Marco Ferraris - Academia.edu (original) (raw)

Papers by Marco Ferraris

Environmental Science and Pollution Research, 2015

This study proposes a model-based evaluation of the effect of different operating conditions with... more This study proposes a model-based evaluation of the effect of different operating conditions with and without pre-denitrification treatment and applying three different solids retention times on the fouling mechanisms involved in membrane bioreactors (MBRs). A total of 11 fouling models obtained from literature were used to fit the transmembrane pressure variations measured in a pilot-scale MBR treating real wastewater for more than 1 year. The results showed that all the models represent reasonable descriptions of the fouling processes in the MBR tested. The model-based analysis confirmed that membrane fouling started by pore blocking (complete blocking model) and by a reduction of the pore diameter (standard blocking) while cake filtration became the dominant fouling mechanism over long-term operation. However, the different fouling mechanisms occurred almost simultaneously making it rather difficult to identify each one. The membrane "history" (i.e. age, lifespan, etc.) seems the most important factor affecting the fouling mechanism more than the applied operating conditions. Nonlinear regression of the most complex models (combined models) evaluated in this study sometimes demonstrated unreliable parameter estimates suggesting that the four basic fouling models (complete, standard, intermediate blocking and cake filtration) contain enough details to represent a reasonable description of the main fouling processes occurring in MBRs.

Journal of Environmental Science and Health, Part A, 2015

Mathematical modelling has been widely applied to membrane bioreactor (MBRs) processes. However, ... more Mathematical modelling has been widely applied to membrane bioreactor (MBRs) processes. However, to date, very few studies have reported on the application of the anaerobic digestion model N.1 (ADM1) to anaerobic membrane processes. The aim of this study was to evaluate the applicability of the ADM1 to a submerged anaerobic MBR (SAMBR) treating simulated industrial wastewater composed of cheese whey and sucrose. This study demonstrated that the biological processes involved in SAMBRs can be modelled by using the ADM1. Moreover, the results showed that very few modifications of the parameters describing the ADM1 were required to reasonably fit the experimental data. In particular, adaptation to the specific conditions of the coefficients describing the wastewater characterisation and the reduction of the hydrolysis rate of particulate carbohydrate (khyd,ch) from 0.25 d(-1) (as suggested by the ADM1 for high-rate mesophilic reactors) to 0.13 d(-1) were required to fit the experimental data.

Separation and Purification Technology, 2014

Several methods have been proposed over the last decade for the monitoring of fouling processes i... more Several methods have been proposed over the last decade for the monitoring of fouling processes in membrane bioreactors (MBRs). Many of these methods aim to acquire information measuring the transmembrane pressure (TMP) and permeability (K) directly on the membrane modules used in wastewater treatment plants. This study assessed in a critical light the use of TMP and K for membrane fouling monitoring. TMP and K were directly measured on a pilot-scale submerged MBR operated continuously for approximately 450 d at different solids retention times and fed with real municipal wastewater. The results showed that under standard operating conditions such as those usually applied in full-scale MBR and with the monitoring instruments typically employed in industrial applications, the identification of specific TMP trends within a filtration phase was often problematic and the results were unreliable, mainly because of the noise and the variability of real wastewater and environmental conditions. Moreover, a non-linear trend of the pressure behaviour within a filtration phase was observed when fouling phenomena were taking place. This study also proposes the use of the ratio between filtration and backwash permeability in order to assess whether the membrane flux is deviating from the ''pressure controlled region'' and, consequently, fouling processes are occurring.

Journal of Environmental Science and Health, Part A, 2012

Although most membrane bioreactors are used under aerobic conditions, over the last few years the... more Although most membrane bioreactors are used under aerobic conditions, over the last few years there has been increased interest in their application for anaerobic processes. This paper presents the results obtained when a bench-scale submerged anaerobic membrane bioreactor was used for the treatment of wastewaters generated in the agro-food industry. The reactor was fed with synthetic wastewater consisting of cheese whey and sucrose, and volumetric organic loading rates (OLRs) ranging from 1.5 to 13 kgCOD/(m(3)*d) were applied. Under the operating conditions studied, the maximum applicable OLR was between 6 and 10 gCOD/(g*L), which fell within the ranges of the high-rate anaerobic wastewater treatment systems, while high concentrations of volatile fatty acids were produced at higher OLR rates. With an OLR of 1.5-10 gCOD/(g*L), the reactor showed 94% COD removal, whereas this value dropped to 33% with the highest applied OLR of 13 gCOD/(g*L). The study therefore confirms that membrane bioreactors can be used for anaerobic wastewater treatment.

Desalination, 2009

The start-up of a pilot-scale membrane bioreactor equipped with submerged ultrafiltration membran... more The start-up of a pilot-scale membrane bioreactor equipped with submerged ultrafiltration membranes to treat municipal wastewater has been studied. Attention has been paid to determine membrane separation effects on biomass development in a reactor operated without inoculation. Moreover, the activated sludge model no. 1 has been applied to model biological removal processes. Filtration alone (without biodegradation) removed more than 70% of the influent total COD due to the high particulate COD fraction typically present in municipal wastewaters. Filtration action, retaining bacteria, allowed a rapid increase of the heterotrophic activity permitting to reach efficiencies in COD removal greater than 90% in one to two days. On the other hand, nitrogen removal process needs a few days (five to twenty depending on operational conditions) to develop and stabilise in the reactors because of the required development of the nitrifying biomass. Biomass development was confirmed using respirometric techniques. The activated sludge model no. 1 with minor modification was capable of simulating reasonably well the biological processes development in the MBR.

Chemical Engineering Journal, 2013

h i g h l i g h t s " A MBR was continuously operated at different solid retention times for 450 ... more h i g h l i g h t s " A MBR was continuously operated at different solid retention times for 450 d. " SRT effects on sludge filterability and biomass activity were evaluated. " The carbohydrate fraction of the SMP was correlated with CST and J c. " J c and CST trends can be used to predict sludge filterability. " The addition of the anoxic process seemed to deteriorate the sludge filterability.

Environmental Science and Pollution Research, 2015

This study proposes a model-based evaluation of the effect of different operating conditions with... more This study proposes a model-based evaluation of the effect of different operating conditions with and without pre-denitrification treatment and applying three different solids retention times on the fouling mechanisms involved in membrane bioreactors (MBRs). A total of 11 fouling models obtained from literature were used to fit the transmembrane pressure variations measured in a pilot-scale MBR treating real wastewater for more than 1 year. The results showed that all the models represent reasonable descriptions of the fouling processes in the MBR tested. The model-based analysis confirmed that membrane fouling started by pore blocking (complete blocking model) and by a reduction of the pore diameter (standard blocking) while cake filtration became the dominant fouling mechanism over long-term operation. However, the different fouling mechanisms occurred almost simultaneously making it rather difficult to identify each one. The membrane "history" (i.e. age, lifespan, etc.) seems the most important factor affecting the fouling mechanism more than the applied operating conditions. Nonlinear regression of the most complex models (combined models) evaluated in this study sometimes demonstrated unreliable parameter estimates suggesting that the four basic fouling models (complete, standard, intermediate blocking and cake filtration) contain enough details to represent a reasonable description of the main fouling processes occurring in MBRs.

Journal of Environmental Science and Health, Part A, 2015

Mathematical modelling has been widely applied to membrane bioreactor (MBRs) processes. However, ... more Mathematical modelling has been widely applied to membrane bioreactor (MBRs) processes. However, to date, very few studies have reported on the application of the anaerobic digestion model N.1 (ADM1) to anaerobic membrane processes. The aim of this study was to evaluate the applicability of the ADM1 to a submerged anaerobic MBR (SAMBR) treating simulated industrial wastewater composed of cheese whey and sucrose. This study demonstrated that the biological processes involved in SAMBRs can be modelled by using the ADM1. Moreover, the results showed that very few modifications of the parameters describing the ADM1 were required to reasonably fit the experimental data. In particular, adaptation to the specific conditions of the coefficients describing the wastewater characterisation and the reduction of the hydrolysis rate of particulate carbohydrate (khyd,ch) from 0.25 d(-1) (as suggested by the ADM1 for high-rate mesophilic reactors) to 0.13 d(-1) were required to fit the experimental data.

Separation and Purification Technology, 2014

Several methods have been proposed over the last decade for the monitoring of fouling processes i... more Several methods have been proposed over the last decade for the monitoring of fouling processes in membrane bioreactors (MBRs). Many of these methods aim to acquire information measuring the transmembrane pressure (TMP) and permeability (K) directly on the membrane modules used in wastewater treatment plants. This study assessed in a critical light the use of TMP and K for membrane fouling monitoring. TMP and K were directly measured on a pilot-scale submerged MBR operated continuously for approximately 450 d at different solids retention times and fed with real municipal wastewater. The results showed that under standard operating conditions such as those usually applied in full-scale MBR and with the monitoring instruments typically employed in industrial applications, the identification of specific TMP trends within a filtration phase was often problematic and the results were unreliable, mainly because of the noise and the variability of real wastewater and environmental conditions. Moreover, a non-linear trend of the pressure behaviour within a filtration phase was observed when fouling phenomena were taking place. This study also proposes the use of the ratio between filtration and backwash permeability in order to assess whether the membrane flux is deviating from the ''pressure controlled region'' and, consequently, fouling processes are occurring.

Journal of Environmental Science and Health, Part A, 2012

Although most membrane bioreactors are used under aerobic conditions, over the last few years the... more Although most membrane bioreactors are used under aerobic conditions, over the last few years there has been increased interest in their application for anaerobic processes. This paper presents the results obtained when a bench-scale submerged anaerobic membrane bioreactor was used for the treatment of wastewaters generated in the agro-food industry. The reactor was fed with synthetic wastewater consisting of cheese whey and sucrose, and volumetric organic loading rates (OLRs) ranging from 1.5 to 13 kgCOD/(m(3)*d) were applied. Under the operating conditions studied, the maximum applicable OLR was between 6 and 10 gCOD/(g*L), which fell within the ranges of the high-rate anaerobic wastewater treatment systems, while high concentrations of volatile fatty acids were produced at higher OLR rates. With an OLR of 1.5-10 gCOD/(g*L), the reactor showed 94% COD removal, whereas this value dropped to 33% with the highest applied OLR of 13 gCOD/(g*L). The study therefore confirms that membrane bioreactors can be used for anaerobic wastewater treatment.

Desalination, 2009

The start-up of a pilot-scale membrane bioreactor equipped with submerged ultrafiltration membran... more The start-up of a pilot-scale membrane bioreactor equipped with submerged ultrafiltration membranes to treat municipal wastewater has been studied. Attention has been paid to determine membrane separation effects on biomass development in a reactor operated without inoculation. Moreover, the activated sludge model no. 1 has been applied to model biological removal processes. Filtration alone (without biodegradation) removed more than 70% of the influent total COD due to the high particulate COD fraction typically present in municipal wastewaters. Filtration action, retaining bacteria, allowed a rapid increase of the heterotrophic activity permitting to reach efficiencies in COD removal greater than 90% in one to two days. On the other hand, nitrogen removal process needs a few days (five to twenty depending on operational conditions) to develop and stabilise in the reactors because of the required development of the nitrifying biomass. Biomass development was confirmed using respirometric techniques. The activated sludge model no. 1 with minor modification was capable of simulating reasonably well the biological processes development in the MBR.

Chemical Engineering Journal, 2013

h i g h l i g h t s " A MBR was continuously operated at different solid retention times for 450 ... more h i g h l i g h t s " A MBR was continuously operated at different solid retention times for 450 d. " SRT effects on sludge filterability and biomass activity were evaluated. " The carbohydrate fraction of the SMP was correlated with CST and J c. " J c and CST trends can be used to predict sludge filterability. " The addition of the anoxic process seemed to deteriorate the sludge filterability.