R. Abejón

Membrane Bioprocesses for Pharmaceutical Micropollutant Removal from Waters

The purpose of this review work is to give an overview of the research reported on bioprocesses for the treatment of domestic or industrial wastewaters (WW) containing pharmaceuticals. Conventional WW treatment technologies are not efficient enough to completely remove all pharmaceuticals from water. Indeed, these compounds are becoming an actual public health problem, because they are more and more present in underground and even in potable waters. Different types of bioprocesses are described in this work: from classical activated sludge systems, which allow the depletion of pharmaceuticals by bio-degradation and adsorption, to enzymatic reactions, which are more focused on the treatment of WW containing a relatively high content of pharmaceuticals and less organic carbon pollution than classical WW. Different aspects concerning the advantages of membrane bioreactors for pharmaceuticals removal are discussed, as well as the more recent studies on enzymatic membrane reactors to the depletion of these recalcitrant compounds.

Large-scale enzymatic membrane reactors for tetracycline degradation in WWTP effluents

A mathematical model to simulate the performance of enzymatic membrane reactors was developed. It was applied to investigate the effectiveness of laccase immobilized over ceramic membranes for the degradation of tetracycline, a common antibiotic appearing as micropollutant in effluents of WWTPs. A process based on large-scale enzymatic membrane reactors in series was proposed for the treatment of the effluents from municipal, hospital and industrial wastewater treatment plants (WWTPs). The obtained results demonstrated the need for high improvements in the amount of enzyme grafted on the membranes or on enzymatic kinetics to afford the technical and economic competitiveness of the investigated designs and the possibility to be implemented within existing installations.

Multiobjective optimization of membrane processes for chemicals ultrapurification

Abstract The present work is focused on the multiobjective optimization of integrated multistage reverse osmosis membrane cascades applied to the ultrapurification of chemicals for the semiconductor industry. The membrane systems were formulated adding product quality metrics to economic criteria to result a bi-criteria nonlinear programming (NLP) problem. The Pareto solutions to the problem were generated via the epsilon constraint method. On the one hand, maximum economic profit solutions corresponded with the configurations applying bypass. The bypass from the feed stream of the last stage was preferred over other proposed options. On the other hand, maximum quality solutions were obtained by low recovery rates (specifically in the last stages of the cascade) and the consequent high flow (and low metallic content) streams recirculated to previous stages.

Membrane process optimization for hydrogen peroxide ultrapurification

Abstract The application of reverse osmosis without any auxiliary technologies to the ultrapurification of technical grade hydrogen peroxide to obtain a quality enough for its use by the semiconductor industry is a great challenge. Through modeling based on membrane transport equations and mass balances, different integrated reverse osmosis cascades have been planned and simulated to produce the several electronic grades chemical. The sensitivity of different design and operation variables (recovery rate and applied pressure) on the system performance was also investigated. Finally, a non linear optimization approach to maximize economic profit while optimizing recovery rates and applied pressures was carried out.

Multiobjective Optimization of Membrane Networks for Fractionation of Protein Hydrolysate from Fish By-Products

Abstract Ultrafiltration and nanofiltration can be very useful technologies to fractionate the different protein fractions obtained after hydrolysis of fish by-products. Simple empirical transport equations derived from experimental data were obtained and a process simulation model was developed and employed for the identification of the optimal design and operation conditions to maximize the product purity or the process yield. More complex scenario appeared when other objectives were added to the optimization problem, including economic considerations, such as the total costs of the process, or environmental considerations, such as the total freshwater consumption by the system. Limitations to the total costs implied reduced membrane area in the UF stages and, consequently, lower process yields. Freshwater consumption could be reduced without worsening product purity or process yield, but limits should be imposed in order to avoid excessive protein contents that would cause problems related to membrane clogging.

Integration of quality-dependent prices in the optimization strategy for chemicals ultrapurification by reverse osmosis membrane cascades

AbstractThe present work is focused on the optimization of multistage reverse osmosis membrane cascades applied to the ultrapurification of chemicals for the semiconductor industry (hydrogen peroxide was chosen as case study). This paper is a part of the author`s overall work on the subject. The novelty of this paper is the introduction of a price-dependent model for the product quality that can be adjusted between customer and producer. The membrane systems were formulated with product quality-dependent price resulting a nonlinear programming problem. The optimal number of stages included in a cascade was strongly dependent of the desired product quality while the formulated quality-dependent price model determined the target purity. Five quality-dependent price fittings were used to illustrate the case study: linear, parabolic, exponential, sigmoidal, and bisigmoidal relationships between product quality and price. For the sigmoidal and bisigmoidal fittings, least operation conditions can afford revenue...

Decision tool for the selection among different reverse osmosis membranes for hydrogen peroxide ultrapurification

Abstract The analysis of transport properties and resistance to oxidative degradation of different reverse osmosis membranes has been carried out to select the most adequate one for the ultrapurification of hydrogen peroxide. An optimization study has been completed to determine the best operation conditions for the membrane cascades and to assess the economic profit of the different ultrapurification processes. The research of conditions where each membrane could be competitive led to the design of a competitiveness map useful as a decision tool.

Water Recovery and Reuse in the Fractionation of Protein Hydrolysate by Ultrafiltration and Nanofiltration Membranes

The fractionation of a protein hydrolysate obtained from tuna processing by-products by means of a membrane cascade integrating ultrafiltration (UF) and nanofiltration (NF) membranes was proposed in order to separate and purify the protein fraction between 1 and 4 kDa, which is the most interesting for nutraceutical purposes. A simulation model, based on mass balances and empirical equations for describing permeate flux and rejection of protein fractions, was developed and complemented with a simple cost estimation model. The product purity (49.3 %) and the process yield (62.6 %) were independent of the total water consumption of the process, but high water consumptions were required to maintain the total protein content of the stream below upper bounds that assured the absence of membrane clogging. The implementation of a water recovery system, based on an additional tight NF stage, implied improvements in both environmental and economic aspects of the process.