Stefano Curcio

An integrated centrifugation–ultrafiltration system in the treatment of olive mill wastewater

Abstract A novel approach in the treatment of olive mill wastewater is presented. Aim of the proposed process is both the reduction of pollution caused by the wastes and the selective separation of some useful products that are present (fats, sugars, polyphenols, etc.). The treatment consists in a preliminary centrifugation step, in which the suspended solids are removed, and in an actual selective separation phase, carried out by ultrafiltration (UF), of the centrifuge supernatant. The combination of centrifugation and ultrafiltration allows a COD reduction of about 90%. Moreover a complete separation of fats, completely rejected by the membrane, from salts, sugars and polyphenols, contained in the permeate, is attained. The present experimental study is directed to investigate the fluid-dynamic aspects related to the ultrafiltration of real olive mill wastewaters. It is based on a preliminary rheological characterization of the waste and on the evaluation of permeation efficiency that was analyzed as a function of several parameters such as the importance of pre-treating wastewater, the effects of localized turbulence, promoted by UF module geometry, and of the main operating variables (trans-membrane pressure and feed flow rate). UF experimental results, obtained in a lab-scale flat-sheet membrane module, are interpreted using both the cake-filtration and the resistance-in-series models, thus allowing the evaluation of Rf parameter that represents the effect of fouling on separation efficiency. An estimation of specific cake resistance, α, is, therefore, performed on the basis of the feed concentration of total non-water compounds present in the waste showing that pre-treated wastewaters give a lower α with respect to raw wastewaters by a factor of about 1000. Moreover, it is found that at the same TMP, lower values of α correspond to a greater Re and that higher local turbulence implies lower specific cake resistances. The results obtained in the present paper could give useful indications for a preliminary characterization of pilot and industrial modules utilized for olive mill wastewaters treatment aimed at a significant COD reduction and a selective separation of valuable compounds that are present in the waste.

Remediation of textile effluents by membrane based treatment techniques: A state of the art review

The textile industries hold an important position in the global industrial arena because of their undeniable contributions to basic human needs satisfaction and to the world economy. These industries are however major consumers of water, dyes and other toxic chemicals. The effluents generated from each processing step comprise substantial quantities of unutilized resources. The effluents if discharged without prior treatment become potential sources of pollution due to their several deleterious effects on the environment. The treatment of heterogeneous textile effluents therefore demands the application of environmentally benign technology with appreciable quality water reclamation potential. These features can be observed in various innovative membrane based techniques. The present review paper thus elucidates the contributions of membrane technology towards textile effluent treatment and unexhausted raw materials recovery. The reuse possibilities of water recovered through membrane based techniques, such as ultrafiltration and nanofiltration in primary dye houses or auxiliary rinse vats have also been explored. Advantages and bottlenecks, such as membrane fouling associated with each of these techniques have also been highlighted. Additionally, several pragmatic models simulating transport mechanism across membranes have been documented. Finally, various accounts dealing with techno-economic evaluation of these membrane based textile wastewater treatment processes have been provided.

The State of the Art in the Production of Fructose from Inulin Enzymatic Hydrolysis

ABSTRACT The present work reviews the main advancements achieved in the last decades in the study of the fructose production process by inulin enzymatic hydrolysis. With the aim of collecting and clarifying the majority of the knowledge in this area, the research on this subject has been divided in three main parts: a) the characteristics of inulin (the process reactant); b) the properties of the enzyme inulinase and its hydrolytic action; c) the advances in the study of the applications of inulinases in bioreactors for fructose production. Many vegetable sources of inulin are reported, including information about their yields in terms of inulin. The properties of inulin that appear relevant for the process are also summarized, with reference to their vegetable origin. The characteristics of the inulinase enzyme that catalyzes inulin hydrolysis, together with the most relevant information for a correct process design and implementation, are described in the paper. An extended collection of data on microorganisms capable of producing inulinase is reported. The following characteristics and properties of inulinase are highlighted: molecular weight, mode of action, activity and stability with respect to changes in temperature and pH, kinetic behavior and effect of inhibitors. The paper describes in detail the main aspects of the enzyme hydrolysis reaction; in particular, how enzyme and reactant properties can affect process performance. The properties of inulinase immobilized on various supports are shown and compared to those of the enzyme in its native state. Finally, a number of applications of free and immobilized inulinases and whole cells in bioreactors are reported, showing the different operating procedures and reactor types adopted for fructose production from inulin on a laboratory scale.

Factor analysis of transesterification reaction of waste oil for biodiesel production.

In the present paper a factor analysis is presented for the enzymatic transesterification of waste oil for biodiesel production. The experimental data on batch reactor evidence two key variables: enzyme loading and mixing conditions. These variables were subjected to a factor analysis and their combined effect on the reaction performance was determined. Response surface methodology (RSM) was used based on a linear first order model (steepest ascent method) and on a second order one in proximity of the optimal solution. The result was a model able to predict reaction performance within the range of mixing rates and enzyme amount considered for model formulation and outside of it, as shown in the final validation. Best performances were obtained at high stirring and high enzyme loading.

Response surface-optimized removal of Reactive Red 120 dye from its aqueous solutions using polyethyleneimine enhanced ultrafiltration

Retention of toxic dyes with molecular weights lower than the molecular weight cut-off (MWCO) of the ultrafiltration membranes can be improved through selective binding of the target dyes to a water-soluble polymer, followed by ultrafiltration of the macromolecular complexes formed. This method, often referred to as polymer enhanced ultrafiltration (PEUF), was investigated in the present study, using polyethyleneimine (PEI) as the chelating agent. Model azo dye Reactive Red 120 was selected as the poorly biodegradable, target contaminant, because of its frequent recalcitrant presence in colored effluents, and its eventual ecotoxicological impacts on the environment. The effects of the governing process factors, namely, cross flow rate, transmembrane pressure polymer to dye ratio and pH, on target dye rejection efficiency were meticulously examined. Additionally, each parameter level was statistically optimized using central composite design (CCD) from the response surface methodology (RSM) toolkit, with an objective to maximize performance efficiency. The results revealed high dye retention efficiency over 99%, accompanied with reasonable permeate flux over 100L/m(2)h under optimal process conditions. The estimated results were elucidated graphically through response surface (RS) plots and validated experimentally. The analyses clearly established PEUF as a novel, reasonably efficient and economical route for recalcitrant dye treatment.

Optimization of ricotta cheese whey (RCW) fermentation by response surface methodology.

A central composite design (CCD) was performed to evaluate the effects of four factors, i.e. temperature (T), pH, agitation rate (K) and initial lactose concentration (L), on ricotta cheese whey batch fermentation and to optimize the process leading to the formation of bio-ethanol. Anaerobic batch fermentation experiments were carried out by using the yeast Kluyveromyces marxianus. After a preliminary experimental analysis, the values of the chosen factors were 32 and 40 degrees C for T, 4 and 6 for pH, 100 and 300 rpm for K, 40 and 80 g L(-1) for L. Response surface methodology (RSM) was used to optimize the fermentation process and an empirical polynomial model was used to fit the experimental data. The best operating conditions resulted to be T=32.35 degrees C, pH 5.41, K=195.56 rpm and L=40 g L(-1) and the model ensured a good fitting of the observed data.

Optimal design of single-screw extruder for liquorice candy production: a rheology based approach

The aim of this work was to investigate the rheological behaviour of liquorice extract to design properly and to optimise a singlescrew extruder dedicated to liquorice production. A stress‐shear rate law was determined and a simplified analysis of the extruder performance was carried out. The velocity profiles in the extruder channel were determined by using a numerical method, while few geometrical parameters, like the channel depth and the helix angle, were optimised to obtain the maximum flow rate as a function of diAerent operating conditions. A power law relationship between either the flow rate or the power consumption and the screw speed was established. The deviation from linearity was expressed by an exponent which, in all the cases examined, was found to be almost constant and ranging from 1.22 to 1.30. ” 2001 Elsevier Science Ltd. All rights reserved.

A hybrid neural approach to model batch fermentation of “ricotta cheese whey” to ethanol

Abstract In this work, the fermentation of “ricotta cheese whey” for the production of ethanol was simulated by means of a multiple hybrid neural model (HNM), obtained by coupling neural network approach to mass balance equations for lactose (substrate), ethanol (product) and biomass. A HNM represents an alternative method that may allow predicting the behaviour of complex systems, such as biotechnological processes, in a more efficient way. Some well-assessed phenomena, in fact, are described by a fundamental theoretical approach; some others, being very difficult to interpret, are analysed by means of rather simple “cause–effect” models, based on artificial neural networks. The experimental data, necessary to develop the model, were collected during batch fermentation runs. For all the proposed networks, the inputs were chosen as the operating variables with the highest influence on reaction rate. Simulation results showed the ability of the developed model to represent the process dynamics. The HNM was capable of an accurate representation of the system behaviour by predicting biomass, lactose and ethanol concentration profiles with an average error percentage lower than 10%. Moreover, the hybrid approach showed the ability to limit error propagation into the models that can be caused by the purely black-box nature, typical of neural networks.

Fructose Production by Inulinase Covalently Immobilized on Sepabeads in Batch and Fluidized Bed Bioreactor

The present work is an experimental study of the performance of a recently designed immobilized enzyme: inulinase from Aspergillus sp. covalently immobilized on Sepabeads. The aim of the work is to test the new biocatalyst in conditions of industrial interest and to assess the feasibility of the process in a fluidized bed bioreactor (FBBR). The catalyst was first tested in a batch reactor at standard conditions and in various sets of conditions of interest for the process. Once the response of the catalyst to different operating conditions was tested and the operational stability assessed, one of the sets of conditions tested in batch was chosen for tests in FBBR. Prior to reaction tests, preliminary fluidization tests were realized in order to define an operating range of admissible flow rates. As a result, the FBR was run at different feed flow rates in a closed cycle configuration and its performance was compared to that of the batch system. The FBBR proved to be performing and suitable for scale up to large fructose production.

Enzymatic transesterification of waste vegetable oil to produce biodiesel.

An experimental study on enzymatic transesterification was performed to produce biodiesel from waste vegetable oils. Lipase from Pseudomonas cepacia was covalently immobilized on a epoxy-acrylic resin support. The immobilized enzyme exhibited high catalytic specific surface and allowed an easy recovery, regeneration and reutilisation of biocatalyst. Waste vegetable oils - such as frying oils, considered not competitive with food applications and wastes to be treated - were used as a source of glycerides. Ethanol was used as a short chain alcohol and was added in three steps with the aim to reduce its inhibitory effect on lipase activity. The effect of biocatalyst/substrate feed mass ratios and the waste oil quality have been investigated in order to estimate the process performances. Biocatalyst recovery and reuse have been also studied with the aim to verify the stability of the biocatalyst for its application in industrial scale.