Hazardous cyanobacteria integrity response to velocity gradient and powdered activated carbon in water treatment plants.

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

The effect of water treatment unit processes on cyanobacterial trichome integrity.

Many toxic and/or noxious cyanobacteria appear in nature with a filamentous, stacked cell arrangement called trichomes. Although water treatment can be optimized to keep cyanobacterial cells intact and to avoid the release of toxic and/or noxious compounds, many physical and chemical stresses encountered during the treatment process may result in trichome truncation, decreasing treatment efficiency by allowing single cells or short trichomes to reach the product water. This makes it possible for harmful/noxious compounds as well as organic matter to enter the distribution system. Investigations in a pilot and three full-scale water treatment plants were carried out in order to elucidate the degree of trichome truncation across different unit processes. It was found that genera (Pseudanabaena, Planktolyngbya) with short trichomes ( < 10–12 cells per trichome), are hardly affected by the unit processes (loss of one to four cells respectively), while genera (Planktothrix, Geitlerinema, Dolichospermum) with longer trichomes (30+ cells per trichome) suffer from high degrees of truncation (up to 63, 30, and 56 cells per trichome respectively). The presence of a rigid sheath and/or mucilaginous layer appears to offer some protection from truncation. It was observed that certain unit processes alter the sensitivity or resilience of trichomes to disruption by physical stress. Some genera (Planktothrix, Geitlerinema) were sensitive to pre-oxidation, making them more susceptible to shear stress, while Dolichospermum sp. appears more robust after pre-oxidation. While the potential of toxicogenic genera breaking through into the product water is a real danger, in the current study no toxicogenic cyanobacteria were observed. This work stresses the need for plant operators to study the incoming cyanobacterial composition in the raw water in order to adjust treatment parameters and thus limit the potential of toxic/noxious compound breakthrough

Internal loading potential of phosphorus in reservoirs along a semiarid watershed.

All rights reserved. Sediments are important to nutrient dynamics, especially due to phosphorus internal loading. Several studies have observed that internal loading could prevent water quality from improving in lakes, even when external phosphorus loading is significantly decreased. Therefore, there is an urgent need to assess the potential release of phosphorus contained in the sediment, and thus, its potential to impact water quality. In this study, the vertical and horizontal distributions of distinct phosphorus forms in the bottom sediments of artificial reservoirs, located at Forquilha watershed (Ceará, Brazil), were investigated through sequential chemical fractionation. The reservoirs Lagoa Cercada (R#1), Riacho do Algodão (R#2), Riacho Verde (R#3), Cachoeira (R#4), Chagas Manu (R#5), Quandu (R#6) and Balanças (R#7) were investigated. Reservoirs R#1 (most downstream reservoir of the watershed) and R#7 (most upstream reservoir of the watershed) had higher concentrations of total phosphorus (PT) and lower pH values, potentially exerting greater influence in phosphorus concentration in the water column. Reservoirs R#3 and R#4 presented a predominance of residual phosphorus (PRe), the least available fractions of phosphorus and thus, presented a lower potential for internal loading. Reservoirs R#5, R#1 and R#2 showed a tendency of decreasing total phosphorus (PT) as the sediment depth increased, probably indicating an increase of allochthonous phosphorus loading along time. Reservoir R#6 showed the predominance of PFeAl and PCa fractions on points A and B, respectively, showing that the characteristics of the sediments may vary in the same reservoir. Mobile (PM) and iron and aluminum-bound phosphorus (PFeAl) were the least and the most abundant fractions in most of the samples analyzed, respectively

Análise de dados categóricos de integridade celular de cianobactérias.

The techniques used in cyanobacterial cell integrity/viability studies provide two outcomes: intact cells or not. These categorical and dichotomous values often make statistical analysis of the results difficult. In this context, the aim of this paper is to present two methodologies for the analysis of these data, showing a detailed sequence of procedures that allow analyzing, with the necessary statistical accuracy, categorized cell integrity data. For this, 3600-records database was used with the results of cellular integrity of Dc and Rr. Among the results, the traditional approach proved appropriate to identify the association between causes and effect respecting the specific characteristics of each species and the odds ratio (OR) calculation allowed to measure the associations. In this multivariate approach, the estimated OR requires a differentiated interpretation in relation to the traditional approach since the estimates are adjusted for the effect of all other variables of the model

A paradigm-shift in water treatment: in-reservoir UV-LED-driven TiO2 photocatalysis for the removal of cyanobacteria: a mesocosm study.

Potentially harmful cyanobacteria challenge potable water treatment globally, with high biomass events, and dissolved toxic and nuisance metabolites. Retrofitting existing water treatment infrastructure is often impractical (if not impossible) and often prohibitively expensive. In a paradigm-shifting move, we propose in-reservoir pre-treatment of cyanobacteria-contaminated raw waters to ease the burden on existing water treatment infrastructure. In an iterative design approach over three years, treatment modules have been designed, refined and optimised, in bench and pilot-scale studies for in-reservoir deployment. TiO2-coated beads made from recycled glass are employed in conjunction with UV-light emitting diodes (LEDs), to create highly reactive hydroxyl radicals that preferably remove cyanobacteria and subsequently released cyanotoxins from raw water. In a mesocosm study using a drinking water reservoir in Brazil, water quality parameters were markedly improved within 72h of deployment and cyanobacterial presence was decreased by over 90% without affecting other phytoplankton communities. The treatment system is virtually plastic-free, low cost, utilises recycled materials and could ultimately be powered by renewable energies, thus providing a true green treatment option. We have conclusively demonstrated that a paradigm-shift towards in-reservoir treatment is not only possible but feasible and can provide a valuable addition to conventional water treatment methods

Effect of hydrogen peroxide on natural phytoplankton and bacterioplankton in a drinking water reservoir: mesocosm-scale study.

Cyanobacterial blooms are increasingly reported worldwide, presenting a challenge to water treatment plants and concerning risks to human health and aquatic ecosystems. Advanced oxidative processes comprise efficient and safe methods for water treatment. Hydrogen peroxide (H2O2) has been proposed as a sustainable solution to mitigate bloom-forming cyanobacteria since this group presents a higher sensitivity compared to other phytoplankton, with no major risks to the environment at low concentrations. Here, we evaluated the effects of a single H2O2 addition (10 mg L−1) over 120 h in mesocosms introduced in a reservoir located in a semi-arid region presenting a Planktothrix-dominated cyanobacterial bloom. We followed changes in physical and chemical parameters and in the bacterioplankton composition. H2O2 efficiently suppressed cyanobacteria, green algae, and diatoms over 72 h, leading to an increase in transparency and dissolved organic carbon, and a decrease in dissolved oxygen and pH, while nutrient concentrations were not affected. After 120 h, cyanobacterial abundance remained low and green algae became dominant. 16S rRNA sequencing revealed that the original cyanobacterial bloom was composed by Planktothrix, Cyanobium and Microcystis. Only Cyanobium increased in relative abundance at 120 h, suggesting regrowth. A prominent change in the composition of heterotrophic bacteria was observed with Exiguobacterium, Paracoccus and Deinococcus becoming the most abundant genera after the H2O2 treatment. Our results indicate that this approach is efficient in suppressing cyanobacterial blooms and improving water quality in tropical environments. Monitoring changes in abiotic parameters and the relative abundance of specific bacterial taxa could be used to anticipate the regrowth of cyanobacteria after H2O2 degradation and to indicate where in the reservoir H2O2 should be applied so the effects are still felt in the water treatment plant intake

Suppressing cyanobacterial dominance by UV-LED TiO2-photocatalysis in a drinking water reservoir: a mesocosm study.

Cyanobacteria and their toxic secondary metabolites present challenges for water treatment globally. In this study we have assessed TiO2 immobilized onto recycled foamed glass beads by a facile calcination method, combined in treatment units with 365 nm UV-LEDs. The treatment system was deployed in mesocosms within a eutrophic Brazilian drinking water reservoir. The treatment units were deployed for 7 days and suppressed cyanobacterial abundance by 85%, while at the same time enhancing other water quality parameters; turbidity and transparency improved by 40 and 81% respectively. Genomic analysis of the microbiota in the treated mesocosms revealed that the composition of the cyanobacterial community was affected and the abundance of Bacteroidetes and Proteobacteria increased during cyanobacterial suppression. The effect of the treatment on zooplankton and other eukaryotes was also monitored. The abundance of zooplankton decreased while Chrysophyte and Alveolata loadings increased. The results of this proof-of-concept study demonstrate the potential for full-scale, in-reservoir application of advanced oxidation processes as complementary water treatment processes

AVALIAÇÃO DO EFEITO GENOTÓXICO DA MEMBRANA POLIHIDROXIBUTIRATO/NORBIXINA/ETILENOGLICOL

Biomateriais são substâncias de origem sintética ou natural que substituem e/ou estimulam sistemas biológicos que deixaram de ter suas funções, como exemplo a restauração de funções teciduais. Tendo em vista o potencial antioxidante da norbixina (carotenoide dicarboxílico encontrado na Bixa orellana L.) e de biodegradabilidade e biocompatibilidade do polihidroxibutirato (PHB) (polímero natural sintetizado a partir de bactérias), objetivou-se preparar uma membrana a partir destes dois constituintes com a adição do reagente etilenoglicol (PHB/norbixina/etilenoglicol) para avaliar seus efeitos genotóxico por meio do teste de micronúcleo. Para este estudo, 15 ratos foram divididos em 3 grupos: A - a membrana foi introduzida no peritônio dos animais através de uma laparotomia; B - apenas uma laparotomia com água destilada; C - injeção de ciclofosfamida em dose única de 50 mg / kg por via intraperitoneal. Foi coletado material de medula óssea de cada rato para realizar o teste de micronúcleo. Em conclusão, o teste de micronúcleo sugere que a membrana não é genotóxica