2 21.1 Water Pollution Degradation of water quality Pollutants include heavy metals, sediment, certain radioactive isotopes, heat, fecal coli- form bacteria, phosphorus, nitrogen, sodium, certain pathogenic bacteria and viruses
3 Primary problem: lack of clean, disease-free drinking water 21.1 (cont.)Primary problem: lack of clean, disease-free drinking waterUnited StatesEpidemics of waterborne diseases have killed thousands of people in the pastNow water is treated prior to consumption (less disease)WorldwideEvery year, several billion people are exposed to water borne diseases
4 Major uses for water: domestic, industrial, agriculture 21.1 (cont.)Major uses for water: domestic, industrial, agricultureDomestic SupplyCannot be harmful to health, taste good, odorless, should not damage plumbing/household appliancesIndustrial PurposesMay require distilled waterMay require noncorrosive water or water free of particles that could damage equipmentAgricultureVegetation tolerates wide range or water qualityCan vary widely in physical, chemical, and biological, properties
6 21.1 (cont.)Increasing population leads to introduction of more pollutants into the environmentOver ¼ of US drinking water systems reported a violation of federal health standardsUS Environmental Protection Agency has set limits on water pollution levels for some pollutantsPollutant maximum concentration standards have been set for only some of the more then 700 possible water contaminants
7 21.2 Biochemical Oxygen Demand Bacteria decays dead organic matter in streamsBacteria uses oxygenA lot of bacterial activity decreases oxygen levels in waterA stream with low oxygen content is a poor environment for fish and most other organisms and is considered polluted.
8 21.2 (cont.)The amount of oxygen required for biochemical decomposition processes is called the biochemical oxygen demand (BOD).Measures the amount of oxygen consumed by microorganisms as they break down organic matterApproximately 33% of all BOD in streams results from agricultural activities.
9 21.2 (cont.)When the BOD is high, the dissolved oxygen content of the water may become too low to support the life in the water.US Environmental Protection AgencyWater pollution alert is when the dissolved oxygen content is less than 5mg/liter of water
10 21.2 (cont.) Example of high BOD from an accidental spill 3 zones: pollution zone, active decomposition zone, recovery zone
11 21.2 (cont.)All streams have some capability to degrade organic waste.Problems occur when the stream is overloaded with biochemical oxygen- demanding waste.This overpowers the stream’s natural cleansing function.
12 21. 9 Groundwater Pollution About half of US people depend on groundwaterCan be easily pollutedDifficult to recognize pollutants75% of the 175,000 known waste disposal sites in the US may be producing plumes of hazardous chemicals that are migrating into groundwater resources.
13 Principles of Groundwater Pollution: An Example 21.9 (cont.)Principles of Groundwater Pollution: An ExampleLeaking buried gasoline tanks caused much pollutionUnderground tanks now strictly regulatedMany thousands have been removedVapor extraction: removal and disposal of soil and treatment of water (expensive)Bioremediation: microorganisms consume gasoline (much less expensive)
14 21.9 (cont.)Leaking buried gasoline tanks led to important points about groundwater pollution:Some pollutants are lighter then water (float on groundwater)Some pollutants have multiple phases: liquid, vapor, and dissolvedSome pollutants are heavy than water (sink through groundwater)Water treatment depends on physical and chemical properties of pollutantPrevent pollutants from entering groundwater in the first place
15 21.9 (cont.)Groundwater pollution differs from surface water pollution.Groundwater kills aerobic types of microorganisms and is home for anaerobic varieties.Groundwater channels are small and variable, therefore dispersion and dilution of pollutants is limited.
16 21.9 (cont.) Long Island, New York Nassau County and Suffolk County (population of several million people) depend entirely on groundwaterTwo major problems: intrusion of salt water and shallow-aquifer contamination
17 21.9 (cont.) Saltwater intrusion Shallow-aquifer pollution Salty groundwater cannot migrate inland due to the large wedge of fresh water moving beneath the islandIntensive pumping has caused water levels to decline as much as 50 feet in some areasShallow-aquifer pollutionAssociated with urbanizationPollutants enter surface waters and then migrate downwardSources of pollution: urban runoff, household sewage, salt, industrial waste, and solid waste
18 21.10 Wastewater TreatmentWastewater treatment, or sewage treatment costs over $15 billion per year in the United States and the cost continues to increase.Conventional methods of wastewater treatment include septic tank disposal systems in rural areas and centralized wastewater treatment plants in cities.
19 21.10 continued… Septic Tank Disposal Systems No central sewage systems or wastewater treatment facilities are available in many rural areas.Basic parts of a septic-tank disposal systemSewer line from the house leads to an underground septic tank in yard.Tank is designed to separate solids from liquid, digest, and store organic matter through a period of detention, and allow the clarified liquid to discharge into the drain field from a system of piping through which the treated sewage seeps into the surrounding soil.It’s then treated by the natural processes of oxidation and filtering.
21 21.10 continued…Wastewater treatment methods are usually divided into 3 categories:Primary Treatment – Removal of large particles and organic materials from wastewater through screening. Removes 30% to 40% of the BOD by volume from the wastewater.Secondary Treatment – Use of biological processes to degrade wastewater in a treatment facility. The most common treatment is know as activated sludge.Advanced Water Treatment – Some additional pollutants can be removed by adding more steps of treatment. Advanced Water Treatment is used when it’s particularly important to maintain good water quality.
22 21.10 continued… Chlorine Treatment Frequently used to disinfect water as part of wastewater treatment.Chlorine Treatment is very effective in killing the pathogens that historically caused outbreaks of serious waterborne diseases.Recently discovered potential is that chlorine treatment produces minute quantities of chemical byproducts, some of which have been identified as potentially hazardous to humans and other animals.The degree of risks is controversial and is currently being debated.
23 21.11 The Wastewater Renovation and Conservation Cycle Wastewater renovation and conservation cycle: Practice of applying wastewater to the land.Steps:1. Return of treated wastewater to crops by irrigation system2. Natural purification (renovation) by slow leaking of the wastewater into the soil to eventually recharge the groundwater resource with clean water3. Treated water reused and pumped out of ground for municipal, industrial, institutional and agricultural purposesSewage is transported by sewers to treatment plant. Wastewater is chlorinated and pumped into a network that transports effluent to a series of spray irrigation rigs. Wastewater trickles down through soil and collected into a network of tile drains. Indirect advanced treatment uses natural, physical, and biological environment as filter.
24 Experimental technique Problems: Resource recovery: the production of resources, including methane gas as well as ornamental plants and flowers that have commercial value.Steps1. Wastewater run through filters that remove large objects2. Water undergoes anaerobic processing (produces methane gas)3. Nutrient-rich water flows over an incline surface with plantsPlants use nutrients and purify waterExperimental techniqueProblems:Huge investment in traditional wastewater treatmentsEconomic incentives to provide for new technologies are not sufficientThere are not sufficient amounts of people trained to design and operate new types of wastewater treatment plants
25 Wastewater and Wetlands Wetlands are very effective in treating water quality problemsMunicipal wastewater from primary or secondary treatment plants (pathogens, phosphorus, nitrate, suspended solids, metals)Stormwater runoff (metals, nitrate, pesticides, oils)Industrial wastewater (metals, acids, oils, solvents)Agricultural wastewater and runoff (nitrate, pesticides, suspended solids)Mining waters (metals, acidic water, sulfates)Groundwater seeping from landfills (metals, oils, pesticides)Wetland systems a lot less expensiveOver 25 year period, $40,000 savings is expectedLouisiana: coastal wetlandsWastewater filled with nitrogen and phosphorusWhen put into wetlands, increases production of wetland plants, which in return improves water qualityWhen plants die their organic material partially lets wetland loose, causing wetlands to grow verticallyWetlands becoming more and more popular as water quality standards are tightened, and cost is very important
26 Phoenix, Arizona: Constructed wetlands Wetlands can be created in arid regions as wellWetland treatment for agricultural waste is sited in residential community4.5 million gallons per dayIncoming water has lots of nitrate20 mg/lNaturally occurring bacteria reduce nitrate to below maximum contaminant level10 mg/lWater flows by pipe to recharge basinSeeps into ground for groundwater resource
27 21.12 Water Reuse Water reuse can be inadvertent, indirect, or direct. Inadvertent water reuse results when water is withdrawn, treated, used, treated, and returned to the environment, followed by further withdrawals and use.Very commonFact of life for millions of people who live along large rivers.
28 21.12 continued… Several risks are associated with inadvertent reuse: Inadequate treatment facilities may deliver contaminated or poor quality water to downstream users.Because the fate of all disease causing viruses during and after treatment is not completely known, the environmental health hazards of treated water remain uncertain.New potentially hazardous chemicals are introduced into the environment every year. Harmful chemicals are often difficult to detect in the water.
29 21.12 continued… Indirect water reuse Direct water reuse Planned endeavorTreated water eventually enters groundwater storage to be reused for agricultural and municipal purposes.Direct water reuseRefers to the use of treated wastewater that is piped directly from a treatment plant to the next user.Used in industry in most cases.Very little direct reuse of water is planned for human consumption due to perceived risks and negative cultural attitudes toward using treated wastewater.
30 21.13 Water Pollution and Environmental Law Environmental law: the branch of law dealing with conservation and use of natural resources and control of pollutionDone on federal, state, and local levelsMid 1990s, water pollution big controversy1994- congress attempted to rewrite major environmental lawsClean water act of 1977Congress wanted to give industry greater felxibilty in choosing how to comply with environmental regulationsIndustry interestes preferred proposed new regulations because more cost effectiveEnvironmentalists viewed this as a giant step backward in trying to clean up the earthPublics views were incorrectly read, most cared more about moneyCongress saw strong support for clean environement and thought people will pay for clean air and water
31 Failed regulationJuly 2000, president imposed new water pollution regulationsPurpose was to protect rivers and lakes from nonpoint sources to agricultural, industrial, and urban population sources.EPA would work with local communities and states to develop detailed plans to reduce pollution.Plan would take 15 years to implementBeen opposed for years by Congress, agricultural groups, utility industry, and U.S. Chamber of CommerceRequirements would be costly, spending billionsLocal and state governments better suited to implement own water pollution regulations