Fresh Water Pollution

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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  Organic Chemicals  Oil, gasoline, pesticides, detergents  Source: surface runoff, industrial effluents, cleansers 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 count

Measuring Water Quality

Water Quality Good Slightly polluted Moderately polluted Heavily polluted Gravely polluted DO (ppm) at 20˚C Below 4.5

Below 4

Dissolved Oxygen Content

4.5-6.7

6.7-8 8-9

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 Point Sources Discharge pollutants at specific locations through drain pipes, ditches, or sewer lines into surface water

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   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 lots

Sources 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

Normal clean water organisms (trout, perch, bass, mayfly, stonefly)

Dissolved oxygen 8 ppm Decomposition Zone Septic Zone Recovery Zone Clean Zone

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 ppm Oxygen sag 2 ppm Biological oxygen demand Direction of flow Point of waste or heat discharge Time or distance downstream

 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