B. Cuartas-Uribe

Study of the behaviour of different NF membranes for the reclamation of a secondary textile effluent in rinsing processes

More demanding legal regulations for the wastewater disposal and water scarcity make necessary wastewater reuse in the industry. In particular, textile industry generates large amounts of wastewater with a high concentration of pollutants. Even though present biological or physical-chemical treatments are broadly in place, the quality of the final effluent is not good enough to allow its direct reuse. Consequently, a complementary membrane process is required in order to improve wastewater characteristics. In this work, six NF membranes were tested at different volume concentration factors in order to select the most appropriate one. The main studied criteria were the permeate quality for its reuse in the textile processes and the minimum membrane fouling effect. The different results obtained for the tested membranes were explained by membrane characterization parameters as contact angle, roughness and size exclusion. Taking these factors into consideration, TFC-SR2 has shown the overall best results because of the high permeate flux and the minimum fouling (in terms of the normalised flux reduction).

Cleaning efficiency enhancement by ultrasounds for membranes used in dairy industries.

Membrane cleaning is a key point for the implementation of membrane technologies in the dairy industry for proteins concentration. In this study, four ultrafiltration (UF) membranes with different molecular weight cut-offs (MWCOs) (5, 15, 30 and 50kDa) and materials (polyethersulfone and ceramics) were fouled with three different whey model solutions: bovine serum albumin (BSA), BSA plus CaCl2 and whey protein concentrate solution (Renylat 45). The purpose of the study was to evaluate the effect of ultrasounds (US) on the membrane cleaning efficiency. The influence of ultrasonic frequency and the US application modes (submerging the membrane module inside the US bath or applying US to the cleaning solution) were also evaluated. The experiments were performed in a laboratory plant which included the US equipment and the possibility of using two membrane modules (flat sheet and tubular). The fouling solution that caused the highest fouling degree for all the membranes was Renylat 45. Results demonstrated that membrane cleaning with US was effective and this effectiveness increased at lower frequencies. Although no significant differences were observed between the two different US applications modes tested, slightly higher cleaning efficiencies values placing the membrane module at the bottom of the tank were achieved.

Autoevaluación y co-evaluación continua del trabajo individual y grupal en una asignatura experimental.

Este trabajo se basa en la evaluacion de la competencia basica “trabajo en grupo” con el fin de obtener una evaluacion que refleje el trabajo de cada alumno dentro de su grupo en una asignatura experimental. Para ello, el alumno participa en un proceso de evaluacion tanto individual (autoevaluacion) como del resto de companeros del grupo (co-evaluacion). Cada evaluacion contempla la valoracion cualitativa del funcionamiento de los miembros del grupo y la valoracion cuantitativa del trabajo academico realizado en funcion del grado de participacion. La evaluacion del funcionamiento del grupo se realiza a traves de encuestas anonimas basandose en los modelos de A. Garcia-Carbonell y F. Watts. En ellas, cada alumno realiza una evaluacion de cada uno de sus miembros y de el mismo en dos momentos diferentes del semestre: inicial y final. En la valoracion cuantitativa, los alumnos distribuyen la nota obtenida en el trabajo academico segun los criterios de P. Morales-Vallejo. Paralelamente los profesores realizan la valoracion de los trabajos academicos realizados y la efectividad del trabajo en grupo a traves de ‘rubricas de evaluacion’. Con estas metodologias de evaluacion se pretende detectar a los alumnos que no contribuyen a la efectividad del grupo, de forma que la nota de los trabajos academicos dependa del grado de participacion de cada alumno. En definitiva, obtener una evaluacion individual mas justa en una asignatura completamente experimental, donde el trabajo en grupo es clave.