Lecture 18 Water quality

Water Resources: U.S. Withdrawal

Pollution Source terminology Point source = pollution comes from single, fixed, often large identifiable sources smoke stacks discharge drains tanker spills Non-point source = pollution comes from dispersed sources agricultural runoff street runoff

Types of Water Pollution Sediment logging, roadbuilding, erosion Oxygen-demanding wastes human waste, storm sewers, runoff from agriculture, grazing and logging, many others Nutrient enrichment = eutrophication N, P from fertilizers, detergents leads to increased growth in aquatic systems, ultimately more non-living organic matter

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.

Eutrophication Eutrophic – well-fed, high nutrient levels present in a lake or river Oligotrophic – poorly-fed, low nutrient levels Water bodies can be naturally eutrophic or oligotrophic, but can also be human-caused

Types of Water Pollution (con’t) Disease-causing organisms from untreated sewage, runoff from feed lots Toxic chemicals pesticides, fertilizers, industrial chemicals Heavy metals lead, mercury Acids (to discuss later) Elevated temperatures = Thermal Pollution water is used for cooling purposes, then heated water is returned to its original source any increase in temperature, even a few degrees, may significantly alter some aquatic ecosystems.

Groundwater Pollution Agricultural products Underground storage tanks Landfills Septic tanks Surface impoundments

Oil Spills Exxon Valdez released 42 million liters of oil in Prince William Sound, contaminating 1500 km of Alaska coastline in 1989 Deepwater Horizon oil spill in 2010 released 800 million liters (210 million gallons) in Gulf of Mexico Was the cleanup effective? Most marine oil pollution comes from non-point sources: runoff from streets improper disposal of used oil discharge of oil-contaminated ballast water from tankers

Water Quality ● Contamination of the water supply ● lead pollution ● radioactive wastes ● microorganisms in water ● other chemical contaminants

Water Quality: Human Contamination

● Reversing contamination ● easier if recharge rate is fast Water Quality ● Reversing contamination ● easier if recharge rate is fast ● usually costly and very slow ● decontamination after pumping ● in-ground water treatments