This research aimed to create facile, reusable, hydrogel-based anion exchange resins that have been modified with two different amines to test their ability to adsorb nitrate and nitrite in water using batch and continuous systems. In the batch experiment, maximum adsorption capacities of nitrate and nitrite onto poly (ethylene glycol) diacrylate methacryloxyethyltrimethyl ammonium chloride (PEGDA-MTAC) and poly (ethylene glycol) diacrylate 2-aminoethyl methacrylate hydrochloride (PEGDA-AMHC) adsorbents can be obtained as 13.51 and 13.16 mg NO₃⁻-N/g sorbent; and 12.36 and 10.99 mg NO₂⁻-N/g sorbent respectively through the Langmuir isotherm model. After 15 adsorption/desorption cycles, PEGDA-MTAC and PEGDA-AMHC retained nitrate adsorption efficiencies of 94.71% and 83.02% and nitrite adsorption efficiencies of 97.38% and 81.15% respectively. In a column experiment, modified adsorbents demonstrated adsorption efficiencies greater than 45% after being recycled five times. Proposed hydrogel-based adsorbents can be more effective than several types of carbon-based sorbents for nitrate and nitrite removal in water and have benefits such as reduced waste generation, cost-effectiveness, and a facile synthesis method.

Glucose can be isomerized into fructose and dehydrated into key platform biochemicals, following the “bio-refinery concept”. However, this process generates black and intractable substances called humin, which possess a polymeric furanic-type structure. In this study, glucose-derived humin (GDH) was obtained by reacting D-glucose with an allylamine catalyst in a deep eutectic solvent medium, followed by a carbonization step. GDH was used as a low-cost, green, and reusable adsorbent for removing cationic methylene blue (MB) dye from water. The morphology of carbonized GDH differs from pristine GDH. The removal efficiencies of MB dye using pristine GDH and carbonized GDH were 52% and 97%, respectively. Temperature measurements indicated an exothermic process following pseudo-first-order kinetics, with adsorption behavior described by the Langmuir isotherm. The optimum parameters were predicted using the response surface methodology and found to be a reaction time of 600 min, an initial dye concentration of 50 ppm, and a GDH weight of 0.11 g with 98.7% desirability. The MB dye removal rate optimized through this model was 96.85%, which was in good agreement with the experimentally obtained value (92.49%). After 10 cycles, the MB removal rate remained above 80%, showcasing the potential for GDH reuse and cost-effective wastewater treatment.

Sustainable aquaculture in inland reservoirs depends on seasonal hydrology, which influences nutrient dynamics and O2 availability. This study aimed to quantify O2 and nutrient-based ecological carrying capacity and seasonal hypoxia risk to support sustainable aquaculture planning. This study evaluated the feasibility and ecological capacity of aquaculture in the Wonorejo Reservoir, Indonesia, using a four-pillar framework: feasibility mapping, ecological assessment, carrying capacity estimation, and risk-based ecological management. Monthly water quality data from 2022–2024, supported by in situ validation in March 2025, were analysed using the Vollenweider phosphorus model, O2 balance calculations, total oxygen demand (TOD), and the ecological balance index (EBI). Spatial analysis identified areas suitable for aquaculture in about 36.2% of the area. Phosphorus loading remained within oligotrophic conditions (0.12–0.28 mg P∙m−2∙y−1), indicating that nutrient enrichment is not the dominant limiting factor. Oxygen availability emerged as the dominant ecological constraint under the applied O2 balance framework. Dry season elevated TOD relative to estimated natural re-aeration capacity. This resulted in chronic O2 deficits (EBI = 0.50–0.60) and reduced the system’s resilience. Under these O2-limited conditions, theoretical N-based aquaculture potential (1,250–1,600 mg∙y−1) declined to a sustainable range of 500–900 mg∙y−1. A hypoxia-focused hazard–exposure–vulnerability (HEV) assessment showed high HEV during dry seasons, moderate risk during transitional periods, and low risk during rainy conditions. The findings emphasise that O2 dynamics, rather than nutrient levels, govern sustainable aquaculture capacity. Oxygen-based stocking regulation, organic load management, aeration, and spatial zoning are recommended to improve ecological stability.