Water Safety Plan (WSP) is an innovative way to ensure the safety of a drinking-water supply: it is a tool which has been introduced in the European Union legislation to apply the typical risk assessment approach to the water sector. This research wants to promote a practical example of WSP application for the waste-water plant in Peschiera Borromeo, one of the first Italian plants for the adoption of a Water Safety Plan for its activity: through this typical way to do, the managing authority has the possibility to solve all the criticalities which will emerge during the plant activities. Thanks to an efficient statistical analysis, the main goal of this research is to estimate the likelihood of all the potential hazardous events associated with each step in the drinking-water supply: this estimation brings about the core of the WSP which is represented by the development of the risk matrix. Depending of the available data from the plant we are able to evaluate the risk only for the microbial hazardous events: taking the bacteriological parameter as our critical variable, the first step is to verify potential correlations with other water-quality parameters so to reach a previsional model which is able to suggest the best predictors, also known as proxy variables with which it’s possible to predict our hazardous events of interest represented by the overrunning of the E. coli concentration released by the plant. The best fitting model is the binary logistic regression with two main parameters as the best predictors for our microbial hazardous events. As we calculate the likelihood, the result is that all the associated risks are classified as medium-high level risks which represent a very serious scenario that must be fixed by the managing authority through appropriate control measures. For this reason, the last part of the research is focused on the development of an efficient EWS (Early Warning System) thanks to some monitoring probes located just before the exit of the plant: this would represent certainly the best control measure to prevent all the possible high level risks.
Il Water Safety Plan (WSP, Piano di Sicurezza dell’Acqua) rappresenta un modo innovativo per assicurare una gestione efficiente dei sistemi idrici: è uno strumento entrato stabilmente da qualche anno nella normativa europea con l’intento di introdurre l’approccio dell’analisi di rischio, già ampiamente adottato in altri settori ambientali, nel settore acque. Il lavoro in questione propone un esempio applicativo di tale approccio per l’impianto di depurazione di Peschiera Borromeo, tra i primi impianti in Italia ad adottare un Water Safety Plan nel proprio sistema idrico: proprio attraverso il modus operandi del WSP, il gestore dell’impianto confida di risolvere le criticità che emergono via via durante l’attività dell’impianto. Adottando un approccio critico, sviluppando un’accurata analisi statistica, l’obiettivo del lavoro consiste nella stima della probabilità di accadimento degli eventi di pericolo individuati lungo la filiera di trattamento: questo conduce allo sviluppo della matrice di valutazione dei rischi, la quale rappresenta il cuore del Water Safety Plan. In funzione dei dati a disposizione, gli eventi di pericolo di cui è possibile stimare il rischio appartengono alla classe degli eventi di tipo microbiologico: si parte così con l’individuazione di parametri di qualità dell’acqua correlabili col parametro batteriologico critico, per poi giungere allo sviluppo di un modello previsionale, capace di indicare quali sono i predittori migliori, ovvero delle variabili proxy capaci di predire l’accadimento dell’evento, rappresentato dal superamento del limite normativo per la concentrazione di E. coli in uscita dall’impianto. Risultato dell’analisi statistica è lo sviluppo del modello di regressione logistica binaria come modello previsionale ideale, con predittori migliori il valore di pH nell’acqua in ingresso all’impianto e la concentrazione di fosforo totale nell’acqua in uscita dall’impianto. Ne consegue una stima della probabilità di accadimento degli eventi di pericolo microbiologico che porta all’individuazione di rischi di medio e alto livello: è emersa così una criticità piuttosto importante a cui il gestore dell’impianto dovrà far fronte con misure di controllo tempestive. Proprio a questo proposito, è stato valutato lo sviluppo di un sistema di early warning mediante sonde di monitoraggio installate in uscita dall’impianto: ciò costituisce una misura ideale per il controllo dei rischi di grado più alto.
Il water safety plan per la gestione dei sistemi idrici : il caso dell'impianto di Peschiera Borromeo
ACCETTA, DANIELE
2020/2021
Abstract
Water Safety Plan (WSP) is an innovative way to ensure the safety of a drinking-water supply: it is a tool which has been introduced in the European Union legislation to apply the typical risk assessment approach to the water sector. This research wants to promote a practical example of WSP application for the waste-water plant in Peschiera Borromeo, one of the first Italian plants for the adoption of a Water Safety Plan for its activity: through this typical way to do, the managing authority has the possibility to solve all the criticalities which will emerge during the plant activities. Thanks to an efficient statistical analysis, the main goal of this research is to estimate the likelihood of all the potential hazardous events associated with each step in the drinking-water supply: this estimation brings about the core of the WSP which is represented by the development of the risk matrix. Depending of the available data from the plant we are able to evaluate the risk only for the microbial hazardous events: taking the bacteriological parameter as our critical variable, the first step is to verify potential correlations with other water-quality parameters so to reach a previsional model which is able to suggest the best predictors, also known as proxy variables with which it’s possible to predict our hazardous events of interest represented by the overrunning of the E. coli concentration released by the plant. The best fitting model is the binary logistic regression with two main parameters as the best predictors for our microbial hazardous events. As we calculate the likelihood, the result is that all the associated risks are classified as medium-high level risks which represent a very serious scenario that must be fixed by the managing authority through appropriate control measures. For this reason, the last part of the research is focused on the development of an efficient EWS (Early Warning System) thanks to some monitoring probes located just before the exit of the plant: this would represent certainly the best control measure to prevent all the possible high level risks.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/179721