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Water. Chapters 15 & 22. Water Wars. Water shortage Growing population Poor irrigation efficiency Economic competition-. Surface runoff Reliable runoff Watershed (drainage basin) Groundwater Zone of aeration Zone of saturation Water table Aquifer Natural recharge. Shortages: - PowerPoint PPT Presentation
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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
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
Decreased Quality of Surface Water Intense downpours = Massive flooding = Overflow of lagoons & sewer lines = Drought = Warm temperatures =
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-
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
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
Householdwastewater
Perforated pipe
Distribution box (optional)
Septic tank with manhole (for cleanout)
Drainfield Vent pipe
Nonperforated pipe
Gravel orcrushedstone
Raw sewagefrom sewers
Bar screenGritchamber Settling tank Aeration tank Settling tank
Chlorinedisinfection tank
Sludge
Sludge digester
Activated sludge
Air pump
(kills bacteria)
To river, lake,or ocean
Sludge drying bed
Disposed of in landfill orocean or applied to cropland,pasture, or rangeland
Primary Secondary
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.
(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.
(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.
45 centimeterlayer of limestonegravel coated with
decomposing bacteriaFirst concrete pool Second concrete pool
Sewage
Wetland typeplants
Wetland typeplants
Treatedwater
Figure 22-18 Page 513
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