Engineering Evaluation of Oxygen Transfer Enhancement Using a Low-Cost Fine-Bubble Spray System for Decentralized Aquaculture

Oxygen transfer enhancement in aquaculture was investigated using a low-cost fine-bubble spray system operated under controlled hydrodynamic conditions. Experiments were conducted under oxygen-depleted conditions (initial DO = 2.4 mg L−1), and oxygen transfer kinetics were evaluated using the dynamic method. The dissolved oxygen concentration increased to 6.2 mg L−1 within 1 h, corresponding to a net oxygen transfer of 9.55 ± 0.46 g. The volumetric mass transfer coefficient (kLa) was determined to be 1.44 h−1 (R2 = 0.97), while the specific oxygen transfer efficiency (SOTE) reached 76.4 ± 7.8 gO2 kWh−1. Dimensionless analysis (Re ≈ 2 × 104, Sc ≈ 500, Sh ≈ 682) indicates a turbulent, convection-dominated transport regime. Biological observations showed a 43% increase in fish growth under spray-assisted conditions, indicating improved oxygen availability. The observed oxygen transfer enhancement was primarily associated with hydrodynamic interfacial area generation rather than diffusion-limited transport. The low-power configuration and simplified system design suggest potential applicability for decentralized aquaculture operations. The proposed approach also provides an engineering framework for evaluating low-cost aeration technologies under aquaculture operating conditions.