Resumo A crescente investigação da contaminação ambiental por cistos de Giardia spp. e seu impacto na saúde pública despertou o interesse em desenvolver métodos mais sensíveis para detectar esses protozoários, especialmente na água. No entanto, esses métodos ainda são complexos e dispendiosos. Este estudo teve como objetivo avaliar a eficiência de concentração e remoção de cistos de Giardia duodenalis usando um polímero floculante aniônico à base de acrilamida (AFP) em amostras de água de retrolavagem de filtro de uma estação de tratamento de água (ETA) localizada na cidade de Blumenau, sul do Brasil, e compará-lo com a técnica de floculação de carbonato de cálcio (CCF), rotineiramente usada em matrizes de água com alta turbidez. A taxa de recuperação média de cistos de G. duodenalis usando CCF e AFP foi de 33,33% e 43,33%, com uma redução média de turbidez de 98,39% e 98,78%, respectivamente. O uso de um polímero floculante aniônico provou ser uma alternativa eficiente para a concentração e remoção de cistos de protozoários em amostras de água com alta turbidez. É importante destacar que o desenvolvimento e a aplicação de novos estudos e estratégias que aumentem a eficiência da remoção desses organismos de matrizes ambientais complexas trariam benefícios tanto do ponto de vista da saúde pública quanto da perspectiva da saúde única. spp entanto dispendiosos (AFP ETA (ETA Blumenau Brasil comparálo compará lo CCF, , (CCF) G 3333 33 33,33 4333 43 43,33% 9839 98 39 98,39 9878 78 98,78% respectivamente única (CCF 333 3 33,3 433 4 43,33 983 9 98,3 987 7 98,78 33, 43,3 98, 98,7 43,

Abstract The increasing investigation into environmental contamination by Giardia spp. cysts and its impact on public health has spurred interest in developing more sensitive methods for detecting these protozoa, particularly in water. However, these methods remain complex and costly. This study evaluated the concentration and removal efficiency of Giardia duodenalis cysts using an acrylamide-based anionic flocculant polymer (AFP) in filter backwash water samples from a water treatment plant (WTP) located in Blumenau City, southern Brazil, and compared them with the calcium carbonate flocculation technique (CCF), which is routinely used for water matrices with high turbidity. The average recovery rates of G. duodenalis cysts using CCF and AFP were 33.33% and 43.33%, respectively, with an average turbidity reduction of 98.39% and 98.78%. The use of an anionic flocculant polymer proved to be an efficient alternative for the concentration and removal of protozoan cysts in water samples with high turbidity. It is important to highlight that the development and application of new studies and strategies aimed at increasing the efficiency of the removal of these organisms from complex environmental matrices would bring benefits to public health and promote a One Health perspective. spp protozoa However costly acrylamidebased acrylamide based (AFP WTP (WTP City Brazil CCF, , (CCF) G 3333 33 33.33 4333 43 43.33% respectively 9839 98 39 98.39 9878 78 98.78% perspective (CCF 333 3 33.3 433 4 43.33 983 9 98.3 987 7 98.78 33. 43.3 98. 98.7 43.

Abstract This research assessed the efficiency of chemically modified tannins as coagulants for water treatment. Tannins from Anacardium occidentale (cashew tree) and Mimosa caesalpiniifolia (‘sabiá’) barks and seedless fruits of Anadenanthera colubrina (‘angico’) and Pityrocarpa moniliformis (‘angico de bezerro’) were evaluated after cationization to remove turbidity from water. After extraction, the total solids content (TSC), Stiasny index (SI), and total condensed tannins content (TCC) of the tannins extracts were determined. Extracted tannins were converted into powders and cationized. Then, the cationized tannins' effectiveness on water turbidity removal, sedimentation time, and effect on pH were assessed. Three concentrations of each type of tannin were used to evaluate flocculant efficiency: 50, 100, and 150 mg L-1. Although the P. moniliformis extract had a higher TSC value (56.06%), it presented the lowest SI (0.42%) and TTC (0.23%) values. M. caesalpiniifolia had the lowest TSC (9.18%) and the highest SI (91.27%), while Ac occidentale stood out with the highest TCC (19.83%). All species have shown potential for tannin production and efficiently removed turbidity at all concentrations. However, only A. occidentale, at a concentration of 100 mg L-1, presented a nephelometric turbidity unit of 2.4, reaching the potability standards required by international specifications and, therefore, being indicated for water treatment. treatment cashew tree ‘sabiá sabiá (‘sabiá’ ‘angico angico (‘angico’ bezerro bezerro’ extraction TSC, , (TSC) SI, (SI) (TCC determined Then removal time 50 15 L1. L1 L 1. 1 L-1 P 56.06%, 5606 56.06% 56 06 (56.06%) 0.42% 042 0 42 (0.42% 0.23% 023 23 (0.23% values M 9.18% 918 9 18 (9.18% 91.27%, 9127 91.27% 91 27 (91.27%) 19.83%. 1983 19.83% . 19 83 (19.83%) However A 10 L1, 1, 24 2 4 2.4 therefore (‘sabiá (TSC (SI 5 L- 560 56.06 (56.06% 0.42 04 (0.42 0.23 02 (0.23 9.18 (9.18 912 91.27 (91.27% 198 19.83 8 (19.83% 2. 56.0 (56.06 0.4 (0.4 0.2 (0.2 9.1 (9.1 91.2 (91.27 19.8 (19.83 56. (56.0 0. (0. 9. (9. 91. (91.2 19. (19.8 (56. (0 (9 (91. (19. (56 ( (91 (19 (5 (1

Resumo O presente trabalho teve como objetivo avaliar a eficiência de taninos quimicamente modificados como coagulantes para tratamento de água. Os taninos das cascas de Anacardium occidentale (cajueiro) e Mimosa caesalpiniifolia (sabiá) e dos frutos sem sementes de Anadenanthera colubrina (angico) e Pityrocarpa moniliformis (angico de bezerro) foram avaliados após cationização para remover a turbidez da água. Após a extração, os extratos de taninos tiveram o teor de sólidos totais (TST), o índice de Stiasny (IS) e o teor de taninos totais condensados (TCT). Os taninos extraídos foram convertidos em pó e cationizados. Em seguida, avaliou-se a eficácia dos taninos cationizados na remoção da turbidez e o tempo de sedimentação além do efeito no pH da água. Para avaliar a eficiência dos taninos cationizados como floculantes foram utilizadas três concentrações de cada tipo de material: 50, 100 e 150 mg L-1. Embora o extrato de P. moniliformis tenha apresentado maior valor de TST (56,06%), apresentou os menores valores de IS (0,42%) e TCT (0,23%). Os taninos da casca de M. caesalpiniifolia apresentou o menor TST (9,18%) e o maior IS (91,27%), enquanto os derivados de A. occidentale se destacaram pelo maior TCT (19,83%). Todas as espécies demonstraram potencial para produção de taninos e foram eficientes em remover a turbidez da água em todas as concentrações. Porém, apenas o A. occidentale, na concentração de 100 mg L-1, apresentou unidade de turbidez nefelométrica de 2,4, atingindo os padrões de potabilidade exigidos pelas especificações internacionais e, portanto, sendo indicado para tratamento de água. cajueiro (cajueiro sabiá (sabiá angico bezerro extração TST, , (TST) (IS TCT. . (TCT) seguida avaliouse avaliou material 50 10 15 L1. L1 L 1. 1 L-1 P 56,06%, 5606 56,06% 56 06 (56,06%) 0,42% 042 0 42 (0,42% 0,23%. 023 0,23% 23 (0,23%) M 9,18% 918 9 18 (9,18% 91,27%, 9127 91,27% 91 27 (91,27%) A 19,83%. 1983 19,83% 19 83 (19,83%) Porém L1, 1, 24 2 4 2,4 portanto (TST (TCT 5 L- 560 56,06 (56,06% 0,42 04 (0,42 02 0,23 (0,23% 9,18 (9,18 912 91,27 (91,27% 198 19,83 8 (19,83% 2, 56,0 (56,06 0,4 (0,4 0,2 (0,23 9,1 (9,1 91,2 (91,27 19,8 (19,83 56, (56,0 0, (0, (0,2 9, (9, 91, (91,2 19, (19,8 (56, (0 (9 (91, (19, (56 ( (91 (19 (5 (1

Resumen Los exopolisacáridos (EPS) pueden ser utilizados como agentes reductores confiriendo mejores propiedades físicas y químicas a las nanopartículas metálicas. Este estudio tuvo como objetivo sintetizar y evaluar las características fisicoquímicas, estructurales y funcionales de nanopartículas de ZnO producidas con EPS de Lactiplantibacillus fabifermentans BAL-27-ITTG. La caracterización estructural de los EPS exhibió una estructura de alto peso molecular compuesta principalmente de manosa y glucosa con enlaces α-1,4, α-1,3, α-1,6 de acuerdo con el espectro de RMN. El aumento de la concentración de EPS en la síntesis provoca el incremento en el tamaño de las partículas en escala micrométrica disminuyendo el índice de polidispersidad. La síntesis de las nanopartículas se confirmó mediante un barrido espectral UV-vis y el espectro FT-IR mostró picos de absorción a 600 cm-1 asociados al enlace Zn-O. Las nano (NP) y micropartículas (MP) sintetizadas mostraron actividades funcionales mejoradas respecto al EPS libre. Los valores máximos en actividad antioxidante (80.25 %), capacidad de retención de agua (3.06 g H2O/g muestra), actividad emulsionante (69.85 %) y actividad floculante (69.07 %) se obtuvieron con las MpZnO-EPS sintetizadas con 6 mg/mL del agente reductor. La actividad bacteriostática fue observada contra S. aureus y L. fabifermentans. La ausencia de hemólisis confirmó la biocompatbilidad de las partículas.

Abstract Exopolysaccharides (EPS) can be used as reducing agents and stabilizers, improving the physical and chemical properties of metallic nanoparticles. This study aimed to synthesize and evaluate the physicochemical, structural, and functional characteristics of ZnO particles obtained from EPS produced by Lactiplantibacillus fabifermentans BAL-27-ITTG. The structural characterization of the EPS exhibited a high molecular weight structure composed mainly of mannose and glucose, possibly linked by α-1-4, α-1-3, α-1-6 according to the RMN spectrum. The increase in EPS concentration during the synthesis leads to an increase of particle size at micrometric scale, decreasing the polydispersity index. The synthesis was confirmed with a UV-vis spectral scan, while the FT-IR spectrum showed absorption peaks at 600 cm-1 associated with the Zn-O bond. SSynthetized nano (NP) and microparticles (MP) showed improved functional characteristics comparing to free EPS. The highest values of antioxidant activity (80.25 %), water holding capacity (3.06 g H2O/g sample), emulsifying activity (69.85 %), and flocculant activity (69.07 %) were obtained from MpZnO-EPS synthetized with a concentration of 6 mg/mL of the reducing agent. Bacteriostatic activity was observed against S. aureus and L. fabifermentans. The absence of hemolysis confirms the biocompatibility of the particles.

Resumen El agua es un recurso cada vez más valioso porque su disponibilidad, principalmente, se limita a la precipitación y al almacenamiento de agua; por esa razón, el aumento de la densidad de población y el cambio climático pueden interferir con la accesibilidad al agua. Las actividades urbanas e industriales pueden producir aguas residuales y contaminar cuerpos de agua que podrían representar una fuente importante de agua; sin embargo, necesita ser tratado antes de su uso. La floculación es un importante método de eliminación de contaminantes para reducir una variedad de moléculas orgánicas e inorgánicas de las aguas residuales, utilizando las cargas intrínsecas del floculante para estabilizarlas/precipitarlas, por diferentes métodos, uno de ellos a través de un complejo polielectrolítico. La versatilidad de los floculantes depende de su capacidad para remover contaminantes y existen floculantes comerciales con eficiencias notables. Sin embargo, su toxicidad puede limitar su uso en cuerpos de agua o para uso humano anterior. Las investigaciones muestran que los polisacáridos son excelentes opciones como floculantes debido a su conformación de fácil carga y alto peso molecular para neutralizar contaminantes y precipitar flóculos, son biocompatibles, biodegradables y fáciles de modificar para modular la interacción floculante debido a la alta densidad del grupo funcional. Esta revisión explora las últimas investigaciones sobre la floculación de polielectrolitos de polisacáridos y sus derivados y su capacidad de remoción de contaminantes, los polisacáridos evaluados fueron los más investigados como quitosano, celulosa, quitina, alginato, gomas, dextrano, entre otros. Las tendencias de investigación recientes sobre la capacidad de floculación de estos polisacáridos mostraron resultados prometedores (hasta un 99% de eficiencia de remoción) con una amplia variedad de contaminantes, lo que los convierte en excelentes candidatos para su aplicación en la floculación verde.

Abstract Water is an increasingly valuable resource because its availability, primarily it is limited to precipitation and water storage; for that reason, increasing population density and climate change can interfere with water accessibility. Urban and industrial activities can produce wastewater and pollute waterbodies that could represent a significant water source; however, it needs to be treated prior to its use. Flocculation is an important pollutants removal method to reduce a variety of organic and inorganic molecules from wastewater, using the flocculant’s intrinsic charges to stabilize/precipitate them, by different methods, one of them being via polyelectrolyte complex. Flocculant versatility depends on its capacity to remove pollutants and there are commercial flocculants with remarkable efficiencies. However, their toxicity can limit their use in waterbodies or for former human use. Research shows that polysaccharides are great option as flocculants because of their easily charged conformation and high molecular weight to neutralize pollutants and precipitate flocs, they are biocompatible, biodegradable, and easy to modify to modulate the flocculant interaction due to the functional group’s high density. This review explores the latest research on polysaccharide polyelectrolyte flocculation and derivatives and their pollutant removal capacity, the polysaccharides evaluated were the most commonly researched such as chitosan, cellulose, chitin, alginate, gums, dextran, among others. Recent research tendencies on these polysaccharides flocculation capacity, showed promising results (up to 99% removal efficiencies) with a wide variety of contaminants, making them excellent candidates for their application in green flocculation.

Abstract Flocculation is a complex process, usually dependant on various conditions to perform adequately. Nevertheless, the relevance and interaction of the process variables are not easily found in literature. In this study, nine variables of ultrafine quartz flocculation systems, defined in Part 1 of this study, were analysed. The effects of each variable and their interactions in the system were investigated based on flocculation and sedimentation tests. The results were statistically evaluated using the supernatant turbidity as experimental response. The evaluations resulting from the statistical approach indicated that suspension pH (5.49%) was the most significant variable, followed by flocculant concentration (4.07%) with the second greatest effect on the turbidity of the supernatant. Solid concentration, agitation intensity, and surfactant conditioning time (4.05%, 3.51% and 3.51%, respectively), also have significant effects on ultrafine quartz flocculation. The flocculant concentration and the surfactant conditioning time were the variables with the most significant interactions with the main variables. The Camp Number values showed a negative exponential relationship with the turbidity results, proving to be an important tool to evaluate flocculation. Backscattered electron scanning microscopy images of flocs formed in the presence of 30 g/t PAM showed compact flocs in the size range between 150 and 365 µm, with noticeable sphericity. adequately Nevertheless literature study systems analysed tests response 5.49% 549 5 49 (5.49% 4.07% 407 4 07 (4.07% intensity 4.05%, 405 05 (4.05% 351 3 51 3.51 respectively, respectively , respectively) gt g t 15 36 µm sphericity 5.49 54 (5.49 4.07 40 0 (4.07 4.05% (4.05 35 3.5 5.4 (5.4 4.0 (4.0 4.05 3. 5. (5. 4. (4. (5 (4 (

Cardanol acts to stabilize asphaltene particles in crude oil, but its derivative polycardanol, synthesized with BF3.O(C2H5)2 as initiator, exhibits divergent behavior, acting as both asphaltenes stabilizer and flocculant. This behavior could be related to structural differences in polycardanol samples. Therefore, in this work, we study the influence of some polymerization conditions (monomer purity, initiator concentration, and reaction time) on the structures and molar masses of the reaction products, and the reaction conversion. The materials were characterized by size exclusion chromatography and hydrogen and carbon nuclear magnetic resonance. When reacting with distilled cardanol, the conversion, the molar mass, and the homogeneity of structures increased as increasing initiator concentration in the range tested (1-3% m/m). For both monomers (different purity degrees), when using a lower initiator concentration (1% m/m), the product contained a larger amount of unreacted monomer and different structures were obtained due to the occurrence of rearrangements. The presence of triolefinic molecules in the monomer provoked crosslinked structures for higher initiator concentration (2-3% m/m). This study elucidated the differences among the reaction products of polycardanol. oil BF3.OC2H52 BF3OC2H52 BFOCH BF3.O C2H5 2 BF3 O BF C H BF3.O(C2H5) flocculant samples Therefore work time conversion resonance cardanol mass 13% 13 1 3% 3 (1-3 m/m. mm m/m . m m/m) degrees, degrees , degrees) 1% (1 m/m, rearrangements 23% 23 (2-3 OC2H52 OC BF3.OC2H5 BF3OC2H5 BF3O BFO CH C2H BF3.O(C2H5 (1- ( (2- OCH OC2H5 BF3.OC2H BF3OC2H BF3.O(C2H (2 OC2H

ABSTRACT Due to a significant amount of nutrients in its composition, swine manure (SM) is commonly used to complement or replace commercial agricultural fertilizers. However, an improper application in crops could cause negative environmental impacts, especially due to the excessive supply of nutrients in its composition. This paper aimed to evaluate the removal of total Kjedahl nitrogen (TKN) and total phosphorus (TP) from SM biodigested by the coagulation/flocculation (CF) process with organic polymers. The SM samples were collected in two distinct seasonal periods (rainy and dry seasons), with CF tests in two stages. During the first stage, slow mixing times (SMTs) of 15, 20, and 25 min were tested, and in the second stage, the coagulant (0 – 1.75 g L-1) and flocculant dosage (0 – 0.0025 g L-1) effects were evaluated. The results show that the optimal SMT was 15 min in both the seasons. In the rainy season, the highest phosphorus and nitrogen removals were 80 and 27%, respectively, while in the dry season, the highest phosphorus and nitrogen removals were 70 and 25%, respectively. The finding shows that the use of flocculants did not improve the removal of TP and TKN when compared with the control conditions. It is concluded that the CF process can be used to remove TP and TKN from SM, with a possible concentration of them in the generated sludge. composition (SM fertilizers However impacts (TKN (TP coagulationflocculation coagulation flocculation (CF polymers seasons, seasons , seasons) stages stage SMTs (SMTs 20 2 tested 0 ( 175 1 75 1.7 L1 L L-1 00025 0025 0.002 evaluated season 8 27 27% respectively 7 25% conditions sludge 17 1. L- 0002 002 0.00 000 00 0.0 0.

RESUMO Por conter uma quantidade significativa de nutrientes em sua composição, a água residual de suinocultura (ARS) é comumente utilizada para complementar ou substituir fertilizantes agrícolas comerciais. No entanto, a aplicação inadequada nas culturas pode causar impactos ambientais negativos, especialmente devido ao aporte excessivo de nutrientes presentes em sua composição. Neste estudo, o objetivo foi avaliar a remoção de nitrogênio total Kjedahl (NTK) e fósforo total (FT) da ARS biodigerida pelo processo de coagulação/floculação com polímeros orgânicos. As amostras de ARS foram coletadas em dois períodos sazonais distintos (estações de chuva e seca), com testes de coagulação/floculação (CF) em duas etapas. Na primeira etapa, foram testados tempos de mistura lenta (TML) de 15, 20 e 25 minutos, e na segunda etapa, foram avaliados os efeitos da dosagem do coagulante (0 – 1,75 g L-1) e do floculante (0 – 0,0025 g L-1). Os resultados indicaram que o TML ótimo foi de 15 minutos em ambas as estações. Na estação chuvosa, as maiores remoções de fósforo e nitrogênio foram de 80 e 27%, respectivamente, enquanto que na estação seca, as maiores remoções de fósforo e nitrogênio foram de 70 e 25%, respectivamente. Verificou-se que a utilização do floculante não trouxe melhorias nas remoções de FT e NTK. Conclui-se que o processo de CF pode ser empregado na remoção de FT e NTK da ARS, com possível concentração desses no lodo gerado. composição (ARS comerciais entanto negativos estudo (NTK (FT coagulaçãofloculação coagulação floculação orgânicos estações seca , seca) (CF etapas etapa (TML 2 0 ( 175 1 75 1,7 L1 L L-1 00025 0025 0,002 L1. . chuvosa 8 27 27% respectivamente 7 25% Verificouse Verificou se Concluise Conclui gerado 17 1, L- 0002 002 0,00 000 00 0,0 0,

Abstract A characterization study was performed to verify the more relevant physicochemical properties for quartz flocculation with polyacrylamide, as well as to define which variables should be further investigated regarding this flocculation system. Polyacrylamide was evaluated through molecular weight, radius of gyration, and infrared spectrometry. A natural quartz sample was investigated regarding its particle size distribution, specific surface area, mineralogical and chemical composition. The zeta potential of quartz with flocculant and surfactant was also analyzed. The results indicated that the quartz had high purity and particle sizes between 38 and 10 µm, which was within the intended particle size range; the flocculant presented a suitable molecular weight for the proposed flocculation system. Based on literature, nine variables were chosen to be investigated in Part II of this study: flocculant and surfactant concentration, flocculant and surfactant conditioning time, flocculation addition time, agitation intensity, pH of the suspension, flocculation time, and solid concentration.

ABSTRACT The objective of the article was to analyze the efficiency of cocoa (Theobroma cacao) shell flour in removing turbidity from domestic wastewater. The coagulant doses were 600, 800, and 1000 mg/L, with a fast speed of 180 RPM for one minute, a slow speed (40 and 60 RPM) for 15 minutes, and a settling time of 15 minutes. The volume of each jar was 1 L. A p-value of 0.001 was found for the slow speed factor; that is, there is a significant difference in turbidity for the two slow speed values. For the flocculant concentration factor, the p-value was 0.737; that is, there is no significant difference in turbidity for the four values of flocculant concentration. Likewise, the p-value for the (slow speed * concentration interaction) was 0.737; that is, it was not significant. It is concluded that the use of natural flocculants is a sustainable alternative for the removal of turbidity from domestic wastewater.

RESUMEN El objetivo del artículo fue analizar la eficiencia de la harina de cáscara de cacao (Theobroma cacao) en la remoción de turbidez de aguas residuales domésticas. Las dosis del coagulante fueron 600, 800 y 1000 mg/L, con velocidad rápida de 180 RPM por un minuto, velocidad lenta (40 y 60 RPM) por 15 minutos y tiempo de sedimentación de 15 minutos. El volumen de cada jarra fue de 1 L. Se encontró un p-valor de 0,001 para el factor velocidad lenta; es decir existe diferencia significativa de la turbidez para los dos valores de velocidad lenta. Para el factor concentración de floculante, el p-valor fue 0,737; es decir, no existe diferencia significativa de la turbidez para los cuatro valores de concentración de floculante. Asimismo, el p-valor para la interacción (velocidad lenta * concentración) fue 0,737; es decir no fue significativo. Se concluye que el uso de floculantes naturales es una alternativa sustentable para la remoción de turbidez del agua residual doméstica.

ABSTRACT Biofloc technology is a culture system that intensively uses microbial communities. Most bacteria can form aggregates around organic or inorganic surfaces. The high adsorption capacity, surface area, and flocculant properties of clay minerals make these compounds good candidates to stimulate biofloc formation, increase bacterial biomass, and improve nitrification. The objective of this study was to evaluate the addition of clay minerals to biofloc formation and its influence on the microbial community, nitrification, and zootechnical performance of Penaeus vannamei cultivated in a biofloc technology system. Experiment 1 involved the following treatments: control (without adding clay minerals), 10, 50, and 100 mg L−1, applied daily in the water. The treatments in experiment 2 were: control without product and inoculum, control without product and with inoculum, 50 mg L−1 clay mineral without inoculum and 50 mg L−1 clay mineral with inoculum. Both experiments with a density of 400 ind m−3. NO2 levels, total suspended solids, turbidity, differed significantly (P < 0.05) between treatments in experiment 1 and zootechnical performance parameters, where higher flocculant concentrations negatively affected these indices. In experiment 2, statistical differences were verified for NH3 and NO2 concentrations and the proximate composition of the bioflocs (P < 0.05), the addition of the inoculum of bioflocs influenced these results. In summary, the addition of clay minerals influenced biofloc formation, proximal composition, and the zootechnical performance of the cultivated shrimp but did not affect the abundance of microorganisms and nitrification.

This study assessed the effects of volume concentration (0.3%, 0.6%, 1.2%, and 12% v/v) and type of polymer flocculant (acrylamide, chitosan, and purified and non-purified acrylamide grafted chitosan) on the flocculation mechanism of kaolinite-rich mining tailings samples. We measured the flocculated samples’ transmittance using UV-VIS spectrometry to check for particles in the supernatant medium in order to verify the flocculation efficiency. It was observed that flocculation directly depends on the pH of the medium, the isoelectric point of the kaolinite, and the polymer chains’ molecular mass. The concentration of H+ and OH- ions is responsible for producing charges of different electrical nature on the particles present in the suspension, thereby affecting the flocculation process. In the acrylamide samples, the aggregation of particles occurs by electrostatic interaction; and in the other samples by bridging, suggesting that the chains’ molecular mass interferes in the coagulation and flocculation mechanisms. Moreover, the results of absorbance measurements and flocs’ apparent density highlight that the grafting of acrylamide on the chitosan chain may improve the kaolin waste flocculation. For flocculant concentrations of up to 1.2% (v/v), the absorbances were mostly below 1.0, indicating removal of suspended materials.

RESUMO: O processo de colheita é um desafio atual para a produção comercial de microalgas porque a biomassa é diluída no meio de cultivo. Diversos métodos têm sido propostos para coletar células de microalgas, porém não existe um consenso sobre um método ótimo para tal aplicação. Neste estudo, métodos baseados em sedimentação, floculação e centrifugação foram avaliados na recuperação de Chlorella sorokiniana BR001 cultivada em um meio com baixo teor de nitrogênio. C. sorokiniana BR001 foi cultivada em um meio com baixo teor de nitrogênio para induzir ao acúmulo de lipídeos e carboidratos neutros. A biomassa de C. sorokiniana BR001 cultivada em um meio com baixo teor de nitrogênio apresentou um teor de lipídeos 1,9 vezes superior (23,8 ± 4,5%), quando comparada à biomassa produzida em um meio com alto teor de nitrogênio (12,3 ± 1,2%). Adicionalmente, a biomassa da linhagem BR001 cultivada em um meio com baixo teor de nitrogênio apresentou alto teor de carboidratos neutros (52,1 ± 1,5%). O processo baseado em sedimentação natural foi avaliado utilizando uma coluna de sedimentação e concluiu-se que C. sorokiniana BR001 é uma linhagem não floculante. Portanto, o efeito de diferentes concentrações de sulfato férrico (0,005 a 1 g L-1) ou sulfato de alumínio (0,025 a 0,83 g L-1) foram avaliados no processo de floculação de C. sorokiniana BR001, mas altas doses de floculantes foram necessárias para uma colheita de biomassa eficiente. Também foi avaliada a centrifugação em baixa velocidade (300 a 3.000 g), e foi possível concluir que este processo constituiu o mais adequado para a colheita da linhagem não floculante C. sorokiniana BR001.

ABSTRACT: The harvesting process is a current challenge for the commercial production of microalgae because the biomass is diluted in the culture medium. Several methods have been proposed to harvest microalgae cells, but there is not a consensus about the optimum method for such application. Herein, the methods based on sedimentation, flocculation, and centrifugation were evaluated on the recovery of Chlorella sorokiniana BR001 cultivated in a low-nitrogen medium. C. sorokiniana BR001 was cultivated using a low-nitrogen medium to trigger the accumulation of neutral lipids and neutral carbohydrates. The biomass of C. sorokiniana BR001 cultivated in a low-nitrogen medium showed a total lipid content of 1.9 times higher (23.8 ± 4.5%) when compared to the biomass produced in a high-nitrogen medium (12.3 ± 1.2%). In addition, the biomass of the BR001 strain cultivated in a low-nitrogen medium showed a high content of neutral carbohydrates (52.1 ± 1.5%). The natural sedimentation-based process was evaluated using a sedimentation column, and it was concluded that C. sorokiniana BR001 is a non-flocculent strain. Therefore, it was evaluated the effect of different concentrations of ferric sulfate (0.005 to 1 g L-1) or aluminum sulfate (0.025 to 0.83 g L-1) on the flocculation process of C. sorokiniana BR001, but high doses of flocculant agents were required for an efficient harvest of biomass. It was evaluated the centrifugation at low speed (300 to 3,000 g) as well, and it was possible to conclude that this process was the most adequate to harvest the non-flocculent strain C. sorokiniana BR001.

Resumo A preocupação com a exploração desenfreada dos recursos naturais tem aumentado nas últimas décadas, principalmente envolvendo a água e seu tratamento. Paradoxalmente, uma das fontes de poluição da água é justamente o seu tratamento, devido ao uso de floculantes químicos, que acabam gerando lodos que podem ser altamente agressivos ao meio ambiente. Uma das formas de resolver este problema é utilizar floculantes naturais para esta finalidade, uma vez que são biodegradáveis e não agridem a natureza. O objetivo deste trabalho foi avaliar a eficiência de um floculante natural produzido com taninos extraídos da casca do cajueiro (Anacardium occidentale) e compará-lo com dois coagulantes comerciais, Tanfloc® e cloreto de ferro. A água para tratamento foi coletada de um açude. A casca do cajueiro foi coletada, moída e submetida à extração em água quente para obtenção dos taninos, e o produto da extração foi cationizado. Os testes de floculação foram realizados utilizando-se o jar test com soluções nas concentrações de 33,3, 66,7 e 100 mg L-1. A turbidez e o pH foram analisados antes e após a floculação. Dentre os floculantes avaliados, os taninos cationizados produziram as melhores respostas tanto para remoção de turbidez quanto para pH final da água tratada. O Tanfloc® também apresentou resultados satisfatórios quanto à remoção de turbidez. O cloreto de ferro, além de não clarificar adequadamente a água, a deixou muito ácida. Como os taninos cationizados praticamente não alteraram o pH e foram eficazes na remoção da turbidez, consistem em um produto interessante para o tratamento da água.

Abstract Concern about the overexploitation of natural resources has increased in recent decades, especially involving water and its treatment. Paradoxically, one of the sources of water pollution is the treatment itself, due to the use of chemical flocculants, which end up generating sludge that may be highly aggressive to the environment. One of the ways to solve this problem is to use natural flocculants for this purpose, since they are biodegradable and do not harm nature. This study evaluated the efficiency of a natural flocculant produced from tannins extracted from the bark of the cashew tree (Anacardium occidentale) and compared it with two commercial coagulants, Tanfloc® and iron chloride. The water for treatment was collected from a weir. The cashew trees’ bark was collected, ground, and submitted to hot-water extraction to yield the tannins, and the extraction product was cationized. The flocculation tests were carried out using the jar test with solutions having concentrations of 33.3, 66.7, and 100 mg L-1. Turbidity and pH were analyzed before and after flocculation. Among the assessed flocculants, the cationized tannins produced the best responses both for removal of turbidity and final pH of the treated water. Tanfloc® also produced satisfactory results regarding turbidity removal. The iron chloride, besides not properly clarifying the water, left it very acidic. Since the cationized tannins practically did not change the pH and were effective in the removal of turbidity, they represent an interesting, sustainable alternative product to treat the water.

RESUMEN La eliminación de iones sulfatos desde aguas naturales, así como de efluentes industriales de diferentes orígenes, es un problema, considerando que la mayoría de los procesos propuestos son ineficientes y de alto costo, principalmente cuando se requiere reducir la concentración de iones sulfato a valores inferiores a 500 mg.L-1. La técnica de flotación combinada con precipitación ha demostrado ser eficiente para la eliminación de iones d metales pesados. Sin embargo, no hay suficientes investigaciones que confirmen su eficiencia para la eliminación de iones sulfato. Este artículo presenta los resultados de la remoción de iones sulfato desde soluciones sintéticas preparadas en un medio ácido, aplicando las técnicas de co-precipitación con policloruro de aluminio (PAC) y separación sólido/líquido mediante flotación por aire disuelto (FAD). Se estudiaron el efecto del pH, la razón [PAC: iones sulfato], el efecto del flujo de agua saturada con aire y las dosis de floculante y colector. Los resultados alcanzados confirman que es posible reducir la concentración de iones sulfato de 1 800 a 350 mg.L-1 (80% de remoción) desde soluciones sintéticas aplicando la técnica de flotación combinada con precipitación.

ABSTRACT The removal of sulfate ions from natural waters, as well as from industrial effluents of different origins, is a problem, considering that most of the proposed processes are inefficient and have a high cost, mainly when reducing the sulfate ion concentration to values below 500 mg.L-1 is required. The flotation technique, combined with precipitation, has proven to be efficient for the removal of heavy metal ions. However, there is not enough research to confirm its efficiency for the removal of sulfate ions. This article presents the results of sulfate ion removal from synthetic solutions prepared in an acidic medium, applying the co-precipitation techniques with polyaluminum chloride (PAC) and solid/liquid separation by dissolved air flotation (DAF). The effect of the pH, the [PAC: sulfate ions] ratio, the effect of saturated water flow with air, and the flocculant and collector doses were studied. The achieved results confirm that it is possible to reduce the concentration of sulfate ions from 1 800 to 350 mg.L-1 (80% removal) from synthetic solutions by applying the flotation technique combined with precipitation.

RESUMEN Se determinaron las condiciones óptimas para maximizar el porcentaje de remoción de los metales pesados como iones Pb 2+ y Zn 2+ de soluciones binarias acuosas mediante el uso de una zeolita químicamente modificada llamado NeoniteMR. De la caracterización por DRX, FRX, FTIR y adsorción-desorción de N , se establece que el NeoniteMR está compuesto principalmente por la zeolita natural clinoptilolita, teniendo SiO2, Na2O, SO3 y Al2O3 como los componentes principales; la relación Si/Al fue de 3,8 y los principales cationes intercambiables son Na+, Ca2+ y K+, el área de superficie BET fue de 24,31 m2/g. El diseño Box Behnken para cuatro factores, [Pb2+], [Zn2+], dosis de Neonite y pH a tres niveles, fue usado para construir modelos cuadráticos de segundo orden, los que presentaron un coeficiente de determinación R2 ajustado de 0.8680 y 0.9614 para el porcentaje remoción de Pb 2+ y Zn 2+ respectivamente; finalmente estos modelos fueron validados mediante los análisis de residuales, distancia de Cook y el valor de apalancamiento. En base a los modelos, no hay una clara influencia de los factores en la remoción del Pb 2+ , mientras que el pH es muy influyente en la remoción del Zn 2+ . Usando la función de deseabilidad global se determinó que la máxima remoción de los iones plomo y zinc fue 98,80% y 93,48% respectivamente, a las condiciones óptimas de concentración de Pb 2+ y Zn 2+ de 20 ppm, dosis del Neonite de 442,42 mg/L y pH igual a 8.

ABSTRACT Optimal conditions were determined to maximize the removal percentage of heavy metals such as Pb2+ and Zn2+ ions from transparent binary solutions by using a zeolite chemically called Neonite™. From the characterization by XRD, XRF, FTIR and adsorption-desorption of N2, it is established that Neonite™ is mainly composed of the natural zeolite clinoptilolite, having SiO2, Na2O, SO3 and Al2O3 as the main components; the Si/Al ratio was 3,8 and the main exchangeable cations are Na+, Ca2+ and K+, the BET surface area was 24,31 m2/g. The Box Behnken design for four factors, [Pb 2+ ], [Zn 2+ ], Neonite dose and pH at three levels, was used to build second order quadratic models, which presented an adjusted coefficient of determination R2 of 0,8680 and 0,9614 for the removal percentage of Pb2+ and Zn2+ respectively; finally, these models were validated through residual analysis, Cook's distance and leverage value. Based on the models, there is no clear influence of the factors on the removal of Pb2+, while the pH is very influential on the removal of Zn2+. Using the global desirability function, it will be shown that the maximum removal of lead and zinc ions was 98,80% and 93,48%, respectively, at the optimal conditions of concentration of Pb 2+ and Zn 2+ of 20 ppm, dose of Neonite of 442,42 mg/L and pH 8.