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Where do we get water?
- Ice caps and glaciers
- Groundwater
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How many people have no access to safe water?
One-sixth of world's population
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How much water does a person need?
1 gallon a day
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How is water polluted?
- Point sources: Sewer outlet, steel mill or septic tank
- Nonpoint sources: Fertilizer runoff from a farm, acid drain from a strip mine
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What are major sources of water pollution? It's types and effects?
- Human and animal waste - causes diseases - bacteria, virus
- Sewage, inorganic fertilizers - cause excessive growth of algae - nitrates
- Industry, farms, households - add toxins to aquatic systems
- Land erosion - disrupt photosynthesis, food webs, other processes
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Common diseases through contaminated drinking water
- Typhoid fever
- Cholera
- Bacterial dysentery
- Enteritis
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What is geochemical cycle?
Passing of elements through a series of reservoirs
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What is residence time?
How much time each element spends in a reservoir such as river stream, lake or ocean
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Why is residence time important?
- If a specific chemical has a residence time of 20 years, then after 20 years about half of the chemical should be gone from the reservoir.
- We can apply this concept to toxic chemicals that are introduced into nature as human-created pollution
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Which elements have the longest residence time?
Chlorine and sodium
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Which element has the shortest residence time?
Iron
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How to monitor water quality?
- Biochemical Oxygen Demand (BOD)
- Amount of oxygen needed to break down the organic matter (sewage) aerobically
- Measures the rate of uptake of oxygen by microorganisms in the sample of water at a fixed temp (20C) and over 5 days in the dark
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What does DO stand for?
Dissolved oxygen - unit is ppm
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When will you consider that the water is good?
- If it has a DO of 8-9
- If the DO is below 4, the water is gravely polluted
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How much BOD do pristine rivers have?
Less than 1 ppm
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How much BOD do pristine rivers have?
More than 10 ppm
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What is oxygen sag curve?
A graph of dissolved oxygen content as a function of distance from the waste source
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What is the major source of water pollution?
Organic matter from human and animal wastes that are dumped into water
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How does water react with organic matter?
- Organic matter is broken down by microorganisms if there is ample oxygen in the water
- Aerobic decomposition occurs until oxygen is used up
- Releases methane and hydrogen sulfide
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What is eutrophication?
The breakdown of excess organic matter not only consumes oxygen but also releases a variety of compounds such as nitrates, phosphates and sulfates
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What are nitrates and phosphates?
Plant nutrients that encourages the rapid and excessive growth of aquatic plants like algae
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What is algal bloom?
- The exuberant algal growth and appears as slimy green scum floating on the water
- Worsen the water quality
- The scum blocks out the sunlight and the aquatic plants begin to die
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What are phosphates?
- They behave as plant nutrients and are harmful to the environment
- Were added to laundry detergents to enhance cleaning ability by softening the water
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What is mercury?
- A neurotoxin that acts on the central nervous system of the human body
- Causes loss of sight, feeling and hearing
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What is Minamata disease?
Adverse effects to nervous system caused by methylmercury
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What is arsenic?
- Lethal and can cause skin and bladder cancer
- Dissolved out of soils and rocks and can enter the groundwater
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Drinking water standard for arsenic
Set at 50 ppb
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What are the other inorganic water pollutants?
- Chlorine
- Acid mine drainage
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What does sediment pollution do?
- Causes water to be murky and unpleasant to look at, swim in or drink
- Reduces the light available to underwater plants and covers food supplies of aquatic animals
- Clogs water filter and damages power-generating equipment
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How much of oil spill can only be recovered?
15%
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How long does it take to clean crude oil spill and refined oil spillage?
- Crude oil - 3 years
- Refined oil - 10-20 years
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How to reduce water pollution?
Sewage treatment - using wetlands to treat sewage
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