Adição de policloreto de alumínio e remoção de peixes bentívoros como técnicas de restauração de lagos rasos do semiárido brasileiro
Eutrophication is the most common cause of water quality degradation in the world. This process occurs by excessive nutrients inputs, nitrogen and phosphorus, to the aquatic systems resulting in algal and cyanobacterial blooms. In shallow lakes these effects are pronounced due to the higher inter...
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| Materialtyp: | doctoralThesis |
| Språk: | por |
| Publicerad: |
Universidade Federal do Rio Grande do Norte
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| Länkar: | https://repositorio.ufrn.br/jspui/handle/123456789/20882 |
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| Sammanfattning: | Eutrophication is the most common cause of water quality degradation in the
world. This process occurs by excessive nutrients inputs, nitrogen and phosphorus, to
the aquatic systems resulting in algal and cyanobacterial blooms. In shallow lakes these
effects are pronounced due to the higher interaction of the lake with watershed, air and
sediment. There are innumerous restoration techniques of eutrophied lakes with a range
of successful results but there is only one case of successful lake restoration in Brazil:
Paranoá Lake in Brasília city. The Brazilian semiarid region has many artificial lakes,
named açudes, which are mostly eutrophic and shallow lakes. The eutrophication in
these lakes is reported and the phytoplankton community is dominated by potentially
toxic cyanobacteria species, mainly Cylindrospermopsis raciborskii. The aim of this
thesis is to test techniques for water quality management which can be easily applied in
Brazilian semiarid lakes. Results from a laboratory experiment suggest that the addition
of a phosphorus sorbent clay associated with an aluminium based coagulant is an
effective technique in removing soluble reactive phosphorus and reducing C. raciborskii
growth rate – cyanobacteria potentially toxic dominant in reservoirs of Brazilian
semiarid – but this effect is dependent on the biomass in the application moment.
Results from a field experiment in mesocosm in a eutrophied lake showed that the
addition of aluminium based coagulant and removal of benthivorous fish is more
efficient in removing total phosphorus and chlorophyll-a from water column than the
isolated application of one of the techniques. Lastly, laboratory tests showed that
aluminium based coagulant exhibited good performance in removing turbidity and total
phosphorus from water of six reservoirs but the efficiency was reduced by algal biomass
and pH. The results of this study showed that the improvement in water quality of
eutrophied reservoirs in semiarid region is possible through internal loading control by
phosphorus precipitation and inactivation in sediments or inhibition of phosphorus
release by benthivorous fishes, and also that these results show are additives in water
quality improvement. |
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