Avaliação da eficiência do processo de tratamento convencional utilizado em uma ETA e os impactos promovidos pelos seus efluentes sobre os rios receptores
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Data
2022-05-31
Autores
Gigeck, Letícia de Souza
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Universidade Estadual Paulista (Unesp)
Resumo
Os recursos hídricos vêm sofrendo diferentes ameaças, a contaminação por uma infinidade de compostos com potencial tóxico. Assim, antes da água ser distribuída para a população, a água bruta precisa ser submetida a um processo de tratamento realizado pelas Estações de Tratamento de Água (ETA). As ETA utilizam etapas, os quais são utilizados compostos químicos, realizados os processos de filtração e desinfecção, para assegurar a qualidade da água a ser distribuída para a população. Contudo, durante o tratamento da água bruta, são gerados resíduos advindos da lavagem dos filtros e dos decantadores, que devem ser tratados, antes de serem descartados em recursos hídricos. A ETA localizada no município de Rio Claro (SP) lança seus resíduos sem tratamento prévio no Córrego Santo Antônio, afluente do Ribeirão Claro. Portanto, o presente estudo avaliou a qualidade da água bruta, captada pela ETA, as águas dos corpos hídricos receptores (pós descarte dos efluentes da ETA), da água destinada ao consumidor. A avaliação da qualidade das águas dos pontos analisados foi baseada em ensaios ecotoxicológicos, e em análises físico-químicos e microbiológicos. Foram realizados ensaios in vivo de fitotoxicidade, com Lactuca sativa e de citogenotóxico e potencial mutagênico com o Allium cepa; ensaios in vitro de citotoxicidade (MTT); genotóxico (ensaio do Micronúcleo com Bloqueio de Citocinese e ensaio do Cometa) com cultura de células HepG2/C3A. Foram realizadas três amostragens de diferentes pontos (duas no período de seca e uma no chuvoso) nos seguintes pontos: água de captação da ETA (CAP); água do Córrego Santo Antônio sem o lançamento do efluente da ETA (SAS); água do Córrego Santo Antônio com o lançamento do efluente da ETA (SAE); amostra a montante do recebimento do efluente da ETA no Ribeirão Claro; (RCM); amostra a jusante do lançamento do efluente da ETA coletada no Ribeirão Claro no ponto de mistura completa (RCJ); água do cavalete do consumidor (AAP). No Córrego Santo Antônio foram observados elevados níveis de pH e condutividade, baixa concentração de oxigênio, aumento da turbidez e salinidade, elevação da concentração de nitrogênio total, elevado valor de DBO, uma maior presença de coliformes totais e Escherichia coli. Nenhuma das amostras de água foram fitotóxicas para o L. sativa, com exceção da RCM, para a primeira coleta. A amostra APP foi genotóxica para A. cepa, para a primeira e as amostras SAS, RCM, RCJ e APP para a terceira coleta; todas as amostras foram não citotóxicas para as células HepG2/C3A; o SAS apresentou potencial genotóxico pelo ensaio do Micronúcleo com as células HepG2/C3A na segunda e terceira coleta. O Córrego Santo Antônio mostrou ser extremamente vulnerável a ação antrópica e pelo lançamento do efluente da ETA. O Ribeirão Claro não foi afetado drasticamente pelo lançamento do resíduo da ETA. A água de abastecimento público ficou dentro da maioria dos padrões físico-químicos estabelecidos pela legislação, sendo que o flúor ficou um pouco abaixo da legislação, na primeira coleta. O APP também apresentou potencial genotóxico, na segunda coleta, para o ensaio do Micronúcleo e na primeira coleta no ensaio do Cometa. Assim, o processo de tratamento da água não se mostrou eficiente, e apresentou um potencial genotóxico, provavelmente, relacionado com a formação de subprodutos da desinfecção por cloro.
The water resources come suffering different threats, contamination by an infinity of toxic potential compounds. Therefore, before the water is distributed by the population the raw water needs to be submitted to a process for treatment realized by Water Treatment Plants (WTP). The WTP uses stages that involve chemic compounds, filtration, and disinfection process of water to ensure the quality of the water distributed to the population. But during the process, wastes are generated from washing filters and decanters that need to be treated without are lanch water resources. The WTP from Rio Claro (SP) city releases its wastes without previous treatment in the Córrego Santo Antônio, affluent of Ribeirão Claro. Therefore, the present study test the quality of the raw water, captured by WTP, water from water resources (after receiving the waste from WTP), as well as water destined for the consumer. The assessment of the quality of water at the points are based on ecotoxicology assays, physical-chemical test, and microbiologic assays. The following bioassay were conducted in vivo phytotoxicity assay with Lactuca sativa, a potential cytogenotoxic and mutagenic assay with Allium cepa; in vitro cytotoxic assay (MTT), and a genotoxic assay (Micronucleus Cytokinesis Block Assay and Comet Assay) with HepG2/C3A cell culture. Three sample collections were carried out (two in the dry season and one in the rainy season) on the following points: WTP captured water (CAP); water from Córrego Santo Antônio without WTP waste (SAS); water from Córrego Santo Antônio with WTP waste (SAE); sample upstream of the receipt of WTP waste in Ribeirão Claro (RCM); sample downstream of WTP waste release collected in Ribeirão Claro at the complete mixing point (RCJ); water from the consumer's easel (AAP). In Santo Antônio stream it was observed high levels of pH and conductivity, low concentration of oxygen, high turbidity and salinity, high concentration of total nitrogen, high level of BOD, and a greater presence of total coliforms and Escherichia coli. None of the samples were phytotoxic to L. sativa, except RCM in the first collection. The sample AAP showed genotoxic potential for A. cepa in the first collection, and the samples SAS, RCM, RCJ, and AAP for the third collection; all the samples weren’t cytotoxic for HepG2/C3A cells culture; SAS showed a genotoxic potential for Micronucleus Assay with HepG2/C3A cells culture. The Córrego Santo Antônio is extremely vulnerable to anthropic action and the release of waste of WTP. Ribeirão Claro wasn't drastically affected by waste from WTP. The public supply of water was within most of the physical-chemical standards established by the legislation. The AAP showed genotoxic potential in the second collection for the Micronucleus assay and in the first collection for the Comet Assay. Thus, the water treatment process wasn't efficient and the public supply of water presented a genotoxic potential related to the formation of chlorine disinfection by-products.
The water resources come suffering different threats, contamination by an infinity of toxic potential compounds. Therefore, before the water is distributed by the population the raw water needs to be submitted to a process for treatment realized by Water Treatment Plants (WTP). The WTP uses stages that involve chemic compounds, filtration, and disinfection process of water to ensure the quality of the water distributed to the population. But during the process, wastes are generated from washing filters and decanters that need to be treated without are lanch water resources. The WTP from Rio Claro (SP) city releases its wastes without previous treatment in the Córrego Santo Antônio, affluent of Ribeirão Claro. Therefore, the present study test the quality of the raw water, captured by WTP, water from water resources (after receiving the waste from WTP), as well as water destined for the consumer. The assessment of the quality of water at the points are based on ecotoxicology assays, physical-chemical test, and microbiologic assays. The following bioassay were conducted in vivo phytotoxicity assay with Lactuca sativa, a potential cytogenotoxic and mutagenic assay with Allium cepa; in vitro cytotoxic assay (MTT), and a genotoxic assay (Micronucleus Cytokinesis Block Assay and Comet Assay) with HepG2/C3A cell culture. Three sample collections were carried out (two in the dry season and one in the rainy season) on the following points: WTP captured water (CAP); water from Córrego Santo Antônio without WTP waste (SAS); water from Córrego Santo Antônio with WTP waste (SAE); sample upstream of the receipt of WTP waste in Ribeirão Claro (RCM); sample downstream of WTP waste release collected in Ribeirão Claro at the complete mixing point (RCJ); water from the consumer's easel (AAP). In Santo Antônio stream it was observed high levels of pH and conductivity, low concentration of oxygen, high turbidity and salinity, high concentration of total nitrogen, high level of BOD, and a greater presence of total coliforms and Escherichia coli. None of the samples were phytotoxic to L. sativa, except RCM in the first collection. The sample AAP showed genotoxic potential for A. cepa in the first collection, and the samples SAS, RCM, RCJ, and AAP for the third collection; all the samples weren’t cytotoxic for HepG2/C3A cells culture; SAS showed a genotoxic potential for Micronucleus Assay with HepG2/C3A cells culture. The Córrego Santo Antônio is extremely vulnerable to anthropic action and the release of waste of WTP. Ribeirão Claro wasn't drastically affected by waste from WTP. The public supply of water was within most of the physical-chemical standards established by the legislation. The AAP showed genotoxic potential in the second collection for the Micronucleus assay and in the first collection for the Comet Assay. Thus, the water treatment process wasn't efficient and the public supply of water presented a genotoxic potential related to the formation of chlorine disinfection by-products.
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Palavras-chave
Poluição hídrica, Efluentes de ETA, Ensaios ecotoxicológicos, Cultura de células, Bioindicadores vegetais, Water pollution, WTP waste, Ecotoxicological tests, Cell culture, Plant bioindicators