Principles of Environmental Engineering and Sustainability Lecture Nine: Water Resources and Water Pollution Department of Environmental Engineering

OUTLINE Water Water Cycle Watershed Water Resources Management Dams and Tapping Groundwater Water Quality Testing Sources and terminology BOD EUtriphication

Water Resources Water Earth’s surface is covered by 71% water Essential for life – can survive only a few days without water

Supply of Water Resources Small fraction (0.014%) is readily available for human use

Importance of Water Cooking Washing Use large amounts for: Agriculture Manufacturing Mining Energy production Waste disposal Use of freshwater is increasing

Properties of Water Composed of 2 Hydrogen and 1 oxygen Exists as solid, liquid or gas High heat capacity Polar One end has (+) charge, one end has (-) charge Forms Hydrogen bond between 2 water molecules H-bonds define water’s physical properties

Freshwater Terminology Surface water Precipitation that remains on the surface and does not seep into soil Runoff Movement of surface water to lakes, rivers, etc. Watershed (drainage basin) Land area that delivers water into a stream or river system Groundwater Freshwater under the earth’s surface stored in aquifers Aquifer Underground caverns and porous layers of sand, gravel and rock in which groundwater is stored

Evaporation and transpiration Water Cycle – continuously collected, purified, recycled and distributed Evaporation and transpiration Evaporation Stream Infiltration Water table Unconfined aquifer Confined aquifer Lake Well requiring a pump Flowing artesian well Runoff Precipitation Confined Recharge Area Aquifer Less permeable material such as clay Confirming permeable rock layer

Watershed A watershed describes the total area contributing drainage to a stream or river May be applied to many scales A large watershed is made up of many small watersheds

Chehalis Basin

Global Water Problems Amount of freshwater on planet CAN meet human needs BUT, it is unevenly distributed and some places lack stable runoff Problems: Climate Change Drinking Water Population Growth Sharing Water Resources Among Countries

Global Water Problems Water and Climate Change Drinking Water Problems Climate change affects the type and distribution of precipitation Potential issues: Reduced snowfall will impact water resources downstream Sea level rise will cause saltwater intrusion into drinking water supplies Drinking Water Problems Many developing countries have insufficient water to meet drinking and household needs Population Growth Increase in population means an increase in freshwater requirements Limits drinking water available Limits water available for agriculture (food)

Water Management Dams and Reservoirs Main Goal: Provide sustainable supply of high-quality water Requires humans to use resource carefully Dams and Reservoirs Water Diversion Projects Desalinization Dams and Reservoirs Benefits: Ensure year-round supply of water with regulated flow Generate electricity Provide recreational activities Disadvantages Alter the ecosystem Reduce sediment load

Using Dams and Reservoirs to Supply More Water Large losses of water through evaporation Flooded land destroys forests or cropland and displaces people Downstream flooding is reduced Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Can produce cheap electricity (hydropower) Migration and spawning of some fish are disrupted Provides water for year-round irrigation of cropland

Groundwater Year-round use No evaporation losses Often less expensive Potential Problems: Water table lowering – too much use Depletion – U.S. groundwater being withdrawn at 4X its replacement rate Saltwater intrusion – near coastal areas Chemical contamination Reduced stream flows

The Ogallala Aquifer The Ogallala Aquifer is an example of groundwater mining or depletion. Water-level change in the High Plains aquifer (the Ogallala aquifer) through 2007, 2005–06, and 2006–07: U. S. Geological Survey Scientific Investigations Report 2009–5019, 9 p., available at: http://pubs.usgs.gov/sir/2009/5019/. FIGURE 8.22 Water-level change in the High Plains aquifer through 2007. Source: McGuire, V. L., 2009. Water-level changes in the High Plains aquifer, predevelopment to 2007, 2005–06, and 2006–07: U. S. Geological Survey Scientific Investigations Report 2009–5019, 9 p., available at: http://pubs.usgs.gov/sir/2009/5019/.

Desalinization Water Conservation Removal of salt from ocean or brackish water Two methods: Distillation- salt water is evaporated, and water vapor is condensed into freshwater (salt left behind) Reverse Osmosis- involves forcing salt water through a membrane permeable to water, but not salt Very expensive Water Conservation Reducing Agricultural Water Waste Agriculture is very inefficient with water Microirrigation- irrigation that conserves waster by piping to crops through sealed systems Also called drip or trickle irrigation

Water Conservation Water Conservation Reducing Industrial Water Waste Stricter laws provide incentive to conserve water Recycling water within the plant Water scarcity (in addition to stricter pollution control requirements) will encourage further industrial recycling Potential to conserve water is huge! Water Conservation Reducing Municipal Water Waste Gray Water Can be used to flush toilets, wash car or water lawn Water saving household fixtures Government incentives

Conserving at Home Install water-saving shower heads and faucets Install low-flush toilets Fix leaky fixtures Purchase high efficiency appliances Modify personal habits Use the dishwasher instead of washing by hand

Testing Water Quality Water quality parameters often tested are: Dissolved oxygen (DO) Water temperature pH Total Ammonia Nitrogen Nitrite/Nitrate Alkalinity/Hardness Salinity Water test kit

How water quality values are expressed Parameter Value Dissolved oxygen mg/L O2 Water temperature C (Celsius) pH ------ Total ammonia nitrogen mg/L N Nitrite mg/L NO2- Nitrate mg/L NO3- Alkalinity/Hardness mg/L CaCO3 Salinity (TDS) g/L salt

Types of Water Pollution Any physical or chemical change in water that adversely affects the health of humans and other organisms Varies in magnitude by location Major water pollution issue globally Lack of disease-free water Eight categories Sewage, disease-causing agents, sediment pollution, inorganic plant and algal nutrients, organic compounds, inorganic chemicals, radioactive substances, and thermal pollution

Sewage The release of wastewater from drains or sewers Includes human wastes, soaps, and detergents Causes 2 serious environmental problems: Enrichment Fertilization of a body of water by high levels of plant and algal nutrients (nitrogen and phosphorus) Increase in Biological Oxygen Demand (BOD) Amount of oxygen needed by microorganisms to decompose biological wastes As BOD increases Dissolve Oxygen (DO) decreases

Sewage- Eutrophication Oligotrophic Unenriched, clear water that supports small populations of aquatic organisms

Sewage- Eutrophication Slow-flowing stream, lake or estuary enriched by inorganic plant and algal nutrients such as phosphorus Often due to fertilizer or sewage runoff

Sediment Pollution Excessive amounts of suspended soil particles Originates from erosion of agricultural lands, forest soils exposed by logging, degraded stream banks, overgrazed rangelands, strip mines, and construction Problems Limits light penetration Covers aquatic animals and plants Brings insoluble toxins into waterways

Inorganic Plant and Algal Nutrients Chemicals such as nitrogen and phosphorus that stimulate the growth of plants and algae Harmful in large concentrations Sources: Human and animal wastes, plant residues, atmospheric deposition, and fertilizer runoff Causes: Enrichment, bad odors, and a high BOD

Organic Compounds Chemicals that contain carbon atoms Natural examples: sugars, amino acids, and oils Human-made examples: pesticides, solvents, industrial chemicals, and plastics

Inorganic Chemicals Contaminants that contain elements other than carbon Examples: acids, salts, and heavy metals Do not degrade easily Lead Found in old paint, industrial pollutants, leaded gasoline Mercury Mercury bioaccumulates in the muscles of top predators of the open ocean

Radioactive Substances Contain atoms of unstable isotopes that spontaneously emit radiation Sources Mining Processing radioactive materials Nuclear power plants Natural sources Thermal Pollution Occurs when heated water produced during industrial processes is released into waterways Organisms affected Temperature affects reproductive cycles, digestion rates, and respiration rates Warm water holds less DO than cold water

Water Quality Today Two Types of Water Pollution -Point Source Pollution water pollution that can be traced to a specific origin Discharge via pipes, sewage, and ditches -Non-point Source Pollution Pollutants that enter bodies of water over large areas rather than being concentrated at a single point of entry Diffuse, but its cumulative effect is very large Ex: runoff from agricultural fields or parking lots

Municipal Water Pollution

Water Pollution from Agriculture Industrial Wastes in Water Different industries generate different pollutants Food processing plants- high BOD Paper mills- High BOD and toxic compounds Many industries recover toxins before they go into the waste stream Water Pollution from Agriculture Agriculture is leading source of water pollution in US Animal wastes and plants residues have high BOD Chemical pesticides can leach into groundwater Almost all streams and rivers are polluted with agricultural pesticides

Biological Oxygen Demand (BOD) As micro-organisms decompose (through respiration) organic matter, they use up all the available oxygen. Biological Oxygen Demand (BOD) Amount of oxygen required to decay a certain amount of organic matter. If too much organic matter is added, the available oxygen supplies will be used up. It is most commonly expressed in milligrams of oxygen consumed per liter of sample during 5 days (BOD5) of incubation at 20°C and is often used as a robust surrogate of the degree of organic pollution of water

DO Sag Curve

Eutrophication Eutrophic – well-fed, high nutrient (N and P) levels present in a lake or river Oligotrophic – poorly-fed, low nutrient levels Eutrophication arises from the oversupply of nutrients, which leads to over growth of plants and algae. After such organisms die, the bacterial degradation of their biomass consumes the oxygen in the water, hence increases BOD

Groundwater Pollution Agricultural products Underground storage tanks Landfills Septic tanks others

End of Lecture Four