Effects of sewage in
freshwater ecosystems
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Dumping sewage into
water bodies, such as rivers or lakes, creates a human health hazard but can
also negatively disrupt the river and lake ecosystems.
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The sewage
contaminates the water, spreads disease, and leads to environmental
degradation.
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Here is a list of
effects of untreated sewage disposal into freshwater ecosystems:
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1. Increased organic matter
(from the sewage) breaking down in the river reduces the amount ofdissolved oxygen in the water body as the decomposition process uses
up the available dissolved oxygen. Fish and other aquatic life need that dissolved oxygen in the water to live.
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2. Sewage heightens the levels
of nutrients, increasing the bioavailability of nutrients, which can increase
productivity of plankton near the sewage outfall and increase the chance of
algal blooms.
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3. Contaminants present in the sewage might be
toxic for some already existing phytoplankton.
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4. Sewage can increase the turbidity and amount of suspended
sediments. This effect reduces light available for plant growth, can smother
in-stream habitats, and damage fish gills and respiratory structures of other
species.
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5. Sewage (and stormwater runoff)
can introduce pesticides, other chemicals, and heavy metals into the water
column. It may also introduce fine sediments, which have the potential to (bio)accumulate
within animal tissues and have long-term toxic effects. Sewage and run off may
increase acidity, such as from acid sulphate soils which kill fish
and crustaceans, cause fish red-spot disease, damage or cause death of oysters,
and interact with sediments to release heavy metals.
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6. Industrial effluents (often a complex
mixture of chemicals) can negatively affect fish by impairing growth and
reproduction and by reducing immune competence. These effects have the
potential to impact fish populations.
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7. Microbial pathogens introduced by sewage into surface or groundwater
can threaten public health, as well as affect ecosystem health and
function.
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8. Sewage can release water that
is either warmer or cooler than the receiving water body. Because
aquatic life has optimal temperature ranges within which it lives, too warm or
too cool water temperatures can harm the aquatic life. For example, cold waters
reduce ecosystem productivity, eliminate temperature-sensitive biota, and
decrease survival of eggs, larvae of fish and aquatic insects.
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9. Release of sewage can degrade
vegetation and soil by depositing harmful
chemicals in bottom
sediment, for example.
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10.With sewage comes water that
has some degree of chlorine or
similar agent. The
chlorine or other disinfectant react with organic matter (such as what's in
sewage) to create different end-products, such as chloroform or haloketons,
which can be harmful in either the short or long term. These reactions happen
faster in warmer water.
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Release of untreated sewage into freshwater bodies
is sometimes necessary. Yet, it not only creates a human health risk but damages the
health of the receiving
water bodies in over short or long time periods.
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Our responsibility to ecosystems means we should
have the capacity to deal with our own waste rather than expecting the rest of
the ecosystem to do it for us.
.
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