Transcript Chapter 14_lecture revised S`13

Chapter 14
Water Pollution
Water Pollution

Water pollution- the contamination of streams, rivers, lakes,
oceans, or groundwater with substances produced through
human activities and that negatively affect organisms.

Point sources- distinct locations that pump waste into a
waterway.

Nonpoint sources- diffuse areas such as an entire farming
region that pollutes a waterway.
Human Wastewater

Water produced by human activities such as human
sewage from toilets and gray water from bathing
and washing clothes or dishes.
Three reasons scientists are concerned about
human wastewater:

Oxygen-demanding wastes like bacteria that put a
large demand for oxygen in the water

Nutrients that are released from wastewater
decomposition can make the water more fertile
causing eutrophication

Wastewater can carry a wide variety of diseasecausing organisms.
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
Biochemical Oxygen Demand (BOD)

BOD- the amount of oxygen a quantity of water uses
over a period of time at a specific temperature.

Lower BOD values indicate the water is less
polluted and higher BOD values indicate it is more
polluted by wastewater.
Oxygen Demanding
Wastes
• organic waste decomposed by aerobic
bacteria
• can be determined by BOD
• BOD: amount of O consumed by
2
decomposers in 5 days at 20oC
Mississippi
River Basin
Ohio
River
Missouri
River
Mississippi
River
LOUISIANA
Mississippi
River
Depleted
Oxygen
Gulf of Mexico
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
Eutrophication

Eutrophication is an abundance of fertility to a body
of water.

Eutrophication is caused by an increase in nutrients,
such as fertilizers.

Eutrophication can cause a rapid growth of algae
which eventually dies, causing the microbes to
increase the BOD.
Oxygen Sag Curve
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
Common Diseases from Human
Wastewater

Cholera

Typhoid fever

Stomach flu

Diarrhea

Hepatitis
•
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
Treatments for Human and Animal
Wastewater

Septic systems- a large container that receives
wastewater from the house.
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
Treatments for Human and Animal
Wastewater

Sewage Treatment Plants- centralized plants in
areas with large populations that receive
wastewater via a network of underground
pipes.
Sewage Treatment
•
•
Primary: mechanical-let solids settle out,
screens filter 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
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
•
•
•
•
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
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
Treatments for Human and Animal
Wastewater

Manure lagoons- large, human-made ponds line with
rubber to prevent the manure from leaking into the
groundwater. After the manure is broken down by
bacteria, it is spread onto fields as fertilizers.
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
Chesapeake Bay
•
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
Heavy Metals and Other Substances that can
threaten human Health and the Environment

Lead

Arsenic

Mercury

Acids

Synthetic compounds (pesticides,
pharmaceuticals, and hormones)
•
•
•
•
•
Minamata disease
Identified in 1959
Affects nervous system, first evident in cats
then humans.
Insoluble metallic mercury was dumped in Bay,
bacteria converted it to soluble methylmercury
It worked its way up the food chain
Worldwide reaction helped to spark the
environmental movement
Mad Hatters Disease
• Mercury was used in production of felt
from fur for hats
• Workers worked with fumes in confined
spaces for the long work day
• Characterized by erratic behavior,
memory loss and shyness (Alice in
Wonderland)
World Mercury
Production
Mostly from coal combustion
Acid Mine Drainage
• Groundwater in mines becomes acidic
(low pH)
• Metal atoms dissolve in acid (Fe, Cu, Al,
etc)
• Low pH water mixes with neutral water
and yellow or red iron cmpds precipitate
Study of 139 streams
in US by USGS
• Next page: percentage of streams with
indicated contaminant
Sources of oil in the
ocean
• Consumption of petroleum = water
bottles, etc
Oil Pollution
Oil Spill
Victim
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
Oil in Oceans
1. In normal operations, 1000x more oil is
spilled per year than the Exxon Valdez (1989)
(11 million gallons)
2. Oil from oil changes=20x Valdez
3. Gulf oil leak, 2010 (206 million gallons)
Oil in Oceans
•
Cleanup?
•
Mechanical methods
•
•
Booms, skimmer boats, absorbent pads
(on beaches)
Chemical methods: coagulating agents,
dispersing agents, fire, natural action
Ways to Remediate Oil Pollution

Containment using booms to keep the floating
oil from spreading.

Chemicals that help break up the oil, making
it disperse before it hits the shoreline.

Bacteria that are genetically engineered to
consume oil
Other Water Pollutants

Solid waste pollution (garbage)

Sediment pollution (sand, silt and clay)

Thermal pollution

Noise pollution
Water Laws

Clean Water Act- (1972) supports the “protection
and propagation of fish, shellfish, and wildlife and
recreation in and on the water”.

Issued water quality standards that defined
acceptable limits of various pollutants in U.S.
waterways.
Water Laws

Safe Drinking Water Act- (1974, 1986, 1996) sets the
national standards for safe drinking water.

It is responsible for establishing maximum
contaminant levels (MCL) for 77 different elements
or substances in both surface water and
groundwater.
Pathogens
•
disease causing agents
•
•
•
bacteria, viruses, protozoa, parasitic worms
lack of clean drinking water causes 80% of
diseases in developing countries
coliform bacteria (eg E. Coli)
•
from human waste, indicates possible
pathogens
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
Thermal Pollution
• Solubility of O
2
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
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