The increasing development of digital textile printing technologies offers significant quality and economical benefits, and is a key factor in maintaining or restoring European activities or processes that have been outsourced abroad or could be in the near future. Together with many characteristic advantages of the process such as, for example, the reduction of the volumes of water used, these recent working processes produce effluents with high nitrogen concentrations, almost entirely in the form of urea. The high nitrogen loads resulting require a specific treatment to reduce the environmental impacts associated with their release into surface water bodies and allow companies to avoid legal sanctions. Due to the need find a suitable treatment for the wastewater originated from rinsing baths of digital textile printing processes, the research project "N-free printing" has been started and the present study is part of it. Purpose of the project is the identification and evaluation of applicability of the total nitrogen removal process by these effluents. Within the panorama of the available treatment options the choice has been to apply the mixed partial nitration (PN) – Anammox process. This process offers, when compared to traditional nitrification-denitrification and nitration-denitration processes, numerous advantages, among which a substantial reduction of operating and investment costs. The thesis analyses the performance of nitrogen removal in an SBR pilot plant fed with two types of wastewater produced by digital printing processes: • wastewater collected from all business processes and sent to an equalization tank: its nitrogen concentration ranges from 0.2 to 0.4 gN/L and is largely made up of ammonium resulting from the degradation of urea used in the digital printing process; • concentrated effluent, collected immediately downstream of the first tanks of printed fabric washing, much more concentrated than the first one (2 to 7.5 gN/L) and characterized by the presence of urea, not yet degraded to ammonium. The experimental activity was then dedicated to the detailed study of the ureolysis kinetics in concentrated wastewater. From previous experience, indeed, the ureolysis process appears to be kinetically limiting and makes it difficult to treat the concentrated wastewater segregated and collected downstream of the first rinsing baths. The obtained results confirm the feasibility of a process in SBR configuration, with removal efficiencies very close to the stoichiometric percentage removal: 80-90% for total nitrogen and up to 100% for the ammonium, under applied loads of over 1 kgN m-3 d-1. The effluent concentration values are fully compliant with regulatory limits for discharge into the public sewer. The process applied to concentrated wastewaters has not provided good results by means of tractability, for two reasons that, together, have slowed down the activity of ammonia-oxidizing bacteria, encouraging the development of nitrite oxidizing bacteria, which have prevented the completion of the PN/Anammox reaction. The yields of total observed nitrogen removal are therefore much smaller, reaching only in rare cases values close to the expected yields. This leads to the conclusion that the concentrated wastewater is not treatable with the PN/Anammox process in single stage, unless submitting concentrated wastewater to a pre-treatment stage consisting of a ureolysis enhancing process, which could be the subject of future research.
Il crescente sviluppo delle tecnologie di stampa tessile digitale offre significativi vantaggi qualitativi ed economici, e rappresenta un fattore strategico per mantenere o riportare in Europa attività o lavorazioni che sono state delocalizzate all’estero o potrebbero esserlo nell’immediato futuro. Ai molti vantaggi caratteristici del processo come, ad esempio, la riduzione dei volumi di acque impiegate, i processi di lavorazione introdotti producono reflui ad elevata concentrazione di azoto, quasi interamente sotto forma di urea. Gli elevati carichi di azoto risultanti necessitano quindi di un processo depurativo che ne riduca gli impatti ambientali legati al loro rilascio nei corpi idrici superficiali e che permetta alle aziende di non incorrere in sanzioni legali. Dalle necessità di depurazione dei reflui prodotti dai cicli di lavaggio dei processi di stampa tessile digitale nasce il progetto di ricerca “N-free printing”, all’interno del quale va a collocarsi l’attività di sperimentazione del presente elaborato. Finalità del progetto è quindi l’individuazione e una valutazione di applicabilità del processo di rimozione dell’azoto totale da questi reflui. All’interno del panorama delle alternative di trattamento disponibili la scelta è ricaduta sul processo misto parziale nitritazione (PN)–Anammox, dal momento in cui offre, se paragonato ai tradizionali processi di nitrificazione-denitrificazione e nitratazione-denitratazione, numerosi vantaggi tra i quali una riduzione consistente dei costi di gestione e di investimento. Nell'elaborato sono analizzate le prestazioni di rimozione dell’azoto in un impianto pilota funzionante SBR alimentato con due tipologie di reflui prodotti da una stamperia digitale: • i reflui raccolti da tutte le lavorazioni aziendali e inviati a una vasca di equalizzazione, più diluiti e il cui contenuto di azoto è in gran parte costituito da azoto ammoniacale derivante dalla degradazione dell'urea utilizzata nel processo di stampa digitale; • i reflui concentrati, raccolti subito a valle delle prime vasche di lavaggio del tessuto stampato, molto più concentrati dei primi e caratterizzati dalla presenza di urea, non ancora degradatasi ad azoto ammoniacale. Parte della sperimentazione è stata poi dedicata allo studio nel dettaglio delle cinetiche del processo di ureolisi nei reflui concentrati. Da esperienze precedenti, infatti, il processo di ureolisi sembra essere cineticamente limitante e rende problematico il trattamento dei reflui concentrati segregati e raccolti a valle delle prima vasche di lavaggio. I risultati ottenuti confermano la fattibilità di un processo in reattore SBR con rimozioni percentuali molto prossime alle rimozioni stechiometriche: 80-90% per l’azoto totale e fino al 100% per l’azoto ammoniacale, con carichi applicati di oltre 1 kgN m-3 d-1. I valori di concentrazione dell'effluente risultano pienamente compatibili con i limiti normativi per lo scarico in fognatura pubblica. Il processo applicato a reflui concentrati non ha invece fornito buoni risultati di trattabilità, per due motivi che, insieme, hanno rallentato l'attività dei batteri ammonio-ossidanti, favorendo lo sviluppo di batteri nitrito ossidanti che hanno impedito il completamento della reazione PN/Anammox Le rese di rimozione dell’azoto totale osservate sono quindi molto più contenute, arrivando solo in rari casi a valori prossimi alle rese attese. Ciò porta a concludere che il refluo concentrato non è trattabile con il processo in singolo stadio PN/Anammox, a meno di sottoporre i reflui concentrati a un pretrattamento costituito da un processo ureolitico ad hoc, che potrebbe essere oggetto di future ricerche.
Rimozione autotrofa dell'azoto da reflui della stampa tessile digitale con processo Anammox : sperimentazione a scala pilota
BELLIENI, MARTINO
2015/2016
Abstract
The increasing development of digital textile printing technologies offers significant quality and economical benefits, and is a key factor in maintaining or restoring European activities or processes that have been outsourced abroad or could be in the near future. Together with many characteristic advantages of the process such as, for example, the reduction of the volumes of water used, these recent working processes produce effluents with high nitrogen concentrations, almost entirely in the form of urea. The high nitrogen loads resulting require a specific treatment to reduce the environmental impacts associated with their release into surface water bodies and allow companies to avoid legal sanctions. Due to the need find a suitable treatment for the wastewater originated from rinsing baths of digital textile printing processes, the research project "N-free printing" has been started and the present study is part of it. Purpose of the project is the identification and evaluation of applicability of the total nitrogen removal process by these effluents. Within the panorama of the available treatment options the choice has been to apply the mixed partial nitration (PN) – Anammox process. This process offers, when compared to traditional nitrification-denitrification and nitration-denitration processes, numerous advantages, among which a substantial reduction of operating and investment costs. The thesis analyses the performance of nitrogen removal in an SBR pilot plant fed with two types of wastewater produced by digital printing processes: • wastewater collected from all business processes and sent to an equalization tank: its nitrogen concentration ranges from 0.2 to 0.4 gN/L and is largely made up of ammonium resulting from the degradation of urea used in the digital printing process; • concentrated effluent, collected immediately downstream of the first tanks of printed fabric washing, much more concentrated than the first one (2 to 7.5 gN/L) and characterized by the presence of urea, not yet degraded to ammonium. The experimental activity was then dedicated to the detailed study of the ureolysis kinetics in concentrated wastewater. From previous experience, indeed, the ureolysis process appears to be kinetically limiting and makes it difficult to treat the concentrated wastewater segregated and collected downstream of the first rinsing baths. The obtained results confirm the feasibility of a process in SBR configuration, with removal efficiencies very close to the stoichiometric percentage removal: 80-90% for total nitrogen and up to 100% for the ammonium, under applied loads of over 1 kgN m-3 d-1. The effluent concentration values are fully compliant with regulatory limits for discharge into the public sewer. The process applied to concentrated wastewaters has not provided good results by means of tractability, for two reasons that, together, have slowed down the activity of ammonia-oxidizing bacteria, encouraging the development of nitrite oxidizing bacteria, which have prevented the completion of the PN/Anammox reaction. The yields of total observed nitrogen removal are therefore much smaller, reaching only in rare cases values close to the expected yields. This leads to the conclusion that the concentrated wastewater is not treatable with the PN/Anammox process in single stage, unless submitting concentrated wastewater to a pre-treatment stage consisting of a ureolysis enhancing process, which could be the subject of future research.File | Dimensione | Formato | |
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RIMOZIONE DELL'AZOTO DA REFLUI DELLA STAMPA TESSILE DIGITALE CON PROCESSO ANAMMOX - SPERIMENTAZIONE A SCALA PILOTA.pdf
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https://hdl.handle.net/10589/123642