Titulo en ingles: C haracterization of Opuntia ficus -indica for using as a natural coagulant Titulo corto: Caracterizacion de Opuntia ficus -indica para coagulante natural Resumen Actualmente municipios de la Costa Atlantica Colombiana no cuentan con suministro de agua potable. La aplicacion artesanal de la Tuna ( Opuntia ficus -indica ) como coagulante es una practica tradicional en comunidades rurales. En esta investigacion se realiza la caracterizacion del tallo de la Tuna que crece de manera silvestre en el departamento de Bolivar, y del polvo extraido de esta planta, con el fin de identificar componentes asociados a su poder coagulante para la remocion de turbidez y de color en aguas crudas. Las pencas de la planta se sometieron a operaciones de corte, pelado, secado, molienda, tamizado y despigmentado para obtener el coagulante. El rendimiento del proceso global fue de 65g de coagulante/Kg de material vegetal. Los resultados indicaron que la penca contiene alto porcentaje de humedad y pequenas proporciones de saponinas, flavonoides, sales minerales de calcio y hierro; lo cual permitio concluir que estos metabolitos y sales no son los responsables de su poder coagulante debido a las cantidades poco significativas en las que se encuentran. Se considero que otras especies quimica tales como el acido poligalacturonico y compuestos alginicos son realmente los que le confieran la cualidad al biomaterial. Tambien, se evaluo el poder coagulante del material extraido, se analizo el efecto de tres dosis sobre el color, la turbidez y el pH del agua tratada. Los resultados indicaron que tiene la capacidad de remover 50% del color y 70% de turbidez de aguas crudas con alta turbidez inicial, y que no altera significativamente su pH. Palabras clave: aguas crudas, clarificacion, flavonoides, saponinas, turbidez . Abstract Currently, municipalities in the Colombian Atlantic Coast do not have potable water supply. The implementation of the Tuna as a coagulant is a traditional practice in rural communities, but is used in craft way. In the present investigation, the characterization of the stalk of Tuna ( Opuntia ficus-indica ) growing in the wild in the Bolivar department, and of the powder extracted from this plant was realized with the purpose to identify components associated with its coagulant power to remove color and turbidity in raw water. The stalks of this plant were subjected to cutting, peeling, drying, grinding, sieving and depigment for obtaining the coagulant. The overall process yield was 65g of coagulant/kg of vegetal material. The results also indicated that the stalk of Tuna contains high moisture content and low amounts of saponins, flavonoids, minerals, calcium and iron. It allowed concluding that these metabolites and salts are not responsible of the coagulant power of plant due to the insignificant amounts in which they are present. Therefore, it is presumed that other chemical species such as polygalacturonic acid and alginic compounds are those that confer the quality to the biomaterial. Also, the coagulant power of extracted material was evaluated. The effect of three dosis on the color, turbidity and pH of trated water was analized. The results indicated that it has the capacity to remove 50% of color and 70% of turbity from crude water with high initial turbidity. Also, it does not affect significantly its pH. Key words: raw water, clarification, flavonoids, saponoids, turbidity. Resumen Actualmente municipios de la Costa Atlantica Colombiana no cuentan con suministro de agua potable. La aplicacion artesanal de la Tuna ( Opuntia ficus -indica ) como coagulante es una practica tradicional en comunidades rurales. En esta investigacion se realiza la caracterizacion del tallo de la Tuna que crece de manera silvestre en el departamento de Bolivar, y del polvo extraido de esta planta, con el fin de identificar componentes asociados a su poder coagulante para la remocion de turbidez y de color en aguas crudas. Las pencas de la planta se sometieron a operaciones de corte, pelado, secado, molienda, tamizado y despigmentado para obtener el coagulante. El rendimiento del proceso global fue de 65g de coagulante/Kg de material vegetal. Los resultados indicaron que la penca contiene alto porcentaje de humedad y pequenas proporciones de saponinas, flavonoides, sales minerales de calcio y hierro; lo cual permitio concluir que estos metabolitos y sales no son los responsables de su poder coagulante debido a las cantidades poco significativas en las que se encuentran. Se considero que otras especies quimica tales como el acido poligalacturonico y compuestos alginicos son realmente los que le confieran la cualidad al biomaterial. Tambien, se evaluo el poder coagulante del material extraido, se analizo el efecto de tres dosis sobre el color, la turbidez y el pH del agua tratada. Los resultados indicaron que tiene la capacidad de remover 50% del color y 70% de turbidez de aguas crudas con alta turbidez inicial, y que no altera significativamente su pH. Palabras clave: aguas crudas, clarificacion, flavonoides, saponinas, turbidez . Abstract Currently, municipalities in the Colombian Atlantic Coast do not have potable water supply. The implementation of the Tuna as a coagulant is a traditional practice in rural communities, but is used in craft way. In the present investigation, the characterization of the stalk of Tuna ( Opuntia ficus-indica ) growing in the wild in the Bolivar department, and of the powder extracted from this plant was realized with the purpose to identify components associated with its coagulant power to remove color and turbidity in raw water. The stalks of this plant were subjected to cutting, peeling, drying, grinding, sieving and depigment for obtaining the coagulant. The overall process yield was 65g of coagulant/kg of vegetal material. The results also indicated that the stalk of Tuna contains high moisture content and low amounts of saponins, flavonoids, minerals, calcium and iron. It allowed concluding that these metabolites and salts are not responsible of the coagulant power of plant due to the insignificant amounts in which they are present. Therefore, it is presumed that other chemical species such as polygalacturonic acid and alginic compounds are those that confer the quality to the biomaterial. Also, the coagulant power of extracted material was evaluated. The effect of three dosis on the color, turbidity and pH of trated water was analized. The results indicated that it has the capacity to remove 50% of color and 70% of turbity from crude water with high initial turbidity. Also, it does not affect significantly its pH. Key words: raw water, clarification, flavonoids, saponoids, turbidity.