Urban Water Quality

Water Quality n Pollution - any departure from “purity” –What is “purity”? –Characteristics of water –Is drinking water “pure”?

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

Water Quality n “Normal” uses of water? –Recreation –Public water supply –Aquatic habitats –Agriculture –Industry

Water Quality n Water Pollutant - any substance that prevents the “normal” use of water –“Normal” implies a value judgement and depends on the particular use

Water Quality n Water Quality - the physical and chemical characteristics of water –Unrelated to the particular use in that no value judgement is assigned

Water Quality - Classification of Water Pollutants n Signs of water pollution? –Bad tasting drinking water –Masses of aquatic weeds –Disgusting odors –Decreasing fish populations –Floating oil and raw sewage

Water Quality - Classification of Water Pollutants n Classification of water pollutants –Oxygen-demanding wastes (ODW) –Pathogenic organisms –Plant nutrients –Synthetic organic compounds (SOCs) –Oil –Sediments –Heat

Water Quality - Classification of Water Pollutants n Oxygen-Demanding Wastes (ODW) –Dissolved Oxygen n Aquatic organisms require oxygen for cellular respiration n Dissolved oxygen (DO) is often a limiting factor for survival of aquatic organisms

Water Quality - Classification of Water Pollutants n ODW –Dissolved Oxygen n Factors that control DO levels: –Water temperature –Elevation above sea level –Degree of turbulence –Stream channel geometry –Density of aquatic plants

Water Quality - Classification of Water Pollutants n ODW –Dissolved Oxygen n Water Temperature –DO decreases with increasing water temperature n Elevation Above Sea Level –DO decreases with increasing elevation

Water Quality - Classification of Water Pollutants n ODW –Dissolved Oxygen n Turbulence –DO increases with increasing turbulence caused by waterfalls, rapids, etc n Stream Channel Geometry –Wide,shallow channel has greater DO than narrow, deep channel

Water Quality - Classification of Water Pollutants n ODW –Organic substances that cause depletion or removal of DO –Food source for aquatic bacteria –DO is removed as bacteria feed on ODW

Water Quality - Classification of Water Pollutants n ODW –Sources of ODW n Sewage n Paper mills n Food processing n Slaughterhouses

Water Quality - Classification of Water Pollutants n ODW –Biochemical Oxygen Demand - the amount of dissolved oxygen that bacteria require to decompose ODW in a given volume of water

Water Quality - Classification of Water Pollutants n ODW –Biochemical Oxygen Demand (BOD) n Measurement –5-day test –Incubation at 20 degrees C –BOD = DO (day 0) - DO (day 5)

Water Quality - Classification of Water Pollutants n ODW –Biochemical Oxygen Demand (BOD) n Characteristic BOD Levels –Untreated Sewage mg/L –Feedlots100-10,000 mg/L –Pure Water1 mg/L

Water Quality - Classification of Water Pollutants n ODW –Environmental Impacts of low DO n Disappearance of plant and animal life n Shift from aerobic to anaerobic conditions n “Oxygen Sag”

Water Quality - Classification of Water Pollutants n Pathogenic Organisms –Types of pathogens: n Viruses n Bacteria n Protozoa (unicellular) n Parasitic worms

Water Quality - Classification of Water Pollutants n Pathogenic Organisms –Diseases caused by water-borne pathogens: n Amoebic Dysentery n Bacterial Dysentery n Typhoid fever n Cholera n Hepatitis n Schistosomiasis

Water Quality - Classification of Water Pollutants n Pathogenic Organisms –Sources of body wastes: n Malfunctioning septic tanks, cesspools n Untreated sewage n Waste discharges from boats and ships n Meat processing plants n Swimmers and hikers

Water Quality - Classification of Water Pollutants n Pathogenic Organisms –Testing for pathogenic organisms n Coliform bacteria –Live in large intestines of warm-blooded animals (even Uncle Monty) and absorb nutrients from their surroundings

Water Quality - Classification of Water Pollutants n Plant Nutrients –Plants require nutrients for growth: n Carbon n Nitrogen n Phosphorus n Potassium n Sulfur

Water Quality - Classification of Water Pollutants n Plant Nutrients –Nitrogen and phosphorus are limiting nutrients for plant growth –Eutrophication - the natural enrichment of water with plant nutrients

Water Quality - Classification of Water Pollutants n Plant Nutrients –Eutrophic Ecosystem - ecosystems that are relatively high in fertility and biological productivity –Oligotrophic Ecosystem - ecosystems that are relatively low in fertility and biological productivity

Water Quality - Classification of Water Pollutants n Plant Nutrients –Cultural Eutrophication - accelerated eutrophication caused by human activities

Water Quality - Classification of Water Pollutants n Plant Nutrients –Signs and effects of cultural eutrophication: n Dense growth of rooted plants n Increased growth of blue-green algae n Increased populations of trash fish n Foamy layers on surface of water

Water Quality - Classification of Water Pollutants n Plant Nutrients –Sources of nutrients responsible for cultural cultural eutrophication: n Domestic Sewage n Urban Runoff n Industrial Sources n Agricultural Sources

Water Quality - Classification of Water Pollutants n Plant Nutrients –Management practices to minimize cultural eutrophication: n Two types of water pollution sources in a watershed: –Point Source –Non-Point Source Pollution

Water Quality - Classification of Water Pollutants n Plant Nutrients –Management practices to minimize cultural eutrophication: n Nutrient management –Determine point and nonpoint sources of nutrients and the size of each source –On-site treatment of nutrients –Rate and timing of nutrient application

Water Quality - Classification of Water Pollutants n Synthetic Organic Compounds (SOCs) –Examples: n Fuels n Plastics n Pesticides n Fertilizers n Food additives n Pharmaceuticals

Water Quality - Classification of Water Pollutants n Synthetic Organic Compounds (SOCs) –Pesticides n Environmental Impacts –Bioaccumulation –Interference with reproduction –Birth Defects –Reduced biodiversity and productivity –Tumors and convulsions

Water Quality - Classification of Water Pollutants n Synthetic Organic Compounds (SOCs) –Oil (Hydrocarbons) n Sources –Impervious surfaces –Oil leaks –Auto emissions –Improper disposal of waste oil

Water Quality - Classification of Water Pollutants n Synthetic Organic Compounds (SOCs) –Oil (Hydrocarbons) n Environmental Impacts –Degrade appearance of water surfaces –Limit air exchange between atmosphere and water –Lowered DO levels –Increased BOD –Impair habitat –Reduced biodiversity –Death

Water Quality - Classification of Water Pollutants n Sediment –Most common of the nonpoint source pollutants –Sediment load in waterways increases with increasing urbanization and landuse intensity

Water Quality - Classification of Water Pollutants n Sediment –Factors controlling sediment loss: n Chemical and physical characteristics of the soil n Slope steepness n Type and density of vegetation cover n Rainfall

Water Quality - Classification of Water Pollutants n Sediment –Environmental Impacts n Filling of channels and harbors with sediment n Decreased biodiversity of aquatic animals n Increased turbidity

Water Quality - Classification of Water Pollutants n Heat (Thermal Pollution) –Sources n Cooling water in industrial processes n Natural heating by sunlight –Environmental Impacts n Decreased DO n Increased rates of chemical reactions n False temperature cues to aquatic life n Death to aquatic organisms

Water Quality - Classification of Water Pollutants n Heat (Thermal Pollution) –Environmental Impacts n Decreased DO –“Thermal Blanket” n Warm water is less dense than cold water n Warm layer forms “blanket” over cooler, more dense water n Warm water cannot dissolve as much atmospheric oxygen as cooler water n Rate of exchange of oxygen between warm water and cooler water is very slow n Cooler water is “atmospherically unreplenished” n Death to aquatic organisms

Water Quality - Classification of Water Pollutants n Heat (Thermal Pollution) –Environmental Impacts n Increased rates of chemical reactions –The rate of any chemical reactions approximately doubles with every 10C increase in temperature –In thermally polluted waters, fish require more DO because of increased respiration rates –Increased respiration occurs in response to higher water temperature

Water Quality - Classification of Water Pollutants n Heat (Thermal Pollution) –Environmental Impacts n False temperature cues given to aquatic life –Fish spawn and migrate in response to temperature cues –Optimum temperature range for fish species