Microplastics (MPs) are emerging pollutants distributed globally in aquatic environments and today little is known about their fate in drinking water treatment plants (DWTPs). The purpose of this study was to analyze the presence of microplastics in the purification plant located in Castreccioni. The sampling campaign was conducted over two months: July and December 2020. The microplastics were sampled by filtering approximately 1000 liters of effluent water from each DWTP treatment process plus from two points of distribution. Then the samples were characterized in the laboratory using µFT-IR in terms of: concentrations, shapes, sizes and polymers. A flocculation sludge sample and a backwash sample were also analyzed. In the summer campaign, microplastics vary from 0.0039 n ° MPs / L in the effluent to 0.012n ° MPs / L in the influent. Synthetic MFs range from 0n ° MFs / L in the effluent to 0.003n ° MFs / L in the influent. Most MPs are fragments included in the 0.5-0.15 mm size class. The greatest removal efficiency occurs in pre-ozonation. In the winter campaign, microplastics vary from 0.00939n ° MPs / L in the effluent to 0.012n ° MPs / L in the influent. Synthetic microfibers range from 0n ° MFS / L in the effluent to 0.003n ° MFs / L in the flocculation effluent. Again, most microplastics are fragments in the 0.5-0.15mm size class. The greatest removal efficiency is found in sand filters. QMRA (quantitative microbial risk assessment) is a quantitative mathematical approach for estimating the risk caused by pathogens for human health. (V. Zhiteneva et al, 2020) In particular, in this study, starting from the E.coli output concentrations from the Peschiera Borromeo drinking water treatment plant, the possible risk connected to a hypothetical reuse of water for irrigate tomato crops has been obtained. Two periods were analyzed: the first in which the plant operated without a reuse logic and the second in which the plant improved disinfection to obtain lower concentrations of effluent E.coli. People exposed to risk are fieldworkers who work the crops, local communities and consumers of final products. Reference pathogens are E. coli, Campylobacter, Cryptosporidium and Rotavirus. Calculating the maximum risk both in the non-reuse and in the reuse scenario, considering the results in terms of DALY only the Rotavirus was found to be a pathogen at risk, while considering them in terms of probability of infection all pathogens are a possible danger for human health. By applying a first level of barriers aimed at obtaining a raw final product, in all the scenarios considered all pathogenic risks were below the maximum permissible levels. Another level of barriers was applied to obtain a finished product but it revelaved to be useless because the first level of barriers was sufficient to guarantee safety. The analysis carried out was of deterministic type, adopting an average value for each input data. An example of stochastic analysis using Monte Carlo simulation is provided to show how the distribution of data over the period is of fundamental importance.
Le microplastiche (MP) sono inquinanti emergenti distribuiti a livello globale negli ambienti acquatici e oggi si sa poco sul loro destino negli impianti di trattamento di acqua potabile (DWTP). Lo scopo di questo studio è stato quello di analizzare la presenza di microplastiche nell’impianto di potabilizzazione situato a Castreccioni. La campagna di campionamento è stata condotta in due mesi: luglio e dicembre 2020. Le microplastiche sono state campionate filtrando circa 1000 litri di acqua effluente da ogni processo di trattamento della DWTP più da due punti della distribuzione. Quindi i campioni sono stati caratterizzati in laboratorio utilizzando µFT-IR in termini di: concentrazioni, forme, dimensioni e polimeri. Sono stati analizzati anche un campione di fanghi di flocculazione e uno di controlavaggio. Nella campagna estiva le microplastiche variano da 0,0039 n°MPs/L nell'effluente a 0,012n°MPs/L nell'influente. Gli MF sintetici variano da 0n°MFs/L nell'effluente a 0,003n°MFs/L nell'influente. La maggior parte delle MP sono frammenti inclusi nella classe di dimensioni 0,5-0,15 mm. La più grande efficienza di rimozione si ha nella pre-ozonizzazione. Nella campagna invernale le microplastiche variano da 0,00939n°MPs/L nell'effluente a 0,012n°MPs/L nell'influente. Le microfibre sintetiche variano da 0n°MFS/L nell'effluente a 0,003n°MFs/L nell'effluente di flocculazione. Anche in questo caso la maggior parte dei parlamentari sono frammenti nella classe di grandezza 0,5-0,15mm. La maggiore efficienza di rimozione si ha nei filtri a sabbia. La QMRA (quantitative microbial risk assessment) è un approccio quantitativo matematico per la stima del rischio causato da patogeni per la salute umana. (V. Zhiteneva et al, 2020).In particolare in questo studio, a partire dalle concentrazioni in uscita di E.coli dall'impianto di depurazione di Peschiera Borromeo, si è ottenuto il possibile rischio connesso ad un ipotetico riutilizzo dell'acqua per irrigare le colture di pomodoro. Sono stati analizzati due periodi: il primo in cui l'impianto ha funzionato senza una logica di riutilizzo e il secondo in cui l'impianto ha migliorato la disinfezione per ottenere minori concentrazioni di E.coli effluenti. I soggetti dell'esposizione sono contadini che lavorano le colture, le comunità locali e i consumatori dei prodotti finali. Mentre i patogeni di riferimento sono E. coli, Campylobacter, Cryptosporidium e Rotavirus. Calcolando il rischio massimo sia nello scenario di non riutilizzo che in quello di riutilizzo, considerando i risultati in termini di DALY solo il Rotavirus è risultato essere un patogeno a rischio, mentre considerandoli in termini di probabilità di rischio tutti i patogeni sono un possibile pericolo per la salute umana. Applicando un primo livello di barriere finalizzate all'ottenimento di un prodotto finale grezzo, in tutti gli scenari considerati tutti i rischi patogeni erano al di sotto dei livelli massimi ammissibili. Un altro livello di barriere è stato applicato per ottenere un prodotto finale lavorato ma si è rivelato inutile perché il primo livello di barriere era sufficiente per garantire la sicurezza. L’analisi effettuata è stata di tipo deterministico adottando un valore medio per ogni dato di input. Un’esempio di analisi stocastica usando la simulazione Monte Carlo è fornito per mostrare quanto la distribuzione di dati nel periodo sia di fondamentale importanza.
Tracing microplastics in drinking water treatment plants and data analysis for water reuse risk management plans
NATICCHIA, GIORGIA
2019/2020
Abstract
Microplastics (MPs) are emerging pollutants distributed globally in aquatic environments and today little is known about their fate in drinking water treatment plants (DWTPs). The purpose of this study was to analyze the presence of microplastics in the purification plant located in Castreccioni. The sampling campaign was conducted over two months: July and December 2020. The microplastics were sampled by filtering approximately 1000 liters of effluent water from each DWTP treatment process plus from two points of distribution. Then the samples were characterized in the laboratory using µFT-IR in terms of: concentrations, shapes, sizes and polymers. A flocculation sludge sample and a backwash sample were also analyzed. In the summer campaign, microplastics vary from 0.0039 n ° MPs / L in the effluent to 0.012n ° MPs / L in the influent. Synthetic MFs range from 0n ° MFs / L in the effluent to 0.003n ° MFs / L in the influent. Most MPs are fragments included in the 0.5-0.15 mm size class. The greatest removal efficiency occurs in pre-ozonation. In the winter campaign, microplastics vary from 0.00939n ° MPs / L in the effluent to 0.012n ° MPs / L in the influent. Synthetic microfibers range from 0n ° MFS / L in the effluent to 0.003n ° MFs / L in the flocculation effluent. Again, most microplastics are fragments in the 0.5-0.15mm size class. The greatest removal efficiency is found in sand filters. QMRA (quantitative microbial risk assessment) is a quantitative mathematical approach for estimating the risk caused by pathogens for human health. (V. Zhiteneva et al, 2020) In particular, in this study, starting from the E.coli output concentrations from the Peschiera Borromeo drinking water treatment plant, the possible risk connected to a hypothetical reuse of water for irrigate tomato crops has been obtained. Two periods were analyzed: the first in which the plant operated without a reuse logic and the second in which the plant improved disinfection to obtain lower concentrations of effluent E.coli. People exposed to risk are fieldworkers who work the crops, local communities and consumers of final products. Reference pathogens are E. coli, Campylobacter, Cryptosporidium and Rotavirus. Calculating the maximum risk both in the non-reuse and in the reuse scenario, considering the results in terms of DALY only the Rotavirus was found to be a pathogen at risk, while considering them in terms of probability of infection all pathogens are a possible danger for human health. By applying a first level of barriers aimed at obtaining a raw final product, in all the scenarios considered all pathogenic risks were below the maximum permissible levels. Another level of barriers was applied to obtain a finished product but it revelaved to be useless because the first level of barriers was sufficient to guarantee safety. The analysis carried out was of deterministic type, adopting an average value for each input data. An example of stochastic analysis using Monte Carlo simulation is provided to show how the distribution of data over the period is of fundamental importance.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12075/4655