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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

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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