Dissertação
Associação da ocorrência de cianobactérias às variações de qualidade do efluente na lagoa de estabilização de Santa Eudóxia – São Carlos, SP e suas interferências no corpo receptor
Date
2015-04-22Registration in:
Author
Morales, Fernanda Igual
Institutions
Abstract
Wastewater stabilization ponds are an efficient method of decomposition organic matter in
sewage treatment. Both biotic factors such as abiotic act in the ponds. Cyanobacteria are one
of biotic factors of great importance to the process of sewage purification. Lot of nutrients can
can result in high density cyanobacteria, characterized as eutrophication. These can release
cyanotoxins that can harm health human and animal when in contact with them. Physical and
chemical parameters are associated with both the presence of cyanobacteria and with the
quality of the receiving body and allows evaluating compliance or not the standards required
by legislation. Correlate the cyanobacteria density with the physical and chemical parameters
and evaluate the receiving body in relation to the released effluent, were the objectives of this
work. Quantitative and qualitative analysis of cyanobacteria were realized, and analyzes of the
physico-chemical parameters according to Hach manual, and statistical analysis (regression
analysis). The phosphorus and nitrogen analyzes have values close to those found in the
literature. But phosphorus values downstream demonstrate inadequacy with the rules. The
temperature in the pond is higher than the river, characterized by biochemical reactions that
take place in this environment. The dissolved oxygen concentration was within the standards
and remained in relation to previous studies. The pH and turbidity also attended the law. It has
been found through mathematical model, which was thermal stratification in most months in
the pond, with the pond in complete mixing in only four months. Statistical analysis showed a
positive correlation between cyanobacteria and total nitrogen concentration, but a negative
correlation with the effluent temperature. About the cyanobacteria in the pond the main
genera found were Merismopedia, Oscillatoria and Pseudanabaena and in the river both
upstream as downstream were Microcystis, Pseudanabaena and Limnothrix, indicating the
toxic potential of these individuals in the water. The cyanobacteria values in the river
downstream mainly, exceeded the value limit of the legislation. In general, some parameters
exceeded the limits, but not damaged strongly the quality of the receiving body.