Unit 9: Water Use and Pollution

hypoxia

excess nutrients cause eutrophic conditions and lower concentrations of dissolved oxygen

dead zone

huge volume of oxygen-depleted water

cultural eutrophication

human activities accelerate the input of plant nutrients to a lake

What are the main factors that cause water scarcity?

- Dry climate - Drought - Too many people using a freshwater supply more quickly that it can be replenished - Inefficient use of freshwater

Using the Core Case Study, summarize the importance of the Colorado River basin in the United States and how human activities are stressing this system.

- Flows 2,300 km through seven U.S. states - Includes 14 dams and reservoirs - Water supplied mostly from snowmelt of the Rocky Mountains - Supplies water and electricity for about 30 million people in arid areas - Las Vegas, Los Angeles, San Diego - Responsible for irrigation of crops that help feed America - The U.S. and Mexico are taking more than the river can supply - Very little water is reaching the Gulf of California - Recent droughts in the southwest - Completely changed the former estuary

List three ways to provide safe drinking water in poor countries.

- LifeStraw- an inexpensive, portable water filter that eliminates many viruses and parasites from water that is drawn through it - Use PUR, a powder containing chlorine and iron sulfate - Purify drinking water by exposing a clear plastic bottle filled with contaminated water to intense sunlight

Describe the environmental problems caused by the widespread use of bottled water.

- They end up in landfills, where they can remain for hundreds of years, or in incinerators, which release some of their harmful chemicals into the atmosphere - Discarded bottles get scattered on the land and wind up in rivers, lakes, and oceans - Toxic gases and liquids are released during the manufacture of plastic water bottles, and greenhouse gases and other air pollutants are emitted by the fossil fuels burned to make them and to deliver bottled water to suppliers - Depletes aquifers

water pollution

any chemical, biological, or physical change in water quality that can harm organisms or make water unfit for human uses

effluent

the treated water that exits the treatment facility

Using Figure 13-6, identify 3 items you use and how much water they require to produce.

- To produce a t-shirt it uses 17 bathtubs full of water - To produce a medium-sized house it takes 16,000 bathtubs full of water - To produce a pair of blue jeans it takes 72 bathtubs full of water

nonpoint sources

- broad, collective area... cannot be traced to a single site of discharge (atmospheric deposition, agricultural / industrial / residential runoff) - Difficult to identify, control and clean up

List two environmental problems that result from the overpumping aquifers.

- can cause the land above the aquifer to subside or sink, a phenomenon known as land subsidence - Groundwater overdrafts in coastal areas, where many of the world's largest cities and industrial areas are found, can pull saltwater into freshwater aquifers. The resulting contaminated groundwater is undrinkable and unusable for irrigation.

Using Figure 20-12, what are some sources of groundwater contamination?

- coal strip mine runoff - waste lagoons - accidental spills - landfills - water pumping wells - gasoline stations - sewers - buried gasoline and solvent tanks - cesspool, septic tank - hazardous waste injection wells - polluted air - pesticides and fertilizers - deicing road salt

Using Figure 20-27, identify some ways to you can personally reduce water pollution?

- do not flush unwanted medicines down the toilet - minimize use of pesticides, especially near bodies of water - fertilize garden and yard plants with manure or compost instead of commercial inorganic fertilizer - prevent yard wastes from entering storm drains - do not use water fresheners in toilets - do not pour pesticides, paints, solvents, oil, antifreeze, or other harmful chemicals down the drain or onto the ground

Using Figure 20-1, identify the major water pollutants.

- infectious agents (pathogens) - oxygen-demanding wastes - plant nutrients - organic chemicals - inorganic chemicals - sediments - heavy metals - thermal

List three major limitations on the widespread use of desalination.

- it's high cost, because it takes a lot of increasingly expensive energy to remove salt from seawater - the pumping of large volumes of seawater through pipes and using chemicals to sterilize the water and keep down algae growth kills many marine organisms and also requires large inputs of energy (and thus money) - desalination produces huge quantities of salty wastewater that must go somewhere

Give two reasons why lakes cannot cleanse themselves as readily as streams can.

- lakes and reservoirs often contain stratified layers that undergo little vertical mixing - they have low flow rates or no flow at all

Using Figure 20-26, what are some solutions to water pollution?

- prevent groundwater contamination - reduce nonpoint runoff - work with nature to treat sewage and reuse treated wastewater - find subsitutes for toxic pollutants - practice the four Rs of resource use (refuse, reduce, reuse, recycle) - reduce air pollution - reduce poverty - slow population growth

Using Figure 13-27, identify some ways to reduce water losses.

- redesign manufacturing processes to use less water - recycle water in industry - fix water leaks - landscape yards with plants that require little water - use drip irrigation on gardens and lawns - use water-saving showerheads, faucets, appliances, and toilets (or waterless composting toilets) - collect and reuse gray water in and around houses, apartments, and office buildings - raise water prices and use meters, especially in dry urban areas

List two human activities that increase the risk of flooding.

- removal of water-absorbing vegetation - draining wetlands

point sources

- specific location (drain pipes, ditches, sewer lines) - Easy to identify, monitor and regulate

List three possible solutions to the supply problems in the Colorado River basin.

- the seven states using the river have to enact and enforce strict water conservation measures and slow population growth and urban development - phasing out state and federal government subsidies for agriculture in this region, shifting water-thirsty crops to less arid areas, and banning or severely restricting the use of surface water and groundwater to keep golf courses and lawns green in the desert areas of the Colorado River basin - sharply raise the historically low price of the river's freshwater over the next decade

Using Figure 13-28, identify some ways to reduce your personal water waste.

- use water-saving toilets, showerheads, and faucets - take short showers instead of baths - turn off sink faucets while brushing teeth, shaving, or washing - wash only full loads of clothes or use the lowest possible water-level setting for smaller loads - repair water leaks - wash your car from a bucket of soapy water, use gray water, and use the hose for rinsing only - if you use a commercial car wash, try to find one that recycles its water - replace your lawn with native plants that need little if any watering - water lawns and gardens only in the early morning or evening and use gray water - use drip irrigation and mulch for gardens and flowerbeds

List four ways to reduce water pollution from non-point sources.

- using fertilizers that release plant nutrients slowly - using no fertilizers on steeply sloped land - reducing soil erosion and fertilizer runoff by keeping cropland covered with vegetation and using conservation tillage and other soil conservation methods - setting discharge standards for nitrate chemicals from sewage treatment and industrial plants

What percentage of the earth's freshwater is readily available to us?

0.024%

What is the leading cause of water pollution? Second? Third?

1. Agricultural activities 2. Industrial facilities 3. Mining

Using Figure 13-17, what are the advantages and disadvantages of dams?

Advantages: - provides irrigation water above and below dam - provides water for drinking - reservoir useful for recreation and fishing - can produce cheap electricity (hydropower) - reduces down-stream flooding of cities and farms Disadvantages: - flooded land destroys forests or cropland and displaces people - large losses of water through evaporation - deprives downstream cropland and estuaries of nutrient-rich silt - risk of failure and devastating downstream flooding - disrupts migration and spawning of some fish

Using Figure 20-24, what are the steps of a sewage treatment plant?

1. Preliminary Treatment - Uses bar screen to trap large materials; grit settling chamber allows sand and gravel to settle out - Collected debris sent to landfill 2. Primary Treatment - The physical removal of suspended particles such as sand and silt in settling tanks (clarifiers) - Water held in a large settling basin where raw sludge settles out - Oils and greases float to the top where they are skimmed off 3. Secondary Treatment - Biological treatment of wastewater - Uses microorganisms to decompose suspended organic material - Water is stirred and aerated so aerobic bacteria break down organic pollutants - Removes up to 90% of oxygen-demanding wastes 4. Advanced or Tertiary Treatment - Uses series of chemical and physical processes to remove specific pollutants left (especially nitrates and phosphates) - Water is disinfected to remove coloration and kill disease-carrying bacteria and some viruses - Bleaching - Chlorination - Ozonation - UV light

water footprint

A rough measure of the volume of water that we use directly and indirectly to keep a person or group alive and to support their lifestyles

dam

A structure built across a river to control the river's flow or to create a reservoir

Using Figure 13-11, what are the advantages and disadvantages of withdrawing groundwater?

Advantages: - useful for drinking and irrigation - exists almost everywhere - renewable if not overpumped or contaminated - cheaper to extract that most surface waters Disadvantages: - aquifer depletion from overpumping - sinking of land (subsidence) from overpumping - some deeper wells are nonrenewable - pollution of aquifers lasts decades or centuries

How is most of the world's water used?

Agriculture 70% Industries 20% Residential 10%

Summarize the Case Study of Arsenic in Drinking Water.

Arsenic contaminates drinking water when a well is drilled into an aquifer where the soil and rock are naturally rich in arsenic, or when human activities such as mining and ore processing release arsenic into drinking water supplies. Some rivers used for drinking water also are contaminated naturally, having originated in springs that have high levels of arsenic. The World Health Organization (WHO) estimates that more than 140 million people in 70 countries are drinking water with arsenic concentrations of 5-100 times the accepted safe level of 10 parts per billion (ppb). Some scientists from the WHO and other organizations argue that even the 10 ppb standard is not safe. The WHO estimates that long-term exposure to nondegradable arsenic in drinking water is likely to cause hundreds of thousands of premature deaths from cancer of the skin, bladder, and lungs.

reservoir

Artificial lake created when a stream is dammed

drought

Condition in which an area does not get enough water because of lower-than-normal precipitation or higher-than-normal temperatures that increase evaporation

Using Figure 13-10, which countries or regions of the world have little access to freshwater?

DR of Congo, Angola, Madagascar, Ethiopia, Somalia, Mozambique, Niger, Mauritania, Sierra Leone, Afghanistan, and Papua New Guinea

Using Figure 20-6, describe an Oxygen Sag Curve.

Decomposition Zone: - trashy fish such as carp and gar can still survive - water is contaminated due to point source - decomposition (of waste or algal blooms) begins causing dissolved oxygen to go down - biological oxygen demand begins to increase Septic Zone: - since massive decomposition is occurring, bacteria consume all of the oxygen, and DO levels are at their all-time low - nothing is able to survive here but decomposers - occurs immediately after point source contamination - massive decomposition occurs, and no other organisms are present - bacteria demand lots of oxygen, but as decomposition slows, BOD begins to decrease as well Recovery Zone: - trashy fish such as carp, gar, and leeches return - clean zones can be found immediately following this zone - BOD is continuing to decrease - decomposition has stopped - DO begin to rise as decomposition has stopped Clean Zone: - normal clean water organisms such as trout, perch, bass, mayfly, and stonefly are present - occurs furthest from point source - water is clear and healthy - biological oxygen demand levels are low - dissolved oxygen levels are high

Describe the pollution of the Great Lakes and the progress made in reducing this pollution.

Despite their enormous size, these lakes are vulnerable to pollution from point and nonpoint sources. One reason is that each year, less than 1% of the water entering these lakes flows east into the St. Lawrence River and then out to the Atlantic Ocean, meaning that pollutants can take as long as 100 years to be flushed out to sea. By the 1960s, many areas of the Great Lakes were suffering from severe cultural eutrophication, huge fish kills, and contamination from bacteria and a variety of toxic industrial wastes. The impact on Lake Erie was particularly intense because it is the shallowest of the Great Lakes and has the highest concentrations of people and industrial activity along its shores. In 1972, the United States and Canada signed the Great Lakes Water Quality Agreement, which is considered a model of international cooperation. They agreed to spend more than $20 billion to maintain and restore the chemical, physical, and biological integrity of the Great Lakes basin ecosystem. This program has helped to cut the number and sizes of algal blooms, raised dissolved oxygen levels, boosted sport and commercial fishing catches in Lake Erie, and allowed most swimming beaches to reopen. These improvements resulted mainly from the use of new or upgraded sewage treatment plants, better treatment of industrial wastes, and bans on the use of detergents, household cleaners, and water conditioners that contain phosphates. Most of these measures were instituted largely as a result of bottom-up citizen pressure.

Explain HOW seasonal dead zones form in the Gulf of Mexico.

During the spring and summer, nitrate-laden freshwater flowing into the Gulf forms an oxygen-rich layer on top of the Gulf's cooler and more dense saltwater. Because there are few storms at this time of year, this sun-heated upper layer of water remains fairly calm and does not mix with the bottom layer of low-oxygen water. The combination of sunlight and large inputs of nitrate plant nutrients from fertilizer and sewage into the freshwater layer leads to massive blooms of phytoplankton, mostly blue-green algae. When these algae die, they sink into the saltier water below where they are decomposed by oxygen-consuming bacteria, which use up nearly all of the dissolved oxygen, leaving less than 2 parts per million in the deeper water. Mobile species can survive this lack of oxygen by migrating to oxygen-rich waters, but certain species of fish, shellfish, and other organisms are not able to escape, and they die off. Thus, the oxygen-depleted bottom layer of water becomes a dead zone for certain species. This disrupts the Gulf's food web, because die-offs of such species lead to the deaths of seabird and marine mammal species that depend on the dying fish and shellfish for their survival.

Describe the Safe Drinking Water Act.

EPA set maximum contaminant levels for pollutants that may have adverse effects on human health

Using the Core Case Study, describe the nature and causes of the annual dead (oxygen-depleted) zone in the Gulf of Mexico.

Each spring and summer, this huge input of plant nutrients, mostly nitrates from crop fertilizers, enters the northern Gulf of Mexico and overfertilizes the coastal waters of the U.S. states of Mississippi, Louisiana, and Texas. One result is an explosion of populations of phytoplankton (mostly algae) that eventually die and fall to the seafloor. Hordes of oxygen-consuming bacteria go to work decomposing the phytoplankton remains and, in the process, deplete the dissolved oxygen in the Gulf's bottom layer of water. The huge volume of oxygen-depleted water resulting from this seasonal event is called a dead zone because it contains little animal marine life. We produce crops for food and ethanol fuel in the vast Mississippi basin, and we end up disrupting coastal aquatic life and seafood production in the Gulf of Mexico. We over-fertilize coastal waters.

floodplain

Flat valley floor next to a stream channel. For legal purposes, the term often applies to any low area that has the potential for flooding, including certain coastal areas

What are the harms of floods?

Floods kill thousands of people every year and cost tens of billions of dollars in property damage. Floods are usually considered natural disasters, but since the 1960s, human activities have contributed to a sharp rise in flood deaths and damages, meaning that such disasters are partly human-made.

groundwater

Freshwater under the earth's surface stored in aquifers that moves very slowly through soil and rock layers

Describe an ocean garbage patch and explain how it can harm marine life and how the growth of such patches could be prevented.

Gigantic, slowly rotating masses of small pieces of plastic and other solid wastes in an ocean Marine life can mistake the tiny plastic particles for food and swallow them. Because these animals cannot digest the plastic, it can cause them to die from starvation, poisoning, or choking. We can try to keep the problem from growing worse by focusing on pollution prevention, which means practicing the four Rs of resource use: Refuse, Reduce, Reuse, and Recycle.

Using Figure 13-22, summarize the three irrigation methods and their water efficiency.

Gravity Flow: - efficiency 60% and 80% with surge values - Water usually comes from an aqueduct system or a nearby river Drip Irrigation: - efficiency 90-95% - Above- or below-ground pipes or tubes deliver water to individual plant roots Center Pivot: - efficiency 80%with low-pressure sprinkler and 90-95% with LEPA sprinkler - Water usually pumped from underground and sprayed from mobile boom with sprinklers

Explain why groundwater cannot cleanse itself very well.

Groundwater flows so slowly—usually less than 0.3 meter (1 foot) per day—that contaminants are not diluted and dispersed effectively. In addition, groundwater usually has much lower concentrations of dissolved oxygen (which helps decompose many contaminants) and smaller populations of decomposing bacteria. The usually cold temperatures of groundwater also slow down chemical reactions that decompose wastes.

Explain why access to water is a health issue, an economic issue, a national and global security issue, and an environmental issue.

Health Issue: - The World Health Organization (WHO) estimates that an average of 9,300 people die each day from waterborne infectious diseases because they do not have access to safe drinking water. Economic Issue: - Water is vital for producing food and energy and for reducing poverty. National and Global Security Issue: - There are increasing tensions within and between some nations over access to limited freshwater resources that they share. Environmental Issue: - Excessive withdrawal of freshwater from rivers and aquifers has resulted in falling water tables, decreasing river flows, shrinking lakes, and disappearing wetlands. This, in combination with water pollution in many areas of the world, has degraded water quality, reduced fish populations, hastened the extinction of some aquatic species, and degraded aquatic ecosystem services.

water table

Highest point in an aquifer. Upper surface of the zone of saturation, in which all available pores in the soil and rock in the earth's crust are filled with water.

Describe how water is recycled by the hydrologic cycle and how human activities can overload and altered this cycle.

Incoming solar energy causes evaporation, or the conversion of water from liquid to vapor from the earth's oceans, lakes, rivers, and soil. This water vapor rises into the atmosphere, where it condenses into droplets, and gravity then draws the water back to the earth's surface as precipitation (rain, snow, sleet, and dew). Over land, about 90% of the water that reaches the atmosphere evaporates from the surfaces of plants, through a process called transpiration, and from the soil. We alter the hydrologic cycle through our influence on projected climate change. We can overload it with pollutants. We withdraw freshwater from underground and surface water supplies faster than it can be replenished.

Using Figure 20-15, what are some sources of ocean pollution?

Industry: - Nitrogen oxides from autos and smokestacks, toxic chemicals, and heavy metals in effluents flow into bays and estuaries Cities: - Toxic metals and oil from streets and parking lots pollute waters; sewage adds nitrogen and phosphorus Urban Sprawl: - Bacteria and viruses from sewers and septic tanks contaminate shellfish beds and close beaches; runoff of fertilizer from lawns adds nitrogen and phosphorus Construction Sites: - Sediments are washed into waterways, choking fish and plants, clouding waters, and blocking sunlight Farms: - Runoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus Red Tides: - Excess nitrogen causes explosive growth of toxic microscopic algae, poisoning fish and marine mammals Healthy Zone: - Clear, oxygen-rich waters promote growth of plankton and sea grasses, and support fish Oxygen-Depleted Zone: - Sedimentation and algae overgrowth reduce sunlight, kill beneficial sea grasses, use up oxygen, and degrade habitat Toxic Sediments: - Chemicals and toxic metals contaminate shellfish beds, kill spawning fish, and accumulate in the tissues of bottom feeders

watershed (drainage basin)

Land area that delivers water into a stream or river system. Usually carries pollution as this area drains.

Summarize the story of the Aral Sea water-transfer project and its disastrous consequences.

Large-scale water transfers in dry central Asia have led to: - Wetland destruction - drop of 22m - Desertification - Greatly increased salinity - Fish extinctions and decline of fishing - Wind-blown salt - Depositing on glaciers in the Himalayas - Altered local climate - Hot dry summers; cold winters

Describe what each water quality test measures: - Turbidity

Measures the scattering effect that suspended solids have on light: the higher the intensity of scattered light, the higher the turbidity

primary sewage treatment

Mechanical sewage treatment in which large solids are filtered out by screens and suspended solids settle out as sludge in a sedimentation tank

Using Figure 13-9, what countries or regions of the world suffer from water scarcity?

More than 30 countries-most of them in the Middle East and Asia

surface water

Precipitation that remains on the surface and does not seep into soil

List ways to prevent or reduce cultural eutrophication.

Prevent: - use advanced (but expensive) waste treatment processes to remove nitrates and phosphates from wastewater before it enters a body of water - use a preventive approach by banning or limiting the use of phosphates in household detergents and other cleaning agents, and by employing soil conservation and other controls to reduce nutrient runoff Clean Up: - mechanically removing excess weeds - controlling undesirable plant growth with herbicides and algaecides - pumping air into lakes and reservoirs to prevent oxygen depletion

Using Figure 13-16, what are some ways to prevent and control groundwater depletion?

Prevent: - use water more efficiently - subsidize water conservation - limit number of wells - stop growing water-intensive crops in dry areas Control: - raise price of water to discourage waste - tax water pumped from wells near surface waters - build rain gardens in urban areas - use permeable paving material on streets, sidewalks, and driveways

Using Figure 13-30, what are some ways to prevent and control flood damage.

Prevention: - preserve forests in watersheds - preserve and restore wetlands on floodplains - tax development on floodplains - increase use of floodplains for sustainable agriculture and forestry Control: - strengthen and deepen streams (channelization) - build levees or floodwalls along streams - build dams

Using Figure 20-21, what are some ways to prevent and control coastal water pollution?

Prevention: - separate sewage and storm water lines - require secondary treatment of coastal sewage - use wetlands and other natural methods to treat sewage - ban dumping of wastes and sewage by ships in coastal waters - strictly regulate coastal development, oil drilling, and oil shipping - require double hulls for oil tankers Cleanup: - improve oil-spill cleanup capabilities - use nanoparticles on sewage and oil spills to dissolve the oil or sewage (still under development)

Using Figure 20-13, what are some ways to prevent and control groundwater pollution?

Prevention: - find substitutes for toxic chemicals - keep toxic chemicals out of the environment - require leak detectors on underground tanks - ban hazardous waste disposal in landfills and injection wells - store harmful liquids in aboveground tanks with leak detection and collection systems Cleanup: - pump to surface, clean, and return to aquifer (very expensive) - inject microorganisms to clean up contamination (less expensive but still costly) - pump nanoparticles of inorganic compounds to remove pollutants (still being developed)

desalination

Purification of saltwater or brackish (slightly salty) water by removal of dissolved salts

What causes harmful algal blooms and what are their effects?

Runoff of sewage and agricultural wastes into coastal waters can carry large quantities of nitrate and phosphate plant nutrients. They can release waterborne and airborne toxins that poison seafood, kill fish and some fish-eating birds, and discourage tourism in the affected coastal areas. Each year, harmful algal blooms lead to the poisoning of about 60,000 Americans who eat shellfish contaminated by the algae.

secondary sewage treatment

Second step in most waste treatment systems in which aerobic bacteria decompose as much as 90% of degradable, oxygen-demanding organic wastes in wastewater. It usually involves bringing sewage and bacteria together in trickling filters or in the activated sludge process.

Describe the Clean Water Act.

Set maximum permissible amounts of water pollutants that can be discharged into waterways (to make water swimmable and fishable)

Explain how certain efforts to clean up the air can contribute to water pollution.

Stricter air pollution control laws have forced coal-burning power plants in more-developed countries to remove many of the harmful gases and particles from their smokestack emissions. But this results in hazardous ash, which is typically placed in slurry ponds that can rupture and cause water pollution.

reliable surface runoff

Surface runoff of water that generally can be counted on as a stable source of water from year to year

Describe California's large water-transfer programs, explain how it came about, and summarize the controversy around the program.

The California State Water Project is one of the world's largest freshwater transfer projects. It uses a maze of giant dams, pumps, and lined canals, or aqueducts, to transport freshwater from the High Sierra Mountains of northeastern California to heavily populated cities and agricultural regions in water-poor central and southern California. These massive water transfers also involve high economic and social costs, large water losses through evaporation and leaks in the water-transfer systems, and degraded ecosystems in areas from which the water was taken.

Summarize the problem of groundwater depletion in the world and in the United States, especially over the Ogallala aquifer.

The widespread drilling of inexpensive tube wells by farmers, especially in India and China, has accelerated aquifer overpumping. As water in aquifers is removed faster than it is renewed, water tables fall. Then farmers drill deeper wells, buy larger pumps, and use more energy to pump water to the surface. This process eventually depletes the groundwater in some aquifers or at least removes all the water that can be pumped at an affordable cost. In the United States, aquifer depletion is a growing problem, especially in the vast Ogallala aquifer. The gigantic Ogallala aquifer supplies about one-third of all the groundwater used in the United States and has helped to turn the Great Plains into one of world's most productive irrigated agricultural regions. The problem is that the Ogallala is essentially a one-time deposit of liquid natural capital with a very slow rate of recharge.

What are the benefits of floods?

They have created some of the world's most productive farmland by depositing nutrient-rich silt on floodplains. They also help recharge groundwater and refill wetlands that are commonly found on floodplains, thereby supporting biodiversity and aquatic ecosystem services.

Describe John Todd's use of living machines to treat sewage.

This purification process begins when sewage flows into a passive solar greenhouse or outdoor site containing rows of large open tanks populated by an increasingly complex series of organisms. In the first set of tanks, algae and microorganisms decompose organic wastes, with sunlight speeding up the process. Water hyacinths, cattails, bulrushes, and other aquatic plants growing in the tanks take up the resulting nutrients. After flowing though several of these natural purification tanks, the water passes through an artificial marsh made of sand, gravel, and bulrushes, which filters out algae and remaining organic waste. Some of the plants also absorb, or sequester, toxic metals such as lead and mercury and secrete natural antibiotic compounds that kill pathogens. Next, the water flows into aquarium tanks, where snails and zooplankton consume microorganisms and are in turn consumed by crayfish, tilapia, and other fish that can be eaten or sold as bait. After 10 days, the clear water flows into a second artificial marsh for final filtering and cleansing. The water can be made pure enough to drink by treating it with ultraviolet light or by passing the water through an ozone generator, usually immersed out of sight in an attractive pond or wetland habitat.

Explain how streams can cleanse themselves and how these cleansing processes can be overwhelmed.

Through a combination of dilution and bacterial biodegradation of such wastes. Streams can become overloaded with such pollutants or when drought, damming, or water diversion reduce their flows.

aquifers

Underground caverns and porous layers of sand, gravel and rock in which groundwater is stored

septic tank

Underground tank for treating wastewater from a home in rural and suburban areas. Bacteria in the tank decompose organic wastes, and the sludge settles to the bottom of the tank. The effluent flows out of the tank into the ground through a field of drainpipes.

What are the effects of oil pollution in the oceans and what can be done to reduce such pollution?

Volatile organic hydrocarbons in oil kill many aquatic organisms immediately upon contact, especially if these animals are in their vulnerable larval forms. Other chemicals in oil form tar-like globs that float on the surface and coat the feathers of seabirds (see chapter-opening photo) and the fur of marine mammals. This oil coating destroys their natural heat insulation and buoyancy, causing many of them to drown or die of exposure from loss of body heat. Heavy oil components that sink to the ocean floor or wash into estuaries and coastal wetlands can smother bottom-dwelling organisms such as crabs, oysters, mussels, and clams, or make them unfit for human consumption. Some oil spills have killed coral reefs. Prevent tanker spills by using oil tankers with double hulls. Stricter safety standards and inspections could help to reduce oil well blowouts at sea. Businesses, institutions, and citizens living in coastal areas must take care to prevent leaks and spillage of even the smallest amounts of oil and oil products such as paint thinners and gasoline.

surface runoff

Water flowing off the land into bodies of surface water

Explain how drinking water is purified typically in more-developed countries.

Water is usually stored in a reservoir for several days. This improves its clarity and taste by increasing its dissolved oxygen content and allowing suspended matter to settle. The water is then pumped to a purification plant and treated to meet government drinking water standards.

freshwater

Water that contains very low levels of dissolved salts

virtual water

Water that is not directly consumed but is used to produce food and other products

zone of saturation

Zone where all available pores in soil and rock in the earth's crust are filled by water

tertiary (advanced) sewage treatment

a physical and chemical process to remove specific pollutants left in the water after primary and secondary treatment

Describe what each water quality test measures: - Dissolved oxygen (DO)

determines the amount of oxygen gas available in the water

distillation

involves heating saltwater until it evaporates (leaving behind salts in solid form) and condenses as freshwater

eutrophication

the natural nutrient enrichment of a shallow lake, estuary or slow moving stream, from runoff of N & P from the surrounding land

water transfer

the transferring of water to provide resources to areas limited in supply

wetland-based sewage treatment systems

unconventional, but highly effective sewage treatment system that works with nature

Describe what each water quality test measures: - Coliform bacteria

used to determine the possibility of fecal contamination from sewage, septic tank leaks, or animal wastes from feedlots

gray water

used water that can be reused and recycled

reverse osmosis

uses high pressure to force saltwater through a membrane filter with pores small enough to remove the salt and other impurities

composting toilet

waterless, odorless toilet that convert nutrient-rich human fecal matter into a soil-like humus that can be used as a fertilizer supplement