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Water and Soil Pollution Objectives w To identify main types, sources and effects of water pollutants w To understand the relationship between water and soil pollution w To review water pollution avoidance and mitigation measures Three “Media” w Air w Water w Ground w Important to understand interactions w Important to identify tradeoffs Types of Water Pollution w Sewage w Infectious agents w Sedimentation w Organic compounds w Inorganic compounds (minerals) w Radioactive isotopes w Thermal pollution Water Pollution Interactions w Warm water holds less O2 w BOD n n Requires O2 Contains and promotes disease Domestic Sewage w Hazardous materials w BOD (Biochemical oxygen demand) w Disease (especially fecal coliform) n Cholera in London w Dissolved solids (minerals) w Suspended solids w Oil and Grease BOD w Biochemical oxygen demand w Fecal matter, food production w Carbon, hydrogen and oxygen w Requires O2 to decompose w Excess BOD exhausts available O2 Agriculture w Mostly “nonpoint” sources w Sediment (erosion) w Persistent pesticides w BOD from fertilizers and wastes w Nutrients from fertilizers Industry w Mostly “point” sources w Oil and grease, BOD (oil refineries) w BOD, dioxin (bleach paper mills) w “Specialty” effluents w BOD, coliform (hog farms) Mining w Arsenic (Nevada problem) w Can contaminate groundwater or surface water w Copper w Uranium tailings w Acidity Las Vegas Wash w All Las Vegas and Henderson treated sewage (point sources) w Storm runoff (non-point sources) w Extremely high periodic storm runoff w Las Vegas Bay: swimming w Water intake: chlorinated Map of LV Wash Eutrophication w Oligotrophic lakes n n Low levels of minerals, low BOD Slow-moving, shallow lakes undergo eutrophication w Artificial eutrophication speeds this process n n Dissolved O2 drops Species change Wastewater treatment w Three stages w Primary treatment w Secondary treatment w Tertiary treatment Primary treatment w Physical removal w Settling ponds w Clarifiers w Bottoms removed to landfill w Occasionally useful as fertilizer w Standard in much of the world Secondary Treatment w Biological removal of organic material w C6H12O6 + 6O2 à 6CO2 and 6H2O w “Bugs” w Oxygen is added (aerators) w Another set of clarifiers w Standard in most of US, Japan Tertiary Treatment w Chemical removal of materials w Can be extremely expensive w Rare Figure 21-13 Wetlands w Wetlands can serve a wastewater treatment function w Some plants absorb minerals very quickly w These can be used as mulch, or even fuel w Increased interest lately Wastewater Control Options w “Mitigation” w Change process n n Recycled paper Non-chlorine bleaching w Reduce waste n Reuse water w Remove pollutants n “end of pipe” solution Groundwater Contamination w Can be a problem around mines, old industrial sites, landfills w Laws restricting land use are recent w Love Canal: legally filled with toxic chemicals w Seeped into basements Soil Salinization w All water contains some minerals w Water is used by plants or evaporates w Leaves minerals behind w Repeated w Plants can’t live when salts are too high w Civilization n Fertile Crescent n California?