Transcript Science 8: Unit E: Salt and Freshwater Systems

Science 8: Unit E: Salt
and Freshwater Systems
Topic 6 – Water Quality and Water
Management
How Can You Determine Water
Quality?
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Just because water is clear, does NOT mean it’s potable.
Amount and types of dissolved minerals in the water; pH
of the water; amount of dissolved oxygen, salinity, presence
of heavy metals and types of micro-organisms living in the
water.
Water quality is periodically checked using water samples
taken from different areas of the water source.
If a water sample is found to be toxic, the water cannot be
used for human or animal consumption.
Direct and Indirect Uses of Water
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Direct Uses – Water used for domestic/personal
uses.
Indirect Uses – Water used for agricultural/
industrial purposes.
73% of water is used for agriculture, 22% for
industry and only 5% for direct domestic uses.
There are benefits and drawbacks to each of the
above uses of water (eg. benefits = jobs,
drawback = harmed ecosystems)
Acids and Bases
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Acids and bases are water-based solutions
containing hydrogen (H+) and hydroxide ions
(OH-).
Measured on a pH scale. The lower the pH, the
more acidic the solution, the higher the pH, the
more basic or alkaline the solution.
If a solution measures 7 on the pH scale, it’s
neutral. Water is neutral.
Bioindicator Species
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Bioindicator Species – species that are very
sensitive to changes in the ecosystems and/or
presence of pollutants. They are helpful because
they can tell scientists about how different
chemicals interact with an ecosystem.
Amphibians and certain invertebrates (insects)
are considered good bioindicators because they
are the most sensitive to pollutants.
Purifying Water
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To be made potable, water must be treated: it must be
screen, mixed, filtered, and healthy chemicals (eg.
fluoride) need to be added.
After water has been used by humans, the solid and
liquid waste (sewage) has to be treated again before it
can go back to the water supply as effluent.
In rural areas a septic tank is used to help treat sewage.
In drier areas, desalination, distillation and reverse
osmosis (forcing water to go from more to less
concentrated solutions) are used to purify water.