The management and application of livestock effluents (LE) pose significant environmental challenges, including nitrogen losses, eutrophication, and greenhouse gas emissions. Treatment methods for NH₄⁺ recovery from livestock effluents based on the adsorption process are highly promising due to their effectiveness, lack of chemicals or toxic substances, and social acceptance. Natural zeolite-rich tuff (NZR) offers a sustainable and effective solution by exploiting its high cation-exchange capacity and molecular sieve properties. NZR enables NH₄⁺ recovery while improving soil fertility and reducing dependency on synthetic fertilizers. The adsorption process is heavily influenced by numerous factors, whose combination determines NH₄⁺ removal efficiency. For this reason, the main focus of this study is to evaluate the interaction among various variables to identify the optimal operating conditions for a wide range of real-world scenarios. Since numerous studies have been conducted on synthetic solutions and few zeolites as adsorbents, this work investigates the NH₄⁺ adsorption process considering the interaction between authentic cattle livestock effluents i) separated liquid manure (SM), ii) separated digestate (SD), and iii) microfiltered digestate (MD) and different types of zeolite-rich tuffs i) chabazite (CHA), ii) clinoptilolite (CLP), and iii) phillipsite (PHP). All materials used in this study were supplied by WAMGROUP S.p.A. Laboratory experiments examined key variables affecting adsorption performance, such as particle size and operating temperature. For each zeolite, two different particle sizes fine and granular were tested. Additionally, two operating temperatures (25°C and 40°C) were tested for digestates, while experiments on SM were conducted only at 25°C. The NH₄⁺ content was measured using the Kjeldahl method, and further data processing was performed with R. Isotherm model fitting was conducted using the PUPAIM package, with the Langmuir Model identified as the most representative for the treated materials, in line with existing literature. Experimental equilibrium data reveal that higher ion exchange capacities are associated with solid-liquid ratios ranging between 3% and 6%; therefore, subsequent kinetic studies were conducted at 3%. All kinetic curves follow similar trends, characterized by an exponential increase in adsorption capacity followed by a plateau phase. The optimal agitation time for cost-effectiveness is 120 minutes for all tested conditions. Higher temperature and fine particle size are associated with increased adsorption capacities; however, the temperature effect is significantly more pronounced than the particle size effect. The interaction between zeolite and MD showed better performance than SD and SM, likely due to greater homogeneity and a slightly higher initial NH₄⁺ concentration, which is also a crucial factor in the adsorption process. CHA and CLP exhibited the most favorable response to treatment compared to PHP. Based on these findings, a prototype machine was developed to test NZR-based treatment at a farm scale. Operational trials demonstrated effective nitrogen recovery, with significant NH₄⁺ reductions across three treatment cycles. However, open-system configurations led to ammonia volatilization, particularly under warmer conditions. The objective of this research to scale up the zeolite-based treatment from a laboratory setting to a real-farm environment has been successfully achieved. Nonetheless, further optimizations of the prototype machine are required to enhance its efficiency and adaptability to diverse operational conditions.
La gestione e l’applicazione dei reflui zootecnici (LE) pongono significative sfide ambientali, tra cui perdite di azoto, eutrofizzazione ed emissioni di gas serra. I metodi di trattamento basati sull’adsorbimento per il recupero dell’NH₄⁺ dai reflui zootecnici sono particolarmente promettenti grazie alla loro efficacia, all’assenza di sostanze chimiche o tossiche e alla loro accettabilità sociale. Il tufo ricco di zeolite naturale (NZR) rappresenta una soluzione sostenibile ed efficiente, sfruttando l’elevata capacità di scambio cationico e le proprietà di setaccio molecolare. L’uso dell’NZR consente il recupero dell’NH₄⁺ migliorando la fertilità del suolo e riducendo la dipendenza dai fertilizzanti sintetici. Il processo di adsorbimento è fortemente influenzato da diversi fattori, la cui combinazione determina l’efficienza della rimozione dell’NH₄⁺; per questo motivo, lo studio si concentra sulla valutazione delle interazioni tra vari parametri, al fine di individuare le condizioni operative ottimali per diversi scenari reali. Poiché numerosi studi si sono focalizzati su soluzioni sintetiche e poche zeoliti come adsorbenti, questa ricerca analizza il processo di adsorbimento dell’NH₄⁺ considerando l’interazione tra reflui autentici derivanti da effluenti zootecnici bovini: i) liquame separato (SM), ii) digestato separato (SD) e iii) digestato microfiltrato (MD), con diverse tipologie di tufo ricco di zeolite: i) chabasite (CHA), ii) clinoptilolite (CLP) e iii) phillipsite (PHP). Tutti i materiali utilizzati nello studio sono stati forniti da WAMGROUP S.p.A. Gli esperimenti di laboratorio hanno indagato variabili chiave che influenzano le prestazioni di adsorbimento, come la granulometria e la temperatura operativa. Per ogni zeolite sono state testate due frazioni granulometriche: fine e granulare. Inoltre, sono state esaminate due temperature operative (25 e 40°C) per i digestati, mentre gli esperimenti sul liquame separato sono stati condotti solo a 25°C. Il contenuto di NH₄⁺ è stato determinato con il metodo Kjeldahl e ulteriori elaborazioni sono state condotte con il software R, mentre l’adattamento ai modelli isotermici è stato eseguito con il pacchetto PUPAIM. Il modello di Langmuir è risultato il più rappresentativo per i materiali trattati, in linea con la letteratura esistente. I dati di equilibrio sperimentali mostrano che le capacità di scambio ionico più elevate si osservano con rapporti solido/liquido tra il 3 e il 6%, pertanto gli studi cinetici successivi sono stati condotti con un rapporto del 3%. Tutte le curve cinetiche mostrano un andamento simile, caratterizzato da un incremento esponenziale della capacità di adsorbimento seguito da una fase di plateau. Il tempo di agitazione ottimale per garantire l’efficacia economica è di 120 minuti in tutte le condizioni testate. Temperature più elevate e granulometria fine sono associate a una maggiore capacità di adsorbimento, tuttavia l’effetto della temperatura risulta significativamente più marcato rispetto a quello della dimensione delle particelle. L’interazione tra zeolite e digestato microfiltrato (MD) ha dimostrato le migliori prestazioni rispetto a SD e SM, probabilmente grazie a una maggiore omogene
Zootechnical wastewater treatments, reduction of the nitrogen load and production of natural amendments for agricultural soils and cultivation substrates
BALZAN, SILVIA
2025
Abstract
The management and application of livestock effluents (LE) pose significant environmental challenges, including nitrogen losses, eutrophication, and greenhouse gas emissions. Treatment methods for NH₄⁺ recovery from livestock effluents based on the adsorption process are highly promising due to their effectiveness, lack of chemicals or toxic substances, and social acceptance. Natural zeolite-rich tuff (NZR) offers a sustainable and effective solution by exploiting its high cation-exchange capacity and molecular sieve properties. NZR enables NH₄⁺ recovery while improving soil fertility and reducing dependency on synthetic fertilizers. The adsorption process is heavily influenced by numerous factors, whose combination determines NH₄⁺ removal efficiency. For this reason, the main focus of this study is to evaluate the interaction among various variables to identify the optimal operating conditions for a wide range of real-world scenarios. Since numerous studies have been conducted on synthetic solutions and few zeolites as adsorbents, this work investigates the NH₄⁺ adsorption process considering the interaction between authentic cattle livestock effluents i) separated liquid manure (SM), ii) separated digestate (SD), and iii) microfiltered digestate (MD) and different types of zeolite-rich tuffs i) chabazite (CHA), ii) clinoptilolite (CLP), and iii) phillipsite (PHP). All materials used in this study were supplied by WAMGROUP S.p.A. Laboratory experiments examined key variables affecting adsorption performance, such as particle size and operating temperature. For each zeolite, two different particle sizes fine and granular were tested. Additionally, two operating temperatures (25°C and 40°C) were tested for digestates, while experiments on SM were conducted only at 25°C. The NH₄⁺ content was measured using the Kjeldahl method, and further data processing was performed with R. Isotherm model fitting was conducted using the PUPAIM package, with the Langmuir Model identified as the most representative for the treated materials, in line with existing literature. Experimental equilibrium data reveal that higher ion exchange capacities are associated with solid-liquid ratios ranging between 3% and 6%; therefore, subsequent kinetic studies were conducted at 3%. All kinetic curves follow similar trends, characterized by an exponential increase in adsorption capacity followed by a plateau phase. The optimal agitation time for cost-effectiveness is 120 minutes for all tested conditions. Higher temperature and fine particle size are associated with increased adsorption capacities; however, the temperature effect is significantly more pronounced than the particle size effect. The interaction between zeolite and MD showed better performance than SD and SM, likely due to greater homogeneity and a slightly higher initial NH₄⁺ concentration, which is also a crucial factor in the adsorption process. CHA and CLP exhibited the most favorable response to treatment compared to PHP. Based on these findings, a prototype machine was developed to test NZR-based treatment at a farm scale. Operational trials demonstrated effective nitrogen recovery, with significant NH₄⁺ reductions across three treatment cycles. However, open-system configurations led to ammonia volatilization, particularly under warmer conditions. The objective of this research to scale up the zeolite-based treatment from a laboratory setting to a real-farm environment has been successfully achieved. Nonetheless, further optimizations of the prototype machine are required to enhance its efficiency and adaptability to diverse operational conditions.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14242/218691
URN:NBN:IT:UNIFE-218691