Water Pollutants Biological Physical Chemical Biological Pollutants Consists
Water Pollutants • Biological • Physical • Chemical
Biological Pollutants • Consists of pathogens (disease-causing agents) • Come from sewage • Diseases include; – Typhoid, cholera, dysentery, polio, infectious hepatitis, salmonella, E-Coli bacteria
Temperature • Referred to as Thermal Pollution • Gases do not readily dissolve in liquids with high temperatures. ↑T → ↓ DO Power plants sometimes use waterways to cool their equipment. Replaced waters are warmer than they were before causing DO ↓ Cooling towers can be built to cool the water before they are discharged back into the water body.
Dissolved Oxygen (DO) • DO gets into the water by: – 1) moving water (riffles, rapids, water falls, etc. ) – 2) photosynthesis of aquatic plants • Gases do not readily dissolve in liquids with high temperatures. ↑T → ↓ DO
BOD (Biological Oxygen Demand) • Can be used as a gauge of the effectiveness of wastewater treatment plants • The amount of oxygen needed for microorganisms to break down organic waste material • High BOD indicates high levels of organic contaminants in the water • Sewage = organic wastes; decomposers work to break down the waste – which takes oxygen; • ↑ BOD → ↓ DO
• Dilution and decay of degradable, oxygendemanding wastes and heat in a stream. Figure 21 -4
Sedimentation • Excessive amounts of suspended solids in water. • Come from soil erosion • Increases turbidity (the cloudiness or haziness of a fluid caused by suspended solids) which reduces the amount of sunlight that penetrates the water • ↓ photosynthesis → ↓ DO • Slows water flow → ↓DO
Chemical Pollutants • • p. H plant nutrients heavy metals radioactive substances
p. H 3. 0 – 3. 5 = toxic to most life 3. 5 – 4. 0 = lethal to trout and other fish 4. 0 – 4. 5 = fish eggs; dead lake 5. 0 – 6. 0 = changes ecology (biodiversity, #, decline is fish species, slow decomposition, nutrients trapped at bottom, algae disappears) • 6. 5 – 9. 0 mostly harmless • 9. 0+ harmful to lethal as p. H goes up to 11. 5 • •
Plant Nutrients • Nitrites/nitrates; phosphorous – increases plant growth; – sources: fertilizers, sewage – causes algal bloom; eutrophication • ↑ plant life → blocks sunlight → ↓ photosynthesis → plants die → ↑BOD → ↓DO → fish kill
Heavy Metals – Mercury (Hg) • Sources – leaching of soil due to acid rain, burning coal, industrial, household and mining wastes. • Health Concerns – damages nervous system, kidneys, vision, Minimata • 1932 – 1968 – Co dumped 27 tons mercury compounds into Minimata Bay – Hg converted to methyl mercury – ingested by eating fish – 43 people died
Heavy Metals – Lead (Pb) • Sources: – paint, mining, incinerator ash, lead pipes and solder (contaminate water), auto exhaust • Health Concerns – damage to kidneys, nervous system (brain), ability to learn, depressed biosynthesis of proteins, nerves, red blood cells; anemia, irritability
Heavy Metals – Cadmium (Cd) • Sources: – electroplating, mining, plastic industries, sewage • Health Concerns – kidney disease
Heavy Metals – Arsenic (As) • Sources: – herbicides, wood preservatives, mining industry • Health Concerns – Damage to eyes, skin, GI tract, liver; cancer
Heavy Metals – Aluminum (Al) • Sources: – leaching due to acid rain • Health Concerns – anemia, loss of bone strength; possible role in dementia, and Alzheimer’s
Radioactive Substances • oceans become contaminated by nuclear waste from illegal dumping, bomb tests, and nuclear accidents
INDIRECT TESTS Monitoring Water Pollution • • • Nitrate and Phosphate tests Fecal Coliform Test Heavy Metal Tests BOD Changes in biodiversity of ecosystems – Mortality of indicator species
Point Source Pollution • a single identifiable localized source of pollution • easier to control emission, attribute responsibility and take legal action – Ex) Water pollution from an oil refinery wastewater discharge outlet
Non-Point Source Pollution • Derived from many different sources often in the form of runoff – It is difficult to regulate.
Reducing Water Pollution through Sewage Treatment • Primary and Secondary sewage treatment. Figure 21 -16
Waste Water Treatment • Removes the following: – Silt – Phosphorus – Dissolved organic wastes – Sludge • Sewage adds nitrogen and phosphorus to the water which can lead to eutrophication in bodies of water • Fecal coliform test is used to detect sewage in contaminated water
Sewage Treatment • Natural and artificial wetlands and other ecological systems can be used to treat sewage. ( Bioremediation)
Bioremediation • the use of microorganismal metabolism to remove pollutants. • Composting can be classified as bioremediation • Heavy metals are not easily treated by bioremediation
Bioremediation
Phytoremediation • consists in mitigating pollutant concentrations with plants able to contain, degrade, or eliminate pollutants from water, soil, or air • Pollutants include: metals, pesticides, solvents, explosives, crude oil and its derivatives, and other contaminants
How do plants do what they do?
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