Water PollutionChapter 20Dave Sang

Nora Tibbetts

20-1 What are the Causes and Effects of Water Pollution?

Causes of Water Pollution

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

Agricultural activities - leading cause

Industrial facilities

Mining

Parking lots

Widespread use of human-made materials (plastics, etc.)

Climate change as a result of global warming

Point Sources

Point sources - discharge pollutants at specific locations through drain pipes, ditches, or sewer lines into bodies of surface water.

Examples: factories, sewage treatment plants, underground mines, oil tankers

Located at specific places, and are easy to identify, monitor, and regulate.

Many developed countries have laws that help to control point-source pollution.

Nonpoint Sources

Nonpoint sources - are broad, and diffuse areas, rather than points, from which pollutants enter bodies of surface water or air.

Examples: runoff of chemicals and sediments from cropland, livestock feedlots, logged forests, urban streets, parking lots, lawns, golf courses

Difficult and expensive to identify and control such discharges, so not much progress has been made.

Effects of Water Pollution

Exposure to infectious disease organisms (pathogens) mostly through contaminated drinking water.

3.2 million people die prematurely each year as a result of contaminated drinking water.

An average of 8,700 premature deaths a day.

20-2What are the Major Water Pollution Problems in Streams and Lakes?

Water Pollution Problems in Streams

Streams can cleanse themselves if we do not overload them: Undergo a natural recovery process

Can remove biodegradable wastes, but not slowly degradable and non-degradable pollutants

The breakdown of biodegradable wastes by bacteria depletes dissolved oxygen and creates an oxygen sag curve

Ohio’s Cuyahoga River

Water pollution control laws enacted in the 1970s have greatly increased the number and quality of waste water treatment plants in the United States and most other developed countries.

Extremely polluted with flammable chemicals.

Prompted by a highly publicized photo of the burning river in 1969, elected officials enacted laws that limited the discharge of industrial wastes into the river and into local sewage systems and provided funds to upgrade sewage treatment facilities.

Today, river is cleaner, no longer flammable, and highly used by boaters and anglers.

Successful use of bottom-up pressure by citizens.

India’s Ganges River

Viewed as a holy river. Each day, large numbers of Hindus bathe,

drink from, or take a dip in the river for religious reasons.

Highly polluted, yet 350 million people live in the Ganges River Basin.

Hindus believe in cremating the dead to free the soul and throwing the ashes into the river.

Indian government plans to build waste treatment plants to ease pollution.

Water Pollution Problems in Lakes

Generally less effective at diluting pollutants than streams are because: Often contain stratified layers that undergo little vertical

mixing

Have little or no flow

Very vulnerable to contamination by runoff

Contaminants can kill bottom life and fish and birds that feed on contaminated aquatic organisms.

Cultural Eutrophication

Cultural eutrophication - over nourishment of aquatic ecosystems with plant nutrients (mostly nitrates and phosphates) because of human activities such as agriculture, urbanization, and discharges from industrial plants and sewage treatment plants.

Produces dense growths or blooms of organisms like algae and cyanobacteria during hot weather or drought.

Reduce lake productivity.

85% of the large lakes near major U.S. population centers have some degree of cultural eutrophication.

Prevention and Reduction of Cultural Eutrophication

Luckily, lakes can usually recover from cultural eutrophication.

Use advanced (and expensive) waste treatment to remove nitrates and phosphates before wastewater enters lakes.

Mechanically remove excess weeds.

Control undesirable plant growth with herbicides and algicides.

Pump air through lakes and reservoirs to prevent oxygen depletion.

20-3What are the Major Pollution Problems Affecting Groundwater and Other Drinking Water Sources?

Major Pollution Problems Affecting Groundwater

Common pollutants can seep into groundwater from numerous sources.

Contaminates are not diluted and dispersed effectively.

Much lower concentrations of dissolved oxygen and smaller populations of decomposing bacteria.

The cold temperatures of groundwater slow down chemical reactions that decompose wastes.

Can take decades to thousands of years for contaminated groundwater to cleanse itself of slowly degradable wastes (like DDT). On a human time scale, non degradable wastes (like toxic lead and arsenic) remain in the water permanently.

Protecting Groundwater

Treating a contaminated aquifer involves eliminating the source of pollution and drilling monitoring wells to determine how far, in what direction, and how fast the contaminated plume is moving.

A computer model is used to project future dispersion of the contaminant in the aquifer.

Develop and implement a strategy to clean up the contamination.

Preventing contamination is the least expensive and most effective way to protect groundwater sources

Purifying Drinking Water

Complex Techniques:

Is usually stored in a reservoir and treated in a purification plant in developed countries.

Countries like Japan are developing plants that process sewer water into drinking water.

El Paso, Texas: 40% of drinking water comes from recycling and purifying waste water.

Orange Country, California: completed the world’s largest plant devoted to making sewer water as pure as distilled water

Simple Techniques:

Exposing a clear plastic bottle filled with contaminated water to intense sunlight

Nanofilters to clean contaminated water

LifeStraw

Laws Protecting Drinking Water Quality

U.S. Safe Drinking Water Act of 1974 - requires the EPA to establish national drinking water standards, called maximum contaminant levels, for any pollutants that may have adverse effects on human health.

Despite this, the UN estimates that 5.6 million Americans drink water that does not meet EPA standards.

Health scientists call for strengthening the U.S. Safe Drink Water Act

Is Bottled Water the Answer?

Between 1976 and 2006, average bottled water consumption per person in the US increased from 7.5 liters (2 gallons) to 113 liters (30 gallons) a year.

About one-fourth of it is ordinary tap water in a bottle.

Bacteria or fungi contaminate about 40% of bottled water.

Many bottles are thrown away without being recycled.

Manufacture of plastic water bottles emits toxic gases and liquids.

Greenhouse gases and other air pollutants are emitted by the fossil fuels burned to make and to deliver bottled water to suppliers.

20-4What are the Major Water Pollution Problems Affecting Oceans?

Ocean Pollution is growing and poorly understood About 40% world population lives on coasts

That population will double by 2050

Ocean pollution has a large effect

85% of sewage in developing countries is dumped untreated into oceans

Cruise ships also dump tons of waste into oceans

This pollution creates and spreads disease

Runoffs release nitrates and phosphates into the water, creating algae blooms

Algae blooms deplete oxygen and kill ocean animals

They also poison seafood, harming humans

Northern Gulf of Mexico

Collects agricultural runoff for 31 states

Has large zone of depleted oxygen due to eutriphication

Many attempts to reduce size

All failed, and zone is still growing

Scientists fear soon it will be uninhabitable

Ocean Oil is a Serious Problem

Oil spills and blowouts spew large amounts of oil into the ocean

Costly to clean up

Most oil pollution comes from leaks from urban runoff

Oil immediately kills many larvae

Oil stuck of birds causes them to drown

Recovery from refined oil usually take triple the time as crude oil

Oil slicks on beaches can destroy fishing and tourist economies

Oil spills can be mechanically cleaned up (booms/skimmers), but only about 15% effective

Preventing pollution is the most important goal (double hull)

20-5How Can We Best Deal with Water Pollution?

We Need to Reduce Surface Water Pollution from Nonpoint Sources

Farmers keep soil vegetated to prevent erosion

Use slow release fertilizer and use buffers to prevent runoff

Use manure for fertilizer

Use less pesticides and use IPM

Laws can Help Reduce Water Pollution from Point Sources

Federal Pollution Control Act

Clean Water Act

Water Quality Act

Sets standards for pollutant limits

EPA : discharge traing policy

Buy credits from other permit holders

Would require heavy scrutiny and gradual lowering of caps

Neither is currently in the policy

Success and Failures of Clean Water Act

Annual wetland loss decreased 80% since 1992

Swimmable US streams increased from 36 to 60%

US population served by sewage treatment increased from 32 to 74%

Number of American getting good water increased from 79 to 94%

40% of streams still too polluted for fishing

Tens of thousands of gas tanks are leaking

Environmentalist want more preventive policies

Very costly to keep testing amounts of water pollution

Sewage Treatment Reduces Water Pollution

25% of US homes use septic tanks

Home wastewater is pumped into the tank

Soil and bacteria are used to treat the water

When the tank fills every few years, it must be pumped into a tank truck

If not maintained, they can cause sewage to back up and

Sewage treatment plants

Sewer pipes bring wastewater to plants

Primary sewage treatment: Physically removes suspended solids with screens/filters

Secondary: Biologically removes dissolved wastes

Tertiary: Uses specialized processes to remove specific pollutants. Very costly

Chlorination: removes disease before discharging

Storm waters can overflow sewer systems and cause sewage discharge

Better to have separate pipe networks

We Can Improve Conventional Sewage Treatment

Composting Toilet Systems

Convert human feces into fertilizer supplement

Cheap, saves water, and saves energy

Wetland Based Sewage Treatment

Series of tanks to purify water

Algae decompose organic waste

Plants take up resulting nutrients

Passes through marsh to filter out more organic waste

Some plants can remove toxins and kill pathogens

Flows into aquarium where microorganisms eaten by snails, which are eaten by larger fish

Fish can be sold as bait or food

Water goes into second marsh for more cleansing

Water can be treated drinkable using UV light

Water is then discharged

Costs as much as conventional sewage plant