Water Pollution

Case Study: The Gulf of Mexico’s Annual Dead Zone Spring and summer – huge inputs of nutrients from the Mississippi River basin Depletion of dissolved oxygen in the Gulf of Mexico’s bottom layer of water Contains little marine life Disrupts nitrogen cycle Figure 20.1 Water containing sediments, dissolved nitrate fertilizers, and other pollutants drains from the Mississippi River basin (top) into the Mississippi River and from there into the northern Gulf of Mexico (bottom). The boxed area at the bottom of the map shows the dead zone with the red area having the lowest oxygen level.

What Are the Causes and Effects of Water Pollution? Water pollution causes illness and death in humans and other species, and disrupts ecosystems Sources: Primarily agricultural activities, industrial facilities, and mining Growth of both the human population and our rate of resource use makes it increasingly worse

Water Pollution Comes from Point and Nonpoint Sources Change in water quality that can harm organisms or make water unfit for human uses Point sources Located at specific places Easy to identify, monitor, and regulate Figure 20-2: This is a point source of water pollution in Gargas, France

Water Pollution Comes from Point and Nonpoint Sources (cont’d.) Broad, diffuse areas Difficult to identify and control Expensive to clean up Figure 20-3: Nonpoint sediment from farmland runoff flows into streams and sometimes changes their courses or dams them up. As measured by weight, it is the largest source of water pollution.

Water Pollution Comes from Point and Nonpoint Sources (cont’d.) Leading causes of water pollution Agriculture activities Sediment eroded from the lands Fertilizers and pesticides Industrial facilities Inorganic and organic chemicals Mining Erosion and toxic chemicals

Major Water Pollutants Have Harmful Effects Infectious disease organisms Contaminated drinking water An estimated 1.6 million people die every year, mostly under the age of five

What Are the Major Water Pollution Problems in Streams and Lakes? Streams and rivers around the world are extensively polluted However, they can cleanse themselves of many pollutants if we do not overload them or reduce their flows Adding excessive nutrients to lakes from human activities can disrupt their ecosystems, and prevention of such pollution is more effective and less costly than cleaning it up

Streams Can Cleanse Themselves, If We Do Not Overload Them Dilution Biodegradation of wastes by bacteria takes time Oxygen sag curve Breakdown of biodegradable wastes by bacteria depletes oxygen Animated Figure 20-6: Natural capital. A stream can dilute and decay degradable, oxygen-demanding wastes, and it can also dilute heated water. This figure shows the oxygen sag curve (blue) and the curve of oxygen demand (red). Streams recover from oxygen-demanding wastes and from the injection of heated water if they are given enough time and are not overloaded

Stream Pollution in More-Developed Countries 1970s – water pollution control laws Successful water clean-up stories Ohio Cuyahoga River, U.S. Thames River, Great Britain Contamination of toxic inorganic and organic chemicals by industries and mines

Stream Pollution in Less-Developed Countries Half of the world’s 500 major rivers are polluted Untreated sewage Industrial waste Water often used for human activities Figure 20-7: Natural capital degradation. This portion of China’s Yangtze River near the Three Gorges dam is heavily polluted with chemicals, sediment, and trash.

Too Little Mixing and Low Water Flow Makes Lakes Vulnerable to Water Pollution Less effective at diluting pollutants than streams Stratified layers Little vertical mixing Little of no water flow Can take up to 100 years to change the water in a lake Biological magnification of pollutants

Cultural Eutrophication Is Too Much of a Good Thing Natural enrichment of a shallow lake, estuary, or slow-moving stream Caused by runoff into lake that contains nitrates and phosphates Oligotrophic lake Low nutrients; clear water

Cultural Eutrophication Is Too Much of a Good Thing Nitrates and phosphates from human sources Farms, feedlots, streets, parking lots Fertilized lawns, mining sites, sewage plants During hot weather or droughts Algal blooms Increased bacteria; anaerobic bacteria More nutrients Figure 20-8: In 2010, severe cultural eutrophication affected Chaohu Lake near Hefei City in China’s Anhui Province.

Cultural Eutrophication Is Too Much of a Good Thing Prevent or reduce cultural eutrophication Remove nitrates and phosphates Diversion of lake water Clean up lakes Remove excess weeds Use herbicides and algaecides Pump in air

Revisiting The Gulf of Mexico: An Extreme Case of Cultural Eutrophication Nitrates discharged from the Mississippi have nearly tripled since 1950 Nitrogen cycle disrupted Blue-green algae blooms Flood-control along the Mississippi Flow faster; increase sediment pollution Fish kills

Case Study: Pollution in the Great Lakes 1960s – many areas with cultural eutrophication 1972 – Canada and the United States Great Lakes pollution control program Decreased algal blooms Increased dissolved oxygen Increased fishing catches Better sewage treatment plants

Case Study: Pollution in the Great Lakes Pollution control program Fewer industrial wastes Bans on phosphate-containing household products Problems still exist Raw sewage and biological pollution Nonpoint runoff of pesticides and fertilizers Atmospheric deposition of pesticides and Hg

Case Study: Pollution in the Great Lakes Continuing problems Urban sprawl and runoff Biological pollution Zebra mussels Atmospheric deposition of pollutants Figure 20-11: The five Great Lakes of North America make up the world’s largest freshwater system. Dozens of major cities in the United States and Canada are located on their shores, and water pollution in the lakes is a growing problem.

What Are the Major Pollution Problems Affecting Groundwater? Chemicals used in agriculture, industry, transportation, and homes can spill and leak into groundwater and make it undrinkable There are both simple ways and complex ways to purify groundwater used as a source of drinking water, but protecting it through pollution prevention is the least expensive and most effective strategy

Groundwater Cannot Cleanse Itself Very Well Source of drinking water for about half of the U.S. population Common pollutants Fertilizers and pesticides Gasoline Organic solvents Fracking Pollutants dispersed in a widening plume Figure 20-12: Natural capital degradation. Principal sources of groundwater contamination in the United States (Concept 20-3A). Another source in coastal areas is saltwater intrusion from excessive groundwater withdrawal. (Figure is not drawn to scale.)

Groundwater Cannot Cleanse Itself Very Well Slower chemical reactions in groundwater due to: Slow flow – contaminants not diluted Less dissolved oxygen Fewer decomposing bacteria Low temperatures

Groundwater Pollution Is a Serious Hidden Threat in Some Areas China – 90% of urban aquifers are contaminated or overexploited U.S. – FDA reports of toxins found in many aquifers Nitrate ions Can turn into cancer causing chemicals Slowly degrading wastes Non-degradable wastes

Case Study: Arsenic in Drinking Water Rocks rich in arsenic can contaminate wells Long-term exposure can lead to: Skin, lung, bladder cancer Treatment Nanoparticles of rust

There Are Many Ways to Purify Drinking Water Reservoirs and purification plants Process sewer water to drinking water Expose clear plastic containers to sunlight (UV) The LifeStraw PUR – chlorine and iron sulfate powder

Case Study: Is Bottled Water a Good Option? Bottled water can be useful but expensive The U.S. has some of the world’s cleanest drinking water Bottled water less regulated than tap water Use of bottled water can create environmental problems

Using Laws to Protect Drinking Water Quality 1974 – U.S. Safe Drinking Water Act Sets maximum contaminant levels for any pollutants that affect human health Health scientists Strengthen the law Water-polluting companies Weaken the law

What Are the Major Water Pollution Problems Affecting Oceans? Most ocean pollution originates on land and includes: Oil and other toxic chemicals Solid waste, which threaten fish and wildlife and disrupt marine ecosystems Key to protecting the oceans Reduce the flow of pollution from land and air and from streams emptying into ocean waters

Ocean Pollution Is a Growing and Poorly Understood Problem Municipal sewage from less-developed countries are often dumped into oceans without treatment Deeper ocean waters Dilution Dispersion Degradation

Ocean Pollution Is a Growing and Poorly Understood Problem U.S. coastal waters Raw sewage – viruses Sewage and agricultural runoff: NO3- and PO43- Harmful algal blooms Oxygen-depleted zones Figure 20-15: Natural capital degradation. Residential areas, factories, and farms all contribute to the pollution of coastal waters.

Case Study: Ocean Garbage Patches: There Is No Away North Pacific Garbage Patch Two rotating gyres On or just beneath the water surface Tiny plastic pieces harmful to wildlife No practical way to clean up Figure 20-17: The North Pacific Garbage Patch is actually two vast, slowly swirling masses of small plastic particles floating just under the water. Four other huge garbage patches have been discovered in the world’s other major oceans.

Ocean Pollution from Oil Crude and refined petroleum Highly disruptive pollutants Largest source of ocean oil pollution Urban and industrial runoff from land 1989 – Exxon Valdez, oil tanker 2010 – BP Deepwater Horizon in the Gulf of Mexico Figure 20-19: The Deepwater Horizon drilling platform burned and sank in the Gulf of Mexico after exploding on April 20, 2010.

Ocean Pollution from Oil Volatile organic hydrocarbons Kill many aquatic organisms Tar-like globs on the ocean’s surface Coat animals Heavy oil components sink Affect the bottom dwellers

Ocean Pollution from Oil Faster recovery in warm water with rapid currents In cold, calm waters recovery can take decades Methods of preventing oil spills Double hulls

Case Study: The BP Deepwater Horizon Oil-Rig Spill Spill from deep-sea oil drilling – 1 mile deep Released 4.9 million barrels of crude oil Contaminated vast areas of coastline Caused by equipment failure and poor decisions Government developed new standards for offshore drilling procedures

How Can We Deal with Water Pollution? Reducing water pollution requires that we: Prevent it Work with nature to treat sewage Use natural resources far more efficiently

Reducing Ocean Water Pollution Reduce flow of pollution from land Land-use Air pollution Linked to energy and climate policy Figure 20-21: Methods for preventing excessive pollution of coastal waters and methods for cleaning it up (Concept 20-4B).

Reducing Surface Water Pollution from Nonpoint Sources Agriculture Reduce erosion Reduce the amount of fertilizers Plant buffer zones of vegetation Use organic farming techniques Use pesticides prudently Institute tougher pollution regulations for livestock operations

Case Study: The U.S. Experience with Reducing Point-Source Pollution 1972 – Clean Water Act 1987 – Water Quality Act Experimenting with a discharge trading policy that uses market forces

Sewage Treatment Reduces Water Pollution How do septic tank systems work? Wastewater or sewage treatment plants Primary sewage treatment Physical process Secondary sewage treatment Biological process with bacteria Tertiary or advance sewage treatment Special filtering processes Bleaching, chlorination Figure 20-23: Solutions. Septic tank systems are often used for disposal of domestic sewage and wastewater in rural and suburban areas. Figure 20-24: Solutions: Primary and secondary sewage treatment systems help to reduce water pollution.

Sewage Treatment Reduces Water Pollution Many cities violate federal standards for sewage treatment plants Federal law requires primary and secondary treatment Exemptions from secondary treatment There are health risks of swimming in water with blended sewage wastes

We Can Improve Conventional Sewage Treatment Remove toxic wastes before water goes to the municipal sewage treatment plants Reduce or eliminate use and waste of toxic chemicals Use composting toilet systems Wetland-based sewage treatment systems Work with nature

There Are Sustainable Ways to Reduce and Prevent Water Pollution Developed countries Bottom-up political pressure to pass laws Developing countries Little has been done to reduce water pollution China Small sewage treatment plants How can we avoid producing water pollutants in the first place?