Maurizio Giugni

Losses Reduction and Energy Production in Water-Distribution Networks

AbstractDuring the past few years, issues concerning sustainable management of water distribution systems have attracted interest through an integrated policy aimed at reducing leakage through a pressure management strategy. Pressure reducing valves (PRVs) are often used in water networks to prevent the downstream hydraulic grade from exceeding a set value, although they must be adequately located to maximize their effectiveness. In recent years, the application of turbines or pumps operating as turbines (PATs) appeared as an alternative and sustainable solution to control network pressure and produce energy. In the present paper, PRVs and PATs were used within a district in a Naples’ water distribution network and showed large potential revenues and an attractive capital payback period.

Polymer functionalized nanocomposites for metals removal from water and wastewater: An overview.

Pollution by metal and metalloid ions is one of the most widespread environmental concerns. They are non-biodegradable, and, generally, present high water solubility facilitating their environmental mobilisation interacting with abiotic and biotic components such as adsorption onto natural colloids or even accumulation by living organisms, thus, threatening human health and ecosystems. Therefore, there is a high demand for effective removal treatments of heavy metals, making the application of adsorption materials such as polymer-functionalized nanocomposites (PFNCs), increasingly attractive. PFNCs retain the inherent remarkable surface properties of nanoparticles, while the polymeric support materials provide high stability and processability. These nanoparticle-matrix materials are of great interest for metals and metalloids removal thanks to the functional groups of the polymeric matrixes that provide specific bindings to target pollutants. This review discusses PFNCs synthesis, characterization and performance in adsorption processes as well as the potential environmental risks and perspectives.

Flood risk assessment for informal settlements

The urban informal settlements are particularly vulnerable to flooding events, due to both their generally poor quality of construction and high population density. An integrated approach to the analysis of flooding risk of informal settlements should take into account, and propagate, the many sources of uncertainty affecting the problem, ranging from the characterization of rainfall curve and flooding hazard to the characterization of the vulnerability of the portfolio of buildings. This paper proposes a probabilistic and modular approach for calculating the flooding risk in terms of the mean annual frequency of exceeding a specific limit state for each building within the informal settlement and the expected number of people affected (if the area is not evacuated). The flooding risk in this approach is calculated by the convolution of flooding hazard and flooding fragility for a specified limit state for each structure within the portfolio of buildings. This is achieved by employing the flooding height as an intermediate variable bridging over the fragility and hazard calculations. The focus of this paper is on an ultimate limit state where the life of slum dwellers is endangered by flooding. The fragility is calculated by using a logic tree procedure where several possible combinations of building features/construction details, and their eventual outcome in terms of the necessity to perform structural analysis or the application of nominal threshold flood heights, are taken into account. The logic tree branch probabilities are characterized based on both the orthophoto recognition and the sample in situ building survey. The application of the methodology is presented for Suna, a sub-ward of Dar es Salaam City (Tanzania) in the Msimbazi River basin having a high concentration of informal settlements.

Optimal Location of PRVs and Turbines in Water Distribution Systems

AbstractPressure reducing valves (PRVs) are often used to manage pressure and reduce losses in water distribution systems (WDS). Different approaches are available in the literature on how to locate and set the PRVs in order to maximize their effectiveness and minimize water losses. The available methodologies minimize the mean square difference between the actual and the target pressure at each node. Since the excess head can be used also to generate hydropower by using turbines and/or pumps as turbines (PATs), a different objective function could be suggested to maximize energy production. Consequently, a comprehensive analysis will be developed in the paper which highlights the differences between the preexisting approach and the suggested one, in terms of device location, pressure reduction, and recoverable energy. Numerical simulations showed that minimizing pressure may also affect the production of energy, while maximizing the energy production itself could be an attractive alternative, leading to ...

Probabilistic GIS-based method for delineation of urban flooding risk hotspots

Abstract Identifying urban flooding risk hotspots is one of the first steps in an integrated methodology for urban flood risk assessment and mitigation. This work employs three GIS-based frameworks for identifying urban flooding risk hotspots for residential buildings and urban corridors. This is done by overlaying a map of potentially flood-prone areas [estimated through the topographic wetness index (TWI)], a map of residential areas and urban corridors [extracted from a city-wide assessment of urban morphology types (UMT)], and a geo-spatial census dataset. A maximum likelihood method (MLE) is employed for estimating the threshold used for identifying the flood-prone areas (the TWI threshold) based on the inundation profiles calculated for various return periods within a given spatial window. Furthermore, Bayesian parameter estimation is employed in order to estimate the TWI threshold based on inundation profiles calculated for more than one spatial window. For different statistics of the TWI threshold (e.g. MLE estimate, 16th percentile, 50th percentile), the map of the potentially flood-prone areas is overlaid with the map of urban morphology units, identified as residential and urban corridors, in order to delineate the urban hotspots for both UMT. Moreover, information related to population density is integrated by overlaying geo-spatial census datasets in order to estimate the number of people affected by flooding. Differences in exposure characteristics have been assessed for a range of different residential types. As a demonstration, urban flooding risk hotspots are delineated for different percentiles of the TWI value for the city of Addis Ababa, Ethiopia.

Photocatalytic degradation of the antibiotic chloramphenicol and effluent toxicity effects

Chloramphenicol sodium succinate (CAP, C15H15Cl2N2 Na2O8) is a broad-spectrum antibiotic exhibiting activity against both Gram-positive and Gram-negative bacteria as well as other groups of microorganisms only partially removed by conventional activated sludge wastewater treatment plants. Thus, CAP and its metabolites can be found in effluents. The present work deals with the photocatalytic degradation of CAP using TiO2 as photocatalyst. We investigated the optimization of reaction contact time and concentration of TiO2 considering CAP and its by-products removal as well as effluent ecotoxicity elimination. Considering a CAP real concentration of 25mgL(-1), kinetic degradation curves were determined at 0.1, 0.2, 0.4, 0.8, 1.6 and 3.2gL(-1) TiO2 after 5, 10, 30, 60 and 120min reaction time. Treated samples were checked for the presence of by-products and residual toxicity (V. fischeri, P. subcapitata, L. sativum and D. magna). Results evidenced that the best combination for CAP and its by-products removal could be set at 1.6gL(-1) of TiO2 for 120min with an average residual toxicity of approximately 10%, that is the threshold set for negative controls in most toxicity tests for blank and general toxicity test acceptability.

DEM-Based Approaches for the Delineation of Flood-Prone Areas in an Ungauged Basin in Africa

AbstractIn the present work, the flood hazard exposure in an ungauged basin in Africa is assessed exploiting the basin morphological characteristics. Flood-prone areas are identified using linear binary classifiers based on several geomorphic descriptors extracted from digital elevation models (DEMs). The classifiers are calibrated individually and evaluated by comparing their outputs with a flood inundation map obtained by two-dimensional (2D) hydraulic simulations and using receiver operating characteristics (ROC) curves as performance measures. The best-performing descriptors for the subcatchment of the Bulbula River, near the city of Addis Ababa (Ethiopia), are the elevation difference, H between the location under exam and the nearest drainage network, and the composite index ln[hr/H], that compares an estimate of the water level in the nearest point of the river network to the difference in elevation between the point under exam and the river. These simple procedures allow extending the flood deline...

A jazz-based approach for optimal setting of pressure reducing valves in water distribution networks

This study presents a model for valve setting in water distribution networks (WDNs), with the aim of reducing the level of leakage. The approach is based on the harmony search (HS) optimization algorithm. The HS mimics a jazz improvisation process able to find the best solutions, in this case corresponding to valve settings in a WDN. The model also interfaces with the improved version of a popular hydraulic simulator, EPANET 2.0, to check the hydraulic constraints and to evaluate the performances of the solutions. Penalties are introduced in the objective function in case of violation of the hydraulic constraints. The model is applied to two case studies, and the obtained results in terms of pressure reductions are comparable with those of competitive metaheuristic algorithms (e.g. genetic algorithms). The results demonstrate the suitability of the HS algorithm for water network management and optimization.

Real Time Control of a Prototype for Pressure Regulation and Energy Production in Water Distribution Networks

AbstractIn recent years, the opportunity of coupling a pressure management strategy with power generation in water distribution networks (WDNs) has attracted increasing interest. Numerical simulations developed for a number of real cases showed attractive profits and capital payback periods. Although many micro- and pico-hydro plants currently are operating along supply water mains, installations in WDNs are quite uncommon because of the high variability of flow and pressure patterns. Aiming at robust and effective industrial-based solutions, a laboratory prototype was developed for hydropower generation in WDNs. A pump as turbine (PAT) was used for generation, although a traditional turbine could be used as well. A control strategy was developed and implemented for automatic setting of regulating valves, aimed at both ensuring adequate pressure over the network and maximizing electric power. Experiments showed that the valves, equipped with the automatic control system previously described, can automatic...

Location and Setting of Valves in Water Distribution Networks Using a Harmony Search Approach

AbstractIn this paper, pressure management through pressure-reducing valves (PRVs) is discussed with particular reference to metaheuristic optimization techniques, which have proven to be very effe...