Ocorrência de oocistos de Cryptosporidium spp. e cistos de Giardia spp. em sistemas de abastecimento de água da Grande Vitória, ES
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Data
2009-07-17
Autores
Covre, Marcus Andrade
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Universidade Federal do Espírito Santo
Resumo
The protozoa Cryptosporidium parvum and Giardia lamblia have emerged as the main causes of waterborne outbreaks, in developed and developing countries. The presence of these parasites in water has drawn the attention of international health organizations to intervent in the patterns of water quality. The Giardiacysts and Cryptosporidiumoocysts are environmentally robust and can survive in aquatic environments for several months. Cysts and oocysts are resistant to standard chlorination disinfection used for drinking water treatment. The aim of this study was to evaluate the occurrence of Giardiaand Cryptosporidiumin two water treatment systems in the city of Vitória, state of Espírito Santo. The study was conducted from April2008 to March2009, on samplesof raw water, filtered effluents and treatedwater. TheCarapinasystem (A) has two treatment options in the same plant: direct filtration and flotofiltration (operated when the raw water turbidity was> 30 uT). Vale Esperança system (B) has two water treatment plants, by direct filtration and conventional treatment. The relative performance of flocculation and membrane filtration methods were evaluated for recovery of Giardia lambliacysts and Cryptosporidium parvumoocysts seeded in distilled, filtered and raw water. The flocculation was better for Giardia(48.30%) but similar to the filtration in the recovery of Cryptosporidium(p > 0.05), suggesting that in same sample the two protozoa must be concentrated by flocculation. Cysts and oocysts were identified by direct immunofluorescence assay and the presence was confirmed by phase contrast microscopy. The raw water from systems A and B were not different in the level of the protozoa contamination (p > 0,05). The conventional treatment had the best performance in the removal of protozoa, because the presence of parasites on its effluent was not detected. The higher frequency of cysts (50.00%) and oocysts (66,67%) were identified at flotofiltration effluent. Giardiaand Cryptosporidiumwere detected in 16.67% and 41.67%, respectively, of the direct filtration system B samples.In the filtered water of flotofiltration and direct filtration the turbidity was > 0.5 uT at 100% and 58.33% of the samples. At the effluent from direct filtration of system A, Cryptosporidiumoocysts were not identified, only Giardiacysts in 16.67% of the samples. In treated water from reservoirs the parasites were not detected. The removal rates of protozoa by flotofiltration ranged from 1.00 to 2.36 log andby direct filtration (systems A and B) was between 0.39 and 1.91 log. That in most months was not possible to frame the efficiency ofrecommendedremoval by theUSEPA (3.0 log forGiardiaand2.0logCryptosporidium),because the concentration found in raw water anddetection limit of the methods.Significant correlations in the raw water were observed between the protozoa and the parameters turbidity, total coliforms, E.coli, true color and apparent color. The results of monitoring may be underestimated, because the detection techniques don’t have 100% recovery. This study was important to show the real situation of water treatment systems in Vitória city, when it comes to the protozoa pathogens removal. Monitoring protozoa is very important to ensure the distribution of drinking water to the population.
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Water , Removal , Vitória, Região Metropolitana de (ES) - Abastecimento de água , Abastecimento , Remoção
Citação
COVRE, Marcus Andrade. Ocorrência de oocistos de Cryptosporidium spp. e cistos de Giardia spp. em sistemas de abastecimento de água da Grande Vitória, ES. 2009. 108 f. Dissertação (Mestrado em Engenharia Ambiental) - Universidade Federal do Espírito Santo, Centro Tecnológico, Vitória, 2009.