Water PollutionWater Pollution

Water pollution is any chemical, physical or biological change in water quality that has a harmful effect on living organisms or makes the water unsuitable for desired uses.

Sources of Pollution

There are two major sources of pollution. Water pollution can come from point sources and non-point sources.

Point sources: • Sources that discharge pollution at a

specific location• Factories, mines, sewage treatment

plants, oil tankers, landfills or septic tanks.

• Controlling or stopping point sources of polluters is easiest

• There is often a direct pipe into a river or lake

Non-point sources:

• can NOT be traced to any one site of discharge

• usually large areas like farm fields, urban streets, golf courses, or logged forests

• very difficult to control non-point sources of pollution

Water Quality Measurements:

1. Coliform Bacteria2. Dissolved Oxygen3. Organic/Inorganic Chemicals4. Bottom-dwelling invertebrates

1. Coliform Bacteria

• Also called E. Coli• Low levels good• Ontario Safe Water Drinking Act requires 0

coliform colonies• Legal limit for safe swimming and boating

is <1000 coliform colonies/100 ml

2. OxygenDissolved oxygen• High levels good• Aquatic plants and animals require oxygen• More oxygen dissolves in cooler water• Oxygen levels increase when stream water

flows over rocks or if water leaves a pipe and drops into a stream

Biological Oxygen Demand• Low levels are good• Dead plants and animals require oxygen

for rotting• Bacteria that consume sewage, manure

or fertilizer require oxygen

3. Organic and Inorganic Chemicals

• Low levels are good• Inorganic substances like the nutrients

nitrogen, phosphates or potassium are indicators of agricultural pollution from fertilizers

• Inorganic substances like lead, mercury, aluminum and arsenic indicate industrial pollution

• Organic pollutants include pesticides, oils, cleaners, plastics or detergents that are made of carbon and hydrogen

• these organic pollutants come from household, agricultural and industrial waste

4. Bottom-dwelling Invertebrates

• Studying small aquatic animals often gives a better long-term indication of the health of a stream

• Dragonfly nymphs and some leeches show a healthy stream

• Only sowbugs present is an indicator of an unhealthy stream