urban water quality. water quality n pollution - any departure from “purity” –what is...

Urban Water Quality Urban Water Quality

Water QualityWater Quality

PollutionPollution - any departure from - any departure from “purity” “purity”

– What is “purity”?What is “purity”?– Characteristics of waterCharacteristics of water– Is drinking water “pure”?Is drinking water “pure”?


Pure WaterPure Water - - in the context of in the context of water pollution, a state of water pollution, a state of water in which no substance is water in which no substance is present in sufficient present in sufficient concentration to prevent the concentration to prevent the water from being used for the water from being used for the purposes thought of as purposes thought of as “normal”“normal”


““Normal” uses of water?Normal” uses of water?– RecreationRecreation– Public water supplyPublic water supply– Aquatic habitatsAquatic habitats– AgricultureAgriculture– IndustryIndustry


Water PollutantWater Pollutant - - any any substance that prevents the substance that prevents the “normal” use of water“normal” use of water

– ““Normal” implies a value Normal” implies a value judgement and depends on the judgement and depends on the particular useparticular use


Water Quality - Water Quality - the physical the physical and chemical characteristics of and chemical characteristics of waterwater

– Unrelated to the particular use in Unrelated to the particular use in that no value judgement is that no value judgement is assignedassigned

Water Quality - Water Quality - Classification of Water Classification of Water

PollutantsPollutants

Signs of water pollution?Signs of water pollution?– Bad tasting drinking waterBad tasting drinking water– Masses of aquatic weedsMasses of aquatic weeds– Disgusting odorsDisgusting odors– Decreasing fish populationsDecreasing fish populations– Floating oil and raw sewageFloating oil and raw sewage



Classification of water pollutantsClassification of water pollutants– Oxygen-demanding wastes (ODW)Oxygen-demanding wastes (ODW)– Pathogenic organismsPathogenic organisms– Plant nutrientsPlant nutrients– Synthetic organic compounds (SOCs)Synthetic organic compounds (SOCs)– OilOil– SedimentsSediments– HeatHeat



Oxygen-Demanding Wastes Oxygen-Demanding Wastes (ODW)(ODW)– Dissolved OxygenDissolved Oxygen

Aquatic organisms require oxygen Aquatic organisms require oxygen for for cellular respirationcellular respiration

Dissolved oxygen (DO) is often a Dissolved oxygen (DO) is often a limiting factor for survival of aquatic limiting factor for survival of aquatic organismsorganisms



ODWODW– Dissolved OxygenDissolved Oxygen

Factors that control DO levels:Factors that control DO levels:– Water temperatureWater temperature– Elevation above sea levelElevation above sea level– Degree of turbulence Degree of turbulence – Stream channel geometryStream channel geometry– Density of aquatic plantsDensity of aquatic plants




Water TemperatureWater Temperature– DO decreases with increasing water DO decreases with increasing water

temperaturetemperature

Elevation Above Sea LevelElevation Above Sea Level– DO decreases with increasing elevationDO decreases with increasing elevation




TurbulenceTurbulence– DO increases with increasing turbulence DO increases with increasing turbulence

caused by waterfalls, rapids, etccaused by waterfalls, rapids, etc

Stream Channel GeometryStream Channel Geometry– Wide,shallow channel has greater DO Wide,shallow channel has greater DO

than narrow, deep channelthan narrow, deep channel



ODWODW– Organic substances that cause Organic substances that cause

depletion or removal of DOdepletion or removal of DO– Food source for aquatic bacteriaFood source for aquatic bacteria– DO is removed as bacteria feed DO is removed as bacteria feed

on ODWon ODW



ODWODW– Sources of ODWSources of ODW

SewageSewage Paper millsPaper mills Food processingFood processing SlaughterhousesSlaughterhouses



ODWODW– Biochemical Oxygen DemandBiochemical Oxygen Demand - -

the amount of dissolved oxygen the amount of dissolved oxygen that bacteria require to that bacteria require to decompose ODW in a given decompose ODW in a given volume of watervolume of water



ODWODW– Biochemical Oxygen Demand Biochemical Oxygen Demand

(BOD)(BOD) MeasurementMeasurement

– 5-day test5-day test– Incubation at 20 degrees CIncubation at 20 degrees C– BOD = DO (day 0) - DO (day 5)BOD = DO (day 0) - DO (day 5)



ODWODW– Biochemical Oxygen Demand Biochemical Oxygen Demand

(BOD)(BOD) Characteristic BOD LevelsCharacteristic BOD Levels

– Untreated SewageUntreated Sewage 100-400 mg/L100-400 mg/L– FeedlotsFeedlots 100-10,000 100-10,000

mg/Lmg/L– Pure WaterPure Water 1 mg/L1 mg/L



ODW ODW – Environmental Impacts of low DOEnvironmental Impacts of low DO

Disappearance of plant and animal lifeDisappearance of plant and animal life Shift from aerobic to anaerobic conditionsShift from aerobic to anaerobic conditions “ “Oxygen Sag”Oxygen Sag”



Pathogenic Organisms Pathogenic Organisms – Types of pathogens:Types of pathogens:

VirusesViruses BacteriaBacteria Protozoa (unicellular)Protozoa (unicellular) Parasitic wormsParasitic worms



Pathogenic Organisms Pathogenic Organisms – Diseases caused by water-borne Diseases caused by water-borne

pathogens:pathogens: Amoebic DysenteryAmoebic Dysentery Bacterial DysenteryBacterial Dysentery Typhoid feverTyphoid fever CholeraCholera HepatitisHepatitis SchistosomiasisSchistosomiasis


PollutantsPollutants Pathogenic Organisms Pathogenic Organisms

– Sources of body wastes:Sources of body wastes: Malfunctioning septic tanks, cesspoolsMalfunctioning septic tanks, cesspools Untreated sewageUntreated sewage Waste discharges from boats and shipsWaste discharges from boats and ships Meat processing plantsMeat processing plants Swimmers and hikersSwimmers and hikers


PollutantsPollutants Pathogenic Organisms Pathogenic Organisms

– Testing for pathogenic organismsTesting for pathogenic organisms Coliform Coliform bacteriabacteria

– Live in large intestines of warm-blooded Live in large intestines of warm-blooded animals (even Uncle Monty) and absorb animals (even Uncle Monty) and absorb nutrients from their surroundingsnutrients from their surroundings


PollutantsPollutants Plant Nutrients Plant Nutrients

– Plants require 15-20 nutrients for Plants require 15-20 nutrients for growth:growth:

CarbonCarbon NitrogenNitrogen PhosphorusPhosphorus PotassiumPotassium SulfurSulfur



– Nitrogen and phosphorus are Nitrogen and phosphorus are limiting nutrients for plant growthlimiting nutrients for plant growth

– EutrophicationEutrophication - - the natural the natural enrichment of water with plant enrichment of water with plant nutrientsnutrients



– Eutrophic EcosystemEutrophic Ecosystem - - ecosystems that ecosystems that are relatively high in fertility and are relatively high in fertility and biological productivitybiological productivity

– Oligotrophic EcosystemOligotrophic Ecosystem - - ecosystems ecosystems that are relatively low in fertility and that are relatively low in fertility and biological productivitybiological productivity



– Cultural EutrophicationCultural Eutrophication - - accelerated accelerated eutrophication caused by human eutrophication caused by human activitiesactivities



– Signs and effects of cultural Signs and effects of cultural eutrophication:eutrophication:

Dense growth of rooted plantsDense growth of rooted plants Increased growth of blue-green algaeIncreased growth of blue-green algae Increased populations of trash fishIncreased populations of trash fish Foamy layers on surface of waterFoamy layers on surface of water



– Sources of nutrients responsible for Sources of nutrients responsible for cultural cultural eutrophication:cultural cultural eutrophication:

Domestic SewageDomestic Sewage Urban RunoffUrban Runoff Industrial SourcesIndustrial Sources Agricultural SourcesAgricultural Sources



– Management practices to minimize Management practices to minimize cultural eutrophication:cultural eutrophication:

Two types of water pollution sources in a Two types of water pollution sources in a watershed:watershed:

– Point SourcePoint Source– Non-Point Source PollutionNon-Point Source Pollution



– Management practices to minimize Management practices to minimize cultural eutrophication:cultural eutrophication:

Nutrient managementNutrient management– Determine point and nonpoint sources of Determine point and nonpoint sources of

nutrients and the size of each sourcenutrients and the size of each source– On-site treatment of nutrientsOn-site treatment of nutrients– Rate and timing of nutrient applicationRate and timing of nutrient application


PollutantsPollutants Synthetic Organic Compounds Synthetic Organic Compounds

(SOCs) (SOCs) – Examples:Examples:

FuelsFuels PlasticsPlastics PesticidesPesticides FertilizersFertilizers Food additivesFood additives PharmaceuticalsPharmaceuticals



(SOCs) (SOCs) – PesticidesPesticides

Environmental ImpactsEnvironmental Impacts– BioaccumulationBioaccumulation– Interference with reproductionInterference with reproduction– Birth DefectsBirth Defects– Reduced biodiversity and productivityReduced biodiversity and productivity– Tumors and convulsions Tumors and convulsions



(SOCs) (SOCs) – Oil (Hydrocarbons)Oil (Hydrocarbons)

SourcesSources– Impervious surfacesImpervious surfaces– Oil leaksOil leaks– Auto emissionsAuto emissions– Improper disposal of waste oilImproper disposal of waste oil



(SOCs) (SOCs) – Oil (Hydrocarbons)Oil (Hydrocarbons)

Environmental ImpactsEnvironmental Impacts– Degrade appearance of water surfacesDegrade appearance of water surfaces– Limit air exchange between atmosphere and Limit air exchange between atmosphere and

waterwater– Lowered DO levelsLowered DO levels– Increased BODIncreased BOD– Impair habitatImpair habitat– Reduced biodiversityReduced biodiversity– DeathDeath


PollutantsPollutants Sediment Sediment

– Most common of the nonpoint source Most common of the nonpoint source pollutantspollutants

– Sediment load in waterways Sediment load in waterways increases with increasing increases with increasing urbanization and landuse intensityurbanization and landuse intensity


PollutantsPollutants Sediment Sediment

– Factors controlling sediment loss:Factors controlling sediment loss: Chemical and physical characteristics of Chemical and physical characteristics of

the soilthe soil Slope steepnessSlope steepness Type and density of vegetation coverType and density of vegetation cover RainfallRainfall


PollutantsPollutants SedimentSediment

– Environmental Impacts Environmental Impacts Filling of channels and harbors with Filling of channels and harbors with

sedimentsediment Decreased biodiversity of aquatic Decreased biodiversity of aquatic

animalsanimals Increased turbidityIncreased turbidity


PollutantsPollutants Heat (Thermal Pollution)Heat (Thermal Pollution)

– SourcesSources Cooling water in industrial processesCooling water in industrial processes Natural heating by sunlightNatural heating by sunlight

– Environmental ImpactsEnvironmental Impacts Decreased DODecreased DO Increased rates of chemical reactionsIncreased rates of chemical reactions False temperature cues to aquatic lifeFalse temperature cues to aquatic life Death to aquatic organismsDeath to aquatic organisms



– Environmental ImpactsEnvironmental Impacts Decreased DODecreased DO

– ““Thermal Blanket”Thermal Blanket” Warm water is less dense than cold waterWarm water is less dense than cold water Warm layer forms “blanket” over cooler, more Warm layer forms “blanket” over cooler, more

dense waterdense water Warm water cannot dissolve as much Warm water cannot dissolve as much

atmospheric oxygen as cooler wateratmospheric oxygen as cooler water Rate of exchange of oxygen between warm Rate of exchange of oxygen between warm

water and cooler water is very slowwater and cooler water is very slow Cooler water is “atmospherically Cooler water is “atmospherically

unreplenished”unreplenished” Death to aquatic organismsDeath to aquatic organisms



– Environmental ImpactsEnvironmental Impacts Increased rates of chemical reactionsIncreased rates of chemical reactions

– The rate of any chemical reactions The rate of any chemical reactions approximately doubles with every 10C approximately doubles with every 10C increase in temperatureincrease in temperature

– In thermally polluted waters, fish require In thermally polluted waters, fish require more DO because of increased respiration more DO because of increased respiration rates rates

– Increased respiration occurs in response to Increased respiration occurs in response to higher water temperaturehigher water temperature



– Environmental ImpactsEnvironmental Impacts False temperature cues given to aquatic False temperature cues given to aquatic

lifelife– Fish spawn and migrate in response to Fish spawn and migrate in response to

temperature cuestemperature cues– Optimum temperature range for fish speciesOptimum temperature range for fish species

urban water quality. water quality n pollution - any departure from “purity” –what is...

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