The 11th International Conference on Water Resource and Environment (WRE 2025)

Abstract: The blue economy, comprising fisheries, tourism, and seafood processing industries, is expected to drive economic development through natural resources and decarbonization through blue carbon. However, the complex interrelationships and conflicting interests between marine ecosystems and socio-economic activities hinder the realization of sustainable blue development. In this context, ESG finance for fisheries and tourism is expected to contribute to the dual goals of environmental conservation and economic development, but its mechanisms are not self-evident. This study uses an R&D-based growth model in the monetary economy to analyze the effects of financial policies targeting R&D, fisheries, and tourism on expenditure, growth, environment, money, and tourism. Rent-seeking behavior toward individual transferable quotas (ITQs) is considered. The lending rates for the fisheries and tourism sectors are lower than those for the R&D sector through risk premiums. In the non-blue economy, lowering interest rates for R&D firms leads to pollution reduction and economic growth, but this effect is undermined in the blue economy. Lowering interest rates for fishing firms through risk premiums creates a trade-off between economic growth and environmental quality. When interest rates for tourism firms are raised to an adequate level through risk premiums, this leads to economic growth, environmental improvement, and expansion of tourism and money supply, but also causes a decline in lending. Here, raising interest rates for R&D firms and increasing ITQs can limit the extent of interest rate hikes for tourism firms. This result implies the finance-led tourism growth hypothesis. This study suggests that a policy mix centered on financial policies targeting tourism is important when aiming for sustainable blue development.

Abstract: Bench-scale plug-flow type reactor with Spirodela polyrhiza and Lemna aequinoctialis duckweeds was applied to treat low-strength municipal wastewater. The experimental unit was operated at a constant hydraulic retention time of 4 days, during which duckweed was initially provided at 100% of the water surface area. During continuous operation, growing duckweed biomass was harvested twice a week to maintain the original coverage condition of duckweed on the water surface, and the amount of excess duckweed biomass was monitored. Municipal wastewaters containing different organic (COD) and nitrogen (TKN) concentrations, with their average values ranging from 45-118 mg/l and 17-70 mg/l, respectively, were examined on their effect on the treatment performance, duckweed biomass production, and associated microbial communities. The experimental results revealed the highest average biomass production of 6.5 g dry mass/m2/day of Spirodela polyrhiza duckweed over 72 days of operation when influent wastewater with the highest COD concentrations was applied. At lower organic concentrations, lower average duckweed biomass production rates, ranging from 3-4 g/m2/day for Spirodela polyrhiza and 0.2-1.5 g/m2/day for Lemna aequinoctialis were observed. During the treatment of wastewaters, moderate average COD removal of 37-59% and TKN 22-47% were achieved. Microbial community analyses revealed predominance of Burkholderiales, Pirellulales, Verrucomicrobiales, and Rhizobiales bacterial consortium associated with Spirodela polyrhiza duckweed under high growth yield conditions, whereas Cyanobacteriales were found predominant on duckweeds cultivated under low COD conditions.

Abstract: Disinfection by-products (DBPs), formed from biofilm extracellular polymeric substances (EPS) and organic matter during regular disinfection practices in drinking water distribution systems, poses a potential threat to drinking water safety. However, the diverse DBP formations induced by the intertwined organic matter and bacterial EPS remains elusive.
In this study, we investigate both disinfectant methods and divalent ions on DBP formation in simulated drinking water distribution system (DWDS). Biofilm analysis results revealed that at 0.5 mg/L of disinfectant residual, both Cl2 and NH2Cl were not effective to remove biofilms. As the disinfectant residual increased, biofilms could be eradicated by Cl2, while remaining biofilms were still present even under the highest allowable NH2Cl dose (4 mg/L). However, when Cl2 residuals reached 2 mg/L, DBP concentrations in bulk water increased sharply, with trihalomethanes and haloacetic acids being the most prevalent DBP species. In addition, divalent ions in bulk water can significantly inhibit DBPs formation. Mechanistically, divalent ions promote the complexation of negative charged groups and thus inhibit carbonaceous DBP formation, while the hindering chlorine substitution of hydrogen atoms on α-carbon and amine groups reduces nitrogenous DBP formation. Conversely, Ca2+ and Mg2+ could facilitate biosorption processes that increased the yields of DBPs. Both EPS and adsorbed algal organic matter can provide halogenated reactive sites for DBP formation, exhibiting diverse aromatic substances and unsaturated (lignin and tannins) compounds. Overall, this study provides insights into optimizing disinfection protocols for water utilities by balancing the benefits of disinfection application for biofilm control with minimized toxic DBP formation in DWDS.