment
– Soil conservation
• Cleanup
– Dredging, remove excess weeds, pump air into lakes
Lake Washington
• Formerly received municipal sewage
effluent from Seattle
• Recovered in 4 years when sewage diverted
to Puget Sound
• Puget Sound enjoys a rapid rate of exchange
with Pacific Ocean
• The solution to pollution is dilution
Case Study: Great Lakes
•
•
•
•
Formed from retreating glaciers 10,500 ya
Little flow (1% out) so toxins concentrate
Acids, pesticides, etc from air deposition
During 1960’s, Lake Erie dies
– $20 billion later, Lake Erie has decreased toxin
levels
1/4 of fish from Great lakes is unsafe for human
consumption
Great Lakes
Nonnative Species
• Zebra mussel arrived in 1986, in water discharged
from a European ship near Detroit
– No natural enemy
– Depletes food supplies, clogs irrigation pipes, shuts
down water intake to power plants and city water, fouls
beaches, grows on boat hulls
– Costs Great Lakes basin $500 million/yr
– Good news: they eat algae, clarify water , increase
photosynthesis and DO
Quagga Mussel
• Invaded Great Lakes in 1991
– Can tolerate more extreme temperatures so
Chesapeake Bay or Florida next?
Lake Baikal
• Siberia, world’s largest fresh water lake
• 20 million years of evolution so biodiverse
• 2 paper mills built in 1960’s
– One converted to furniture factory
– Example of sustainable development
Groundwater Pollution
Prevention
• Harder to eliminate pollution naturally: colder,
lower rate of flow (1 foot per day), low DO so less
decomp from oxygen and aerobic bacteria
• US Geological Survey: 9% of drinking water in
US has high nitrate levels
• 25% of all aquifers are contaminated
• Naturally occuring arsenic may enter aquifer
• 1 million underground tanks are leaking
• German company has developed process to
convert nitrates to nitrogen
Groundwater Pollutants
• MTBE is a gasoline additive
– Suspected carcinogen since 1990s
– Being phased out, but lasts for decades
– Leaks from underground storage tanks
Nitrates convert to nitrites causing “blue baby
syndrome”
Polluted air
Hazardous waste
injection well
Coal strip
mine runoff
Pesticides
and
fertilizers
De-icing
road salt
Buried gasoline
and solvent tank
Pumping
well
Cesspool
septic tank
Gasoline station
Waste lagoon
Water
pumping well
Sewer
Landfill
Leakage
from faulty
casing
Accidental
spills
Discharge
Confined
aquifer
Groundwater
flow
Figur
Ocean Pollution
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; sewage
adds nitrogen and
phosphorus.
Urban sprawl
Bacteria and
viruses from sewers
and septic tanks
contaminate shellfish
beds and close
beaches; runoff
of fertilization from
lawns adds nitrogen
and phosphorus.
Figure 22-11
Page 504
Closed
beach
Construction sites
Sediments are washed into waterways,
choking fish and plants, clouding
waters, and blocking sunlight.
Farms
Run off of pesticides, manure, and
fertilizers adds toxins and excess
nitrogen and phosphorus.
Red tides
Excess nitrogen causes explosive
growth of toxic microscopic algae,
poisoning fish and marine mammals.
Closed
shellfish beds
Oxygen-depleted
zone
Toxic sediments
Chemicals and toxic metals
contaminate shellfish beds,
kill spawning fish, and
accumulate in the tissues
of bottom feeders.
Healthy zone
Clear, oxygen-rich waters
promote growth of plankton
and sea grasses, and support fish.
Oxygen-depleted zone
Sedimentation and algae
overgrowth reduce sunlight,
kill beneficial sea grasses,
use up oxygen, and degrade habitat.
Figure 22-12
Page 505
Mississippi
River Basin
Missouri
River
Ohio
River
Mississippi
River
LOUISIANA
Mississippi
River
Depleted
Oxygen
Gulf of Mexico
Pros
• Marine life in oceans is more resilient than
previously thought
• Is ocean dumping worse than landfilling or
incinerating?
Coastal Areas
• Most polluted areas are near big cities, 85%
of municipal waste is dumped untreated in
Mediterranean Sea
• In US, 35% ends up untreated in ocean,
bays and harbors
• Baywatch actors got extra pay for entering
Santa Monica bay
Chesapeake Bay
• Point sources e.g. sew treatment plants--> 60% of
phosphates
• Nonpoint sources --> 60% of nitrates
– Air pollution --> 35% nitrates
• Commercial fishing, decline since 1960’s due to
overfishing, pollution and disease
• 1980’s, Chesapeake Bay program (ICM)
– Composed of state, fed, indust, sport, envir, etc
– Results: P levels down 27%, N down 16%,
– So submerged veg up 75%
Cooperstown
NEW YORK
PENNSYLVANIA
ATLANTIC
OCEAN
Harrisburg
NEW
JERSEY
MARYLAND
Baltimore
WEST
VIRGINIA
Washington
DELAWARE
Richmond
VIRGINIA
Drainage
basin
Norfolk
Chesapeake Bay
No oxygen
Low concentrations
of oxygen
Fig. 19.13, p. 490
Ocean Pollutants
• Dredge spoils (from dredging: metals, etc)
• sewage sludge (from sewage treatment
plant) dumping, banned in US, since 1992
• London dumping convention, 1972
– 100 countries agreed: no dumping toxics in
open sea
Oil in Oceans
In normal operations 1000x more oil is
spilled per year than the Exxon Valdez
oil from oil changes=20x Valdez
• Cleanup?
– Mechanical methods
• Booms, skimmer boats, absorbent pads (on beaches)
• Chemical methods: coagulating agents, dispersing
agents, fire, natural action
Exxon Valdez
•
•
•
•
March 24, 1989, Prince William Sound
Double hull could have prevented spill
Best technology can only recover 11-15%
Oil Protection Act, 1990 is ineffective
Solutions
Nonpoint
• (agriculture): fertilizer (rotate crops),
pesticide use down
– Collect runoff in retention basin, use as
fertilizer
– Reforest to lower erosion
Solutions
Point
• Laws
– Water Pollution Control Act, 1972
– Success: % lakes swimable and fishable
36--->62%
• Became Clean Water Act, 1977
-Water Quality Act, 1987
-discharges trading policy, EPA, 1995 sell credits
Solutions
Technology
• Septic tanks are used by 25% of all US
homes, should be cleaned out every 3-5
years
• 1200 US cities (including Wilmington) have
combined wastewater, stormwater pipelines
Sewage Treatment
• Primary: mechanical-let solids settle out
• Secondary: aerobic bacteria remove 90% of
organic waste
– Trickling filters:sewage seeps through crushed
stone (bacteria and protozoa ) 202 in WC
– Or Activated sludge: bacteria rich sludge and
air bubbles
– Doesn’t do much for removal of chemicals
Sewage Treatment
• Advanced
– Removes nitrates and phosphates, expensive
– May use reverse osmosis or flocculation (ppt)
• Chlorinated water
– may cause 7-10% of cancer in US
– Ozone or UV can be used as a substitute
• Sludge as fertilizer
– May lead to health problem (metals)
• Natural methods, using bacteria and plants is
better than secondary treatment
(1) Raw sewage drains by
gravity into the first pool
and flows through a long
perforated PVC pipe into
a bed of limestone gravel.
(3) Wastewater flows through
another perforated pipe
into a second pool, where
the same process is repeated.
Sewage
Treated
water
Wetland type
plants
First concrete pool
Wetland type
plants
45 centimeter
layer of limestone
gravel coated with
decomposing bacteria
(2) Microbes in the limestone gravel
break down the sewage into
chemicals, that can be absorbed
by the plant roots, and the gravel
absorbs phosphorus.
Second concrete pool
(4) Treated water flowing from the
second pool is nearly free of
bacteria and plant nutrients.
Treated water can be recycled
for irrigation and flushing toilets.
Fig. 19.17, p. 497
Secondary
Primary
Bar screen
Grit
chamber
Settling tank
Aeration tank
Settling tank
Chlorine
disinfection tank
To river, lake,
or ocean
Raw sewage
from sewers
(kills bacteria)
Sludge
Activated sludge
Air pump
Sludge digester
Sludge drying bed
Disposed of in landfill or
ocean or applied to cropland,
pasture, or rangeland
Fig. 19.15, p. 494
Septic tank
Nonperforated
pipe
Manhole (for
cleanout)
Household
wastewater
Perforated
pipe
Distribution
box
(optional)
Drain
field
Vent pipe
Gravel or
crushed
stone
Fig. 19.14, p. 494
Waste lagoon,
pond, or basin
Hazardous
waste
injection
well
Mining
site
Water
pumping
well
Pumping
well
Road
salt
Buried gasoline
and solvent
tanks
Sewer
Landfill
Cesspoll,
septic
tank
Leakage
from faulty
casing
Unconfined freshwater aquifer
Groundwater
Confined freshwater aquifer
Groundwater flow
Confined aquifer
Discharge
Fig. 19.9, p. 487
Industrial
pollution
Suffocated
fish
Beaches
closed
Sewage
runoff
Dead algae
Low
dissolved
oxygen
Mercurytainted fish
Decreased fish
population
Fig. 19.8a, p. 485
Fig. 19.6, p. 483
Discharge of untreated
municipal sewage
(nitrates and phosphates)
Nitrogen compounds
produced by cars
and factories
Discharge of
detergents
( phosphates)
Discharge of treated
municipal sewage
(primary and secondary
treatment:
nitrates and phosphates)
Lake ecosystem
nutrient overload
and breakdown of
chemical cycling
Dissolving of
nitrogen oxides
(from internal combustion
engines and furnaces)
Natural runoff
(nitrates and
phosphates
Manure runoff
From feedlots
(nitrates and
Phosphates,
ammonia)
Runoff from streets,
lawns, and construction
lots (nitrates and
phosphates)
Runoff and erosion
(from from cultivation,
mining, construction,
and poor land use)
Fig. 19.5, p. 482
CANADA
Nipigon Bay
Jackfish Bay
Thunder Bay
Silver Bay
St. Mary’s R.
St. Lawrence R.
Spanish R.
St. Louis R.
MICHIGAN
Penetary Bay
Sturgeon Bay
WISCONSIN
MICHIGAN
Saginaw
Bay
Niagara Falls
NEW
Saginaw R.
Grand R.
System
Niagara R.
St. Clair R. Thames R.
Buffalo R.
Detroit R.
Rouge R.
Raisin R.
Ashtabula R.
Cuyahoga R. PENNSYLVANIA
Maumee R.
Rocky R.
Black R.
MINNESOTA
IOWA
ILLINOIS
INDIANA
YORK
OHIO
Great Lakes drainage basin
Most polluted areas, according to the Great Lakes Water Quality Board
“Hot spots” of toxic concentrations in water and sediments
Eutrophic areas
Fig. 19.7, p. 484
Suburban
sprawl
Clear
water
PCB’s in
sediment
Lower
water
levels
High
dissolved
oxygen
Thriving fish
population
Fig. 19.8b, p. 485
Contaminated Probability
10 to 20 percent
Greater than 20 percent
Not tested
Fig. 19.10, p. 488