Analysis of fouling resistances under dynamic filtration of pretreated olive mill wastewater on a loose reverse osmosis membrane

In this work, a loose reverse osmosis (RO) membrane (Osmonics AK model), capable of offering beforehand higher fluxes under lower operating pressure than typical tight reverse osmosis membranes but still offering similar rejection, was used for the final purification of olive mill wastewater. However, the output that a membrane may offer when it is virgin and readily used will change in time due to membrane fouling. If not properly considered, the advantages that a chosen membrane may offer in contrast with others would quickly and often irreversibly vanish, with the consequences in terms of capital expenses that this will represent. One approach to meet the investor's needs to trust membrane technology is to guarantee that fouling will be inhibited as much as possible, but to overcome the loss of performance that fouling carries engineers overdesign the membrane plants by using too wide safety margins that trigger the costs sensibly. Since the mechanisms by which fouling phenomena are triggered are always complex, the osmotic-pressure resistances-in-series model can be a simple but reliable model to describe the membrane response and predict its performance in time. In this context, the normalized fouling measured on the examined RO membrane was found to be minimum in the operating pressure range between 5 and 8 bar (0.65-0.98, respectively), and it decreased down to 0.51 upon increasing the crossflow up to 5.09 m s-1, avoiding irreversible fouling. Moreover, significantly minor fouling (0.33) was attained at the lowest temperature, regularly experienced during the olive oil production campaign. On another hand, the rejection towards organic solutes was maintained above 97%

A focus on fouling of nanofiltration membranes in the treatment of two-phase olive mill wastewater by boundary flux and pore blocking theories

The implementation of membranes in water and wastewater treatment processes has significantly increased in the last decades. However, membrane fouling leads to increased expenses if not properly examined and considered, and this is especially problematic in wastewater treatments. For this reason, fouling minimization represents the key factor to make those processes feasible. The use of NF membranes is especially problematic regarding fouling problems. In first place, adequate fouling inhibition methods should be designed upstream the membrane operation, in order to make the downstream membrane processes for wastewater treatment technically and economically feasible. In the present work, fouling build-up on a nanofiltration (NF) membrane during the treatment of olive mill wastewater coming from Spain (OMW-S) is addressed by the boundary flux theory, and the results were compared and complemented by using the pore blocking models. Fouling mechanisms are important to fully understand what is happening between the membrane and the effluent, to take the adequate decisions with respect to the design of the membrane plant and set-up of optimized operating conditions. The goal is to operate membranes modules by avoiding irreversible fouling for a long period of time, that is, several years of service lifetime. Thereafter, the operating parameters should be carefully chosen to avoid working beyond the conditions that the selected membrane can stand for the specific feedstream. The followed strategy allows the operation of the membranes system in a controlled framework that permits the stable operation of the plant. Moreover, the required membrane area is minimized and the constancy of the permeate productivity is also narrowed by following the proposed methodology

Optimization study of the fouling build-up on a RO membrane for pretrated olive mill wastewater purification

Even though membranes are considered in many aspects a mature technology, a range of features are still in development and under investigation. Regarding this, the main handicap of this technology is inevitably membrane fouling. Fouling issues have investigated by many research groups in the last years to convince investors to implement membranes as substitutes of a range of unit operations at industrial scale. In the wastewater treatment field, this is especially problematic, given the low economic value of the product, that is, treated water. On another hand, the management of the effluents generated by olive oil industries, olive mill wastewaters (OMW), is a task of global concern not anymore constrained to a specific region. These wastewaters represent an ever-increasing problem still unresolved. The present work was aimed for the modelling and optimization of a reverse osmosis (RO) membrane operation for the purification of pretreated olive mill wastewater, with a focus on the dynamic fouling development minimization on the selected membrane as a function of the set-up of the operating conditions. For this goal, beforehand a factorial design was implemented for the optimization of the RO treatment of the OMW stream. The results gathered were thereafter interpreted by means of the response surface methodology. A significant impact was noted to be driven by the operating pressure and the tangential velocity on the fouling rate on the RO membrane. The response surfaces withdrawn from the experimental data support the previous results, and the optimised parameters - ambient temperature range (24 - 25 °C), moderate operating pressure (25 - 30 bar) and turbulent tangential flow (3.1 - 3.5 m s -1 ) - were found to provide a stable permeate flux of 32.3 - 38.5 L h -1 m -2 . These results reveal the proposed process could be operated successfully at ambient temperature conditions and medium operating pressure, boosting the economic efficiency of the RO purification of this effluent. Finally, the parametric quality standards stablished to reuse the purified effluent for irrigation purposes were checked and found to be satisfactory

Comparison of the performance of two reverse osmosis membranes for the final purification of olive mill wastewater

Two quite different reverse osmosis (RO) polymeric membranes were examined for the final purification of olive mill wastewater from two-phase olive mills (OMW2): the first one is a thin-film composite (TFC) membrane consisting of polyamide active layer on polysulfone ultrafiltration support, whereas the other one is a low-pressure membrane made of asymmetric polyamide. A net operating pressure (PTM) of 25 bar was found as the target for the TFC membrane, whereas for the asymmetric one a PTM of 8 bar was chosen, given that similar flux decay but still significant productivity was observed by increasing the PTM for this membrane. These results are confirmed by the fouling index (b) values calculated for each membrane. Complete removal of suspended solids, phenolic compounds and iron was achieved by both membranes. Otherwise, the asymmetric membrane ensured slightly higher organic matter (COD) and electroconductivity (EC) reduction, leading to a COD concentration in the permeate stream equal to 3.7 mg L-1 and 1.4 mg L-1 (TFC vs. asymmetric), whereas the EC values were 97.0 and 31.0 μs cm-1, respectively. This would permit reusing the purified effluent provided by both membranes in the production process and close the loop at industrial scale. Moreover, the asymmetric membrane provides a steady-state flux value of the same order of that yielded by the TFC membrane upon more than three times less PTM (14.9 L h-1m-2 at PTM = 8 bar vs. 15.2 L h-1m-2 at PTM = 25 bar), implying a reduction of the specific energy consumption above 50 %, from 0.30 ? m-3 for the TFC membrane to 0.14? m-3 for the asymmetric one. Copyright © 2015, AIDIC Servizi S.r.l

Total positivity and least squares problems in the Lagrange basis

The problem of polynomial least squares fitting in the standard Lagrange basis is addressed in this work. Although the matrices involved in the corresponding overdetermined linear systems are not totally positive, rectangular totally positive Lagrange-Vandermonde matrices are used to take advantage of total positivity in the construction of accurate algorithms to solve the considered problem. In particular, a fast and accurate algorithm to compute the bidiagonal decomposition of such rectangular totally positive matrices is crucial to solve the problem. This algorithm also allows the accurate computation of the Moore-Penrose inverse and the projection matrix of the collocation matrices involved in these problems. Numerical experiments showing the good behaviour of the proposed algorithms are included

Programación didáctica para 4º de la ESO. Lengua Castellana y Literatura

Máster Universitario en Formación del Profesorado de ESO, Bachillerato, Formación Profesional y Enseñanza de Idiomas. Especialidad en Lengua Castellana y Literatura (M087

Accurate bidiagonal decomposition of totally positive Cauchy-Vandermonde matrices and applications

Cauchy–Vandermonde matrices play a fundamental role in rational interpolation theory and in other fields. When all their corresponding nodes are different and positive and all poles are different and negative and follow adequate orderings, these matrices are totally positive. In this paper we provide fast algorithms for computing bidiagonal factorizations of these matrices and their inverses with high relative accuracy. These algorithms can be used to solve with high relative accuracy other algebraic problems, such as the computation of all singular values, all eigenvalues or the solution of certain linear systems. The error analysis of the algorithm for computing the bidiagonal factorization and the corresponding perturbation theory are also performed

Analysis of the Flux Performance of Different RO/NF Membranes in the Treatment of Agroindustrial Wastewater by Means of the Boundary Flux Theory

Dynamic membrane system behaviour must be adequately addressed to avoid process unfeasibility. The lack of proper analysis will mean relying on erroneous permeate flux values in the system design, which will lead to quick and/or steady high fouling rates. In this paper, the authors present additional data supporting the boundary flux theory as a helpful tool for membrane engineers to carefully avoid process failures. By fitting the dynamic permeate flux data to the boundary flux model, it was possible to calculate the fouling index for the three selected membranes (one nanofiltration (NF) and two reverse osmosis (RO) ones). The dynamic flux given by the low-pressure RO membrane did not follow sub-boundary operating conditions, since a sharp flux loss was measured throughout the whole operating cycle, pinpointing that supra-boundary flux conditions were governing the system. This was supported by the calculated value of the fouling parameter, which resulted to be in the order of ten times higher for this membrane. However, the values of !0 for the SC-RO and DK-NF ones, supported by the very low value of the sub-boundary fouling parameter α (0.002 and 0.007 L.h-1.m-2.bar-2, respectively), ensure nearly boundary operating conditions for these membranes.The Spanish Ministry of Economy and Competitiveness is acknowledged for having funded the project CTM2014-61105-JIN: “Design and development of an integral process for revalorization and treatment of the effluents from olive oil industry”

La orientación emprendedora como fuente de innovación para las empresas: un análisis aplicado

El entorno actual fuerza a las empresas a realizar esfuerzos constantes en innovación, al ser un factor clave para su competitividad en los mercados. Debido a su importancia, en los últimos años el estudio de las principales fuentes de innovación empresarial ha adquirido gran relevancia, si bien todavía existe cierta ambigüedad en relación con los principales factores que afectan a la generación y desarrollo de innovaciones. El principal objetivo de esta investigación es analizar la relación existente entre la orientación emprendedora de las empresas y su capacidad de innovación, así como el posible efecto mediador del capital social y la capacidad de absorción en esta relación. Para ello, se realiza un análisis empírico sobre una muestra de 197 empresas españolas del sector de suministro de energía eléctrica. Para realizar el análisis estadístico, se ha utilizado la técnica de modelización de ecuaciones estructurales basadas en la varianza (PLS-SEM) y, particularmente, el software “SmartPLS” en su versión 3.9. Los resultados desvelan que la orientación emprendedora de las empresas afecta de forma positiva y significativa a su capacidad para innovar. Además, el capital social y la capacidad de absorción se establecen como variables mediadoras en esta relación. Se concluye que las empresas pueden impulsar su capacidad de innovación favoreciendo el desarrollo de un clima emprendedor en la empresa, incentivando la participación de todos los miembros de la empresa en la identificación y explotación de oportunidades de negocio. Este clima puede favorecer el desarrollo de amplias redes de contactos valiosos, y la capacidad de absorción de nuevo conocimiento de la empresa lo cual, en última instancia, permitiría incrementar su capacidad de innovación