Study Guide Questions: 30 - 32

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Study Guide Questions 30 - 32
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Turbidity (cloudiness of water)
Turbidity is caused by particulates suspended in
water Particulates can be either organic or
inorganic
Turbidity can occlude sunlight in water bodies
harming photosynthetic plants Particulates can
act as habitat for microorganisms removal of
particulate removes organisms. Flocculation is a
common way to remove particulates. It brings
together large numbers of small particles to make
larger particles which will settle out of water.
When the particles settle out, they take the
organisms (potentially pathogenic) with them.
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BOD Biological Oxygen Demand
organic
Additionally, organic particulates can be a
carbon source for organisms
Aerobic Heterotrophic organisms consume carbon
compounds and as part of their metabolism and
growth, they also consume O2
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So, if water containing high amounts of organic
materials is added to a water body, for example,
treated wastewater, aerobic heterotrophs
will consume those organic materials and in the
process use up oxygen reducing the amount of
oxygen available to other life in the lake or
stream.
The ability of water (e.g. wastewater) to promote
this activity is indicated By its biological
oxygen demand (BOD). If there is a large quantity
of organic waste in the water supply, there will
also be a lot of bacteria present working to
decompose this waste. In essence it creates a
demand on oxygen due to the activity of aerobic
heterotrophic organisms.
The higher the BOD the greater the potential to
lower oxygen contents of surface water bodies
including rivers and lakes.
Pristine rivers lt 1 mg/L Moderately polluted
rivers 2 8 mg/L Treated wastewater 20 mg/L