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This mini-review is intended to explore the innovative applications of nanoparticles (NPs) in biogas upgrading, emphasizing their capacity to enhance biogas quality. Numerous studies underscore how NPs, when applied during anaerobic digestion, can boost not only the quantity but also the quality of the produced biogas, leading to reduce significantly the concentration of hydrogen sulphide or even to remove it completely. Moreover, NPs are proving to be excellent alternatives as adsorbent materials, achieving up to 400mgH2S g−1 NPs. In addition, new studies are exploring the application of NPs to increase the efficiency of biological treatments thanks to their unique features. This review also emphasizes the potential benefits and addresses the challenges that need to be overcome for these technologies to reach their full potential, ultimately contributing to the development of a sustainable and environmentally friendly energy landscape.

Large amounts of produced water are extracted by the Oil and Gas energy sector since the industrial revolution. This available water, often salty, can be used to dilute liquid digestate from the anaerobic digestion process, a promising source of nutrients for microalgae cultivation. The study investigates the growth of halotolerant microalgae and their associated bacteria in column photobioreactors (PBRs) and open raceway pond (RWP), to treat industrial wastewaters while producing biomass for energy valorisation. Microalgae were cultured in mixtures of saline artificial produced water (7–44 %v/v), liquid digestate (5 %v/v using PBRs, 29–63 %v/v using RWP) and seawater. Nannochloropsis oceanica and Tetraselmis suecica strains were firstly cultivated in 70 L PBRs in indoor conditions for 3 months and later in 1.1 m3 RWP operated in outdoor conditions for 5 months in spring-summer period. In PBRs, average productivity was 9.0 ± 4.2 gVSS·m−2·d−1 (102–153 mgVSS·L−1·d−1), with daily removal efficiencies for chemical oxygen demand, nitrogen and phosphorous up to 61.8, 31.6 and 97.2 %, respectively. In RWP, strong changes in the microalgae populations were observed. Productivity was 6.7 ± 5.2 gVSS·m−2·d−1 (30 ± 23 mgVSS·L−1·d−1), with daily removal efficiencies for chemical oxygen demand, nitrogen and phosphorous up to 48.4, 44.4 and 88.1 %, respectively. In parallel with the production of microalgae, a nitrifying microbial population grew in the RWP despite the high salinity (70 g L−1). Over these periods of several months, microalgae production was maintained using a culture medium containing high salt concentration, metals and harmful aromatic compounds.

La temperatura è un fattore cruciale che influenza la struttura e il funzionamento degli ecosistemi; tuttavia, manca ancora un monitoraggio sistematico di tale parametro nei fiumi. La maggior parte dei dati riguarda misure sporadiche e sparse che forniscono stime approssimative del regime termico dell'acqua, soprattutto in montagna dove le fluttuazioni non sono trascurabili. Inoltre, gli studi in campo che indagano la relazione tra la temperatura e il biota acquatico raramente affrontano il ruolo della variabilità intra-annuale e non sempre disgiungono gli effetti di altri fattori ambientali. Date queste lacune, questa tesi presenta sei lavori riguardanti il regime termico dell'acqua e il suo effetto sul biota. Innanzitutto, dato che il regime termico varia a seconda del tipo di corpo idrico, è stata monitorata la temperatura dell'acqua in 16 siti situati in torrenti montani e sono state descritte le variazioni giornaliere e stagionali. I risultati mostrano che diversi tipi di sorgente e la presenza di bacini idrici, insieme, promuovono un'elevata eterogeneità termica tra i corsi d’acqua appartenenti allo stesso bacino idrografico, con importanti implicazioni ecologiche. Inoltre, gli impianti idroelettrici ad acqua fluente possono influenzare il regime termico fluviale, ma il loro impatto non è stato ancora considerato, nonostante essi siano molto diffusi. Dunque, è stata monitorata la temperatura dell’acqua lungo una sequenza di tratti fluviali interessati da derivazioni idroelettriche. L'analisi del regime termico ha rivelato che nei tratti derivati il tasso di riscaldamento è doppio rispetto a quello naturale mentre nei canali di derivazione la temperatura dell’acqua rimane pressoché costante. La presenza di centrali idroelettriche in sequenza determina un cambiamento del profilo termico longitudinale del fiume che passa da continuo a “gradini”. Negli studi successivi è stata indagata la relazione tra il regime termico e il biota acquatico combinando una, Temperature has been recognized as a pivotal factor shaping ecosystem structure and functioning; nevertheless, there is still a lack of systematic water temperature monitoring in rivers. Most of the data are scattered and have been measured sporadically providing rough estimations of the water thermal regime, especially in mountain streams where fluctuations are not negligible. Moreover, field studies investigating the relationship between water temperature and the aquatic biota rarely address the role of intra annual variability and not always disentangle the effects of other environmental factors. Given these gaps, this thesis presents six pieces of work regarding the water thermal regime and its effect on the aquatic biota. First, since the thermal regime varies depending on the type of watercourse, the water temperature of 16 mid-altitude stream sites was monitored, and the daily and seasonal patterns were described. The results show that the interaction of different water sources and the presence of reservoirs promote a high stream thermal heterogeneity within the watershed, outlining important ecological implications. Then, hydroelectric plants powered by flowing water can affect the water thermal regime, but their impacts have not yet been considered. Thus, the water temperature was monitored along a sequence of riverine stretches subjected to water diversion. The analysis of the thermal regimes revealed that within the by-passed stretches, due to the low flow, the rate of warming doubles the natural gradient while in the diverted channel the water temperature remains almost constant. In the following studies, the relationship between the water thermal regime and the aquatic biota was investigated by combining a systematic literature review focusing on the effects of water temperature on freshwater macroinvertebrates with three field studies carried out on biofilm, macroinvertebrates, and fish, respectively. A one-year survey with monthly samplings of biofilm

The integration of microalgae-bacteria consortia within existing wastewater treatment plants as alternative biological treatment could be an interesting option to improve the sustainability of these facilities. However, the fate of the produced biomass is decisive to make that option economically attractive. The present study aimed to valorize the microalgae grown at a pilot scale and used for the treatment of the centrate from municipal sewage sludge, producing microalgal-based iron nanoparticles (ME-nFe), by hydrothermal carbonization. The final product had high carbon content, strong sorbent power, and reducing properties, due to the presence of zerovalent iron. Different synthesis conditions were tested, comparing iron (III) nitrate nonahydrate (Fe (NO3)(3)center dot 9H(2)O) and ammonium iron (III) sulfate dodecahydrate (NH4 Fe (SO4)(2)center dot 12 H2O) as iron sources, four different Fe/C molar ratios (0.02, 0.05, 0.1, 0.2), and three process temperatures (180, 200, 225 degrees C). Based on the characterization of all the prototypes, the best one (having a specific area of 110 m(2)g(-1)) was chosen and tested for the removal of selected heavy metals by Jar tests. The removal of copper, zinc, cadmium, and nickel from the treated effluent from the wastewater treatment plant was 99.6%, 97.8%, 96.4%, and 80.3%, respectively, also for very low starting concentrations (1 mg L-1). The removal of total chromium, on the contrary, was only 12.4%. Thanks to the magnetic properties, the same batch of ME-nFe was recovered and used effectively for three consecutive Jar tests.