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Integrated urban drainage systems (IUDS) (i.e., sewer systems, wastewater treatment plants and receiving water bodies) contribute to climate change being sources of greenhouse gas emissions (GHG). This paper, produced by the International Working Group on Data and Models, which works under the IWA/IAHR Joint Committee on Urban Drainage, reviews the state-of-the-art and the recently developed modelling tools used to understand and manage GHG emissions from IUDS. Further, open problems and research gaps are discussed, while proposing a framework for handling GHG from IUDS. The literature review reveals that there is a need to strengthen and partially adequate already available mathematical models for IUDS to take GHG into account.

The aim of the present study was to investigate the nitrous oxide (N2O) emissions from a University of Cape Town (UCT) moving bed membrane bioreactor pilot plant. An experimental campaign was carried out during 60 days with three different sludge retention time (SRT). The pilot plant reactor was provided of funnel shape covers that guaranteed gas accumulation in the headspace. The results highlighted that N2O concentrations significantly increased when the biofilm concentrations increased within the aerobic and anoxic compartments. Furthermore, results have shown an increase of N2O with the decrease of SRT. Moreover, the MBR tank resulted the key emission source (up to 70% of the total N2O emission during SRT=∞ period) whereas the highest N2O production occurred in the anoxic reactor. Moreover, N2O concentrations measured in the permeate flow were not negligible, thus highlighting its potential detrimental contribution for the receiving water body.

The paper reports the main results of a respirometric experimental survey carried out on several membrane bioreactor pilot plants, characterized by different pilot plant layouts as well as operational conditions. The main aim was to assess the influence of specific conditions on biokinetic/stoichiometric parameters. In particular, the respirometric tests were specifically aimed at investigating the activity of both heterotrophic and autotrophic bacterial species. The achieved results showed that the plant configuration and the features of the feeding wastewater and operational conditions determine significant variation of the kinetic coefficients. The respirometric analysis was confirmed to be a simple and effective tool for the evaluation of the actual biomass kinetic parameters, to be used in mathematical models for the design phase as well as for monitoring the biomass viability during plant operations.

The paper presents the sensitivity analysis of an integrated urban water quality system by means of the global sensitivity analysis (GSA). Specifically, an home-made integrated model developed in previous studies has been modified in order to include the micropollutant assessment (namely, sulfamethoxazole - SMX). The model takes into account also the interactions between the three components of the system: sewer system (SS), wastewater treatment plant (WWTP) and the receiving water body (RWB). The analysis has been applied to an experimental catchment nearby Palermo (Italy): the Nocella catchment. Five scenarios each characterized by different combinations of sub-systems (i.e., SS, WWTP and RWB) have been considered applying the Extended-FAST method in order to select the key factors affecting the RWB quality and to design a reliable/useful experimental campaign. Results demonstrated that GSA is a powerful tool for increasing operator confidence in the modelling results; the approach can be used for blocking some non-identifiable parameters thus wisely modifying the structure of the model and reducing the related uncertainty. The model factors related to the SS have been found to be the most relevant factors affecting the SMX modeling

The current study explores the influence of the air flow rate on greenhouse gas (GHG) emissions (direct and indirect), the operational costs (OCs), the effluent quality index (EQI) and effluent fines (EF). An University Cape Town (UCT) moving bed (MB) membrane bioreactor (MBR) pilot plant has been considered as case study where the influence of the air flow rate on the biological and physical processes has been analyzed. Constitutive relationships between the air flow rate and some performance indicators (i.e., EQI, OCs, direct and indirect GHG emissions) have been identified. Results showed that the EQI increases at low flow rate likely due to the dissolved oxygen (DO) limitation in the biological processes. Direct GHGs are influenced by air flow exponentially increasing with the increase of the air flow due to the anoxic N2O contribution. Irreversible membrane fouling reduce from 98% to 85% with the increasing of the air flow rate from 0.57 m3 h-1 to 2.56 m3 h- 1. However, the increase of the air flow rate leads to the increase of the N2O-N flux emitted from the MBR (from 40% to 80%). In order to establish a mathematical tool to reduce GHG emissions maintaining good effluent quality, results suggest of adopting a relationship based on a “multiple objective”.

Sanitary landfills for municipal solid wastes can be considered as large biological reactors where the organic fraction of municipal solid waste undergoes anaerobic digestion producing gas and liquid emissions. Leachate production from municipal sanitary landfills is currently recognized as a major environmental burden associated with municipal solid waste management and it may be responsible for local pollution of groundwater and soil. Moreover, the fate of the organic compounds within the landfill body is of primary importance since it directly influences the production of landfill gas. The aim of the paper is to propose an integrated mathematical model able to simulate, on one hand, the vertical leachate fluxes throughout a municipal solid waste landfill (considering the fate of both inorganic and organic contaminants within the landfill leachate pathway), while, on the other hand, the production of landfill gas by means of two different approaches. In detail, the mathematical model was based on mass balance equations and was composed by two sub-models: one for the simulation of moisture distribution, whilst the other one for the simulation of the organic/inorganic contaminant concentrations. The simulation of landfill gas production was based on two different approaches. The integrated model has been applied to a real landfill considered as a case study, the landfill of Pescantina (Italy), with the landfill body divided into N horizontal layers. The results confirmed that the proposed integrated model can be a useful tool for the landfill operator in order to analyze the physical, chemical and biological phenomena occurring within the landfill body.

A mathematical model to quantify the nitrogen removal for a membrane bioreactor (MBR) has been presented in this study. The model has been applied to a pilot plant having a pre-denitrification MBR scheme. The pilot plant was cyclically filled with real saline wastewater according to the fill-draw-batch operation. The model was calibrated by adopting a specific protocol based on extensive field dataset. The Standardized Regression Coefficient (SRC) method was adopted to select the most influential model factors to be calibrated. Results related to the SRC method have shown that model factors of the efficiency of backwashing and the biological factors affecting the soluble microbial products (utilization-associated products) (namely, fUAP and KH,UAP) strongly affects the membrane resistance. In terms of model calibration excellent results in terms of model efficiency were found for the total membrane resistance model output (efficiency equal to 0.79). Regarding the biological model outputs acceptable were found in the case an high number of measured data was available. In terms of uncertainty, it was found that for the great part of the analyzed model outputs the measured data lay inside the uncertainty bands.

The influence of the sludge origin on the dewaterability features has been investigated by comparing the experimental results of six membrane bioreactor pilot plants with different configurations. The capillary suction time (CST) and the specific resistance to filtration (SRF), identified as representative of sludge dewaterability features, were measured. The results were related to operational parameters, such as extracellular polymeric substances (EPS) and soluble microbial product (SMP), influent salinity and hydrocarbon, in order to elucidate the influence exerted on the dewaterability. Furthermore, the effect of biofilm and suspended biomass was also investigated. The results showed that during the experimentation carried out with salt and hydrocarbon the sludge dewaterability features significantly worsened (CST above 120 s and SRF above 20 * 1012 m kg-1). Furthermore, the sludge derived from the anoxic reactor resulted as the most affected by EPS and SMP concentration.

This paper investigates the behavior of different sludges from several treatment plants at full and pilot scale configured as Conventional Activated Sludge (CAS) and Membrane Bio Reactor (MBR) plants treating different kinds of wastewaters. The sludges collected were subjected to complete analytical and technological characterization in order to correlate the rheological properties that affect the dewatering behavior to the sludge chemical physical properties. In detail the EPS from the samples collected is extracted and characterized in terms of carbohydrates, proteins, uronic acids and humic acids content. Moreover, once characterized, the sludges were subjected to AD in order to assess their bio-methanation potential and hence their biological stability. The final aim was to find correlations between the WWTP operational parameters (i.e. HRT, SRT, volumetric load coefficient, aeration) that finally affect its chemical composition (i.e. BMP, EPS composition) and the physical behavior of the sludge.

Municipal solid waste management significantly contributes to the emission in the atmosphere of greenhouse gases (e.g. CO2, CH4, N2O) and therefore the management process from collection to treatment and disposal has to be optimized in order to reduce these emissions. Many literature models developed for the evaluation of greenhouses gases emissions from the waste management system are based on the analysis of the life cycle. These models are not optimized for evaluation of emissions. The aim of this study is to overcome these limitations by proposing a mathematical model to estimate greenhouse gas emissions resulting from the integrated waste management. The model is aimed to be a verification tool for assessing the optimum system management in terms of greenhouse gas emissions. The model quantify the emissions associated with: heat treatment, landfill disposal, anaerobic digestion plants, recycling, composting. Different combinations of collection scenarios and disposal options have been considered in the Municipal Solid Waste management of the Province of Palermo. The obtained results applying the model show that limits to solid waste management must be clearly defined. In fact changing the limits, the emissions vary. The lower emissions are due to the use of different energy sources.

The increasing interest in greenhouse gas emissions from WWTPs has been leading to new tools for their designing and managing. The activated sludge models have been modified in order to consider on – site emissions from nitrification and denitrification, in particular. The biological nitrogen removal processes have been mainly assessing due to nitrous oxide (N2O) production as intermediate. The IPCC suggests that N2O contributes to climate change because it has a global warming potential 298-fold stronger than carbon dioxide. Even if the mathematical modelling is wide regarding the activated sludge models for greenhouse gases, a model for aerobic digestion is still not available. In this paper, the development of the Aerobic Digestion Model for Greenhouse Gas n.1 (AeDMG1) is described.

MSW sanitary landfills represent nowadays one of the most important issue related to the waste management cycle. In particular, knowledge about biogas production is a key aspect for a proper exploitation of this energy source, even in the after-care phase. In the present study, a simple mathematical model was proposed for the simulation of biogas production. The model is based on 1st order biodegradation kinetic and takes also into account the temperature variation in time and depth and the landfill settlement. The model was applied to a real landfill located in Sicily (ITALY) and its simulation result was compared with experimental data (volumes of biogas collected by the recovery system and diffuse emissions directly measured by authors). The obtained result showed a good fitting between simulation results and methane production evaluated with experimental data, suggesting that the model can be the proposed model can be applied for reliable estimates of landfill gas production, thus representing a useful tool for landfill operators also for a reliable estimate of the after-care phase duration.

Mathematical modelling of membrane bioreactors (MBRs) for wastewater treatment has targeted either the biological processes (treatment quality target) as well as various aspects of system management. However, the high number of interactions among the involved physical – chemical processes, hampers a straightforward mathematical modelling. This circumstance is much more emphasized for submerged MBR systems where the membrane is immersed in an aeration tank. One of the main crucial point that prevents a comprehensive understanding is the interpretation of the fouling phenomenon and its connections with the biological processes. An overall mathematical model for MBR has not been completely established yet. Indeed, existing MBR models are generally focused only on some of the involved processes (e.g. biological, physical, chemical, etc.) to analyze limited MBR aspects. However, a comprehensive integrated mathematical approach aimed at an in-depth analysis is warmly recommended in order to optimize the whole MBR system. Seeking the development of the area, the abstract presents an integrated MBR model that simulates and takes into account both biological and physical processes.

The paper reports the main results from an experimental gathering campaign carried out on a bench scale plant for the evaluation of hydrocarbon effect on the system performance. In particular, a membrane bioreactor (MBR) under submerged configuration was analysed. The MBR plant was fed with synthetic wastewater containing hydrocarbons. Organic carbon, hydrocarbons and ammonium removal, kinetic constants, extracellular polymeric substances (EPSs) production and membranes fouling rates have been assessed. The observed results highlighted good system performance in terms of both COD removal and nitrification, thus showing a sort of biomass adaptation to hydrocarbon. Such a result has been also confirmed by the biomass respirometric tests. Moreover, membrane fouling analysis showed an increase of the total resistance in the last period of the experiments. Such a result was most likely due to the hydrocarbon which caused an irreversible fouling due to oil deposition onto the membrane surface.

During the last years many advances have matured in wastewater treatment both in terms of processes and mathematical modelling approaches. For a new generation of new scientists and engineers entering/working in the wastewater treatment field, the quantity, complexity and diversity of these new developments can be overwhelming. This Advanced Course on Innovative wastewater treatment processes and mathematical modelling will provide a comprehensive overview and a discussion platform for recent advances and trends currently under development in the context of wastewater treatment. This course is aimed at professionals (Master, PhD or equivalent experience) in wastewater treatment and mathematical modelling with a basic working knowledge of the two other disciplines. The course is primarily aimed at those already employed in industry who wish to up- date their theoretical knowledge and practical insight in this field.

Greenhouse gases (GHGs) emission from wastewater treatment plants (WWTPs) represents an increasing interest in the water industry at the present moment. The biological processes needed for treating wastewater have been found responsible for the unintentional generation of GHGs, such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The quality and quantity of a GHG emitted from a WWTP can significantly vary with the wastewater treated, the process configuration, and the strategies employed in process control. In the recent past, efforts for monitoring and accounting for GHGs emissions from WWTPs have considerably increased, and classifications of emission type were proposed to facilitate reporting. However, knowledge gaps (e.g., N2O production dynamics) and data availability mar the quantification of a WWTP carbon footprint. Moreover, too often the acquired information is insufficient to understand the dynamics responsible for GHG production. Further, it is not even comparable with measurements from different plants due to the heterogeneity of materials, methods, and instrumentation used. For these reasons, in order to produce useful and comparable information for assessing the carbon footprint of WWTPs, there is a crescent need for a generally accepted methodology for GHGs measurement. This paper proposes a comprehensive protocol for monitoring and accounting for direct and internal indirect GHG emissions related to the aerated compartments of biological WWTPs. The proposed protocol also provides important guidelines for quantifying the contribution of anaerobic processes to the carbon footprint of the plant.

Membrane fouling represents one of the major crucial issues for membrane bioreactor (MBR). Membrane fouling and high aeration requirements (for inducing shear stress to limit fouling) make MBR operation economically demanding due to high energy costs. Although several studies on MBR fouling have been performed, a comprehensive knowledge on how to reduce membrane fouling and consequently energy saving is still lacking. Two scenarios are analyzed and compared each implementing different operating conditions. As expected, MBR operation at low air flow rate (qa) leads to a substantial reduction of the operational costs (namely, 20% respect to the suggested manufacturers ones in terms of qa).

The paper presents the sensitivity analysis of an integrated urban water quality system by means of the global sensitivity analysis (GSA). Specifically, an home-made integrated model developed in previous studies has been modified in order to include the micropollutant assessment (namely, sulfamethoxazole - SMX). The model is able to estimate also the interactions between the three components of the system: sewer system (SS), wastewater treatment plant (WWTP) and the receiving water body (RWB). The analysis has been applied to an experimental catchment nearby Palermo (Italy): the Nocella catchment. Five scenarios each characterized by different combinations of sub-systems (i.e., SS, WWTP and RWB) have been considered applying the Extended-FAST method. Results demonstrated that GSA is a powerful tool for increasing operator confidence in the modelling results; the approach can be used for blocking some non-identifiable parameters thus wisely modifying the structure of the model and reducing the related uncertainty. The model factors related to the SS have been found to be the most relevant factors affecting the SMX modeling.

Landfill leachate represents nowadays one of the most important issue related to the waste management cycle. Knowledge about leachate distribution and transport as well as fate of pollutants is fundamental for understanding the behavior of the landfill reactor. In the present study, a simple 1-D mathematical model was developed for the simulation of the vertical leachate fluxes throughout a landfill for MSW as well as the fate of inorganic pollutants within the landfill leachate pathway. The model was based on mass balance equations, which allowed to evaluate the moisture accumulation inside the landfill body as well as contaminant transport processes. The model enables to calculate the moisture content and the simulation of continuous moisture distribution was carried out on the basis of the theory of the vertically distributed unsaturated flow. The model has been applied to a real landfill considered as a case study. The observed results highlight that the proposed simple 1-D model can be a useful tool to analyze the landfill body as an unsaturated porous medium. The simulation results were in good agreement with the real leachate data provided by the landfill operator.

COD AND TPH ANALYSIS IN SLOPS EXPERIMENTAL TREATMENT PLANTS: ANALYTICAL PROBLEMS. In the last years, the persistence and accumulation of xenobiotic compounds in the environment created many disposal problems of oily wastewater generated by ships, mainly in engine-rooms (bilge waters) and by cleaning of tanker (slops). The high salinity levels (up to 25.000 mgL-1) and the pollutants concentration, both limit the chances of discharge into the sewer systems and address the disposal of these wastewaters to the sea. For these reasons it is necessary to treat such wastewater efficiently before discharging [1]. As a part of a broader project concerning slops treatments, this work addresses issues related to the analytical methods of the COD and TPH parameters, chosen under the provisions of Italian Legislative Decree 152/06, that implements the European directives on environmental protection. In the COD analysis the greatest difficulty was the high salinity levels corresponding to high chlorides levels. Chlorides cause a positive interference in the measurement, and this interference during the analysis of COD was investigated at various concentrations of mercury in order to try to minimize the use of this reagent that causes many problems of safety and disposal, and at different times reaction [2][3][4]. The major problems in TPH analysis concerned correct setup of the gas chromatographic separation, high variability in sample composition and the high capacity of the sample to form emulsions during the liquid-liquid extraction procedure. This paper reports the results of the analysis of COD and TPH and the problems related to the development of a suitable analytical method for the analysis of these specimens. This study is part of STITAM European project, created with the aim to develop innovative technologies for the treatment of liquid wastes of navigation, in order to better safeguard marine environment. [1] G. Mancini, S. Cappello, M.M. Yakimov, A. Polizzi, M. Torregrossa, Chemical Engineering Transactions 27 (2012) 37-42. [2] I. Vyrides, D.C. Stuckey, Bioresource Technology 100 (2009) 979–982 [3] Alexandra M.E. Viana da Silva, Ricardo J.N. Bettencourt da Silva , M. Filomena G.F.C. Camoes, Analytica Chimica Acta 699 (2011) 161– 169 [4] D.D.C. Freire, G.L. Sant’anna jr, Environmental Technology 19 (1998) 1243- 1247

Sensitivity analysis (SA) is a valuable tool to support the use of mathematical models for environmental systems. Local or global SA (namely, LSA and GSA) are performed in order to better understand processes and to select the most influential factors affecting processes. The main objective of this extended abstract is to provide an informed problem statement of the issues surrounding LSA and GSA applications in the environmental water quality modelling field. Specifically, this paper aims at identifying, for the most popular methods, their potential use, the critical issues to be solved and the limits identified in a comprehensive literature review.

Global sensitivity analysis (GSA) is a valuable tool to support the use of mathematical models that characterise technical or natural systems. In the field of wastewater modelling, most of the recent applications of GSA use either regression-based methods, which require close to linear relationships between the model outputs and model factors, or screening methods, which only yield qualitative results. However, due to the characteristics of membrane bioreactors (MBR) (non-linear kinetics, complexity, etc.) there is an interest to adequately quantify the effects of non-linearity and interactions. This can be achieved with variance-based sensitivity analysis methods. In this paper, the Extended Fourier Amplitude Sensitivity Testing (Extended-FAST) method is applied to an integrated activated sludge model (ASM2d) for an MBR system including microbial product formation and physical separation processes. Twenty-one model outputs located throughout the different sections of the bioreactor and 79 model factors are considered. Significant interactions among the model factors are found. Contrary to previous GSA studies for ASM models, we find the relationship between variables and factors to be non-linear and non-additive. By analysing the pattern of the variance decomposition along the plant, the model factors having the highest variance contributions were identified. This study demonstrates the usefulness of variance-based methods in membrane bioreactor modelling where, due to the presence of membranes and different operating conditions than those typically found in conventional activated sludge systems, several highly non-linear effects are present. Further, the obtained results highlight the relevant role played by the modelling approach for MBR taking into account simultaneously biological and physical processes.

Two pilot plants were investigated for the treatment of wastewater subject to a gradual increase of salinity. In particular, a membrane bioreactor (MBR) and a moving bed biofilm membrane bioreactor (MB-MBR) were studied. Carbon and ammonium removal, kinetic constants and membranes fouling rates have been assessed. Both plants showed very high efficiency in terms of carbon and ammonium removal and the gradual salinity increase led to a good acclimation of the biomass, as confirmed by the respirometric tests. Significant biofilm detachments from carriers were experienced, which contributed to increase the irreversible superficial cake deposition. However, this aspect prevented the pore fouling tendency in the membrane module of MB-MBR system. On the contrary, the MBR pilot, even showing a lower irreversible cake deposition, was characterized by a higher pore fouling tendency.

The aim of this study is to detect a possible relationship between EPS and fouling and EPS and foaming in a University Cape Town (UCT) membrane bioreactor (MBR) pilot plant. The UCT-MBR pilot plant was fed with 40 L/h of real wastewater and monitored for 165 days. Specifically physical/chemical features of influent, permeate and mixed liquor in different sections were analyzed. The fouling phenomenon was studied monitoring the hydraulic resistances of the membrane. The extracellular polymeric substances (EPSs) concentration inside the aerobic tank were also measured. The foaming phenomenon was monitored by performing the Foam Power and Scum Index testes. Results have shown a high correlation between fouling and EPS distribution and foaming and bound EPSs concentration. None correlation was found comparing foaming and fouling indicating that further studies have to be performed in order to deep this issue

Membrane fouling represents one of the major limiting issue for membrane bioreactor (MBR) in the wastewater treatment field. Membrane fouling and high aeration requirement (for inducing shear stress to limit fouling) in MBR systems make the operation of such systems economically demanding due to high energetic costs. Despite several studies on MBR fouling have been performed a comprehensive knowledge on how to reduce membrane fouling and consequently energy saving is still lacking and controversial. The aim of this study is to gain insights on the optimization of the operating conditions in an MBR system. In particular, the influence of the aeration intensity and the durations of filtration and backwashing phase were analyzed in order to optimize the energy saving and effluent quality. To accomplish such goals an integrated MBR model developed and calibrated in previous studies was employed. Monte Carlo simulations were performed for different scenarios each implementing different operating conditions. The results demonstrated that the air flow rate is a key parameter for controlling and reducing the energetic demand and for maintaining a high quality effluent.

Climate is one of the most important factors leading to changes in the hydrologic and environmental characteristics of river basins. When considering water quality, the natural factors should be weighed against anthropogenic factors (such as urbanization, increased population, and higher water demand) that may increase or decrease the effect of climatic modifications. Any prediction of future climatic and anthropogenic scenarios is affected by uncertainty and the modelling tools that are used for evaluating their impact on receiving water bodies. The present paper is aimed at investigating the complexity of such analyses and the uncertainty related to future impact predictions based on limited databases. Specifically, the study is focused on quantifying the impact of urbanization and social changes coupled with climate on river water quality under uncertainty. The study was carried out at a small catchment scale (less than 100 km2), an analysis that has been lacking from the field so far. The analysis took into account both anthropogenic change and climate determined from observed data. Because of inherent uncertainty in the model caused by the complexity of the model and its calibration, the analysis was performed considering the effect of such uncertainty on reliability by means of Monte Carlo simulations. This analysis has been applied to a monitored semiurbanized basin in Sicily (Italy). The study showed that the proposed analyses can useful for planners and urban managers; however, the uncertainty connected with mathematical modeling and small available databases has to be taken into account because it can affect decision making. The impacts of anthropogenic changes and climate can interact, thus requiring that such factors be jointly analyzed. A larger effort in monitoring and characterization of natural and urban water systems is needed to increase the reliability of models and to improve the effectiveness of decision making based on such models

During the last decades, the largest part of municipal solid waste (MSW) generated world wide has been disposed of in landfills without any pre-treatment. The main environmental impacts of such landfills, containing high amounts of biodegradable organic matter, are caused by emissions of liq-uid effluents and landfill gas. With no collection and treatment, leachates from landfills pollute groundwater and soils locally. Furthermore, besides the biological processes, many physical phe-nomena occur inside the landfill body which negatively affect landfill management. Indeed, the waste settlement inside the landfill body, with a consequent increase of its density, corresponds to a proportional decrease of waste permeability; such aspect may cause serious problems to leachate drainage through the waste body, with the possible formation of the so-called suspended “perched leachate zone”. The perched leachate zone is a temporary phenomenon, which evolves downwards, reaching the bottom of the MSW landfill and producing a leachate head above the leachate collec-tion system. Such phenomenon is strongly influenced by many factors and, among others, the rain infiltration rate, waste moisture content and landfill height are of great concern. Bearing in mind such considerations, the main aim of the paper is to present a mathematical modelling survey to gain insights about the role played by the landfill height and the initial MSW moisture content. To accomplish such a goal, a previously developed 1D mathematical model was employed. The math-ematical model allows the simulation of the percolation fluxes throughout a MSW landfill. Specifi-cally, the model is based on mass balance equations and considers the landfill divided in several layers evaluating the inflow to and outflow from each layer as well as the continuous moisture dis-tribution. Several model simulations were performed considering different landfill heights and MSW initial moisture. The model results showed a different response of the landfill in terms of flow rates throughout the landfill. Indeed, the landfill height content drastically influenced not only the formation of perched leachate zones but also their extension. In particular, the model results showed that there is a sort of landfill threshold height, below which, the perched leachate zone does not appear.

The paper presents a mathematical model for the simulation of the ecological status of a wastewater stabilization reservoir (WSR). WSRs are hypertrophic aquatic systems devoted to storage of water resources in warm countries where shortage conditions have quite often to be faced. Several factors that affect the stabilization reservoir effluent quality were taken into account: hydraulics and hydrology, solar radiation, atmospheric reaeration, algae, zooplankton, organic matter, pathogen bacteria, and sediment-water interaction. The model quantifies the specific influence of each factor on effluent quality, evaluating the correlation between the different considered factors. State variables included in the model were: algae, dissolved oxygen, organic matter, zooplankton and indicator bacteria. The model was applied to an Italian stabilization reservoir located in the south part of Sardinia: the Simbirizzi’s lag. The model showed satisfactory results and can be employed as an useful tool for environmental water quality management of stabilization reservoirs.

The magnificence of Roman buildings is very well-known from historical books, notes etc.. In contraposition to this, generally speaking, less is known about the majesty of Roman sewer systems in terms of structures, facilities and the very advanced as well as rudimental complexity. The Roman sewers have been over-praised. Indeed, despite their longevity, they ignored basic sanitary principles as well as design rules. The Roman Empire is in many ways the highest point of sewage management in the ancient world. Famous for public baths and latrines with quite complex engineering, Rome also excelled in the use of covered drains for stormwater and waste-sewage, with some houses directly connected to the drainage system. Water conveyance in large-scale aqueducts was another impressive accomplishment. With the Roman Empire, these technologies were introduced across large geographic parts.

The paper presents an experimental study on a lab scale pilot plant in a Hybrid Moving Bed Biofilm Reactor. The pilot plant was fed with synthetic wastewater and was in operation considering two different operating conditions: continuous aeration and intermittent aeration. Both continuous and intermittent aeration were monitored and compared in order to seek the best conditions for carbon and nitrogen removal. At the beginning of the experimentation, an initial period of about 90 days was considered during which the pilot plant worked in bench scale configuration for allowing the formation of biofilm on the carriers. Once the biofilm growth was accomplished, the pilot plant worked for a first period in continuous aeration and in a second period in intermittent aeration. The efficiency of organic matters removal was similar between the two periods. Contrarily, the efficiency of N-removal improved by 50 % and more. More specifically, the efficiency to remove the carbon and nitrogen using intermittent aeration were about 93% and 90%, respectively.

The increasing sensitivity towards water quality environmental issues led to the setting up of water quality integrated modelling approaches and the definition of water quality criteria that better represent the receiving water body quality status. More specifically, compared to the past, the tendency today is to design and manage the whole integrated urban drainage system, i.e. , wastewater treatment plant and receiving water body (RWB) considering each component not separately but jointly. Despite the advantages of a holistic approach for the assessment of the RWB quality state there are some limits that may prevent a straightforward application. Indeed, integrated models are generally characterized by a high level of model complexity which increases rapidly involving tenth of parameters and requiring large measurements databases for calibration. In this context sensitivity analysis represents a very powerful tool, as it is able to provide information about how the variation in the output of the model can be apportioned to the variation of the input factors and may help in reducing model complexity. The paper presents a study on an integrated urban water quality system applying the global sensitivity analysis (GSA). Specifically, a home-made integrated model previously developed has been employed to a real case study. GSA allowed to identify the most influential model parameters thus reducing model complexity and enabling a better assessment of the RWB quality state.

Over the last two decades, Membrane Bioreactors (MBR) are increasingly used for wastewater treatment. Mathematical modelling of MBR systems has played a key role in order to better explain the effect of their peculiarities. Indeed, several MBR models have been presented in literature in order to improve the knowledge on MBR systems: biological models, hybrid models which include soluble microbial product (SMP) modelling, physical models able to describe the membrane fouling and integrated models which couple the hybrid models with the physical ones. However, among the existing MBR models only few integrated models have been developed which take into account the existing relationship between fouling and the biological processes. Also, with respect to modelling of biological phosphorus removal in MBR systems, due to the complexity of the process, practical use of the models is still limited. There is a vast knowledge (and consequently a vast amount of data) on nutrient removal for conventional activated sludge (CAS) systems but only limited information on phosphorus removal for MBRs. Moreover, calibration of these complex integrated models still remains the main bottleneck to their employment. The paper presents an integrated mathematical model able to simultaneously describe biological nutrient removal, the SMP formation/degradation and the physical removal of organics. The model has been calibrated by using data collected in a UCT-MBR pilot plant, built at the Palermo WWTP and fed with real wastewater, applying an innovative calibration protocol. The calibrated model provides acceptable correspondence with experimental data.

I modelli di qualità fluviale possono essere dei validi strumenti per la valutazione e la gestione della qualità dei corpi idrici ricettori. Tuttavia tali modelli richiedono una calibrazione accurata al fine di valutare i parametri che in essi compaiono; ciò richiede una vasta banca dati di qualità, raramente disponibile nel caso di piccoli corsi d’acqua fluviali a carattere torrentizio, per il limitato interesse spesso prestato a tali tipologie di corpi idrici. Nella memoria viene presentato un modello semplificato di qualità fluviale; il modello trae spunto dal classico modello di Streeter e Phelps, integrato al fine di tener conto dei principali processi fisici, chimici e biologici per la modellazione della qualità dei corpi idrici ricettori. Il modello è stato applicato a un caso di studio italiano, il fiume Oreto, corso d’acqua a carattere torrentizio che attraversa il territorio del Comune di Palermo, il cui stato di qualità è alterato dalla presenza di scarichi concentrati e diffusi. La calibrazione del modello è stata eseguita utilizzando le misure rilevate in una campagna d’indagine appositamente condotta sulle acque del fiume; essa ha confermato il differente comportamento che il regime torrentizio comporta nei fenomeni di deossigenazione e riossigenazione delle acque, rispetto ai casi più ricorrenti in letteratura di fiumi a portata perenne.

In this study global sensitivity analysis is performed to identify influential as well as non-influential parameters in a model of a University Cape Town Membrane Bioreactor (UCT-MBR). In particular, the Standardised Regression Coefficients (SRC) and Extended-FAST sensitivity analysis methods are applied. The sensitivity of model variables towards parameter variation is analysed for CODTOT, SNH4, SNO3, SPO, and MLSS along five reactor compartments. Both methods indicate that the parameters identified as being influential differ from section to section due to the different processes involved. Moreover, the relevant influence of the membrane filtration parameters is detected in the first plant section due to the influence of the recycled sludge. It is found that the computationally less expensive SRC method is applied outside its range of applicability with R2 = (0.3-0.6) < 0.7. Nevertheless, the ranking obtained with the SRC method for the influential parameters is very similar to that of the Extended-FAST method, except for MLSS. However, to obtain reliable quantitative information on variance decomposition and to detect and quantify (in some cases considerable) interactions present among parameters the use of the computationally more expensive Extended-FAST is found to be necessary in this case study.

In the last years, there has been an increasing awareness about the environment pollution protection. As a consequence, the Environmental Regulation has increased the emission limits imposing, for instance, lower concentrations at the wastewater treatment plant (WWTP) outlets. As a consequence of this fact, several WWTPs are not able to respect the emission limits and need to be upgraded. In view of such needs new technology are emerging and new WWTP solution schemes are being realized. With respects to the nutrient removal enhancing, a possible solution can be the UCT-MBR which couples the University of Cape Town scheme with a Membrane Bioreactor. In the light of such considerations, the study presents a survey about the performance of a UCT-MBR pilot plant, which may offer high performance in terms of carbon and nutrient removals. Specifically, a UCT-MBR pilot plant has been designed, realized and monitored with the aim of investigating the efficiency in treating real municipal wastewater. The pilot plant has been operated for a period of 165 days during which an extensive data gathering campaign has been carried out. The pilot-plant showed good performances in terms of effluent pollutant concentrations. Further, although the pilot plant showed an overall good efficiency in terms of both carbon and nutrients removal, nitrogen and phosphorus removal efficiencies showed sometimes negative efficiencies fluctuations likely due to sporadic discharges of industrial wastewater and landfill leachate. Such a fact was justified by assuming a sensitivity of the heterotrophic biomass during the biological phosphorus and denitrification removal processes.

Over the last two decades, Membrane Bioreactors (MBRs) emerged even more for wastewater treatment, ensuring high removal efficiencies as well as very small footprint required. Indeed, in this kind of process, a modification in biomass activity and viability can exist compared to that of a conventional activated sludge (CAS) process. In this context, respirometric analysis represents a reliable tool in order to evaluate the actual biomass kinetic parameters, to insert in mathematical models in the design phase, as well as to monitor the biomass viability, especially when these processes are operated with high sludge retention time (SRT) values. The paper presents some results of respirometric techniques applied for the characterisation of wastewater and biomass activity in a pilot UCT-MBR plant for nutrient removal, operating with high SRT. In particular, the respirometric tests were specifically aimed at investigating heterotrophic and autotrophic bacterial activity. The pilot plant was built at the Acqua dei Corsari (Palermo) wastewater treatment plant and consisted of three reactors in the following order: anaerobic (mean volume 71.6 L), anoxic (mean volume 165 L) and aerobic (mean volume 327 L) tanks, followed by an aerobic compartment (mean volume 52 L) containing two submerged hollow fibre membrane modules (Zenon Zeeweed, ZW 10) with typical recycling lines

The paper presents a 1D mathematical model for the simulation of the percolation fluxes throughout a landfill for municipal solid waste (MSW). Specifically, the model is based on mass balance equations, that enable one to simulate the formation of perched leachate zones in a landfill for MSW. The model considers the landfill divided in several layers evaluating the in and out flow throughout each layer as well as the continuous moisture distribution. The infiltration flow is evaluated by means of the Darcy’s law for an unsaturated porous medium, while the moisture distribution evaluation has been carried out on the basis of the theory of the vertically distributed unsaturated flow. The solution of the model has been obtained by means of the finite difference scheme. The model has been applied to a semi-idealized landfill located in Palermo landfill (Bellolampo). Specifically, field measurements enable us to assess a relationship between porosity variation and applied vertical strain. Such relationship has been applied in order to relate vertical strain to waste porosity. The inflow rate was simulated by considering a synthetic hyetograph whose characteristics have been assessed throughout an hydrologic study previously developed. Three cases have been considered in the model application characterized by different initial moisture contents. The model results showed a different response of the landfill in terms both of flow rates throughout the landfill and moisture profile. Indeed, the initial moisture content drastically influence not only the formation of perched leachate zones but also their extension. The model can be a useful tool in design and management optimization of landfill.

Identifiability analysis enables one the quantification of the number of model parameters that can be assessed by calibration with respect to a data set. Such a methodology is based on the appraisal of sensitivity coefficients of the model parameters by means of Monte Carlo runs. By employing the Fisher Information Matrix, the methodology is able to gain insights with respect to the number of model parameters that can be reliably assessed. The paper presents a study where identifiability analysis is used as a tool for the setting up of measuring campaigns for integrated water quality modelling. The analysis has been applied to a real case study characterized by a partially urbanized catchment represented by two sewer systems, two wastewater treatment plants and a river. Several scenarios of measuring campaigns have been considered; each scenario was characterized by different monitoring stations for the gathering of quantity and quality data. The results enabled us to assess the maximum number of model parameter quantifiable for each scenario i.e. for each data set. The methodology resulted to be a powerful tool for designing measuring campaign for integrated water quality modelling. Indeed, the crucial cross sections throughout the integrated wastewater system were detected optimizing both human and economic efforts in the gathering of field data.

The study presents an integrated approach in order to analyse and quantify pollution dynamics at basin scale depending on concentrated and diffuse sources. More specifically, an integrated model for urban drainage system has been exploited in order to simulate the complex sewer network - wastewater treatment plant and receiving water body. Moreover, a quali-quantitative model has been developped in order to simulate the non-point sources pollutant (agricultural and zoo-technical) in term of water river discharges and nutrient, produced from the wash off of soils. Finally, different models have been coupled in order to reconstruct the whole pollutant load for the receiving water body and to single out the different pollution sources. The proposed approach has been applied to the experimental Nocella catchment located in Sicily (Italy), with an area of about 50 km2. The river receives wastewater and stormwater from two urban areas drained by combined sewers. The study demonstrates that the analysis of water quality in partially urbanised natural basins is complex depending on variable polluting contributions of the different parts of the system.

Il cambiamento climatico è una delle principali cause che possono indurre a una modifica delle caratteristiche idrologiche e ambientali dei bacini naturali. Per quanto attiene la qualità delle acque naturali superficiali, tale fattore va combinato con quello antropogenico (urbanizzazione, variazione di popolazione e domanda idrica, etc.), che può ridurre o incrementare l‟effetto delle variazioni climatiche. Un aspetto che merita un‟attenta valutazione è l‟analisi degli effetti che i cambiamenti sia climatici che antropogenici hanno sulla qualità di un corpo idrico ricettore. Al fine di valutare tali effetti, nel presente studio è stato impiegato un modello di tipo integrato messo a punto in precedenza al fine di predire la qualità delle acque in fognatura, nell‟impianto di depurazione e nel corpo idrico ricettore in modo congiunto. Nel caso di valutazioni dello stato di qualità di un corpo idrico ricettore a scala di bacino secondo un approccio modellistico di tipo integrato, il sistema nel suo insieme può divenire abbastanza complesso a seguito della presenza di uno o più centri abitati che ricadono nel bacino in esame. In tali casi, la complessità dell‟approccio modellistico integrato diviene elevata e richiede la stima di numerosi parametri di calibrazione e quindi la necessità di una estesa banca dati. Quest‟ultima raramente è disponibile e spesso occorre metterla a punto con la mobilitazione di notevoli risorse sia economiche che umane. Nonostante le difficoltà insite nell‟approccio modellistico di tipo integrato, questo riveste spesso notevole importanza ed è, ad oggi, l‟unico strumento per una corretta valutazione sia della qualità di un corpo idrico, sia dell‟efficacia di opere di mitigazione mirate a salvaguardare lo stesso o a migliorane lo stato di qualità. Invero, tali concetti sono contenuti nella direttiva quadro EU Water Framework Directive, che contiene al proprio interno il concetto di approccio integrato. L‟impatto inquinante dei cambiamenti sia climatici che antropogenici è stato valutato immaginando dei nuovi sviluppi per un bacino urbano. L‟analisi è stata applicata al bacino Nocella, bacino naturale urbanizzato ricadente nella parte nord-occidentale della Sicilia.

Over the last decade new technologies are emerging even more for wastewater treatment. Among the new technologies, a recent possible solution regards membrane bioreactors (MBRs) that represent a promising alternative to conventional processes. Nowadays, the recurrence to mathematical models as reliable tools in planning as well as management issues is of growing interest in Wastewater Treatment Plants field. Regarding MBR modelling, due to the intrinsic complexity and uncertainty in some processes, basic models that can provide a holistic understanding of the technology at a fundamental level are of great necessity. Many mathematical models have been developed for modelling the MBR which basically combine the activated sludge models with the membrane fouling ones. This paper presents the uncertainty assessment of a mathematical model for the simulation of physicalbiological organic removal. In particular, the uncertainty analysis was carried out using the GLUE procedure. The model was applied to a MBR pilot plant located at the Acqua dei Corsari WWTP (Palermo, IT) where water quality data were gathered. In particular, the MBR pilot plant consists of a lab-scale hollow fibre membrane module in submerged configuration. The results showed that the biological process is influenced mainly by the parameters characterizing the formation and degradation of SMP. Instead, regarding the fouling phenomenon, it is mainly influenced by the backwashing efficiency.

The paper presents the setting up of a mathematical model for membrane bioreactor able to simulate physical-biological wastewater organic removal. The model is basically divided into two sub-models: the first sub-model is basically devoted for the simulation of the biological features and the second one for the physical processes. In particular regarding the biological aspects, the ASM concept has been employed. On the other hand, the physical processes have been modelled considering the deep-bed theory taking into account not only the effect of the physical membrane filtration but also the cake layer effect. This latter operates as a biological membrane leading to a further reduction of the effluent COD. The model was applied to a SMBR pilot plant characterized by hollow fibre membrane module in submerged configuration. The SMBR was fed by raw wastewater, only screened with a sieve of 2 mm, collected from the Palermo (IT) WWTP. The SMBR was characterized by an operating volume of 190 litres and it was equipped with an aeration system located on the bottom of the reactor. The whole experimentation was divided in two subsequent experimental phases: a former one where, the SMBR pilot plant started-up was carried out without inoculum of activated sludge, and a second one considering the inoculum. The pilot plant was in operation for a total period of 130 days. The model results are interesting and confirm the importance of cake deposition in the filtration process. The developed model can be employed as a useful tool in optimizing operation conditions as well as design parameters for SMBR systems.

The use of decision support systems (DSS) allows integrating all the issues related with sustainable development in view of providing a useful support to solve multi-scenario problems. In this work an extensive review on the DSSs applied to wastewater treatment plants (WWTPs) is presented. The main aim of the work is to provide an updated compendium on DSSs in view of supporting researchers and engineers on the selection of the most suitable method to address their management/operation/design problems. Results showed that DSSs were mostly used as a comprehensive tool that is capable of integrating several data and a multi-criteria perspective in order to provide more reliable results. Only one energy-focused DSS was found in literature, while DSSs based on quality and operational issues are very often applied to site-specific conditions. Finally, it would be important to encourage the development of more user-friendly DSSs to increase general interest and usability., This work is part of a research project supported by grant of the Italian Ministry of Education, University and Research (MIUR) through the Research project of national interest PRIN2012 (D.M. 28 December 2012 n. 957/Ric – Prot. 2012PTZAMC) entitled “Energy consumption and Greenhouse Gas (GHG) emissions in the wastewater treatment plants: a decision support system for planning and management – http://ghgfromwwtp.unipa.it” in which the first author is the Principal Investigator. In addition, some coauthors acknowledge the partial support of the Industrial Doctorate Programme (2017-DI-006) and the Research Consolidated Groups/Centres Grant (2017 SGR 574) from the Catalan Agency of University and Research Grants Management (AGAUR), from Catalan Government.