3Chapter OutlinePhysical PropertiesHydrologic CycleDomestic Water UseAgricultural Water UseIndustrial Water UseKinds and Sources of Water PollutionWater Use Planning IssuesWastewater TreatmentPreserving Scenic Water Areas
4The Water IssuePhysical Properties:Polar: One molecule is slightly positive, and the other is slightly negative.Molecules tend to stick together.Separate other molecules from each other (solvent).Stores HeatIndustrial coolantModifies local climates
5The Water Issue70% of earth’s surface is covered by water.Fresh Water = 3%Potable: Unpolluted, fresh water, suitable for drinking.Shortages can be directly attributed to human-induced water pollution.WHO estimates 25% of world population does not have access to safe drinking water.
7Hydrologic CycleAll water is locked into a constant recycling process—Hydrologic Cycle.Solar energy evaporates water.Evapotranspiration—Plants giving off water.Warm, moist air rises, cools, condenses, and falls as precipitation.Some precipitation remains on the surface and evaporates, while most sinks into the soil or returns to the oceans.
9Hydrologic CycleGroundwater—Water entering the soil is either taken up by plant roots or moves downward until it reaches an impervious layer of rock, and accumulates in porous strata called an aquifer.
11AquifersAquifer—Porous soil saturated with water.Unconfined Aquifer—Usually near land’s surface. Lower boundary is impermeable layer of clay or rock. Water at atmospheric pressure and recharged by rainfall and percolation.Water Table—Top layer.Vadose Zone (Zone of Aeration)—Area above water table unsaturated with water.
12AquifersConfined Aquifer—(Artesian) Bounded on top and bottom by impermeable layer.Water stored under high pressure and recharged from a geologic recharge zone.Aquiclude—Impervious confining layer.Aquitard—Permeable confining layer.Porosity—Measure of size and number of species in the substrate.
13Human Influences On The Hydrologic Cycle Runoff and infiltration rate are greatly influenced by human activity.Major concern in many urban areas is transportation of storm water.Water Withdrawal—Withdrawing water and returning it to its original source.Water Consumption—Withdrawing water and incorporating it into a product, or otherwise moving it to another area, so it does not make it back to original source.
14Domestic Water UseAverage person in N.A. home uses approximately 400 liters of water per day.70% used as solvent to carry wastes.30% used for lawn and garden.Very small fraction used for drinking.Natural processes cannot cope with highly concentrated urban wastes.Must be treated before release.
18Agricultural Water Use Four common irrigation methods:Surface / FloodSprayTrickleSub-irrigation
19Industrial Water UseAccounts for nearly 50% of all water withdrawal in U.S., and 23% worldwide.90% of water used by industry is for cooling, and is returned to the source.Very little actually consumed.Most processes involve heat exchange.Water used to dissipate and transport waste.Stream and lake degradation.
20In-Stream UsesIn-stream uses make use of water in its channels and basins.Non-consumptive.Major in-stream uses are hydroelectric power, recreation, and navigation.Presently, hydroelectric power plants produce 13% of a electricity generated in U.S.
21DamsAlthough hydroelectric dams control flooding and create electricity, they have drawbacks.High construction costs.Habitat destruction (above and below dam).Retard stream flow and silt deposition.Impounded water has elevated evaporation rate.Retard scouring effects of flooding.Reduced habitat regeneration.
22Kinds and Sources of Water Pollution Dissolved organic matter is a significant water pollution problem.Biochemical Oxygen Demand (BOD)Amount of oxygen required to decay a certain amount of organic matter.If too much organic matter is added, all available oxygen will be used up.Anaerobic bacteria begins to break-down waste.
23Kinds and Sources of Water Pollution Nutrients can also be a pollution problem.Eutrophication—Excessive growth of algae and aquatic plants due to added nutrients.Particulate matter can also affect quality.
25Kinds and Sources of Water Pollution Pollution Sources:Point—Source of pollution readily located and identified.Municipal and industrial waste discharge pipes.Non-Point—Diffuse pollutants.Agricultural runoff
26Kinds and Sources of Water Pollution Municipal Water PollutionWastes from homes consists primarily of organic matter from garbage, food production, and human waste.Fecal Coliform Bacteria—Generic term for bacteria found in warm-blooded animal intestines.Numbers and types of bacteria present are directly related to amount of fecal matter entering system.
27Municipal Water Pollution At one time, many detergents contained phosphates which contributed to eutrophication.Eliminated from most major detergents since 1994.Pharmaceuticals, hormones, insecticides, caffeine, cholesterol, and coprostanol, among other chemicals, also found in municipal water discharge.
28Agricultural Water Pollution Excessive fertilizer use may lead to eutrophication in many aquatic habitats.Runoff from animal feedlots carries nutrients, organic matter, and bacteria.Agricultural runoff from large, open expanses is major source of water pollution.Leave conservation buffer.Keep soil covered with crop.Control amount and timing of fertilizer application.
29Industrial Water Pollution Factories and industrial complexes frequently dispose of waste in municipal sewage systems.May require special wastewater treatment.Often point sources.MiningChemical run-off.Acid mine drainage.
30Thermal PollutionThermal Pollution—Occurs when water is withdrawn, used for cooling purposes, and heated water then returned to original source.Steam from steam turbines must be condensed into water after leaving turbine for maximum efficiency.An increase in temperature, even a few degrees, may significantly alter some aquatic ecosystems.
31Marine Oil PollutionTanker accidents are spectacular, but more oil is released as a result of small, regular releases from other sources.2/3 of all human-caused marine oil from:Street run-off.Improper disposal of lubricating oil.Intentional oil discharges during tanker loading and unloading.1992—New oil tankers must be double-hulled.Currently 15% of all tankers double-hulled.
32Groundwater Pollution Major Sources:Agricultural ProductsUnderground Storage TanksLandfillsSeptic TanksSurface Impoundments
34Water Use Planning Issues Metropolitan areas must deal with and provide three basic services:Water supply for industrial needs.Wastewater collection and treatment.Storm-water collection and management.Must also deal with great volumes of excess water during storms (Storm-Water Runoff).Urban areas are paved, thus little water can be absorbed into the ground.
35Water Use Planning Issues Water Purity Act (1987) requires municipalities obtain permits for discharges of storm-water runoff so that non-point pollution sources are controlled.Many cities have separated storm sewers from sanitary sewers to avoid contamination under time of flooding and heavy storm-water runoff.
36Water DiversionWater diversion is seen as a necessity in many parts of the world.One major consequence of diverting water for irrigation and other purposes is water bodies downstream are deprived of their source of water.Ecological EffectsLake Levels DeclineFish Population Issues
37Wastewater TreatmentPrimary TreatmentRemoves large particles via filtration and then pumps remaining water into settling ponds and lakes.After settling, water is drawn off the top, and although devoid of large particulate matter, it still has a heavy load of organic matter, dissolved salts, bacteria, and microorganisms.
38Secondary TreatmentFacilities designed to degrade organic matter by promoting bacterial and other microorganism growth.Wastewater mixed with large quantities of highly oxygenated water.Trickling Filtering System—Provides anchor substrate for bacteria.
39Secondary TreatmentOrganic waste concentrated into particles large enough to settle out.Sewage SludgeActivated-sludge sewage treatment plants hold wastewater in settling tanks with air continuously bubbled through it, and water and sludge separate.
40Tertiary Treatment and Runoff Some plants now utilize an additional stage to remove even more dissolved pollutants i.e. phosphorous and nitrogen.Extremely costlySome municipalities using natural or constructed wetlands.Some areas use effluent as fertilizer.
41SalinizationAs plants extract water from the ground, salt content of the ground increases.Irrigation of arid farmland can make salinization more acute due to increased evaporation rates.
42Groundwater MiningRemoving water from an aquifer faster than it can be replenished.Extended periods of mining can lead to:Land subsidence.Lowering of the water table.Salt-water intrusion of wells near coastal areas.
44Preserving Scenic Water Areas United States Federal Wild and Scenic Rivers Act (1968).Established system to protect wild and scenic rivers from development.All federal agencies must take these areas into consideration when planning and implementing procedures.Only recently has natural and economic importance of wetlands been recognized.
46Chapter SummaryPhysical PropertiesHydrologic CycleDomestic Water UseAgricultural Water UseIndustrial Water UseKinds and Sources of Water PollutionWater Use Planning IssuesWastewater TreatmentPreserving Scenic Water Areas