Uso sustentável do lodo de tratamento de água e esgoto: efeitos fitotóxicos, genotóxicos e possibilidade de uso antes e depois da biorremediação
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2021-11-01
Autores
Souza, Ana Cristina Zullo de
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Universidade Estadual Paulista (Unesp)
Resumo
O crescimento da densidade populacional vem contribuindo, cada vez mais, para o aumento dos níveis da poluição dos recursos hídricos, o que vem causando severos danos aos ecossistemas associados. Como esses impactos podem atingir as águas utilizadas no abastecimento público, têm sido cobradas das Estações de Tratamento de Água (ETA) uma alta eficiência de seus processos, para que sejam atingidos os índices desejados de potabilidade da água. Do mesmo modo, as Estações de Tratamento de Esgoto (ETE) devem remover, efetivamente, os poluentes orgânicos, inorgânicos e patógenos dos efluentes, antes dos mesmos serem descartados nos corpos receptores, visando a assegurar a qualidade ambiental. Embora a potabilidade da água seja obtida nas ETA e grande parte das partículas potencialmente tóxicas seja removida dos efluentes urbanos pelas ETE, estas estações de tratamento também produzem resíduos, como os lodos de ETA (LA) e de ETE (LE), que podem conter inúmeros contaminantes prejudiciais aos organismos, que coloca em risco tanto a biota exposta como a saúde humana. Desta forma, existe uma preocupação quanto a disposição desses lodos, que não devem ser descartados in natura, e sim submetidos a processo de detoxificação, antes de serem encaminhados ao seu destino final. Dentre as possíveis formas de detoxificação desses resíduos, destaca-se o processo de biorremediação, prática esta que pode ser ainda maximizada pela técnica de bioestimulação. Essa técnica pode ser implementada pela adição de subprodutos agroindustriais ao substrato a ser degradado, que promovam uma melhor aeração e também um maior aporte de nutrientes ao sistema que, consequentemente, levará a uma maior efetividade microbiana na degradação. Este estudo teve como objetivo monitorar a efetividade da detoxificação de LA e LE, associados a fibra de coco (FC) e ao composto exaurido (CE) do fungo lignolítico Pleorotus ostreatus (, em diferentes tempos de degradação (T1 = 0; T2 = 30; T3 = 90 e T4 = 150 dias), por meio de bioensaios ecotoxicogenéticos com Allium cepa e de fitotoxicidade com Lactuca sativa, bem como avaliar o potencial agronômico do composto biorremediado, após 150 dias, utilizando plântulas de L. sativa e Zea mays. As amostras estudadas foram LE; LA; LA+FC; LA+FC+CE; LA+FC+LE e LA+FC+LE+CE). Além disso, foi realizada uma revisão das informações sobre os aspectos ecotoxicológicos e implicações para o aproveitamento desses resíduos provenientes das estações de tratamento de água e esgoto. Os resultados mostraram que, para o teste de fitoxicidade, foi observado indução de toxicidade para o bioindicador L. sativa, para todas as associações testadas do T1 ao T3, exceto para LA+FC. Após 150 dias (T4), todas as amostras estimularam o crescimento de L. sativa. 17 Já, na avaliação do potencial agronômico pôde-se observar que as misturas foram mais satisfatórias para o cultivo de L.sativa quando comparadas a Z. mays. Os resultados referentes ao teste com A. cepa, demonstraram que, para o parâmetro de citotoxicidade, algumas amostras foram tóxicas ao bioindicador, apenas no tempo inicial de biorremediação, e que a mistura LA+FC apresentou citotoxicidade no T3 (90 dias). Quanto à genotoxicidade, os resultados apontam que nenhuma das amostras apresentou potencial genotóxico para a espécie A. cepa. N a avaliação do potencial mutagênico em células meristemáticas de A. cepa apontaram que as associações LA; e LA+FC+CE (T1); LA e LA+FC (T2); LA+FC e LA+FC+CE (T3) foram estatisticamente mutagênicas, quando comparadas ao CN. Já, para o potencial mutagênico em células da região F1 de A. cepa, os resultados demonstraram que os micronúcleos estatisticamente significativos encontrados nas células meristemáticas não prgrediram para as células da região F1 do vegetal. Para o uso das misturas aqui analisadas (LA, LA+FC, LA+FC+CE, LA+FC+LE e LA+FC+LE+CE), como condicionantes de solos agricultáveis, seria necessário monitorar, toxicologicamente, os produtos obtidos na biorremediação, para a certificação da sua adequação para o uso pretendido. Essa necessidade é justificada pelo fato de algumas misturas terem sido mais satisfatórias para o cultivo de L. sativa do que para Z. mays, uma vez que induziram a diminuição da biomassa seca radicular de Z. mays e que os resultados da análise química apontaram um aumento de concentração de metais, durante o processo de biorremediação.
The growth in population density has increasingly contributed to the increase in the levels of pollution of water resources, which has been causing severe damage to associated ecosystems. As these impacts can affect the water used in public supply, the Water Treatment Stations (WTS) have been charged with high efficiency in their processes, so that the desired levels of potability of water are achieved. Likewise, the Sewage Treatment Plants (STP) must effectively remove organic and inorganic pollutants and pathogens from the effluents, before they are discarded in the receiving bodies, in order to ensure the environmental quality. Although water potability is obtained at the WTS and a large part of the potentially toxic particles is removed from urban effluents by the STP, these treatment plants also produce residues, such as the sludge from the WTS (WTS sludge) and STP (SS), which may contain numerous contaminants harmful to organisms, which put both exposed biota and human health at risk. Thus, there is a concern about the disposal of these sludges, which should not be discarded in natura, but submitted to a detoxification process, before being sent to their final destination. Among the possible ways of detoxifying these residues, the bioremediation process stands out, a practice that can be further maximized by the biostimulation technique. This technique can be implemented by adding agro-industrial by-products to the substrate to be degraded, which promote better aeration and a greater supply of nutrients to the system, which, consequently, will lead to greater microbial effectiveness in degradation. This study aimed to monitor the effectiveness of the detoxification of WTS sludge and SS, associated with coconut fiber (CF) and depleted compost (DC) of the lignolytic fungus Pleorotus ostreatus, at different degradation times (T1 = 0; T2 = 30; , T3 = 90 and T4 = 150 days), through ecotoxigogenetic bioassays with Allium cepa and phytotoxicity with Lactuca sativa, as well as evaluating the agronomic potential of the bioremediated compost, after 150 days, using seedlings of L. sativa and Zea mays. In addition, a review of information on ecotoxicological aspects and implications for the use of these wastes from water and sewage treatment plants was carried out. Our results showed that, for the phytotoxicity test, it was observed induction of toxicity for the bioindicator L. sativa, for all tested associations from T1 to T3, except for WTS sludge+CF. After 150 days (T4), all samples stimulated L. sativa growth. In the evaluation of the agronomic potential, it could be observed that the mixtures were more satisfactory for the cultivation of L.sativa. The results referring to the test with A. cepa showed that, for the cytotoxicity parameter, some samples were toxic to the bioindicator, only in the initial time of bioremediation, and that the 19 WTS sludge+CF mixture showed cytotoxicity in T3 (90 days). As for genotoxicity, the results indicate that none of the samples showed genotoxic potential for the species A. cepa. The evaluation of the mutagenic potential in A. cepa meristematic cells showed that the associations WTS sludge; and WTS sludge+CF+DC (T1); WTS sludge and WTS sludge+CF (T2); WTS sludge+CF and WTS sludge+CF+DC (T3) were statistically mutagenic when compared to negative control. For the evaluation of mutagenicity in cells of the F1 region of A. cepa, the results showed that the mutagenic damage caused in the meristematic cells did not progress to the cells of the F1 region of the plant. However, for the use of the mixtures analyzed here (WTS sludge, WTS sludge+CF, WTS sludge+CF+DC, WTS sludge+CF +SS WTS sludge+CF +SS +DC) as conditions for arable soils, it would be necessary to toxicologically monitor the products obtained in bioremediation, for the certification of their suitability for the intended use. This need is justified by the fact that some mixtures induced a decrease in the root dry biomass of Z. mays and that the results of the chemical analysis pointed to an increase in the concentration of metals during the bioremediation process.
The growth in population density has increasingly contributed to the increase in the levels of pollution of water resources, which has been causing severe damage to associated ecosystems. As these impacts can affect the water used in public supply, the Water Treatment Stations (WTS) have been charged with high efficiency in their processes, so that the desired levels of potability of water are achieved. Likewise, the Sewage Treatment Plants (STP) must effectively remove organic and inorganic pollutants and pathogens from the effluents, before they are discarded in the receiving bodies, in order to ensure the environmental quality. Although water potability is obtained at the WTS and a large part of the potentially toxic particles is removed from urban effluents by the STP, these treatment plants also produce residues, such as the sludge from the WTS (WTS sludge) and STP (SS), which may contain numerous contaminants harmful to organisms, which put both exposed biota and human health at risk. Thus, there is a concern about the disposal of these sludges, which should not be discarded in natura, but submitted to a detoxification process, before being sent to their final destination. Among the possible ways of detoxifying these residues, the bioremediation process stands out, a practice that can be further maximized by the biostimulation technique. This technique can be implemented by adding agro-industrial by-products to the substrate to be degraded, which promote better aeration and a greater supply of nutrients to the system, which, consequently, will lead to greater microbial effectiveness in degradation. This study aimed to monitor the effectiveness of the detoxification of WTS sludge and SS, associated with coconut fiber (CF) and depleted compost (DC) of the lignolytic fungus Pleorotus ostreatus, at different degradation times (T1 = 0; T2 = 30; , T3 = 90 and T4 = 150 days), through ecotoxigogenetic bioassays with Allium cepa and phytotoxicity with Lactuca sativa, as well as evaluating the agronomic potential of the bioremediated compost, after 150 days, using seedlings of L. sativa and Zea mays. In addition, a review of information on ecotoxicological aspects and implications for the use of these wastes from water and sewage treatment plants was carried out. Our results showed that, for the phytotoxicity test, it was observed induction of toxicity for the bioindicator L. sativa, for all tested associations from T1 to T3, except for WTS sludge+CF. After 150 days (T4), all samples stimulated L. sativa growth. In the evaluation of the agronomic potential, it could be observed that the mixtures were more satisfactory for the cultivation of L.sativa. The results referring to the test with A. cepa showed that, for the cytotoxicity parameter, some samples were toxic to the bioindicator, only in the initial time of bioremediation, and that the 19 WTS sludge+CF mixture showed cytotoxicity in T3 (90 days). As for genotoxicity, the results indicate that none of the samples showed genotoxic potential for the species A. cepa. The evaluation of the mutagenic potential in A. cepa meristematic cells showed that the associations WTS sludge; and WTS sludge+CF+DC (T1); WTS sludge and WTS sludge+CF (T2); WTS sludge+CF and WTS sludge+CF+DC (T3) were statistically mutagenic when compared to negative control. For the evaluation of mutagenicity in cells of the F1 region of A. cepa, the results showed that the mutagenic damage caused in the meristematic cells did not progress to the cells of the F1 region of the plant. However, for the use of the mixtures analyzed here (WTS sludge, WTS sludge+CF, WTS sludge+CF+DC, WTS sludge+CF +SS WTS sludge+CF +SS +DC) as conditions for arable soils, it would be necessary to toxicologically monitor the products obtained in bioremediation, for the certification of their suitability for the intended use. This need is justified by the fact that some mixtures induced a decrease in the root dry biomass of Z. mays and that the results of the chemical analysis pointed to an increase in the concentration of metals during the bioremediation process.
Descrição
Palavras-chave
Biodegradação, lodo de ETA, lodo de ETE, Allium cepa, Lactuca sativa, Zea mays, Pleorotus ostreatus, Fibra de coco, Biodegradation, WTS sludge, Sewage sludge, Coconut fiber