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BACKGROUND: Effluents from Food Services Establishments (FSEs) contain primarily Fats, Oil and Grease (FOG) which severely impact on sewers and the environment when released in high concentrations. In Trinidad & Tobago, it is estimated that approximately 231,304 kg/day of unaccounted for FOG bearing wastewaters from FSEs, are released into the environment with no viable treatment in the country. This research explored the optimization of physico-chemical processes for the treatment of FOGs for subsequent release into sewers. RESULTS: Bench-scale studies analysed the characteristics of FSE's effluents from three popular sources, conducted the treatment of these effluents using Jar Tests, and subsequently confirm results via a pilot plant study. Characterization showed the mean concentration of the parameters examined to be; FOG (511 mg/l ± 116 mg/l), Suspended Solids (446 mg/l ± 146 mg/l), Chemical Oxygen Demand (2229 mg/l ± 963 mg/l) and pH (6 ± 0.3). Jar Tests were conducted using Poly-aluminium Chloride (PACl) as coagulant, anionic and cationic polyelectrolytes as flocculant aids with suitable pH adjustments of samples to determine the isoelectric point for the coagulant. Effluent results showed FOG removal levels of 99.9% and final effluent concentration of 0.17 mg/l. This was attained using PACl concentration of 250 mg/l, a 0.1% low cationic polyelectrolyte (CP 1154) at 4 mg/l with the pH of sample adjusted to 8. The pilot plant achieved a 97.4% removal of FOG (residual of 16.8 mg/l) using the same coagulant dosing, and pH value, but increasing the strength of the flocculant aid to 0.1% medium cationic (CP1156) at 5 mg/l. CONCLUSION: Experimentation showed high concentrations of emulsified FOG can be efficiently removed to levels below the permissible requirements (20 mg/l) for entry into sewer systems in Trinidad and Tobago using coagulation, flocculation and sedimentation techniques. Pilot scale study also revealed that a higher strength and/or dose of the cationic polyelectrolyte and increased times in primary and final tanks were required to attain the desired results as in the bench level study, where equipment limitations in the flocculation tank were faced. This is in alignment with theory where factors critical for agglomeration is equipment type and density charge. It is, concluded that the optimum combination of chemicals and the respective dosages attained at the bench level study should prove effective should the right equipment be made available.

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Natural coagulants derived from by-products have gained popularity as sustainable alternatives to inorganic coagulants in water/wastewater treatment due to their abundant availability, biodegradability, low cost, easy disposal and low sludge volumes. In this study, the mucilage obtained from the peel of Opuntia ficus-indica fruit was evaluated as a biocoagulant for treating synthetic turbid water and compared with a traditional chemical coagulant (FeCl3). The effects of coagulant dosage and pH on the turbidity and color-removal efficiency of synthetic turbid water were analyzed. To estimate the coagulation mechanism, the flocs produced under optimal values were characterized structurally (FTIR and zeta potential) and morphologically (SEM). The optimal condition for the removal of turbidity and color was a coagulant dose of 12 mg/L at pH 13. For the optimal values, the biocoagulant and the FeCl3 presented a maximum removal of 82.7 ± 3.28% and 94.63 ± 0.98% for turbidity and 71.82 ± 2.72% and 79.94 ± 1.77% for color, respectively. The structure and morphology of the flocs revealed that the coagulation mechanism of the mucilage was adsorption and bridging, whereas that of FeCl3 was charge neutralization. The results obtained showed that the mucilage could be used as an alternative coagulant to replace FeCl3.

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The main aim of this research was to compare a bio-coagulant, organic coagulant, and a conventional coagulant applied to the treatment of leachates. Coagulant options were Stage 1 FeCl3, Stage 2 Polyamine, and Stage 3 Opuntia ficus mucilage (OFM). Optimal conditions for maximum chemical oxygen demand (COD) removal were determined by experimental data and Response Surface Methodology. The application of Multiple Criteria Decision Analysis using Multi-Criteria Matrix (MCM) was explored by evaluating the Coagulation-Flocculation processes. Maximum COD removal (%) and the best MCM scores (on a scale from 0 to 100) were: Stage 1: 69.2±0.9 and 48.50, Stage 2: 37.8±1.1 and 79.0, and Stage 3: 71.1±1.7, and 81.5. Maximum COD removal using FeCl3 and OFM was not statistically different (p 0.15 < 0.05). OFM extraction process was evaluated (yield 0.70 ± 1.17%, carbohydrate content 32.6 ± 1.18%). MCM allows the evaluation of additional technical aspects, besides oxygen COD removal, as well as economic aspects, permitting a more comprehensive analysis. Significant COD removals indicate that the use of OFM as a coagulant in the treatment of stabilized leachate was effective. Opuntia ficus cladodes, a residue, were used to treat another residue (leachates).

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Treatment of effluents from animal slaughterhouse industries is indispensable, standing out coagulation/flocculation/sedimentation processes. Bionanoparticles (BioNPs) (nanoparticles (NPs) functionalized with Moringa extracts (MO)) were studied as an alternative natural coagulant that would contribute to the microbial load reduction, without increasing the treated effluent toxicity. MO extracts were prepared with different salts, and then, in a kinetics study, different NPs mass and coagulant dosages were evaluated. In the best-defined conditions, microbial load, toxicity tests for the bioindicator Lactuca sativa, and NPs reuse evaluation were performed. Removals of 96.14% turbidity and 43.63% UV254nm were achieved when using 500 mg L-1 of BioNPs containing 60 mg of NPs for every 20 mL of MO extract prepared with 0.1 M CaCl2. The BioNPs with an external magnetic field also decreased the sedimentation time from 140 to 10 min compared to MO, and the process efficiency did not expressively decrease after reusing the recovered NPs. Through toxicity tests, BioNPs were not considered to leave residuals toxic to the Lactuca sativa in the treated effluent. Besides, the microbial load reduction was 97.33% for heterotrophic microorganisms and total mesophiles and 99.25% for moulds/yeasts. Therefore, a satisfactory primary treatment was achieved, contributing to the sustainability of industries.

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RESUMO O sulfato de alumínio (SA) é amplamente utilizado como coagulante no tratamento de água de abastecimento via ciclo completo. Coagulantes alternativos estão disponíveis no mercado, dentre eles o cloreto de polialumínio (PAC). Porém, estudos comparativos entre o SA e os PACs de alta (PAC-AB) e baixa (PAC-BB) basicidade em relação à cinética de floculação ainda são escassos. Nesse sentido, o intuito deste trabalho foi comparar o uso de PAC-BB, PAC-AB e SA via coagulação, floculação e sedimentação, bem como avaliar o efeito na condutividade elétrica, na formação de lodo, na alcalinidade, no pH e na remoção de turbidez baseado na cinética de floculação e morfologia do floco formado. Os resultados indicaram aumento de 8,1% na condutividade elétrica e de 30,6 mg.L-1 na formação de lodo; não houve diferença significativa entre os coagulantes. O PAC-AB apresentou menor consumo de alcalinidade e, consequentemente, menor redução no pH. A remoção de turbidez foi estatisticamente igual entre o PAC-BB (91,8 ± 3,7%) e o PAC-AB (91,5 ± 1,1%), porém maior que no SA (82,2 ± 6,4%). Essa diferença se acentua com o aumento da velocidade crítica de sedimentação. A constante de agregação dos flocos (K A ) apresenta resultados estatisticamente iguais entre os coagulantes, e o melhor desempenho de remoção de turbidez dos PACs em relação ao SA se deve à menor constante de ruptura do floco (K B ), podendo-se inferir, portanto, que os flocos formados com o PAC-AB e o PAC-BB são mais fortes que os formados com o SA.

ABSTRACT Aluminum sulfate (AS) is widely used as a coagulant in conventional drinking water treatment facilities. Alternative coagulants are commercially available, including polyaluminium chloride (PAC). However, comparative studies between AS and PAC with high (PAC-AB) and low (PAC-BB) basicity regarding flocculation kinetics are still scarce. In this sense, the aim of this work is to compare the use of PAC-BB, PAC-AB, and AS via coagulation, flocculation, and sedimentation as well as to evaluate the effect on electrical conductivity, sludge formation, alkalinity, pH, and turbidity removal based on flocculation kinetic and floc morphology. The results indicated that the increase in electrical conductivity was 8.1% and the sludge formation was 30.6 mg.L-1, and that there was no significant difference between coagulants. PAC-AB presented the lowest alkalinity consumption and, consequently, the lowest pH reduction. Turbidity removal was statistically equal between PAC-BB (91.8 ± 3.7%) and PAC-AB (91.5 ± 1.1%), but higher than in AS (82.2 ± 6.4%). This difference is accentuated with the increase in critical settling velocity. The floc aggregation constant (K A ) is statistically equal among the coagulants, and the better turbidity removal performance of the PACs in relation to the AS is due to the lower floc breaking constant (K B ) and may, therefore, infer that the flocs formed with PAC-AB and PAC-BB are stronger than those formed with SA.

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The recovery of microalgae by means of coagulation-flocculation is efficient, simple and low operating costs. The addition of coagulants makes it possible to destabilize the microalgae surface loads and recover their biomass. Chemical coagulants can contaminate the environment and negatively affect human health. Thus, the exploration of natural coagulants, such as Moringa oleifera and Guazuma ulmifolia, are innovative. Thus, this study aimed to evaluate the efficiency of biomass separation from the microalgae Scenedesmus obliquuos by means of coagulation-flocculation. M. oleifera and G. ulmifolia were used in order to optimize the variables dose, pH and settling time, through a central composite rotational design, which presented recovery efficiencies above 80.0% and 60.0%, respectively. In relation to M. oleifera, optimum regions were obtained for biomass recovery at both pH 4.0 with a dose of 40.0 mg L-1 and pH 9.0 with a dose of 80.0 mg L-1, both in 30 min of settling times. For G. ulmifolia, an optimum dose of 30.0 mg L-1 at pH 4.0 with a 3 min settling time demonstrated that this new coagulant for microalgae recovery has potential for application. Thus, these natural coagulants are promising and can be used in coagulation-flocculation to recover biomass from Scenedesmus obliquuos and, thus, minimize the use of synthetic or metallic products.

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This work focuses on the evaluation of the electrochemical dewatering of sludge obtained in the coagulation of wastes polluted with oxyfluorfen. To do this, sludge samples were treated, aiming not only to reduce the sludge volume, but also to facilitate the degradation of oxyfluorfen contained in the cake via electrolysis with a boron-doped diamond anode. Results show that water can be effectively recovered through three sequential stages. First, a gravity-driven stage, that can recover around 60% of initial volume and where no oxyfluorfen is dragged. Then, a second stage that involves the application of pressure and which accounts for the recuperation of an additional 25% of the total volume of the water removed and in which oxyfluorfen also remained in the cake. Finally, an electrochemical stage, which involves the application of electricity with increasing electric fields (1.0, 2.0, 4.0, and 16.0 V cm-1), accounting for the recovery of the rest of water released and where an electrolytic degradation of oxyfluorfen is obtained, whose extension depends on the electrode configuration used in the electro-dewatering cell. This electrode configuration also influences the retention or loss of oxyfluorfen from the cake, being the optimum choice the placement of the cathode downstream, next to the outlet of the dewatering cell.

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The present study investigated the efficiency of physicochemical processes of coagulation and flocculation and Fenton advanced oxidative process in reducing the parameters of colour, turbidity and Chemical Oxygen Demand (COD) of a real effluent from a textile industry. During the physicochemical process, the efficiencies of different coagulants (aluminium polychloride (Polifloc 18), ferric chloride (Acquafloc FC40), aluminium sulphate combined with organic coagulant (AST) and aluminium sulphate) and nonionic (FX NS2), cationic (FX CS6 and FX CS7) and anionic (FX AS6 and AN905) flocculants were tested. After the tests, 72.60% of COD, 36.25% of colour and 98.59% of turbidity were removed, using aluminium polychloride coagulant and AN 905 flocculant. It was also evaluated the effect of Fenton advanced oxidative process application in removal of colour, COD and turbidity of the effluent previously treated through the physicochemical process. Removals of these parameters were analysed in two different pH ranges (pH 6.0 and 7.0). In both pH 6.0 and pH 7.0, reductions were observed in all analysed parameters, obtaining 170.78 mg O2/L of COD, 22.19 mg/L of colour and 0.80 NTU of turbidity (at pH 6.0) and 151.80 mg O2/L of COD, 26.73 mg/L of colour, 0.94 NTU of turbidity (at pH 7.0), which demonstrates the efficiency of this process in the reduction of parameters analysed.

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A combination of electrocoagulation and coagulation-flocculation processes was used for re-refining effluent from lubricating oils. The efficiency of the process was evaluated based on the chemical oxygen demand (COD), color, and turbidity of the refined effluent. Electrocoagulation (EC) and coagulation-flocculation parameters, such as the initial pH (3.00, 4.41, and 9.00), and current density (4, 9, and 16 A/m2), and the use of aluminum polychloride coagulant and superfloc A300 flocculant were studied. EC performed at pH 9, with a current density of 16 A/m2 and 7 V, resulted in removal efficiencies of 85.14%, 99.81%, and 99.85%, for COD, color, and turbidity, respectively. The removal efficiencies increased to 96%, 99.87%, and 99.94% for COD, color, and turbidity, respectively, by the further coagulation-flocculation treatment in the presence of 13.8 mg/L aluminum polychloride coagulant and 80 mg/L Superfloc A300 flocculant.

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Biodigested coffee processing wastewater (CPW) presents a high organic load and does not meet the limits imposed by legislation (namely in Brazil) for discharge into water bodies. Anaerobic digestion generally cannot provide a satisfactory organic matter reduction in CPW as a significant fraction of recalcitrant compounds still persists in the treated effluent. So, this study aims to find alternative ways to remove refractory organic compounds from this wastewater in order to improve the biodegradability and reduce the toxicity, which will allow its recirculation back into the anaerobic digester. Three treatment approaches (Fenton's oxidation - Approach 1, Coagulation/flocculation (C/F) - Approach 2, and the combination of C/F with Fenton's process - Approach 3) were selected to be applied to the biodigested CPW in order to achieve that objective. The application of the Fenton process under the optimal operating conditions (initial pH = 5.0; T = 55 °C, [Fe3+] = 1.8 g L-1 and [H2O2] = 9.0 g L-1) increased the biodegradability (the BOD5:COD ratio raised from 0.34 ± 0.02 in biodigested CPW to 0.44 ± 0.01 after treatment) and eliminated the toxicity (0.0% of Vibrio fischeri inhibition) along with moderate removals of organic matter (51.3%, 55.7% and 39.7% for total organic carbon - TOC, chemical oxygen demand - COD and biochemical oxygen demand - BOD5, respectively). The implementation of a coagulation/flocculation process upstream from Fenton's oxidation, under the best operating conditions (pH 10-11 and [Fe3+] = 250 mg L-1), also allowed to slightly increase the biodegradability (from 0.34 to 0.47) and reduce the toxicity, whereas providing a higher removal of organic matter (TOC = 76.2%, COD = 76.5 and BOD5 = 66.3% for both processes together). Approach 1 and Approach 3 showed to be the best ones, implying similar operating costs (∼74 R$ m-3/∼17 € m-3) and constitute an attractive option for managing biodigested CPW.

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Resumen Los efluentes provenientes del sacrificio de cerdos son una fuente de contaminación debido a las altas concentraciones de materia orgánica, nitrógeno, fósforo, grasas, sólidos totales y coliformes fecales. En esta investigación se evaluó la efectividad del quitosano como coagulante en el postratamiento de efluentes porcícolas provenientes de un reactor discontinuo secuencial, con el fin de remover las fracciones no biodegradables remanentes del proceso biológico. El tratamiento terciario consistió en la coagulación, floculación y sedimentación. Se caracterizó el efluente tratado biológicamente mediante los siguientes parámetros: pH, DQO, turbidez, color, sólidos totales (ST), nitrógeno total Kjeldahl (NTK), nitrito, nitrato, fosforo total (PT) y alcalinidad total (AT). El tratamiento fisicoquímico se llevó a cabo mediante el uso de la prueba de Jarra a través de corridas exploratorias con dosis entre 50 y 800 mg/L de quitosano disuelto en ácido acético. Se comparó la efectividad del quitosano (700 mg/l) con sulfato de aluminio (430mg/l) y poliacrilamida (90 mg/l), los cuales son utilizados como coagulantes de uso convencional en el tratamiento de aguas residuales. El experimento se condujo mediante un diseño completamente al azar con un total de tres tratamientos (quitosano, sulfato de aluminio y poliacrilamida) y tres repeticiones cada uno. La dosis de quitosano (700 mg/l) permitió obtener porcentajes de reducción de turbidez de 83,1%, color de 64,7%, DQO de 84,6%, y 78,2% de NT para valores iniciales de 15,6 NTU, 26 UC Pt-Co, 865 mg DQO/L y 89 mg NT/L. Se encontraron diferencias significativas (P≤0,05) entre la dosis quitosano (700 mg/l) y los coagulantes convencionales (430 mg/l de sulfato de aluminio y 90 mg/l de poliacrilamida) en la reducción de NT, siendo el tratamiento con quitosano el coagulante con las mayores eficiencias de reducción. El tratamiento con quitosano con una dosis de 700 mg/l representó una opción viable para el tratamiento terciario de los efluentes proveniente del proceso de sacrificio de cerdos tratados biológicamente.

Abstract Effluents from pig slaughter are a source of contamination due to high concentrations of organic matter, nitrogen, phosphorus, fats, total solids and fecal coliforms. This research evaluated the effectiveness of chitosan as a coagulant in the post-treatment of wastewater from the slaughter of pigs, in order to remove the remaining recalcitrant fractions from the biological process in a sequential batch reactor. The tertiary treatment consisted of coagulation, flocculation and sedimentation. The effluent was characterized by the parameters: pH, COD, turbidity, color, total solids (ST), Kjeldahl total nitrogen (NTK), nitrite, nitrate, total phosphorus (PT) and total alkalinity (AT). The treatment was carried out by using the jar test through exploratory runs with doses between 50 and 800 mg/L of chitosan dissolved in acetic acid. The effectiveness of chitosan with conventional coagulants in the treatment of wastewater, such as aluminum sulphate and polyacrylamide, was compared. The experiment was conducted using a completely randomized design with a total of three treatments and three replicates each. The evaluated range of doses of chitosan allowed to obtain percentages of turbidity removal of 83,1%, color of 64,7%, COD of 84,6%, and 78,2% NT for initial values ​​of 15,6 NTU, 26 UC, 865 mg COD/L and 89 mg NT/L, using as optimal dose 700 mg chitosan /L. Significant differences (P≤0,05) were found between chitosan and conventional coagulants in NT removal, with chitosan being the coagulant with the highest removal efficiencies. The treatment with chitosan represents a viable option for the tertiary treatment of the effluents coming from the slaughter of pigs.

Resumo Efluentes de abate de suínos são uma fonte de contaminação devido às elevadas concentrações de matéria orgânica, azoto, fósforo, gordura, sólidos totais e coliformes fecais. Nesta pesquisa foi avaliada a eficácia de quitosana como um coagulante nos efluentes porcícolas de pós-tratamento, a fim de remover restantes fracções recalcitrantes de um processo biológico em um reactor de carregamento sequencial. O tratamento terciário consistiu em coagulação, floculação e sedimentação. O efluente tratado foi caracterizado biologicamente pelos parâmetros: pH, DQO, turbidez, cor, sólidos totais (ST), nitrogênio total Kjeldahl (NTK), nitrito, nitrato, fósforo total (PT) e alcalinidade total (AT). O tratamento foi realizado usando jarro teste é executado através exploratórios com doses entre 50 e 1250 mg / L de quitosano dissolvido em ácido acético. A eficácia do quitosano com sulfato de alumínio y poliacrilamida foi comparada. O experimento foi conduzido usando um desenho completamente aleatório com um total de três tratamentos e três repetições. A gama de dose de quitosana avaliada produziu percentagens de remoção de turvação de 83,1% cor 64,7% de CQO de 84,6%, e 78,2% de NT para os valores iniciais de 15,6 NTU, 26 UC Pt-Co, 865 mg CQO / L e 89 mg de NT / L, usando dose óptima de 700 mg de quitosana/L. Diferenças significativas (P≤0,05) entre quitosano e coagulantes convencionais na remoção de NT foram encontrados para ser um tratamento com o coagulante quitosano com as eficiências mais altas de remoção. O tratamento com quitosana representa uma opção viável para o tratamento terciário do efluente opção abate de porco.

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RESUMO O efluente gerado em um abatedouro de aves, contendo gordura (quantificada pela análise de Óleos e Graxas - O&G) na concentração de 1.100 mg.L-1, foi submetido a dois pré-tratamentos para redução da concentração de material orgânico particulado: um tratamento físico-químico convencional (coagulação/floculação com cloreto férrico) ou um tratamento enzimático alternativo (hidrólise enzimática), aplicados isoladamente antes do processo biológico para remoção de material orgânico dissolvido. A hidrólise foi realizada com 0,5% (m/v) de um preparado enzimático sólido (PES - contendo oito unidades de atividade lipásica por grama) produzido pelo fungo Penicillium sp. por 8 h a 30ºC. Diferentes condições foram avaliadas na coagulação/floculação, sendo selecionada a que apresentou melhor remoção de demanda química de oxigênio (DQO) total para alimentação de biorreatores aeróbios e anaeróbios de bancada: pH = 5,0 e 400 mg de FeCl3.6H2O.L-1. Melhores resultados foram alcançados ao se utilizar o pré-tratamento físico-químico, com remoções médias de DQO de 91% nos tratamentos aeróbio e anaeróbio.

ABSTRACT The effluent generated in a poultry slaughterhouse, containing fat (quantified by oil and grease - O&G analysis) at a concentration of 1,100 mg.L-1, was subjected to two pre-treatments to reduce the particulate organic matter concentration: a conventional physicochemical treatment (coagulation/flocculation with ferric chloride) or an alternative enzymatic treatment (enzymatic hydrolysis), applied alone prior to the biological process for removing dissolved organic material. Hydrolysis was performed with 0.5% (m/v) of a solid enzymatic preparation (SEP - containing 8 lipase activity units per gram) produced by the fungus Penicillium sp. for 8 h at 30ºC. Different conditions were evaluated in the coagulation/flocculation, and the one with the best total COD removal for feeding bench top aerobic and anaerobic bioreactors was selected: pH = 5.0 and 400 mg FeCl3.6H2O.L-1. Better results were achieved when using the physicochemical pre-treatment with average COD removals of 91% in aerobic and anaerobic treatments.

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Sugarcane vinasse is a by-product obtained during ethanol production in sugar-ethanol plants. For each 1 L of ethanol produced approximately 11 L of vinasse are generated. As this residue is obtained in high amounts, it is used as fertilizer in sugarcane crops. However, despite being rich in nutrients, sugarcane vinasse is approximately one hundred times more polluting than domestic sewage, making it an environmental problem. Thus, the aim of the present study was to propose a treatment sequence for sugarcane vinasse and evaluate the possibility of energetic use of the generated sludge in the coagulation/flocculation stage. pH, conductivity, turbidity and decreases in UV/Vis absorption spectra were determined for each treatment step. In addition, the upper calorific value of the generated sludge was also determined, while ash (adsorption treatment) and catalyst (heterogeneous photocatalysis) characterizations were also carried out. At the end of the treatment, initial vinasse turbidity was reduced by 100% and pH and conductivity values were stabilized. The sludge presented a higher calorific value of approximately 3,000 kcal kg-1 and the ash and catalyst displayed favorable characteristics to be applied to the sugarcane vinasse treatment stages.

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Landfill leachate consists mostly of a high content of refractory organic matter, ammonia and toxic compounds. All these compounds, regardless of their nature, have a potential pollution effect on local ground and surface waters. In this context, the purpose of the present study was to evaluate a treatment process (coagulation-flocculation with lime coupled with nanofiltration) applied to landfill leachate from Seropédica, Rio de Janeiro (Brazil). Jar tests were conducted to determine the optimum dosage of lime (ranged from 0 to 10 g L-1) and, at optimum lime dose, ammonia nitrogen was removed during coagulation-flocculation process due to high pH. The process was settled for 6 h with slow stirring (50 rpm) to promote air entrainment and NH3-N stripping before using the final treatment step of nanofiltration at 8 bar. After ammonia stripping, NH3-N was reduced from 1,236 mg L-1 to 353 mg L-1 (71% removal efficiency). At the end of the combined treatment, TOC (total organic carbon), HS (humic substances) and COD (chemical oxygen demand) removals were 89%, 80% and 94%, respectively. The results showed that the combined process was effective in the removal of recalcitrant compounds and NH3-N.

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In this work, the coagulation/flocculation/sedimentation treatment of dairy wastewater samples was investigated through serial factorial designs utilizing the saline extract obtained from Moringa oleifera (Moringa) as a coagulant. The sedimentation time (ST), pH, Moringa coagulant (MC) dose and concentration of CaCl2 have been evaluated through the response surface methodology in order to obtain the ideal turbidity removal (TR) conditions. The empirical quadratic model, in conjunction with the desirability function, demonstrated that it is possible to obtain TRs of 98.35% using a coagulant dose, concentration of CaCl2 and pH of 280 mg L-1, 0.8 mol L-1 and 9, respectively. The saline extract from Moringa presented its best efficiency at an alkaline pH, which influenced the reduction of the ST to a value of 25 min. It was verified that the increase in the solubility of the proteins in the Moringa stimulated the reduction of the coagulant content in the reaction medium, and it is related to the use of calcium chloride as an extracting agent of these proteins. The MC proved to be an excellent alternative for the dairy wastewater treatment, compared to the traditional coagulants.

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In this work, water-based paint (WBP) wastewater was treated using a natural coagulant, Moringa oleifera aqueous extract (MOAE), fortified with Ca2+ (from nitrate and chloride salts). In order to improve the quality of the treated wastewater and render it suitable for disposal, an electrolytic flow process was associated with the wastewater treatment using a filter-press reactor with a boron doped diamond (BDD) electrode. The feasibility of the treatment was evidenced by the reuse of the treated wastewater in the production of a new paint (manufactured by the company supplying the raw wastewater), whose quality was compatible with the water used by the manufacturer. The best conditions for the coagulation-flocculation process involved the use of 80 mL of MOAE (50 g/L of MO and 0.125 mol/L of Ca2+) for every 1.0 L of wastewater at pH 6.5. The limiting current density (35 mA/cm2) and an electrolysis time of 90 min (charge passed of 3.68 A h/L) were used in the electrochemical treatment. Biotoxicity assays using the brine shrimp Artemia salina revealed that the mortality (in %) of microcrustaceans was reduced from 100% (raw wastewater) to only 11% at the end of the electrolysis process, in addition to eliminating the strong odor and 85% of the organic load. Moreover, microbiological tests showed that the number of mesophiles decreased by more than six orders of magnitude and there was no growth of thermotolerant coliforms (TC).

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The removal of nutrients by Scenedesmus sp. in a high-rate algal pond, and subsequent algal separation by coagulation-flocculation or flotation with ozone to recover biomolecules, were evaluated. Cultivation of Scenedesmus sp. in wastewater resulted in complete NH3-H removal, plus 93% total nitrogen and 61% orthophosphate removals. Ozone-flotation obtained better water quality results than coagulation-flocculation for most parameters (NH3-N, NTK, nitrate and nitrite) except orthophosphate. Ozone-flotation, also produced the highest recovery of lipids, carbohydrates and proteins which were 0.32 ±â€¯0.03, 0.33 ±â€¯0.025 and 0.58 ±â€¯0.014 mg/mg of biomass, respectively. In contrast, there was a low lipid extraction of 0.21 mg of lipids/mg of biomass and 0.12-0.23 mg of protein/mg of biomass in the coagulation-flocculation process. In terms of biomolecule recovery and water quality, ozone showed better results than coagulation-flocculation.

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This study aimed to evaluate the use of coagulation/flocculation and Fenton processes for the removal of the recalcitrant component, in particular humic substances, from two different leachates generated in the Gericinó and Gramacho landfills in Rio de Janeiro State (Brazil). A coagulation/flocculation process, using FeCl3·6H2O as the coagulant, was applied to the two leachate samples. In the case of the leachate from Gericinó landfill, the treatment removed 93% of color, 71% of TOC, 69% of COD, 76% of HS, 73% of humic acids (HA) and 82% of fulvic acids (FA). In addition, there was a 75% reduction in the absorbance at 254 nm, using 3,000 mg L-1 of coagulant. In the case of the leachate from Gramacho landfill, the treatment removed 91% of color, 69% of TOC, 68% of COD, 77% of HS, 75% of HA and 80% of FA. In addition, there was a 70% reduction in the absorbance at 254 nm using the same concentration of coagulant (3,000 mg L-1). The Fenton processes, using FeSO4·7H2O and H2O2 in a ratio of 1:5, were also applied to the two leachate samples. In the case of the Gericinó leachate, the Fenton treatment removed 95% of color, 75% of TOC, 68% of COD, 82% of HS, 77% of HA and 93% of FA. In addition, there was a 93% reduction in the absorbance at 254 nm. In the case of the Gramacho leachate, the Fenton treatment removed 93% of color, 73% of TOC, 71% of COD, 81% of HS, 76% of HA, 90% of FA, and there was an 84% reduction in the absorbance at 254 nm. The results of humic substances, color, organic matter and aromatic organic matter (absorbance at 254 nm) demonstrate that the coagulation/flocculation and Fenton processes were efficient in the removal of recalcitrant organic matter from landfill leachates.

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Hospitals consume a large volume of water to carry out their activities and, hence, generate a large volume of effluent that is commonly discharged into the local sewage system without any treatment. Among the various sectors of healthcare facilities, the laundry is responsible for the majority of water consumption and generates a highly complex effluent. Although several advanced oxidation processes (AOPs) are currently under investigation on the degradation of a variety of contaminants, few of them are based on real wastewater samples. In this paper, the UV/H2O2 AOP was evaluated on the treatment of a hospital laundry wastewater, after the application of a physicochemical pretreatment composed of coagulation-flocculation and anthracite filtration. For the UV/H2O2 process, a photoreactor equipped with a low-pressure UV-C lamp was used and the effects of initial pH and [H2O2]/chemical oxygen demand (COD) ratio on COD removal were investigated through a randomized factorial block design that considered the batches of effluent as blocks. The results indicated that the initial pH had no significant effect on the COD removal, and the process was favored by the increase in [H2O2]/COD ratio. Color and turbidity were satisfactorily reduced after the application of the physicochemical pretreatment, and COD was completely removed by the UV/H2O2 process under suitable conditions. The results of this study show that the UV/H2O2 AOP is a promising candidate for hospital laundry wastewater treatment and should be explored to enable wastewater reuse in the washing process.

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ABSTRACT Harvesting is a critical step in microalgal biomass production process for many reasons. Among the existing techniques available for harvesting and dewatering microalgal biomass, recovery from aqueous medium by coagulation-flocculation has been the most economically viable process, althoughit is highly dependent on pH. This study aims to assess alternative coagulants compared to the standard coagulant aluminum sulfate for microalgal biomass recovery from anaerobic effluent of domestic sewage treatment. The effluent quality was also analyzed after biomass recovery. Coagulants represented by modified tannin, cationic starch and aluminum sulfate recovered more than 90% of algae biomass, at concentrations greater than 80 mg/L, in the pH range 7-10. Cationic starch promoted higher microalgal biomass recovery with a wider pH range. Powdered seeds of Moringa oleifera and Hibiscus esculentus(okra) gum promoted biomass removal of 50%, only in the acidic range of pH. After sedimentation of the microalgal biomass, the effluents showed a removal of >80% for phosphorus and nitrogen values and >50% for BOD and COD when using aluminum sulfate, cationic starch and modified tannin as coagulants. Natural organic coagulants in a wide pH range can replace aluminum sulfate, a reference coagulant in microalgal biomass recovery, without decreasing microalgal biomass harvesting efficiency and the quality of the final effluent.