Water quality monitoring in southern Brazil and the assessment of risk factors related to contamination by coliforms and Escherichia coli.

The potability of water, including underground sources, is constantly affected by human activities. To assess water quality and water security in rural and urban areas of southern Brazil, a quantitative, retrospective analysis of water samples collected monthly by the Brazilian health authorities (19,687 samples from 2013 to 2021) was performed. In rural areas, 5,979 water samples (77.54%) were found to be contaminated by coliform bacteria and 3,431 (44.50%) by Escherichia coli. In addition, 1,616 (20.95%) of the contaminated samples were significantly correlated with rainfall amount. In urban areas, 1,268 (10.95%) of the samples contained coliform bacteria and 293 (2.53%) of these samples contained E. coli, with the factor of rainfall associated with 1,081 samples (9.33%) with bacterial contamination. In terms of physicochemical parameters, turbidity exceeded the national standard (5 uT) in 448 (2.32%) samples and fluoride fell below the required level (0.8 mg/L) in 106 samples (0.54%). The presence of free residual chlorine (0.2-2.0 mg/L) was verified in 846 samples (14.38%) in rural areas and in 10,825 samples (56.13%) in urban areas. These results suggest a strong association between rainfall factors and physicochemical alterations, as well as the risk of greater microbial contamination of water for human consumption.

Microcystin-Detoxifying Recombinant Saccharomyces cerevisiae Expressing the mlrA Gene from Sphingosinicella microcystinivorans B9.

Contamination of water by microcystins is a global problem. These potent hepatotoxins demand constant monitoring and control methods in potable water. Promising approaches to reduce contamination risks have focused on natural microcystin biodegradation led by enzymes encoded by the mlrABCD genes. The first enzyme of this system (mlrA) linearizes microcystin structure, reducing toxicity and stability. Heterologous expression of mlrA in different microorganisms may enhance its production and activity, promote additional knowledge on the enzyme, and support feasible applications. In this context, we intended to express the mlrA gene from Sphingosinicella microcystinivorans B9 in an industrial Saccharomyces cerevisiae strain as an innovative biological alternative to degrade microcystins. The mlrA gene was codon-optimized for expression in yeast, and either expressed from a plasmid or through chromosomal integration at the URA3 locus. Recombinant and wild yeasts were cultivated in medium contaminated with microcystins, and the toxin content was analyzed during growth. Whereas no difference in microcystins content was observed in cultivation with the chromosomally integrated strain, the yeast strain hosting the mlrA expression plasmid reduced 83% of toxins within 120 h of cultivation. Our results show microcystinase A expressed by industrial yeast strains as a viable option for practical applications in water treatment.

Pesticides removal from water using activated carbons and carbon nanotubes.

The conventional water treatment technique (CT) widely applied cannot alone remove pesticides efficiently from water. Therefore, this work aimed to provide technical and scientific support for the association of pulverized activated carbon (PACs), granular activated carbon (GACs), and carbon nanotubes (CNT) with CT concerning atrazine (ATZ), simazine (SMZ), and diuron (DIU) removal. Actual conditions of pre/during, and post-treatment points of application, within water production process line, in water treatment plants (WTPs), using the pesticides in two forms, commercial product (CP) and analytical standard (SD). It was possible to demonstrate significant differences regarding the removal of ATZ, SMZ, and DIU in their SD and CP forms for the PACs, GACs, and CNTs. The minimum dosage of CNT required for adequate adsorption of all pesticides was superior to 160 mg. L-1; is 400% higher than the minimum dosage of 40 mg. L-1 is required for PAC application. ATZ, SMZ, and DIU in the SD form were more efficiently removed with percentages superior to 96.4% for ATZ, 98.2% for SMZ, and 99.1% for DIU. The characteristics of the adsorptive materials did not guide the adsorption efficacy. Instead, chemical interaction, contact time, and point application were critical factors. The pre-treatment and post-treatment applications were the most efficient, with removals oscillating from 97.7% to 100% for ATZ, 97.7% to 100% for SMZ, and 99.1 to 100% for DIU PAC and GAC, respectively.

Adsorbent selection for pesticides removal from drinking water.

Pesticides present in water resources can cause adverse health effects even in low concentrations, due to their bio-accumulative character. Therefore, the challenge for drinking water production increases, due to the limitations of conventional water treatment technologies in the removal of small molecular weight dissolved compounds. This work aimed to provide technical and scientific support for the selection of pulverized activated carbon - PACs, granular activated carbon - GACs, and carbon nanotubes - CNT concerning atrazine - ATZ, simazine - SMZ, and diuron - DIU adsorption for application in water treatment plants, considering two forms of application commercial product - CP and analytical standard - SD. These forms of application were tested aiming to verify the influence of the purity of the products used in experiments on the adsorption efficiency. It was possible to verify the adsorption efficiencies were not guided only by the characteristics of the adsorptive materials used, and that the selection should not be carried out only based on the, specific superficial area - BET size and distribution of specific pore volume. The isotherms demonstrated that the parameter Kf associated with the results of the selection experiment can be considered an alternative technical tool of simple application and sufficient for this purpose. Also, the capacity of activated carbons - ACs and nanomaterials - NMs were affected by the application of the compounds, highlighting the importance of using commercial product - CP in scientific research and technical investigations.Hightlights The pesticides efficiency removal was affected due to the forms of application, SD and CP;The parameters IN and MBI were not decisive in the selection of the activated carbon;The main adsorption mechanism in all the materials was chemical;GAC was the most efficient adsorbent in the removal of the pesticides;An adequate adsorbent selection is crucial for satisfactory removal of pesticides in water.

Post-treatment of stabilized landfill leachate by upflow gravel filtration and granular activated carbon adsorption.

Stabilized leachates from sanitary landfills generally display high levels of recalcitrant organic matter, sometimes requiring a combination of biological and physicochemical treatment processes. This study evaluated the post-treatment by Upflow Gravel Filtration (UGF) followed by Granular Activated Carbon Adsorption (GACA) on a pilot scale of two different landfill leachates previously treated by biological processes. The system design was proven technically feasible for a continuous flow post-treatment in relation to recalcitrant organic matter removal efficiency. The UGF experiments presented 83.9% and 82.0% COD removals for leachates A and B, respectively, with residual values of 107 and 194 mg L-1. The UGF-GACA experiments, in turn, produced effluents with residual COD values of 67 and <60 mg L-1 for leachates A and B, respectively, corresponding to 89.9% and >94.6% efficiencies.

Composição granulométrica do filtro ascendente para pós-tratamento de lixiviado de aterro sanitário / Granulometric composition of the upflow filter for post-treatment of landfill leachate

RESUMO O lixiviado de aterro sanitário apresenta composição variável e complexa e pode ter elevadas concentrações de nitrogênio amoniacal e matéria orgânica biodegradável e recalcitrante. Devido ao potencial altamente poluidor dos lixiviados estabilizados, além do tratamento biológico convencional, faz-se necessária, em alguns casos, a realização de pós-tratamento para remoção da matéria orgânica recalcitrante, de maneira a atender à legislação vigente. Nesse contexto, os ensaios de coagulação seguida de filtração ascendente em pedregulho como pós-tratamento foram realizados com o objetivo de estabelecer a composição granulométrica que resultasse na melhor condição de eficiência em relação à remoção de matéria orgânica recalcitrante e operação, visando à aplicação do sistema em escala real. Para todos os ensaios, foram aplicados taxa de filtração constante de 15 m3.m-2.dia-1 e dosagem de ferro de 400 mg.L-1 em pH 4,0. A duração das carreiras de filtração, bem como a qualidade do efluente tiveram forte influência em relação à composição granulométrica do filtro, podendo-se constatar a necessidade do emprego de areia fina em sua composição, a fim de garantir a eficiência do tratamento. A concepção técnica de pós-tratamento por coagulação seguida da filtração ascendente com a composição granulométrica definida neste trabalho (tipo 4) foi eficiente para a remoção de matéria orgânica recalcitrante, com remoções de 82,4% de demanda química de oxigênio (valor residual de 194 mg.L-1), de 98,8% de cor verdadeira (valor residual de 49 uH), de 94,3% de carbono orgânico total (valor residual de 52 mg.L-1) e duração de carreira de filtração de 22,6 horas, sem ocorrência de transpasse.

ABSTRACT Landfill leachate presents variable and complex composition and may have high concentrations of ammoniacal nitrogen and biodegradable and recalcitrant organic matter. Due to the high polluting potential of stabilized leachate, in addition to conventional biological treatment, it is necessary in some cases to perform post-treatment to remove recalcitrant organic matter to meet the current legislation. In this context, the coagulation followed by upflow gravel filtration experiments were carried out with the objective of establishing the granulometric composition that resulted in the best efficiency condition in relation to the removal of recalcitrant organic matter and operation, aiming at the system's application in real scale. For all the tests, a constant filtration rate of 15 m3 m-2 day-1 and an iron dosage of 400 mg L-1 at pH 4.0 were applied. The duration of filtration cycles, as well as the quality of the effluent were strongly influenced by the filter's particle size, and it is possible to verify the need of using fine sand in its composition to guarantee the treatment's efficiency. The technical design of post-treatment by coagulation followed by upflow gravel filtration with the granulometric composition defined in this study (type 4) was efficient in removing recalcitrant organic matter, with removals of 82.4% for COD (residual value of 194 mg L-1), 98.8% for true color (with residual value of 49 uH), and 94.3% for TOC (residual value of 52 mg L-1), resulting in a filtration cycle duration of 22.6 h, with no loss of filtered solids.

Seleção de carvões ativados para adsorção de microcistinas / Selection of activated carbons for adsorption of microcystins

RESUMO A presença das cianobactérias é uma das grandes preocupações para o tratamento de água, uma vez que esses microrganismos podem ser produtores de metabólitos tóxicos, como as microcistinas (MCs), que não são efetivamente removidas no tratamento usualmente empregado de ciclo completo. Para a remoção dessas toxinas, pode-se, de forma complementar, utilizar adsorvedores como o carvão ativado (CA), que apresenta eficiência variada, em função de suas características. Este trabalho teve como objetivo fornecer subsídios técnicos e científicos para a seleção de carvões ativados pulverizados (CAPs) e carvões ativados granulares (CAGs) como adsorvedores de MCs. Para tanto, foi realizado, primeiramente, um experimento de seleção de CAs com maior capacidade adsortiva para MCs, em escala de bancada. Em seguida, para os CAPs e CAGs selecionados, foi realizada caracterização complementar para a distribuição de volume específico em função do tamanho do poro. Posteriormente, foram elaboradas isotermas de adsorção de Freundlich e curvas de ruptura. Pôde-se constatar que, dentre os CAs amostrados, os importados apresentaram maior capacidade adsortiva para MCs do que os nacionais. Além disso, foi possível concluir que a escolha do CA pode ser determinada pelos parâmetros índice de azul de metileno (IAM), volume de mesoporos e coeficiente Kf, associados aos resultados do experimento de seleção, considerado uma ferramenta técnica alternativa de simples aplicação e suficiente para esse fim.

ABSTRACT The presence of cyanobacteria is a major concern for water treatment, since these microorganisms can be toxic metabolic producers, such as microcystins (MCs), which are not effectively removed in the usually employed full cycle treatment. In order to remove these toxins, it is possible to use absorbers such as activated carbon (AC), which presents a varied efficiency, depending on its characteristics. The general objective of this research was to provide technical and scientific subsidies for the selection of powdered activated carbons (PACs) and granular activated carbons (GACs) in relation to the adsorption of microcystins. A bench scale experiment was carried out to select activated carbons with higher adsorptive capacity for microcystins. Then, for the selected PACs and GACs, complementary characterization was performed for the specific volume distribution as function of pore size and, afterwards, Freundlich adsorption isotherms and breakthrough curves were elaborated. It was possible to verify that among the sampled activated carbons, the imported ones presented greater adsorption capacity for microcystins in relation to the nationals. In addition, it was possible to conclude that the selection of an activated carbon can be done regarding methylene blue index (MBI) parameters, volume of mesoporous and Kf, associated to the selection experiment's results, considered an alternative technical tool of simple application and sufficient for this purpose.

Occurrence of Cryptosporidium spp. and Giardia spp. in a public water-treatment system, Paraná, Southern Brazil / Ocorrência de Cryptosporidium spp. e Giardia spp. em uma estação pública de tratamento de água, Paraná, Sul do Brasil

The purpose of this study was to investigate the occurrence of Cryptosporidium spp. and Giardia spp. in a public water-treatment system. Samples of raw and treated water were collected and concentrated using the membrane filtration technique. Direct Immunofluorescence Test was performed on the samples. DNA extraction using a commercial kit was performed and the DNA extracted was submitted to a nested-PCR reaction (n-PCR) and sequencing. In the immunofluorescence, 2/24 (8.33%) samples of raw water were positive for Giardia spp.. In n-PCR and sequencing, 2/24 (8.33%) samples of raw water were positive for Giardia spp., and 2/24 (8.33%) samples were positive for Cryptosporidium spp.. The sequencing showed Cryptosporidium parvum and Giardia duodenalis DNA. In raw water, there was moderate correlation among turbidity, color and Cryptosporidium spp. and between turbidity and Giardia spp.. The presence of these protozoans in the water indicates the need for monitoring for water-treatment companies.

O objetivo deste estudo foi investigar a ocorrência de Cryptosporidium spp. e Giardia spp. em um sistema público de tratamento de água. Amostras de água bruta e tratada foram coletadas e concentradas, utilizando-se a técnica de filtração em membranas. Foi realizada a técnica de Imunofluorescência Direta nas amostras. A extração de DNA foi realizada, utilizando-se um kit comercial, e o DNA extraído foi submetido a uma reação de nested-PCR (n-PCR). Na imunofluorescência, 2/24 (8,33%) amostras de água bruta foram positivas para Giardiaspp.. Na n-PCR, 2/24 (8,33%) amostras de água bruta foram positivas para Giardia spp., e 2/24 (8,33%) amostras foram positivas para Cryptosporidium spp.. O sequenciamento demonstrou DNA de Cryptosporidium parvum e de Giardia duodenalis. Na água bruta, houve correlação moderada entre turbidez, cor e Cryptosporidium spp. e entre a turbidez e Giardia spp.. A presença desses protozoários na água indica a necessidade de monitoramento pelas empresas de tratamento de água.

Occurrence of Cryptosporidium spp. and Giardia spp. in a public water-treatment system, Paraná, Southern Brazil.

The purpose of this study was to investigate the occurrence of Cryptosporidium spp. and Giardia spp. in a public water-treatment system. Samples of raw and treated water were collected and concentrated using the membrane filtration technique. Direct Immunofluorescence Test was performed on the samples. DNA extraction using a commercial kit was performed and the DNA extracted was submitted to a nested-PCR reaction (n-PCR) and sequencing. In the immunofluorescence, 2/24 (8.33%) samples of raw water were positive for Giardia spp.. In n-PCR and sequencing, 2/24 (8.33%) samples of raw water were positive for Giardia spp., and 2/24 (8.33%) samples were positive for Cryptosporidium spp.. The sequencing showed Cryptosporidium parvum and Giardia duodenalis DNA. In raw water, there was moderate correlation among turbidity, color and Cryptosporidium spp. and between turbidity and Giardia spp.. The presence of these protozoans in the water indicates the need for monitoring for water-treatment companies.

Desaguamento do lodo de estações de tratamento de água por leito de drenagem/secagem / Dewatering of sludge from water treatment plants using drainage/drying bed

Vários estudos têm mostrado a eficiência das técnicas naturais de desaguamento do lodo das estações de tratamento de água no Brasil. O objetivo deste estudo foi avaliar o sistema de desaguamento por leito de drenagem/secagem, com manta geotêxtil dos lodos de decantadores de duas diferentes estações de tratamento de água, em ensaios de laboratório e escala reduzida. Foram considerados os parâmetros técnicos de projeto: densidade da manta; taxa de aplicação dos sólidos; taxa de aplicação volumétrica e secagem em diferentes condições climáticas. Na fase de drenagem, entre 78 a 91% do volume total dos líquidos percolados apresentaram qualidade compatível com o padrão de enquadramento dos corpos de água doce classes I e II, segundo a Resolução 357/05 do Conama. Na fase de secagem, foi possível obter teores de sólidos totais entre 15,9 e 20,3%, cujos valores são da mesma ordem de grandeza que aqueles obtidos por desaguamentos mecânicos, mesmo em condições críticas de secagem.

Several studies have showed the efficiency of natural techniques to dewater the sludge from water treatment plants in Brazil. The objective of this study was to evaluate the dewatering system through drainage/drying with a geotextile blanket using the sludge of decanters from two types of water treatment plants, in laboratory experiments and reduced scale. The following technical parameters of project were considered: density of blanket, application rate of solids, volumetric application rate, and drying in different climate conditions. In the drainage phase, 78 to 91% of the total volume of percolated liquid presented a compatible quality to the standardized limits for freshwater bodies from classes I and II, according to Resolution 357/05 from the National Council of Environment. In the drying phase, it was possible to obtain total solid rates between 15.9 and 20.3%, values of the same magnitude order as those obtained by mechanical drainages, even in critical drying conditions.

Pós-tratamento de lixiviado de aterro sanitário com carvão ativado / Post-treatment of landfill leachate using activated carbon

A degradação física, química e biológica da matéria orgânica presente dos resíduos sólidos gera um subproduto altamente poluidor, denominado lixiviado. Várias técnicas de tratamento aplicadas a esse efluente vêm sendo investigadas a fim de adequá-lo ao lançamento no corpo receptor sem causar prejuízos ao meio ambiente. Este trabalho teve como objetivo avaliar a aplicabilidade do Carvão Ativado Granular (CAG) na remoção de compostos poluentes presentes no lixiviado. Os ensaios em CAG foram divididos em duas fases. A fase A para a seleção do CAG de maior eficiência e a fase B para a avaliação da eficiência ao longo de sucessivos ensaios de adsorção/filtração com o CAG selecionado na fase A. O lixiviado produzido pelo CAG selecionado apresentou, ao longo dos 4 ensaios, elevada eficiência com remoções variando entre 94 e 100% para a cor verdadeira, entre 45 e 76% para a demanda química de oxigênio e entre 23 e 67% para o carbono orgânico total, com valores máximos absolutos de 8 uH, 167 mg.L−1 e 93 mg.L−1, respectivamente.

The physical, chemical and biological degradation of waste disposed in sanitary landfill generates a highly polluting product, known as leachate. Several treatment techniques have been investigated to treat leachate in order to meet the discharge limits before its disposal into superficial waters and not cause impacts to the environment. This study evaluated the applicability of granular activated carbon (CAG) in the removal of pollutants from the effluent. Adsorption tests on CAG were divided in two phases. The phase A for the selection of higher efficiency CAG, and phase B to evaluate the efficiency of successive adsorption/filtration tests with the CAG selected in phase A. The leachate produced using the selected CAG showed high efficiency with removals ranging between 94–100% for true color, between 45–76% for chemical oxygen demand and between 23-67% for total organic carbon, with maximum absolute values of 8 uH, 167 mg.L−1 and 93 mg.L−1, respectively.

Remoção de carga orgânica recalcitrante de lixiviado de resíduos sólidos urbanos pré-tratado biologicamente por coagulação química-floculação-sedimentação / Removing recalcitrant organic load of landfill leachate from urban solid waste pretreated biologically by coagulation-flocculation-sedimentation

A utilização de pós-tratamentos físico-químicos no tratamento de lixiviados tem sido uma alternativa utilizada para a remoção da carga orgânica presente nesse efluente. Dessa forma, este artigo teve como objetivo avaliar a técnica de tratamento físico-químico pelo processo de coagulação química-floculação-sedimentação como alternativa para pós-tratamento de lixiviado tratado biologicamente. Para isso, utilizou-se o equipamento de reatores estáticos Jarteste, e os parâmetros monitorados para avaliar a eficiência do tratamento físico-químico foram cor verdadeira e demanda química de oxigênio (DQO). Por meio da técnica de planejamento fatorial e analisando-se os resultados obtidos, pôde-se verificar que as maiores remoções de cor e de DQO foram encontradas combinando-se dosagem de 400 mgFe+3/L com pH 3,0, alcançando-se 98 e 81% de remoção de cor e DQO, respectivamente.

The utilization of physical-chemical post treatment on landfill leachate has been an option employed to remove organic compounds from this effluent. In this way, this article aimed to evaluate the physical-chemical treatment by coagulation-flocculation-sedimentation as an alternative in the post-treatment of landfill leachate submitted to biological treatment. Consequently, it was used a Jar-test to monitor true color and chemical oxygen demand (COD) in order to evaluate the efficiency of the physical-chemical treatment. By means of factorial design and analyzing the results, it was found that the best removals of color and COD were attained by combining a dosage of 400 mg Fe+3/L with pH 3.0, achieving 98 and 81% of color removal and COD, respectively.

Potencial de biodegradação de microcistinas por microrganismos / Biodegradation potential of microcystins by microorganisms

Para minimizar os problemas relacionados à ocorrência de cianobactéria em águas destinadas ao consumo humano há necessidade de se realizar estudos de alternativas técnicas de tratamento com destaque aos biofilmes com potencial de degradação de microcistinas (MC). O presente trabalho teve como objetivo avaliar o potencial de degradação de MC pela bactéria Sphingosinicella microcystinivorans B9, diferentes cepas de leveduras e bactérias probióticas. O teste foi efetuado com extrato de MC e diferentes quantidades de biovolume e densidade celular dos microrganismos. Os tratamentos foram mantidos a 27ºC com rotação de 100 rpm e as amostras para análise de MC e contagem dos microrganismos foram retiradas após 0 e 96 horas de contato. A bactéria B9 apresentou maior degradação de MC, chegando a 98% após 96 horas.

To minimize problems related to the occurrence of cyanobacteria in water for human consumption there is need to investigate alternative treatment techniques with emphasis on biofilms with the potential degradation of microcystins (MC). This study aimed to evaluate the potential degradation of MC by bacteria Sphingosinicella microcystinivorans B9, different strains of yeast and probiotic bacteria. The test was carried out with the extract obtained from strain Microcystis sp. In the tests biomass and cultures of microorganisms were used and the treatments were maintained at 27ºC with 100 rpm. Samples for analysis of MC and for counting the microorganisms were collected at 0 and 96 hours. The bacterium B9 presented the highest potential of degradation of MC reaching 98% after 96 hours.

Biomonitoring of microcystin and aflatoxin co-occurrence in aquaculture using immunohistochemistry and genotoxicity assays

This work investigated the effects of co-occurring aflatoxin B1 (AFB1) and microcystin (MC) in aquaculture, using immunohistochemistry and genotoxicity methods. Tilapia (Oreochromis niloticus) were exposed to AFB1 by intraperitoneal and MC (cell extract of Microcystis aeruginosa) by intraperitoneal and immersion routes. The interaction of MC-AFB1 was evaluated co-exposing the intraperitoneal doses. Blood samples were collected after 8, 24, and 48h to analyze the micronucleus frequency and comet score. The interaction of MC-AFB1 showed a synergic mutagenic response by higher micronucleus frequency of co-exposed group. A slight genotoxic synergism was also observed in the comet score. Immunohistochemistry detected MC in al lthe fish liver tissues exposed to MC by intraperitoneal route, and only the immersed group with the highest dose of MC showed a positive response. Although MC was non-detectable in the edible muscle, the combination of immunohistochemistry with genotoxicity assay was an attractive biomonitoring tool in aquaculture, where the animals were frequently exposed to co-occurring synergic hazards.

Avaliação da toxicidade aguda de uma cepa de Microcystis spp. por meio de testes com camundongos / Acute toxicity evaluation for a Microcystis spp. strain by bioassay with male swiss albino mice

Este estudo teve como objetivo complementar a caracterização da toxicidade de uma cepa de Microcystis spp., por meio de testes de toxicidade aguda com camundongos, após caracterização química preliminar de microcictinas - MCs realizada por cromatografia líquida de alta eficiência com detector de diodo HPLC-PDA e espectrometria de massas com ionização por electrospray MS-ESI. Os testes de toxicidade aguda com camundongos demonstraram, segundo classificação proposta por Lawton et al (1994b), que a cepa tóxica testada enquadra-se no grau de elevada toxicidade com valor de DL50 24h de extrato seco menor que 100 mg/kg p.c. (peso corpóreo) (13,7 mg/kg p.c.), de DL50 24h de microcistinas totais estimada de 24,2 µg/kg p.c. e concentração de MCs no material seco maior que 1,0 µg/mg p.s. (entre 1,64 e 1,86 µg/mg p.s.).

This study was carried out to evaluate the toxicity of a strain of Microcystis spp, using acute toxicity bioassays with swiss albino mice and to characterize chemically the microcistins using high efficiency liquid chromatography with photodiode array detector (HPLC-PDA) and mass spectrometry with electrospray ionization (MS-ESI). The acute toxicity tests with mice showed that according to the classification proposed by Lawton et al (1994b), the toxic strain here tested corresponds to the degree of high toxicity with DL50 24h values for the dry extract lower than 100 mg/kg corporal weight (13,7 mg/kg corporal weight), while DL50(24h) for total microcystin - MCs concentration around 24,2 µg/kg corporal weight. and concentration of MCs in the dry material higher than 1,0 µg/mg dry weight (between 1.64 and 1.86 µg/mg d.w.).