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Fresh Water Pollution
Types, Effects, and Sources of Water Pollution
Infection Agents Bacteria, viruses, protozoa, and
parasitic worms Source: human and animal
wastes Oxygen-Demanding Wastes
Organic waste (animal manure, plant matter)
Source: human sewage, feedlots, paper mills
Inorganic Chemicals Acids, lead, arsenic, salts,
fluorides Source: surface runoff,
industrial effluents, cleansers Organic Chemicals
Oil, gasoline, pesticides, detergents
Source: industrial effluents,
solvents, runoff from farms Plant Nutrients
Nitrate, phosphate, ammonium Source: sewage, manure,
fertilizers Sediment
Soil, silt Source: land erosion
Radioactive Materials Iodine, radon, uranium, cesium,
and thorium Source: Nuclear and coal power
plants, mining, nuclear weapons production
Heat (Thermal Pollution) Excessive heat Source: Water cooling of
electric and industrial plants
Major Categories of Water Pollutants
Fecal Coliform Test: measure number of colonies of coliform bacteria present in a 100 mL sample of water
Safe drinking water contains no colonies Safe swimming water contains a maximum of
200 colonies BOD Test: the amount of oxygen
demanding wastes in water The amount of dissolved oxygen needed by
aerobic decomposers to break down organic materials in a certain volume of water
Chemical Analysis: determines the presence and concentrations of inorganic and organic chemicals
Indicator Species: can analyze tissues of organisms found in water, or do a biodiversity countMeasuring Water Quality
Dissolved Oxygen Content
WaterQuality
Good 8-9
DO (ppm) at 20˚C
Slightlypolluted
Moderatelypolluted
Heavilypolluted
Gravelypolluted
6.7-8
4.5-6.7
Below 4.5
Below 4
{ {Point Sources
Discharge pollutants at specific locations through drain pipes, ditches, or sewer lines into surface water Factories Sewage treatment
plants Underground mines Oil tankers
Nonpoint Sources
Scattered and diffuse and hard to trace to a specific site of discharge Acid deposition Runoff Logged forests Urban streets Lawns and parking
lotsSources of Water Pollution
Which is easier to monitor and control?
Water that flows recovers rapidly from degradable oxygen-demanding wastes and thermal pollution (dilution)
This works as long as the stream is not overloaded with pollutants and something does not reduce the flow of the stream (damming, drought, etc.)
Oxygen Sag Curve
Freshwater Streams and Rivers
Clean Zone DecompositionZone
Septic ZoneRecovery ZoneClean Zone
Normal clean water organisms
(trout, perch, bass,mayfly, stonefly)
Trash fish(carp, gar,leeches)
Fish absent, fungi,sludge worms,bacteria
(anaerobic)
Trash fish(carp, gar,leeches)
Normal clean water organisms
(trout, perch, bass,mayfly, stonefly)
8 ppmDissolved oxygen
Biological oxygendemand
Oxygen sag
2 ppm
8 ppm
Con
cen
trati
on
Typ
es
of
org
an
ism
s
Time or distance downstream
Direction of flow
Point of waste orheat discharge
Water Pollution Control laws (1970s)
Increased the number and quality of waste-water plants in US and most other developed countries
Require industries to reduce or eliminate point-source discharges
Problem: the developing world
Problem: “accidents” 2014 Elk River
chemical spill of MCHM
What has been done?
Dilution does not work as well as in running water
Often contain stratified layers that do not mix
Have little flow Ponds contain small volumes of
water Much more vulnerable to
pollution Plant nutrients, oil, pesticides,
and heavy metals Can kill benthic life, fish, and
birds Cultural eutrophication
Freshwater Lakes
Very vulnerable because it cannot effectively cleanse itself and dilute and disperse contaminants
Clean up is also almost impossible
Sources: storage lagoons, septic tanks, landfills, hazardous waste dumps, deep injection wells
We store gasoline, oil, solvents, and hazardous wastes in metal underground tanks that can leak over time
High health risks in drinking water
Groundwater Pollution