Utilization of Tests of Toxicity With Embryos of Oyster Crassostrea rhizophoroae (Guilding, 1828) for Evaluation the Efficiency of the Sewage Treatment Plant in the City of Vitória (ES)
DOI:
https://doi.org/10.5132/jbse.2006.01.010Keywords:
toxicity test, crude sewage, treated sewage, STP, Crassostrea rhizophoraeAbstract
The Sewage Treatmant Plant of Federal University of Espírito Santo (STP-UFES) is located in university campus of Goiabeiras, Vitória (ES). The technology of treatment of this STP consist in the set association of anerobics reactors of UASB (Upflow Anaerobic Sludge Blanket) type and submersed aered biofilters constituing in a biological process that makes the treatment of sewage at secondary level. This research proposes a prelimilarly evaluation of the ecotoxicological features of the crude sewage and the treated sewage of the STP-UFES, through the utilization of bioassays with Crassostrea rhizophorae oyster embryos, and still examine the efficiency of the STP in terms of toxic reduction of the system over oyster embryonary development. Adults animals collected in clean areas were utilized for obtainment of embryos, that were exposed at different concentrations of compost samples of crude and treated sewage in a period of 24 hours. After this period, it was counted the numbers of embryos, normal larvae and abnormal larvae. With the data obtained, the EC50 was determined through the Trimmed Spearman-Karber method. It was noticed the occurrence of different types of abnormalities envolving the bad formation of shell or the retarded development inside the expected time. The EC50 obtained for the crude sewage was 13.02% and for the treated sewage 25.73%. The founded values indicated that there exists a severe harmful effect of the crude and treated sewages over the embryo-larval development of C. rhizophorae oyster. The STP-UFES presents a low efficiency in removal of toxicity indicating that toxines likely persist in the treatment, being responsable for the remaining toxicity. The utilization of tests of toxicity with embryos of oyster showed be appropriate for evaluate the STP’s efficiency because they respond at a harmful action as a whole and for have been self presented as highly sensitive.
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