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AP Environmental Science

Mr. Grant

Lesson 76

Fresh Water Pollution and Its Control

&

Wastewater and Its Treatment

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Objectives:

• Define the terms point-source pollution and non-point-source pollution.

• Assess problems of water quality and propose solutions to address water pollution.

• Explain how we treat drinking water and wastewater.

• TED - Too much of the world lacks access to clean drinking water. Engineer Michael Pritchard did something about it -- inventing the portable Lifesaver filter, which can make the most revolting water drinkable in seconds. An amazing demo from TEDGlobal 2009.

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Point-Source Pollution: A source of pollution that involves the discharge of wastes from an identifiable point, such as a smokestack or sewage treatment plant.

Non-Point-Source Pollution: A source of pollution that cannot always be traced to an exact point of entry.

Define the terms point-source pollution and non-point-source pollution.

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Assess problems of water quality and propose solutions to address water pollution.

• Water pollution stems from point sources and nonpoint sources.

• Water pollutants include toxic chemicals, sediment, thermal pollution, excessive nutrients, and microbial pathogens,

• Scientists who monitor water quality use biological, chemical, and physical indicators.

• Groundwater pollution can be more persistent and difficult to address than surface water pollution.

• Preventing water pollution is better than mitigation.

• Legislation and regulation have improved water quality in developed nations in recent decades.

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Freshwater pollution and its control

• Water for human consumption and other organisms needs to be:- Disease-free- Nontoxic

• Half of the world’s major rivers are seriously depleted and polluted- They poison surrounding ecosystems- Threatening the health and livelihood of people

• The invisible pollution of groundwater has been called a “covert crisis”

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Point and nonpoint sources of pollution

• Pollution = the release of matter or energy that causes undesirable impacts on the health and well-being of humans or other organisms

• Point sources = discrete locations of water pollution- Factories, sewer pipes- Addressed by the U.S. Clean Water Act

• Nonpoint sources = pollution arises from multiple inputs over larger areas (farms, city streets, neighborhoods)- The major source of U.S. water pollution

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Freshwater pollution sources

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Nutrient pollution

• Nutrient pollution from fertilizers, farms, sewage, lawns, golf courses leads to eutrophication- Fertilizers add phosphorus to water, which boosts

algal and aquatic plant growth- Spreading algae cover the surface, decreasing sunlight- Bacteria eat dead algae, reducing dissolved oxygen- Fish and shellfish die

• Solutions include treating wastewater- Reducing fertilizer application- Using phosphate-free detergents- Planting vegetation to increase nutrient uptake

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Eutrophication is a natural process, but…

• Human activities dramatically increase the rate at which it occurs

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Pathogens and waterborne diseases

• Enter water supplies through inadequately treated human waste and animal waste from feedlots

• Fecal coliform bacteria indicate fecal contamination- They are not pathogenic organisms- But the water may also hold other disease-causing

pathogens (e.g., giardiasis, typhoid, hepatitis A)• Bacterial pollution causes more human health problems

than any other type of water pollution- Conditions are improving- 86% of people now have safe water

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Pathogens cause human health problems

• 1 billion are still without safe water• 2.6 billion have inadequate sewer or sanitary facilities

- Mostly rural Asians and Africans• Health impacts kill 5 million people per year• Solutions:

- Disinfect drinking water- Treat sewage- Public education to encourage personal hygiene- Government enforcement of regulations protecting

food

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Toxic chemicals

• Pesticides, petroleum products, synthetic chemicals- Arsenic, lead, mercury, acid rain, acid drainage from

mines• Effects include poisoned animals and plants, altered

aquatic ecosystems, and decreased human health• Solutions:

- Issue and enforce more stringent regulations of industry

- Modify industrial processes- Modify our purchasing decisions

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Sediment pollution

• Sediment in rivers can impair aquatic ecosystems• Clear-cutting, mining, clearing land for housing, and

cultivating farm fields expose soil to erosion• It dramatically changes aquatic habitats

- Fish may not survive• Solutions:

- Better management of farms and forests- Avoid large-scale disturbance of vegetation

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Thermal pollution

• Water that is too warm causes problems- Warmer water holds less oxygen- Dissolved oxygen decreases as temperature increases - Industrial cooling heats water- Removing streamside cover raises water temperature

• Water that is too cold also causes problems- Water at the bottom of reservoirs behind dams is

colder- When water is released, downstream water

temperatures drop suddenly, killing aquatic organisms

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Indicators of water quality

• Scientists measure properties of water to characterize its quality- Biological indicators: presence of fecal coliform

bacteria, disease-causing organisms, algae, etc.- Chemical indicators: nutrient concentrations, pH,

taste, odor, hardness, dissolved oxygen- Physical indicators: color, temperature, turbidity

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Groundwater pollution is a difficult problem

• Groundwater is increasingly contaminated- But is hidden from view and difficult to monitor- “Out of sight, out of mind”

• Groundwater pollution is hard to address- It retains contaminants for decades and longer- It takes longer for contaminants to break down because

of lower sunlight, microbes, and dissolved oxygen

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Sources of groundwater pollution

• Some toxic chemicals occur naturally- Aluminum, fluoride,

sulfates• Pollution from human

causes wastes leach through soils- Pathogens enter through

improperly designed wells

- Leaking underground storage and septic tanks

So far, the EPA has cleaned up 388,000 leaking tanks

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Agriculture and industry pollute groundwater

• Agricultural pollution comes from several sources- Pesticides are in most of the shallow aquifers tested- Nitrates from fertilizers have caused cancer,

miscarriages, and “blue-baby” syndrome- Pathogens like Escherichia coli (E. coli)

• Manufacturing industries and military sites have been heavy polluters- By-products seep into water from miles around- Radioactive wastes will contaminate water for 750,000

years

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It is best to prevent pollution

• It is far better to prevent pollution than use “end-of-pipe” treatment and cleanup

• Other options are not as good:- Removing just one herbicide from water in the U.S.

Midwest costs $400 million/year- Pumping, treating, and re-injecting it takes too long

• Consumers can purchase sustainably made products- Become involved in local “riverwatch” projects- Urge government to pursue policies to fight pollution

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Legislative efforts reduce pollution

• Water pollution was worse decades ago- Citizen activism and government response resulted in

legislation during the 1960s and 1970s- The situation is much better now

• The Federal Water Pollution Control Act (1972)- Renamed the Clean Water Act in 1977- It is illegal to discharge pollution without a permit- Sets standards for industrial wastewater- Funded sewage treatment plants

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Enforcement of water quality is decreasing

• Underfunded and understaffed state and federal regulatory agencies were pressured by industries and politicians

• Violations of the Clean Water Act have risen to over 100,000 documented violations/year- 10% of Americans are unknowingly exposed to unsafe

drinking water- The new EPA administrator has promised to improve

• Citizens pushed politicians to improve the Great Lakes- The water quality of the lakes has dramatically

improved

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Explain how we treat drinking water and wastewater.

• Municipalities treat drinking water by filtering and disinfection in a multistep process.

• Septic systems are used to treat wastewater in rural areas.

• Wastewater is treated physically, biologically, and chemically in a series of steps at municipal wastewater treatment facilities.

• Artificial wetlands enhance wastewater treatment while restoring habitat for wildlife.

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We treat our drinking water

• Technology and government regulation have improved our pollution control- Treated drinking water is widespread and successful in

developed nations• Before water reaches the user, it is chemically treated,

filtered, and disinfected• The EPA sets standards for over 90 drinking water

contaminants- Local governments and private water suppliers must

meet these standards

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We treat our wastewater

• Wastewater = water people have used in some way- Household, manufacturing, stormwater runoff, etc.- It is treated before being released into the environment

• Septic systems = the most popular method of wastewater disposal in rural areas- Underground septic tanks separate solids and oils from

wastewater- The water drains into a drain field, where microbes

decompose the pollutants- Solid waste is periodically pumped out and landfilled

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Municipal sewer systems

• In populated areas, sewer systems carry wastewater to treatment locations

• Primary treatment = physically removes contaminants in settling tanks (clarifiers)

• Secondary treatment = water is stirred and aerated - Aerobic bacteria degrade organic pollutants- Water treated with chlorine (and/or ultraviolet light) is

piped into rivers or the ocean• Reclaimed water is used for lawns, irrigation, or industry

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A typical wastewater treatment facility

• Sludge = solid material resulting from treatment- Is decomposed

microbially- Then landfilled,

incinerated, or used as fertilizer on cropland

• Methane-rich gas created by decomposition can be burned to generate electricity

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Artificial wetlands clean wastewater

• After primary treatment at a conventional facility- Water is pumped into the wetland- Microbes decompose the

remaining pollutants• Cleansed water is released into

waterways - Or percolates underground

• They are havens for wildlife and areas for human recreation

The U.S. has over 500 artificially constructed or restored wetlands

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TED Video

With cutting-edge nanotech, Michael Pritchard's Lifesaver water-purification bottle could revolutionize water-delivery systems in disaster-stricken areas around the globe.

"On the outside, it looks like an ordinary sports bottle. On the inside, there's a miracle: an extremely advanced filtration system that makes murky water filled with deadly viruses and bacteria completely clean in just seconds."

Allison Barrie, FoxNews.com

Michael Pritchard's water filter turns filthy water drinkable (9:29)