Although some studies have investigated the impact caused by chemicals used on water treatment (c... more Although some studies have investigated the impact caused by chemicals used on water treatment (coagulants and oxidants) on cyanobacteria integrity, the isolated effect of shear stress during coagulation is still not fully understood. This study evaluated the impact of different velocity gradients, mixing times, and the addition of powdered activated carbon (PAC) on the integrity of Microcystis aeruginosa, Raphidiopsis raciborskii, and Dolichospermum circinale, known producers of toxin and taste and odor (T&O) compounds. No association was found between R. raciborskii cell lysis and velocity gradient, with or without PAC, demonstrating the high resilience of this taxon to shear stress. In contrast, an association was found for M. aeruginosa at the highest velocity gradient evaluated (1000 s-1) and for D. circinale above the lowest velocity gradient studied (600 s-1). After PAC addition, there was a reduction in the chances of finding M. aeruginosa intact cells above velocity gradient 800 s-1 at 45 s, while D. circinale show cell lysis in all the scenarios expect at 600 s-1 and 10 s of agitation. The additional impact of PAC on cell lysis may lead to more release of metabolites and shows the need to adjust the hydraulic conditions in the rapid mixing stage, especially when more-fragile‖ cyanobacteria are present. Neither cyanobacterial cell size nor morphology was shown to be relevant to shear stress sensitivity, indicating that cell wall composition might have been an important factor in controlling cell lysis.
As técnicas utilizadas em estudos de integridade/viabilidade celular de cianobactérias fornecem d... more As técnicas utilizadas em estudos de integridade/viabilidade celular de cianobactérias fornecem duas respostas: células intactas ou não. Esses valores categóricos e dicotômicos dificultam muitas vezes a análise estatística dos resultados. Nesse contexto, o objetivo desse trabalho é apresentar duas metodologias para análise desses dados, mostrando uma sequência detalhada de procedimentos que permitam avaliar, com o rigor estatístico necessário, dados categorizados de integridade celular. Para tal, foram utilizados 3600 registros de integridade celular de Dc e Rr. Na abordagem tradicional identificou-se associação entre causa (perda de integridade celular) e efeito (condições de mistura) somente para Dc. Todavia, para quantificar essas associações, fez-se necessário o cálculo da razão de chances (OR), o que tornou o processo mais laborioso. Já na abordagem alternativa (regressão logística), as OR foram estimadas por meio da comparação das chances de dois cenários, tornando o processo ...
O reservatório Gavião, no Estado do Ceará, é considerado estratégico já que é ponto final do sist... more O reservatório Gavião, no Estado do Ceará, é considerado estratégico já que é ponto final do sistema que atende às demandas do abastecimento de água de Fortaleza. A presente pesquisa focou na dinâmica dos processos de estratificação térmica e seus impactos na qualidade da água. Para essa avaliação, foram analisados dados climatológicos, de gestão do regime operacional e do monitoramento das variáveis ambientais. Foi observada forte estratificação da coluna d’água em vários momentos do primeiro semestre do ano com termoclina na profundidade de 6,50 a 7,50 m abaixo da superfície. Nesse período, ocorreu maior densidade de cianobactérias, com predominância da Pseudonabaena sp em relação às demais espécies. No segundo semestre, constataram-se processos de desestratificação com mais frequência e predominância da Planktothix sp devido ao menor aquecimento da camada superficial, à maior velocidade dos ventos, ao manejo operacional da transferência de água entre bacias hidrográficas e à reti...
Highlights • UV-A photolysis was effective for elimination of cyanobacteria and toxins • Complete... more Highlights • UV-A photolysis was effective for elimination of cyanobacteria and toxins • Complete inhibition of M. aeruginosa PCC7813 by UV-A photolysis • 92% removal of four microcystins after UV-A photolysis (intra-and extracellular) • TiO2 photocatalysis was less effective in M. aeruginosa PCC7813 cell removal
Journal of Water Supply: Research and Technology-Aqua, 2020
Microcystis sp. is one of the most studied genus of cyanobacteria worldwide. Once it has been ide... more Microcystis sp. is one of the most studied genus of cyanobacteria worldwide. Once it has been identified in raw water, frequent analyses of cell density and toxic metabolites (microcystins) are recommended at the water treatment plants. However, both analytical procedures are highly time-consuming and labor-intensive, allowing the potentially contaminated finished water to reach customers. The identification of easily measurable parameters related to toxin production, preferably by on-line equipment, would mitigate this issue and help water companies to improve water safety and decrease operating costs. However, these devices still have precision limitations and need efficient mathematical models for converting light signals into cyanobacteria densities or cyanotoxin concentrations. In this scenario, this research aimed to develop a mathematical correlation between microcystin production and cell age and density, chlorophyll-a, pheophytin and phycocyanin in a Microcystis aeruginosa ...
Hydraulic conditions suggested by technical standards can damage filamentous cyanobacteria. • D. ... more Hydraulic conditions suggested by technical standards can damage filamentous cyanobacteria. • D. circinale intact cells and trichome length are substantially reduced after rapid mixing. • Damage to R. raciborskii was not significant during rapid mixing. • Unlike rapid mixing, slow mixing didn't compromise organisms significantly.
While it has been known that toxic and non-toxic Microcystis coexist in lakes and their relative ... more While it has been known that toxic and non-toxic Microcystis coexist in lakes and their relative proportions vary depending on environmental factors, the main driving force for such variations is still unclear. Therefore, this study attempted to verify the environmental factors related to the dynamics of the abundance of toxic and non-toxic Microcystis in the Daechung Reservoir, Korea. Water samples were collected at weekly intervals from June to October, 2006. Microcystis was a dominant cyanobacterial genus during this period. The proportion of toxic Microcystis genotypes was quantified using a real-time PCR with 2 primer sets for the cpcBA-IGS and mcyJ genes to determine the total Microcystis and potentially toxic genotypes, respectively. Cell densities of toxic and non-toxic Microcystis were strongly related, implying that their growth may be governed by the same environmental factors. Although nontoxic Microcystis was generally dominant over potentially toxic genotypes, the toxic proportion briefly predominated during the Microcystis bloom. While the phosphorus concentration was the fundamental regulating factor for cyanobacterial proliferation, the proportion changes of potentially toxic Microcystis genotypes were more closely related with the water temperature (P < 0.01), suggesting that eutrophication together with global warming could lead to more frequent toxic blooms. ß
Although some studies have investigated the impact caused by chemicals used on water treatment (c... more Although some studies have investigated the impact caused by chemicals used on water treatment (coagulants and oxidants) on cyanobacteria integrity, the isolated effect of shear stress during coagulation is still not fully understood. This study evaluated the impact of different velocity gradients, mixing times, and the addition of powdered activated carbon (PAC) on the integrity of Microcystis aeruginosa, Raphidiopsis raciborskii, and Dolichospermum circinale, known producers of toxin and taste and odor (T&O) compounds. No association was found between R. raciborskii cell lysis and velocity gradient, with or without PAC, demonstrating the high resilience of this taxon to shear stress. In contrast, an association was found for M. aeruginosa at the highest velocity gradient evaluated (1000 s-1) and for D. circinale above the lowest velocity gradient studied (600 s-1). After PAC addition, there was a reduction in the chances of finding M. aeruginosa intact cells above velocity gradient 800 s-1 at 45 s, while D. circinale show cell lysis in all the scenarios expect at 600 s-1 and 10 s of agitation. The additional impact of PAC on cell lysis may lead to more release of metabolites and shows the need to adjust the hydraulic conditions in the rapid mixing stage, especially when more-fragile‖ cyanobacteria are present. Neither cyanobacterial cell size nor morphology was shown to be relevant to shear stress sensitivity, indicating that cell wall composition might have been an important factor in controlling cell lysis.
As técnicas utilizadas em estudos de integridade/viabilidade celular de cianobactérias fornecem d... more As técnicas utilizadas em estudos de integridade/viabilidade celular de cianobactérias fornecem duas respostas: células intactas ou não. Esses valores categóricos e dicotômicos dificultam muitas vezes a análise estatística dos resultados. Nesse contexto, o objetivo desse trabalho é apresentar duas metodologias para análise desses dados, mostrando uma sequência detalhada de procedimentos que permitam avaliar, com o rigor estatístico necessário, dados categorizados de integridade celular. Para tal, foram utilizados 3600 registros de integridade celular de Dc e Rr. Na abordagem tradicional identificou-se associação entre causa (perda de integridade celular) e efeito (condições de mistura) somente para Dc. Todavia, para quantificar essas associações, fez-se necessário o cálculo da razão de chances (OR), o que tornou o processo mais laborioso. Já na abordagem alternativa (regressão logística), as OR foram estimadas por meio da comparação das chances de dois cenários, tornando o processo ...
O reservatório Gavião, no Estado do Ceará, é considerado estratégico já que é ponto final do sist... more O reservatório Gavião, no Estado do Ceará, é considerado estratégico já que é ponto final do sistema que atende às demandas do abastecimento de água de Fortaleza. A presente pesquisa focou na dinâmica dos processos de estratificação térmica e seus impactos na qualidade da água. Para essa avaliação, foram analisados dados climatológicos, de gestão do regime operacional e do monitoramento das variáveis ambientais. Foi observada forte estratificação da coluna d’água em vários momentos do primeiro semestre do ano com termoclina na profundidade de 6,50 a 7,50 m abaixo da superfície. Nesse período, ocorreu maior densidade de cianobactérias, com predominância da Pseudonabaena sp em relação às demais espécies. No segundo semestre, constataram-se processos de desestratificação com mais frequência e predominância da Planktothix sp devido ao menor aquecimento da camada superficial, à maior velocidade dos ventos, ao manejo operacional da transferência de água entre bacias hidrográficas e à reti...
Highlights • UV-A photolysis was effective for elimination of cyanobacteria and toxins • Complete... more Highlights • UV-A photolysis was effective for elimination of cyanobacteria and toxins • Complete inhibition of M. aeruginosa PCC7813 by UV-A photolysis • 92% removal of four microcystins after UV-A photolysis (intra-and extracellular) • TiO2 photocatalysis was less effective in M. aeruginosa PCC7813 cell removal
Journal of Water Supply: Research and Technology-Aqua, 2020
Microcystis sp. is one of the most studied genus of cyanobacteria worldwide. Once it has been ide... more Microcystis sp. is one of the most studied genus of cyanobacteria worldwide. Once it has been identified in raw water, frequent analyses of cell density and toxic metabolites (microcystins) are recommended at the water treatment plants. However, both analytical procedures are highly time-consuming and labor-intensive, allowing the potentially contaminated finished water to reach customers. The identification of easily measurable parameters related to toxin production, preferably by on-line equipment, would mitigate this issue and help water companies to improve water safety and decrease operating costs. However, these devices still have precision limitations and need efficient mathematical models for converting light signals into cyanobacteria densities or cyanotoxin concentrations. In this scenario, this research aimed to develop a mathematical correlation between microcystin production and cell age and density, chlorophyll-a, pheophytin and phycocyanin in a Microcystis aeruginosa ...
Hydraulic conditions suggested by technical standards can damage filamentous cyanobacteria. • D. ... more Hydraulic conditions suggested by technical standards can damage filamentous cyanobacteria. • D. circinale intact cells and trichome length are substantially reduced after rapid mixing. • Damage to R. raciborskii was not significant during rapid mixing. • Unlike rapid mixing, slow mixing didn't compromise organisms significantly.
While it has been known that toxic and non-toxic Microcystis coexist in lakes and their relative ... more While it has been known that toxic and non-toxic Microcystis coexist in lakes and their relative proportions vary depending on environmental factors, the main driving force for such variations is still unclear. Therefore, this study attempted to verify the environmental factors related to the dynamics of the abundance of toxic and non-toxic Microcystis in the Daechung Reservoir, Korea. Water samples were collected at weekly intervals from June to October, 2006. Microcystis was a dominant cyanobacterial genus during this period. The proportion of toxic Microcystis genotypes was quantified using a real-time PCR with 2 primer sets for the cpcBA-IGS and mcyJ genes to determine the total Microcystis and potentially toxic genotypes, respectively. Cell densities of toxic and non-toxic Microcystis were strongly related, implying that their growth may be governed by the same environmental factors. Although nontoxic Microcystis was generally dominant over potentially toxic genotypes, the toxic proportion briefly predominated during the Microcystis bloom. While the phosphorus concentration was the fundamental regulating factor for cyanobacterial proliferation, the proportion changes of potentially toxic Microcystis genotypes were more closely related with the water temperature (P < 0.01), suggesting that eutrophication together with global warming could lead to more frequent toxic blooms. ß
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