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Chapter 9 : Water Chapter 19 : Water Pollution Chapter 10 : Ocean. Important properties of water o Changes temperature very slowly due to its high specific heat capacity - Protects living things from temperature fluctuations - Moderates the earth’s climate
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Important properties of water o Changes temperature very slowly due to its high specific heat capacity - Protects living things from temperature fluctuations - Moderates the earth’s climate - Makes water a coolant for car engines, & heat producing industrial processes o High heat of vaporization - Works in distributing heat throughout the world - Evaporative cooling of organisms o Liquid water can dissolve a variety of compounds - Can carry dissolved nutrients into living tissues - Flush waste products from organisms - Serve as an all-purpose cleanser - Help remove & dilute many wastes o Filters out wavelengths of UV radiation that would harm some aquatic organisms o High surface tension & high wetting ability - Capillary action allows water to move through a plant o Water expands upon freezing - Eliminates bodies of water from freezing solid - Break up streets & fracture rocks (forming soils)
Freshwater Ecosystems : Just 2.4% of all freshwater Types of Water Resources o 97.6% is oceanic and too salty for consumption o 2.4% is fresh water and locked in polar icecaps o 0.312% exists as groundwater, lakes, streams, & water vapor
Hydrologic Cycle o Continuous evaporation, transpiration, precipitation, & surface runoff o Driven by solar energy Use of Water Supply o Only 30% of the global runoff can be used by humans o Expected to double in the next 20 years o Water availability does not match up with population distribution - Asia : 61% of world’s population & 36% of reliable runoff - South America : 26% of reliable runoff & 8% of world’s population o Uses of freshwater - 70% of all water is used to irrigate 17% of world’s croplands - 20% is used by industry & 10% by cities and residences
Freshwater Shortages : o Dry climate o Drought o Drying of soil because of deforestations & overgrazing o Low per capita availability of water caused by increasing population - 500 million people in 34 nations are water stressed Increasing freshwater supplies : o Build dams & reservoirs to store runoff o Bring in surface water from other sources o Withdraw groundwater o Convert salt water to fresh water (desalination) o Improve the efficiency of water use * Other means of increasing water supplies o Seeding clouds with silver iodide that act as condensation nuclei o Towing massive icebergs to arid coastal areas
Groundwater—precipitation that infiltrates the ground and percolates downward through pores, fractures, crevices, & spaces o Bedrock : supports the soil & rocks and cannot be penetrated o Zone of saturation : cracks above bedrock that fill with water o Water table : located at the top of the zone of saturation falling in dry weather and rising in wet weather o Aquifers : porous water-saturated layers of sand, gravel, or bedrock through which groundwater flows o Recharge area : any area of land through which water passes downward into aquifer o Natural recharge : replenishing of an aquifer by precipitation - Groundwater moves from recharge area through an aquifer and out to a discharge area (well, spring, lake, stream, ocean) - Movement is quite slow (1 m/yr)
Groundwater o Can be removed as needed year-round o Is not lost by evaporation o Usually is less expensive to develop than surface water systems o Aquifers provide drinking water for ¼ of world’s population . Problems associated with using groundwater o Water table lowering o Aquifer depletion o Aquifer subsidence (sinking of land when groundwater is withdrawn) o Intrusion of salt water into aquifers o Drawing of chemical contamination in groundwater through wells o Reduced stream flow
Water pollution : defined as "the presence of a substance in the environment that because of its chemical composition or quantity prevents the functioning of natural processes and produces undesirable environmental and (human) health effects” 수질환경보전법 ◦ 수질오염물질이라 함은 수질오염의 요인이 되는 물질로서 환경부령으로 정하는 것을 말하며, ◦ 이중 특히 사람의 건강, 재산이나 동․식물의 생육에 직접 또는 간접으로 위해를 줄 우려가 있는 수질오염물질로서 환경부령으로 정하는 것을 특정수질유해물질이라 한다. ◦ 하천 및 호소의 수질환경기준 오․폐수의 배출허용기준(폐수배출허용기준.hwp) 오․폐수의 방류수수질기준 지하수의 수질기준 수질오염공정시험방법
수질오염물질 목록 특정수질유해물질 목록
Categories of Water Pollutants • Biodegradable • Rapidly degradable (non-persistent) • Slowly degradable (persistent) • Nonbiodegradable Non-pont-source pollutants:are diffused across a broad area Point-source pollutants: direct discharges to a single point − dischargesfrom sewage treatment plants, injection wells, and some industrial sources Water Pollutants : - Pathogens - Organic wastes - Chemical pollutants - Sediments - Nutrients
Pathogens : - Examples include bacteria, viruses, protozoa, & parasitic worms - Major human sources : human & animal wastes - Effects : diseases (Typhoid fever, Cholera, Dysentary, Giardiasis, Hepatitis) - Good indicator of water quality in terms of infectious agents is the number of colonies of coliform bacteria present in a 100-mL sample of water - In developing countries : 80% of diseases in developing countries originate with contaminated drinking water Disinfection on Typhoid Deaths
Indicator Organisms • Indicators of fecal contamination • Used to characterize wastewater in/out of treatment process, and to monitor water safety • Total coliform, fecal coliform, entercocci • •Raw Wastewater • – 106 - 1010 MPN TC • – 103 - 108 MPN FC • • AB411 (Beach stnd) • – 1000 MPN TC • – 400 MPN FC • – 104 MPN entercoccus
Organic wastes : Lo L=L0e-kt - Examples include decomposition of animal & plant matter by aerobic bacteria - Major human sources : sewage, animal feed lots, paper mills - Effects : depletion of dissolved oxygen leading to death of aquatic organisms - Biological Oxygen Demand (BOD) : amount of dissolved oxygen needed by aerobic decomposers to break down the organic matter in a certain volume of water in a 5-day incubation period at 20oC Biochemical Oxygen Demand (BOD or BOD5)
Biochemical Oxygen Demand: measurement • 5 days a 20oC • 300 mL glass BOD bottles • two D.O.(Dissolved Oxygen) readings: initial and after 5 days’ incubation in dark at 20oC • BOD = D.O.Day 0 - D.O.5days • very clean waters = BOD5 of 1.0 mg/L(ppm) • sewage level = BOD5 greater than 10 mg/L
Total BOD Nitrogenous BOD Carbonaceous BOD BOD (mg/mL) Ultimate BOD BOD5 Time (days) Carbonaceous and Nitrogenous BOD
Dissolved oxygen (DO) : the amount of oxygen gas dissolved in water • The higher the temperature the less oxygen dissolves in water because heat increases molecular motion • Increased salinity also decreases DO because salts compete fore hydrogen bonding sites in water • DO saturationis the maximum concentration of oxygen gas that typically dissolves in an aquatic system and depends mainly on temperature and salinity • . 9 to 14 mg Do/L in freshwater • . 7 to 11 mg DO/L in marine waters • Do is important because most aquatic plants and animals require oxygen for aerobic respiration • Most fish require at least 5 mg DO/L to survive (salmon 6 to 8 mg DO/L) • Anoxic waters have no dissolved oxygen and cannot support plant and animal life, which can lead to fish kills.
Ultimate BOD : − The total amount of oxygen required to “stabilize” all biodegradable organic compounds is the UBOD or BODL − Amount expressed in mg/L of oxygen − Normal sewage levels = 250 mg/L (ppm : parts per million) Chemical Oxygen Demand (COD) : −Another way (faster) of determining the oxygen demand by using strong oxidizer dichromate ion Cr2O7- Total Organic Carbon (TOC) : • Sample is burned in a combustion tube, and amount of carbon dioxide produced is measured
Solids Defined by residue remaining following test – TS: Total Solids left after evaporating at 103° C – TVS: Total Volatile Solids that combust at 500° C – TFS: Total Fixed Solids that remains after combustion – TSS: Total Suspended Solids - dry (103° C) solids retained on filter (2 μm) – VSS: Volatile Suspended Solids - combustible TSS – FSS: Fixed Suspended Solids - noncombustible TSS – TDS: Total Dissolved Solids - dry solids that pass through filter – VDS: VolatileDissolved Solids - combustible TDS –FDS: FixedDissolved Solids - noncombustible TDS – Settleable solids: what settles out over a set time period
Chemical pollutants : 1. Inorganic chemicals - Examples : acids, toxic metals (Pb, As, Se), & salts (NaCl, Fl-) - Major human sources:surface runoff, industrial effluents, household cleansers - Effects : damage human systems (cancers), harm aquatic life, lower crop yields, accelerate corrosion, make water non-potable 2. Organic chemicals - Examples : gasoline, oil, plastics, pesticides, detergents - Major human sources : industrial effluents, household cleansers, surface runoff from farms & yards - Effects : threaten human health & harm wildlife Sediments : - Examples : soil & silt - Major human sources : land erosion - Harmful effects : reduce photosynthesis, disrupt aquatic food webs, destroy spawning grounds of benthic species, clog harbors & lakes
Nutrients : • Organic wastes(N,P,C…) provide nutrients for phytoplankton and algal blooms that also decrease oxygen (cultural eutrophication)
Eutrophication • Eutrophicationis the excessive nutrient loadings that result in excessive growth of algae and weeds that leads to the loss of water clarity (turbidity), low dissolved oxygen (DO), and changes in fish and wildlife. • Natural eutrophicationis slow aging of surface waters, especially in lakes. • It results from the gradual addition of soil and nutrient runoff from undisturbed watersheds. • No rapid or dramatic changes in water quality, fish populations, or aquatic wildlife occurs • Cultural eutrophicationis rapid aging of surface waters usually resulting from human, agricultural, or cultural activities. • It often leads to turbidity (loss of clarity), excessive growth of algae and weeds, and changes in fish and wildlife
Eutrophication Leads to a potential algal bloom - Decreases light penetration - Decreases DO levels due to the action of decomposers - Disrupts nitrogen & phosphorus cycles Methods to control eutrophication - Planting vegetation along streambeds to slow erosion - Controlling application & timing of fertilizer - Controlling runoff from feedlots, golf courses, & fields - Use of biological control agents such as denitrification