FRESHWATER POLLUTION by zie20290

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									FRESHWATER POLLUTION

The Effects of Pollution Caused by
 Treated Domestic Sewage on a
     Freshwater Ecosystem
Specific Information:
   The sewage treatment works is in St. Jean du Bleymard.
   It serves two settlements - St. Jean du Bleymard and Le
    Bleymard.
   These two settlements have a combined population of 446
    (1999 census).
   It also receives waste from a small holiday village when it
    is open in July and August.
   The total population may then reach 1200 people.
   The liquid waste from the treatment works is discharged
    almost continuously in low volumes, and diluted by the
    river Lot.

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         Map of Study Sites:



Site 1 – Upstream (control)
Site 2 – Outfall
Site 3 – 5m downstream
Site 4 – 50m downstream



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What is a Pollutant??
   A pollutant may be natural or unnatural.
   Pollutants are not necessarily highly toxic chemical
    compounds.
   It is the concentration of the substance that defines it
    as a pollutant.
   Domestic sewage is rich in ammonium from urine
    and faecal matter, phosphates from detergents and
    particulate matter.
   By proportion, it is approximately 45% carbohydrate,
    45% fat and 10% protein.

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    Sewage Treatment Process:
       Tank 1                Tank 2              Tank 3




                            Liquid and
                             solid
                                               Solid storage
   Sewage is stirred
    by a propeller.          separation.       Farmers collect
                            Liquid           >it in Autumn
   This increases its
                             continues onto   >and Winter to
    surface area.
                             biological       >be used as
   Air (esp.                treatment.       >organic
    Oxygen) mixed                             >fertiliser.
    with the sewage.

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    Biological Treatment:
  Urea from domestic sewage       2NO2- + O2  2NO3-
   breaks down into Ammonium     (Carried out by nitrobacter)
   (NH4+).                        Nitrobacter use the Nitrites
  Aerobic bacteria carry out       from the previous reaction
   oxidation reactions,             and produce Nitrates (NO3-).
   converting the ammonium        Both reactions use up
   ions to nitrate.                 Oxygen.
The reactions:                    Nitrosomonas and
                                    nitrobacter occur naturally in
  2NH4+ + 3O2  2NO2-+ 4H+         watercourses therefore if the
(Carried out by nitrosomonas)       treatment process is
 Ammonium is used as food          insufficient, the ammonia will
                                    be converted to nitrate and
   for Nitrosomonas to produce      cause Oxygen depletion in
   nitrite (NO2-).                  the receiving water.
                                                               6
Abiotic Hypothesis:
Abiotic Variable     Site 1     Site 2
                   (Control)   (Outfall)
  Oxygen %
      pH
 Temperature
    Nitrate
  Phosphate
  Ammonium
Dissolved Load                             7
Biotic Indicators
   There are a huge diversity of invertebrates living in
    rivers.
   They have a range of tolerances to different water
    qualities, especially different levels of oxygen
    concentrations.
   Therefore there are ‘Indicator Species’ which can
    help determine the long term quality of the river
    water.
   Biological Monitoring Party Score (BMWP) can be
    used as a biotic index. Invertebrates with a low
    BMWP can tolerate low levels of Oxygen and are
    therefore good indicators of poor water quality.
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Aims:
   To determine the effects of point source
    organic pollution from a small rural
    sewage treatment works on the water
    quality of an upland stream.

   To investigate the effects of water
    quality changes on stream fauna.

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Objectives:
 To determine how             To determine the
    treated sewage affects      susceptibility of
    the abiotic conditions:     freshwater
   Oxygen concentration        invertebrates to organic
                                pollution, using
   Temperature                 indicator species to give
   pH                          an indication of the
   Ammonium                    extent of long term
   Nitrates                    pollution.
   Phosphates                 To determine the
                                effects of pollution on
   Dissolved Load              species diversity and
                                abundance.
                                                     10
Species we may find!!




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Stonefly nymph
                Stonefly nymphs prefer
                 rocky, stony, or gravel
                 bottoms in cool, well-
                 oxygenated, swift-moving
                 streams or small rivers.
                 Any effluent that reduces
                 the oxygen content of the
                 stream quickly kills the
                 nymphs.
                BMWP = 10


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Flattened Mayfly Nymph
                 These are only found in
                  very clean water
                  containing lots of
                  oxygen. They absorb
                  oxygen from the water
                  through their gills.
                 They are primary
                  consumers that eat
                  plants and algae.
                 BMWP = 10

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     Cased caddis Fly Larvae



   Caddisflies use silk (like butterflies) to build cases
    from gravel, twigs, needles, or sand. Different species
    build distinct cases, but they often lose them when
    removed from a stream.
   BMWP = 8 -10


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Cranefly Larvae
                     Up to four inches long
                      with a Fleshy, plump,
                      rounded segmented body
                     Its digestive track
                      (internal organs) can be
                      seen moving back and
                      forth as it crawls.
                     No legs and the back end
                      usually has several
                      extensions or finger-like
                      lobes.
                     BMWP = 5


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Flatworms
               Flatworms are
                unsegmented worms with
                flattened bodies.
               Their flatness allows them
                to shelter beneath stones.
               Being flat increases the
                area of skin exposed to
                the water, which improves
                the flatworm's oxygen
                uptake.
               BMWP = 5

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Freshwater Mite
                     Tiny animals related to
                      spiders.
                     Up to 8mm.
                     They have an oval body and
                      8 legs.
                     Many are brightly coloured.
                     BMWP = 4




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Leeches
           Flat, Worm-like,
              segmented body.
             Many are scavengers or
              feed on other
              invertebrates.
             Suckers at both ends are
              used for attachment,
              feeding, and locomotion.
             They swim gracefully and
              quickly in an up-and-down
              motion.
             BMWP = 3

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Red Midge Larvae
(Bloodworms)
                 These are sometimes
                  called 'bloodworms'
                  because of their bright red
                  colour, but they are not
                  worms at all.
                 They are midge larvae.
                 They eat dead organic
                  matter and can tolerate
                  very low oxygen levels.
                 BMWP = 2



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Tubifex Worms
                   These are thread-like
                    worms that live in the
                    mud on stream bottoms.
                   They are filterfeeders
                   They can tolerate
                    extremely low levels of
                    oxygen and are therefore
                    found in polluted water.
                   BMWP = 1




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   This shows
    freshwater
    fauna as
    indicators
    of river
    pollution.



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