Studies on water and oil two–phase flows, developed in helical pipe separators, are not numerous and seem to be currently restricted to the petrochemical industry. The present work has been done to study the performance of these devices when they are applied to water–olive oil dispersions at different oil cuts. In this line, two experimental devices have been constructed to analyze the separation yields achieved under different operating conditions. Variables like the Reynolds number, the pressure head losses or the outflow ratios have been taken into account to determine their optimal performance range. The results obtained indicate that, in water–olive oil systems, it is possible to obtain separation yields of close to 100% with small pipe diameters, reduced helix radii and low energy requirements. This fact opens up the way to carry out the design of these devices from other points of view. | Los estudios sobre flujos bifásicos de agua y aceite, desarrollados con separadores helicoidales, no son numerosos y parecen estar restringidos, actualmente, a la industria petroquímica. El presente trabajo ha sido realizado para estudiar el comportamiento de estos dispositivos cuando son empleados con dispersiones de agua y aceite de oliva a diferentes concentraciones. A tal fin, se han construido dos modelos experimentales para analizar los rendimientos de separación alcanzados bajo diferentes condiciones de funcionamiento. Se han tenido en cuenta variables como el número de Reynolds, las pérdidas de carga o la relación entre flujos descargados para determinar su rango óptimo de operación. Los resultados obtenidos indican que en sistemas de agua-aceite de oliva es posible obtener rendimientos de separación cercanos al 100% con tuberías de diámetro pequeño, radios de hélice reducidos y bajos requerimientos energéticos. Este hecho abre una vía para diseñar estos dispositivos desde otros puntos de vista.

A utilização da Moringa oleifera (M.O) na clarificação de água seguida pela exposição solar como forma de desinfecção vem sendo usada em regiões desfavorecidas em infraestrutura e recursos financeiros. Essas tecnologias proporcionam as pessoas que habitam nessas regiões, água, de maneira fácil, autossustentável e a custo baixo. O objetivo do estudo foi de avaliar o uso conjunto da M.O na coagulação-floculação e do sistema solar na desinfeção da água para consumo humano. Os objetivos específicos da pesquisa foram: a) determinar a dose de M.O na remoção da turbidez e cor aparente da água bruta; b) determinar o tempo de exposição solar necessário para a remoção de E. coli e coliformes totais presentes na água clarificada com M.O; c) identificar com a técnica delineamento composto central rotacional (DCCR) quais variáveis independentes (pH, dosagem, tempo de mistura lenta e rápida) exerceram maior remoção da cor aparente e turbidez na água bruta. Na desinfeção solar foi considerado um tempo de exposição de 2, 4 e 6 horas, e para a determinação da dosagem e tempos ótimos foram realizados 28 ensaios em Jarteste. Os dados obtidos foram analisados através da Metodologia de Superfície de Resposta do DCCR do programa Statistic 8. As condições do ensaio que apresentou os melhores resultados foram: pH, 6,3; tempos de mistura rápida e lenta de 4 e 25 minutos, respectivamente; dosagem ótima de Moringa de 950 mg/L. Nestas condições, houve remoção de 80% da cor e 94% da turbidez. Adicionalmente, a clarificação com Moringa removeu 98,5 e 96,3% de coliformes totais e E. coli presentes na água bruta. A análise de variância mostrou que a dosagem ótima, os tempos de mistura rápida e lenta e a interação dos tempos de mistura lenta e rápida influenciaram na remoção da turbidez, enquanto a remoção de cor foi influenciada pela dosagem ótima e tempo de mistura lenta. As amostras com e sem filtração em filtro quantitativo de porosidade disforme (tecido de algodão de uso doméstico) foram expostas a desinfeção solar para a remoção de E. coli e coliformes totais. Houve eliminação de 64,8 e 59,7% em 2 horas; 100% e 99,7% em 4 horas e 100% em 6 horas para água não filtrada. Para água filtrada, as remoções foram de 70 e 19,2% (2 horas); 100 e 46% (4 horas) e 100% (6 horas). A desinfecção solar mostrou-se mais eficiente na exposição da água por 6 horas. Assim sendo, o uso conjunto da Moringa e da desinfeção solar em geral promoveram a clarificação e a desinfecção da água, reduzindo significativamente a turbidez e deixando-a livre de E. coli e coliformes totais. | The use of Moringa oleifera (M.O) in clarifying water followed by sunlight exposure as a means of disinfection has been used in disadvantaged areas with lack of infrastructure and financial resources. These technologies provide the people living in these regions, water in self-sustainable and cost-effective way. The objective of the study was to evaluate the combined use of M.O in coagulation-flocculation followed by solar disinfection to produce water suitable for human consumption. The specific objectives of the research were: a) to determine the optimal dose of M.O for removing turbidity and apparent color of the raw water; b) to determine the exposure time required for solar disinfection and removal from E. coli and total coliforms (TC) in the clarified water with M.O; c) to identify with the technical design central composite (CCRD) which independent variables (pH, dosage, slow and fast mixing time) had higher removal of apparent color and turbidity in the raw water. Exposure times tested in solar disinfection were 2, 4 and 6 hours. Twenty eight jartests were performed to determine the optimal dose, slow and fast mixing time and pH. Data were analyzed by CCRD Response Surface Methodology using the program Statistic 8. Test conditions that showed the best results were: pH, 6.3; fast and slow mixing times of 4 and 25 minutes, respectively; Moringa optimum dose of 950 mg/L. Under these optimal conditions, removals efficiencies for color and turbidity were, respectively, 80% of color and 94%. In additional, clarification with Moringa removed 98.5 and 96.3% of total coliforms and E. coli present in the raw water. Analysis of variance showed that the optimal dosage of the fast and slow mixing times, and the interaction of the fast and slow mixing times influenced the removal of turbidity, while the color removal was influenced by the optimum dosage and duration of slow mixing. The samples filtered in filter quantitative without unsightly porosity and were exposed to solar disinfection for removal of E. coli and total coliforms. There elimination 64.8 and 59.7% at 2 hours; 100% and 99.7% in 4 hours and 100% at 6 hours for unfiltered water. For filtered water removals were 70 and 19.2% (2 hours); 100 and 46% (4 hours) and 100% (6 h). Solar disinfection was more efficient in water exposure for 6 hours. It could be concluded that the joint use of the Moringa and solar disinfection generally promoted the clarification and disinfection of water, significantly reducing turbidity and leaving the water free of E. coli and total coliforms.

Intensive use of water, growing cities, and lack of wastewater treatment are some factors increasing hydric stress worldwide. Coagulation/flocculation is one of the preferred treatments for wastewater. However, aluminum salts are traditionally used in this process. This coagulant has a high environmental footprint and residual aluminum in wastewater is a public health concern. The preparation and use of chitosan as a coagulant aid in coagulation/flocculation with aluminum sulfate were investigated. The ef fect of the order of addition of coagulants (aluminum sulfate followed by chitosan, or chitosan followed by aluminum sulfate), dose of the coagulants, pH, and slow mixing velocity for flocculation were studied. It was found that the removal of total suspended solids (TSS) with aluminum sulfate was relatively unaf fected by pH (aluminum sulfate dose of 100 mg L-1 at pH of 5 units achieved 94% removal of TSS and at pH of 8.2 units 89% removal of TSS), whereas with chitosan was highly af fected (chitosan dose of 180 mg L-1 at pH of 4 units achieved 96% removal of TSS and at pH of 8.2 units 25% removal of TSS). In the coagulation/flocculation experiments where both coagulants were used, it was found that the order of coagulant addition and pH of wastewater have a statistically significant ef fect (P-value < 0.05) on the removal of TSS. Higher removal of TSS was achieved when aluminum sulfate was added followed by chitosan at a wastewater pH of 5 units. Chitosan can be ef fectively used to reduce the use of aluminum salts in wastewater treatment. However, it is necessary to optimize the preparation of this coagulant and investigate other factors, such as variation in the wastewater quality, that can af fect the robustness of the process. | Entre los factores que aumentan el estrés hídrico se encuentran la creciente demanda de agua, el incremento de las zonas urbanas y la falta de tratamiento de aguas residuales, entre otros. La coagulación/floculación con sales de aluminio está entre los tratamientos para aguas residuales más utilizados. Sin embargo, estas sales tienen una huella ambiental alta y el aluminio residual en el agua tratada está asociado a problemas de salud. En este trabajo se investigó la preparación y uso de quitosano como coadyuvante en la coagulación/floculación con sulfato de aluminio. Se estudió el efecto del orden de adición de los coagulantes (sulfato de aluminio seguido de quitosano o quitosano seguido de sulfato de aluminio), la dosis de los coagulantes, el pH del tratamiento y la velocidad lenta de floculación. Se encontró que la remoción de los sólidos suspendidos totales (SST) con sulfato de aluminio no presentó  cambios  significativos  en  el  rango  de  pH  estudiado ( remoción  de 94%  de SST con dosis de 100 mg L-1 y pH 5, y remoción de 89% con pH 8.2), mientras que la remoción con quitosano es altamente dependiente del pH (remoción de 96% de SST con dosis de 180 mg L-1 y pH 4, y remoción de 25% con pH 8.2). En los experimentos donde los dos coagulantes se usaron se encontró que el orden de adición de los coagulantes y el pH tienen un efecto estadísticamente significativo (P < 0.05) en la remoción de SST. La mayor remoción de SST se encontró al adicionar sulfato de aluminio seguido de quitosano a un pH de 5. El quitosano se puede utilizar para disminuir el uso de sales de aluminio en el tratamiento de agua residual. Sin embargo, es necesario optimizar su preparación e investigar otros factores que pueden afectar el proceso de coagulación/floculación.