Transcript Water
Water Chapters 15 & 22 Water Wars Water shortage Growing population Poor irrigation efficiency Economic competition- Water Cycle Surface runoff Reliable runoff Watershed (drainage basin) Groundwater Zone of aeration Zone of saturation Water table Aquifer Natural recharge Shortages: Removal Lack of recharge Water Use Withdrawal Consumptive water use- Ownership Government Private Excessive Withdrawal Unsustainable Limits Increases Needs Causes sinkholes Saltwater Intrusion Movement of salt water Unusable Deep Aquifer Concerns: Knowledge No international water treaties Wasted Water 65-70% of world water is wasted Causes: Underpricing Lack of government subsidies Reducing Water Used to Remove Waste Use pollution prevention Bans Uses Floods + Fertile soils + Ample water for irrigation + Rivers for transportation & recreation + Flat land suitable for crops, buildings, highways, & railroads - Removal of water-absorbing vegetation Increasing Flood Damage Removal of water-absorbing vegetation Draining wetlands Living on floodplains Pavement & buildings End of Ch. 15 Water Pollution Any chemical, biological, or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses Coliform Bacteria Count Dissolved Oxygen Biological Indicators Point Source Pollution Discharge of pollutants Sources: Easy to identify, monitor, & regulate – due to specific location Nonpoint Source Pollution Large or dispersed land areas that discharge pollutants into environment over a large area Acid deposition Runoff from croplands, feedlots for livestock, logged forests, urban streets, lawns, golf courses, parking lots Safe Drinking Water + 74-95% of people have access to clean drinking water - 1.4 billion people do NOT - 9,300 die daily due to infectious diseases spread by contaminated water or lack of water for adequate hygiene Developing Countries 26% of people do not have access to clean drinking water Decreased Quality of Surface Water Intense downpours = Massive flooding = Overflow of lagoons & sewer lines = Drought = Warm temperatures = Limiting Factors Volume of degradable waste Stream volume Flow rate Temperature pH level Controlling Stream Pollution in Developed Countries + Increased number & quality of waste-water treatment plants + Industries are required to reduce or eliminate point-source pollution - Accidental or deliberate release of toxic, inorganic, & organic chemicals causes fish kills & contaminates drinking water - Sewage treatment plants malfunction - Nonpoint runoff of pesticides & excess plant nutrients from cropland & animal feedlots Controlling Stream Pollution in Developing Countries - Discharge of untreated sewage & industrial waste - Only 10% of Chinese city sewage is treated Diluting Lake Pollution Less effective Stratified layers with little vertical mixing Little flow – water is replaced every 1-100 years (unlike days to weeks for streams) Eutrophication Physical, chemical, & biological changes that take place after receiving inputs of plant nutrients (nitrates & phosphates) from natural erosion & runoff Cultural Prevention Cleanup Examples- Lake Washington & the Great Lakes Ocean Pollution Coastal areas- dumping of sewage & industrial waste, agricultural waste, algal blooms, oxygen-depleted zones (excessive fertilizers & animal wastes) 40% of world population lives with 100km (62mi) of coast From rivers Chesapeake Bay ICM- Types of Ocean Pollution Dredge spoils Sewage sludge- Reducing Nonpoint Source Pollution Prevent soil erosion by keeping cropland covered with vegetation Use slow-release fertilizer Apply pesticides only when needed Use buffer zone around animal feedlots, animal waste sites, & cultivated fields Use biological controls Legislature Clean Water Act Water Quality Act- Septic Tanks Underground tank for treating wastewater from a home in rural & suburban areas Bacteria decomposes organic waste Sludge settles to bottom Effluent flows out of tank into ground Primary Sewage Treatment Mechanical sewage treatment where large solids are filtered out by screens & suspended solids settle out as sludge in sedimentation tank Secondary Sewage Treatment 2nd step- aerobic bacteria decomposes 90% of degradable, oxygen-demanding organic wastes Sewage & bacteria is brought together in trickling filters or in activated sludge process Household wastewater Gravel or crushed stone Septic tank with manhole (for cleanout) Nonperforated pipe Distribution box (optional) Drain field Vent pipe Perforated pipe Secondary Primary Bar screen Grit chamber Settling tank Aeration tank Settling tank Chlorine disinfection tank To river, lake, or ocean Raw sewage from sewers (kills bacteria) Sludge Activated sludge Air pump Sludge digester Sludge drying bed Disposed of in landfill or ocean or applied to cropland, pasture, or rangeland Wetlands Sewage goes into sedimentation tanks (solids settle out as sludge) Liquid is pumped into oxidation ponds where bacteria breaks down remaining wastes Water released 1 month later into artificial marsh (plants & bacteria carry out further filtration & cleansing) Wastewater Garden Small, low-tech inexpensive artificial wetland Removes 99.9% of fecal coliform bacteria Removes 80% of nitrates & phosphates from incoming sewage (1) Raw sewage drains by gravity into the first pool and flows through a long perforated PVC pipe into a bed of limestone gravel. (3) Wastewater flows through another perforated pipe into a second pool, where the same process is repeated. Sewage Treated water Wetland type plants First concrete pool Wetland type plants 45 centimeter layer of limestone gravel coated with decomposing bacteria (2) Microbes in the limestone gravel break down the sewage into chemicals that can be absorbed by the plant roots, and the gravel absorbs phosphorus. Figure 22-18 Page 513 Second concrete pool (4) Treated water flowing from the second pool is nearly free of bacteria and plant nutrients. Treated water can be recycled for irrigation and flushing toilets. Water Purification Stored in reservoir for several days (increases DO level & suspended matter settles) Water is pumped to purification plant for filtration & chlorination Vulnerability to Terrorist Attacks Fear of added chemicals or biological agents Hard to protect due to large numbers of reservoirs, vast network of purification plants & distribution systems, & accessibility of water systems through fire hydrants & service connections Purification in Developing Countries Exposing water in clear plastic bottle to intense sunlight (heat & UV will kill infectious microbes in 3 hrs) Strips of cloth for filtering cholera-producing bacteria Add small amount of chlorine-disinfectant solution to plastic or clay storage containers with narrow mouth, cap, & spigot