solutions to water pollution

sprocketflipPétrole et offshore

8 nov. 2013 (il y a 7 années et 11 mois)

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Water Pollution

Chapter 20

Lake Washington

Puget Sound

Due to population growth, treated wastewater dumped, encouraging algae growth. Dead
algae stank and cloudy water resulted. Fish died. Lake was nicknamed Lake Stinko. The
public was alerted and citizens pressured officials to take action. Action was diversion of
effluents into Puget sound. 3 years later the lake had cleared up, fish populations
recovered and public use of Lake Washington resumed. Population is still growing and
this same issue could happen again.

non point source pollution

Terms to Know:

Water pollution
any chemical, biological or physical change in water quality that harms living
organisms or makes water unsuitable for desired use.

point source pollution
discharge pollutants at specific location through drain pipes, ditches or
sewer lines into bodies of water (ex. factories, sewage treatment plants, underground mines, & oil

non point source pollution
broad, diffuse areas, rather than points from which pollutants enter
bodies of surface water or air. (ex. livestock feedlots, logged forests, urban streets, parking lots,
lawns & golf courses)

Read page 533, 1st column***

Human impact
of water

Bacteria :

typhoid fever, cholera,
bacterial dysentery, enteritis


Hepatitis B,

parasitic protozoa:

amoebic dysentery, giardiasis,

parasitic worms:

Water testing: to be considered safe for drinking, no coliform bacteria. safe for swimming:
no more than 200 colonies of bacteria.

sample of raw sewage would have several million colonies of bacteria.

Indicator of water quality: level of dissolved oxygen (DO).

May use an indicator species. Some aquatic animals may not be able to live when the
oxygen level is too low. Bottom dwellers like mussels which feed by filtering water can
indicate the quality of the water. Also plants can be analyzed for the pollutant amount.

What are major water pollution problems in streams & lakes?

section 20

Flowing rivers & streams can recover rapidly from moderate levels of degradable, oxygen
demanding wastes through a combination of dilution & biodegradation of such wastes by

BUT.... this natural recovery process does not work when streams become overloaded
with pollutants or when drought, damming, or water diversion reduces their flow. Neither
will it eliminate slowly degradable and non
degradable pollutants.

oxygen sag curve

stream pollution in developed countries:

*laws enacted in 1970s have increased # & quality of
water treatment plants in U.S.

Some Success stories:

Ohio’s Cuyahoga River

So polluted it caught fire during the 50s & 60s. clean

Thames River in Great Britain:

In 50s it was a flowing smelly sewer. now commercial
fishing thrives, # of fish species is 20x higher.

Still there is a problem sometimes:

Fish kills & drinking water contamination happen on

This is usually due to accidental or deliberate release of
toxic inorganic & organic chemicals by mines.
Sometimes the waste treatment plant malfunctions.
Cropland and animal feedlots can be responsible for
point runoff and excess plant nutrients.

Stream pollution in developing countries

A serious and growing problem

half the world’s 500 rivers are heavily polluted & most run through developing countries
which cannot afford to build water treatment plants & do not enforce or have pollution

Most discharge 80
90% of untreated sewage directly into rivers & streams then using
these same waters to drink bathe and wash clothes.

2/3 of India’s water resources are polluted

1/3 of china’s rivers are unfit for agricultural or industrial use

The man who planted trees to restore a stream

1980. health issues for John Beal to take time off. He started walking, passing a stream every day. The stream was
polluted. He hauled out truck loads of garbage. He planted thousands of trees over 15 years. He restored natural
waterfalls, ponds & salmon spawning beds. He inspired others to help him. Today the water is clear.

read page 538

solutions: water treatment plants being built (not yet and
they do not work very well)

other problems: Gangotri Glacier which is the source of
the Ganges River, is melting at a rapid rate. This will be
a loss of water devastating to the 400 million people in
the Ganges Basin.




a place to

bathe, drink

from, swim in,

bury the dead

& pray.

What about lakes & reservoirs?

less effective at diluting pollutants than streams

because: 1) contain stratified layers that do not mix

2) have little or no flow

so....flushing and changing of water in lakes & reservoirs can take from 1 to 100 years
compared to several days or weeks for the change of water in a stream

natural nutrient enrichment of a shallow lake, estuary or stream

cultural eutrophication
: human activities accelerate the input of plant nutrients. ex. farmland, feedlots, yards
mining sites, discharge of municipal sewage.

ways to prevent or reduce cultural eutrophication:

use advanced waste treatment to remove nitrates & phosphates before wastewater enters

ban or limit the use of phosphates in detergents & cleaning agents.

employ soil conservation & land use control to reduce runoff

clean up
: mechanically remove weeds

control undesirable growth with herbicides

pump air through lakes

read page 541

Great Lakes contain 95% of the fresh surface water in the

What are the major pollution problems affecting groundwater & other drinking water

section 20

ground water cannot cleanse itself.

drinking water for about 1/2 of u.s. population comes from groundwater

common pollutants: fertilizers, pesticides, gasoline, organic solvents.

once a pollutant contaminates groundwater it fills the aquifer’s porous layers of
sand, gravel or bedrock like water saturates a sponge.

This makes removal difficult.

movement of groundwater is slow

less than .3 meter per day

groundwater has lower oxygen concentration so decomposing bacteria less

usually cold temperature of groundwater slows down chemical reactions that
decompose waste.

can take thousands of years for poisons like DDt to degrade , so on a human
timescale these are non
degradable wastes.

groundwater pollution threats

read page 543

Arsenic contamination in drinking wells: can cause premature death due to skin, bladder
& lung cancer

problem in western half of our country

research done at Rice University to remove arsenic from water

preventing contamination is the least expensive and most effective way to protect

Ways to purify drinking water

store in reservoir to improve clarity :& taste

process waste water for drinking water

researchers developing nanofilters to clean contaminated water


solutions to groundwater pollution


substitute for toxic chemicals

keep toxins out of environment

install monitoring wells near landfills & underground tanks

require leak detectors on underground tanks

ban hazardous waste disposal in landfills & injection wells

store harmful liquid in above ground tanks w/ leak detection & collection

clean up

pump to surface, clean & return to aquifer

inject microorganisms to clean up contamination

pump nano particles of inorganic compounds to remove pollutants

What are the major water pollution problems affecting oceans?

section 20

coastal areas bear the brunt of our pollution & waste dumped in the ocean.

80% of marine pollution originates on land

dumping overwhelms ability of coastal waters to degrade waste

many want to deposit sewage sludge in deep ocean

cruise ship pollution ,

page 548

viral infections harbored in raw sewage near shoreline

harmful algal blooms deplete oxygen.

called dead zones because oxygen level is so low

200 dead zones and increasing
read page 550 dead zone in Gulf of mexico

oil pollution in ocean: tanker accidents & blowout at offshore drilling sites

Largest sources of ocean oil pollution is urban & industrial runoff from land.

VOC’s kill aquatic organisms, coat feathers of birds & fur of marine mammals

Heavy oil sinks to ocean floor & smothers bottom dwellers

exposure to crude oil: recovery w/in 3 years

exposure to refined oil: recovery between 10

20 years.

Ocean pollution

solution to coastal water pollution


reduce input of toxins

separate sewage & storm lines

ban dumping by ships

regulate coastal development, oil drilling & oil shipping

require double hulls for oil tankers

clean up:

improve oil clean up technology

use nanoparticles on sewage & oil spills

require secondary treatment of coastal sewage

use wetlands, solar aquatic, etc. to treat sewate

How can we best deal with water pollution

section 20

reduce surface water pollution from non
point sources

farmers: reduce soil erosion, reduce fertilizer runoff; plant buffer zones of vegetation b/n cultivated fields

use manure for fertilizer;use pesticides only when needed rely on integrated pest management; tougher pollution regulation

Laws can help reduce water pollution from point sources

federal water pollution control act of 1972

1987 water quality act

sets standards for allowed levels of key water pollutants

requires polluters to get permits limiting discharge amounts

read page 553, case study for successes in reducing point source pollution

septic tank needs suitable soil

used in 1/4 of u.s. homes

household sewage & wastewater is pumped into a settling tank, where
grease & oil rise to the top & solids fall to the bottom & are decomposed by

the resulting partially treated wastewater is discharged into a large drainage
field through small holes in perforated pipes embedded in porous gravel or
crushed stone just below the soil’s surface

As these wastes drain from the pipes and percolate downward, the soil filters
out some potential pollutants and soil bacteria decomposes biodegradable

Sewage treatment

primary sewage treatment is physical
(use screens; grit tanks, removes suspended solids)

secondary sewage treatment is a biological process

(uses bacteria but does not
remove radioactive isotopes or pathogens)

advanced, 3rd level treatment uses chemicals and physical processes to
remove specific pollutants remaining.

before discharge, bleaching, disinfection, chlorination

Suggested improvements to conventional sewage treatment

composting toilet systems

wetland based sewage treatment systems.

living machine waste treatment

(insert page 556)

sewage flows into passive solar greenhouse containing rows of large open tanks
populated by increasingly complex series of organisms

through which in ten days clear water flows into a marsh

for final filtering and cleansing.

operating costs are about the same as conventional sewage treatment plant.

solutions to water pollution

prevent groundwater contamination

reduce non
point runoff

reuse treated wastewater for irrigation

find substitutes for toxic pollutants

work with nature to treat sewage

practice the three r’s of resource use

reduce air pollution

reduce poverty

slow population growth