Soka University Repository / 創価大学機関リポジトリ
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A Study on the Activation of In-class Group Work at a Junior College
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Effects of short hydraulic retention time on UASB reactor performance inoculated with pre-aggregated anaerobic digestion granular sludge
No full textWater hyacinth, a high-strength lignocellulosic macrophyte, poses a serious ecological threat by disrupting aquatic ecosystems and hindering water transport. The juice extracted from water hyacinth, commonly known as water hyacinth juice, is particularly rich in soluble organic compounds and has been demonstrated to enhance hydrolysis and acidogenesis rates when used as a substrate in high-rate anaerobic digestion using up-flow anaerobic sludge blanket reactors. The performance of up-flow anaerobic sludge blanket reactors relies heavily on the formation and maintenance of granules. However, a major challenge in the practical implementation of up-flow anaerobic sludge blanket reactors lies in optimizing the operational conditions like hydraulic retention time (HRT), that balance process kinetics, microbial retention, and system stability. Shortening the HRT can improve volumetric biogas production rates and reduce reactor footprint by utilizing more substrate volume, but it can also disrupt microbial stratification leading to biomass washout and process instability. The use of pre-aggregated anaerobic digestion granules, rich in mature methanogens, has been suggested as a viable strategy to mitigate washout under high loading conditions. This study investigated the effectiveness of up-flow anaerobic sludge blanket reactors for high-rate anaerobic digestion of water hyacinth juice at shortened HRTs, using pre-aggregated anaerobic digestion granular sludge as inoculum. The experiments were conducted in a 430 mL up-flow anaerobic sludge blanket reactors operating for 107 days, at four different HRTs, (2, 1.5, 1.0, and 0.5 days). Despite the high suspended solids concentration of water hyacinth juice (3.3 ± 0.7 g L-1) and increasing organic loading rates at shorter HRTs, the reactor maintained consistent stability and performance. The total organic carbon removal efficiencies ranged from 35.3% at the shortest HRT of 0.5 days to 82.1% at HRT = 1.5 days, indicating effective substrate degradation across varying loading conditions. The suspended solids and volatile suspended solids removal efficiencies were 56.9 ± 14.1% and 74.9 ± 7.0%, respectively,recorded at HRT = 1.0 day. These results highlight the reactor's ability to retain and degrade particulate matter despite short retention times. The Biogas production rates increased significantly with decreasing HRTs, from 201.1 ± 37.4 mL d-1 at HRT = 2 days to a peak of 903.8 ± 307.2 mL d-1 at HRT = 0.5 days, with methane content consistently above 79%. The maximum SS removal of 56.9 ± 14.1% was achieved at HRT = 1 while the highest biogas production rate (903.8 ± 307.2 mL d-1) was achieved at HRT = 0.5 days. This study demonstrates that the up-flow anaerobic sludge blanket reactors inoculated with pre-aggregated anaerobic digestion granular sludge can effectively treat high-strength lignocellulosic substrates such as water hyacinth juice under high loading conditions. Even at extremely short HRTs, the system maintained stable removal efficiency and robust biogas production, showcasing its potential for efficient valorization of invasive aquatic biomass. These findings support the deployment of the up-flow anaerobic sludge blanket reactor as a viable technology for the dual purpose of environmental management and renewable energy generation, particularly in regions plagued by water hyacinth overgrowth.departmental bulletin pape
From The Collective Rise of the Global South to a Return of the "Three Worlds" : The Future of China's Non-Alignment Diplomacy
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Beyond the borders: exploring the contribution of migration for a more sustainable and inclusive future
Full text linkThis research examines the migration phenomenon in Italy, focusing on its relationship with the achievement of Sustainable Development Goals (SDGs) 5 (Gender Equality), 8 (Decent Work and Economic Growth), and 10 (Reduced Inequalities). The study highlights the significant role social media plays in shaping and disseminating a negative image of migration and migrants, often supported by the current Italian government. The analysis reveals that alarmism surrounding migration, often fueled by certain politicians and media outlets, creates a climate of fear and xenophobia, leading to increased racism and a diminished understanding of the positive contributions migration can offer. The research emphasizes the potential of migration to contribute to the realization of the SDGs, highlighting how it can empower women, boost economic growth, and reduce inequalities. For example, supporting migrants in developing new skills and creating job opportunities can contribute significantly to economic growth and development.
The research underscores the need for a more nuanced understanding of migration, advocating for a shift in perspective from seeing migrants as a threat to recognizing their potential to enrich societies. It concludes that a more sustainable and inclusive world requires a conscious effort to deconstruct the colonized mindset that often views migration negatively, and instead embraces the potential of migration to foster a more diverse and equitable society. The ultimate success of migration in contributing to the SDGs depends on the willingness of destination countries to create a welcoming environment and actively engage in the deconstruction of existing power structures.departmental bulletin pape