This paper proposes a scientific and modeling study for the realization of an anaerobic sludge digestion phase with thermal pre-treatment the biggest wastewater plant in Milan. It is managed by the MM company which plans to replace the current aerobic digestion phase with the construction of an anaerobic digestion reactor with thermal pretreatment. The aim is to reduce the quantity of sludge destined for disposal and to improve the energy balance through the production of biogas. At the first time an analysis from the literature was carried out on the pretreatment techniques for anaerobic digestion, with analysis of the commercial applications currently present. At the second time an analysis of the main parameters that describe the wastewater plant was carried out, in particular rifer to the years 2018,2019 and 2020. The main objective of the processing was to quantify and interpret the production of biological sludge in recent years, in order to obtain the quantitative elements necessary for the scenario analysis and the comparative evaluation of the sludge reduction obtainable with anaerobic digestion. Subsequently, two BMP (Biochemical Methane Potential) experimental tests were carried out to verify the anaerobic biodegradability of the Nosedo’s biological sludge; reasonable BMP values were obtained in mesophilic conditions and high values, above expectations, in thermophilic conditions. Possible scenarios based on mass balances were evaluated, both in the presence of a conventional anaerobic digestion in mesophilic and thermophilic conditions, and with a pre thermal treatment and intermediate thermal treatment. The best results, in terms of methane production and reduction of the quantity of sludge, were obtained for the scenario with pre thermal treatment and scenario with thermophilic anaerobic digester. However, the scenario with thermophilic anaerobic digester requires further checks because it is based only on two BMP tests carried out in thermophilic conditions. Finally, the process was simulated with the WEST software, for the years 2018 and 2020 without the anaerobic digestion, and with anaerobic digestion in mesophilic and thermophilic conditions. The results for the simulation of the wastewater plant are comparable with the data of the plant. Following the application of the digester, a decreasing exponential trend of biogas production is obrained as the SRT increases.
Il presente elaborato propone uno studio scientifico e modellistico per la realizzazione di una fase di digestione anaerobica fanghi con pretrattamento termico presso l’impianto di Milano Nosedo. È gestito dalla società MM che ha in progetto la sostituzione dell’attuale fase di digestione aerobica con la realizzazione di un reattore di digestione anaerobica con pretrattamento termico. Lo scopo è quello di ridurre più efficacemente il quantitativo di fango destinato allo smaltimento e di migliorare il bilancio energetico mediante la produzione di biogas. In questo lavoro, inizialmente, è stata svolta un approfondita analisi da letteratura sulle tecniche di pretrattamento alla digestione anaerobica, con analisi delle applicazioni commerciali ad oggi presenti. Ci si è dedicati allo studio di inquadramento dello stato di fatto dell’impianto con elaborazione dei principali parametri operativi di funzionamento e stato, inerenti agli anni 2018, 2019 e 2020. Obiettivo principale delle elaborazioni è stato quello di quantificare ed interpretare la produzione di fanghi biologici degli ultimi anni, al fine di ricavare gli elementi quantitativi necessari alle analisi di scenario ed alla valutazione comparativa della riduzione fanghi ottenibile con la digestione anaerobica. Successivamente sono state svolte due prove sperimentali di BMP (Biochemical Methane Potential) atte a verificare la biodegradabilità anaerobica del fango biologico di Nosedo; sono stati ottenuti valori ragionevoli di BMP in condizione mesofile e valori elevati, sopra le attese, in condizioni termofile. Sono quindi stati valutati i possibili scenari basati su bilanci di massa, sia in presenza di una digestione anaerobica convenzionale in condizioni mesofile e termofile, sia con trattamento termico a monte e intermedio tra due digestori. I risultati migliori, in termini di produzione di metano e riduzione del quantitativo dei fanghi, sono stati ottenuti per lo scenario con trattamento termico a monte e scenario con digestore anaerobico termofilo. Quest’ultimo, però, richiede ulteriori verifiche, in quanto basato solo su due prove di BMP effettuate in condizioni di termofilia. Infine, è stato simulato il processo con il software WEST, sia per lo stato attuale relativo agli anni 2018 e 2020, sia considerando un digestore anaerobico in condizioni mesofile per l’anno 2020. I risultati a valle della simulazione dello stato attuale sono confrontabili con i dati dell’impianto. Si ottiene, a seguito dell’inserimento del digestore, un andamento esponenziale decrescente della produzione di biogas al crescere dell’SRT.
Analisi tecnica e modellistica della digestione anaerobica fanghi con pretrattamento termico : il caso di un grande impianto di depurazione
LANZINI, CARLA
2020/2021
Abstract
This paper proposes a scientific and modeling study for the realization of an anaerobic sludge digestion phase with thermal pre-treatment the biggest wastewater plant in Milan. It is managed by the MM company which plans to replace the current aerobic digestion phase with the construction of an anaerobic digestion reactor with thermal pretreatment. The aim is to reduce the quantity of sludge destined for disposal and to improve the energy balance through the production of biogas. At the first time an analysis from the literature was carried out on the pretreatment techniques for anaerobic digestion, with analysis of the commercial applications currently present. At the second time an analysis of the main parameters that describe the wastewater plant was carried out, in particular rifer to the years 2018,2019 and 2020. The main objective of the processing was to quantify and interpret the production of biological sludge in recent years, in order to obtain the quantitative elements necessary for the scenario analysis and the comparative evaluation of the sludge reduction obtainable with anaerobic digestion. Subsequently, two BMP (Biochemical Methane Potential) experimental tests were carried out to verify the anaerobic biodegradability of the Nosedo’s biological sludge; reasonable BMP values were obtained in mesophilic conditions and high values, above expectations, in thermophilic conditions. Possible scenarios based on mass balances were evaluated, both in the presence of a conventional anaerobic digestion in mesophilic and thermophilic conditions, and with a pre thermal treatment and intermediate thermal treatment. The best results, in terms of methane production and reduction of the quantity of sludge, were obtained for the scenario with pre thermal treatment and scenario with thermophilic anaerobic digester. However, the scenario with thermophilic anaerobic digester requires further checks because it is based only on two BMP tests carried out in thermophilic conditions. Finally, the process was simulated with the WEST software, for the years 2018 and 2020 without the anaerobic digestion, and with anaerobic digestion in mesophilic and thermophilic conditions. The results for the simulation of the wastewater plant are comparable with the data of the plant. Following the application of the digester, a decreasing exponential trend of biogas production is obrained as the SRT increases.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/175350