Enhanced Oxygen Mass Transfer in Aquaculture Using a Low-Cost Nanobubble Fluid Spray System

Dissolved oxygen (DO) management is a primary challenge in intensive aquaculture, where conventional aeration often suffers from high energy costs and low efficiency in decentralized systems. Oxygen transfer kinetics were investigated under oxygen-depleted conditions (initial DO = 2.4 mg L⁻¹) using the dynamic method. The system's performance was characterized through the volumetric mass transfer coefficient (kLa), Specific Oxygen Transfer Efficiency (SOTE), and dimensionless analysis (Reynolds, Schmidt, and Sherwood numbers). After 1 hour of operation, the DO concentration increased to 6.2 mg L⁻¹, achieving a net oxygen transfer of 9.55 ± 0.46 g. The system yielded a kLa of 1.44 h⁻¹ (R² = 0.97) and a SOTE of 76.4 ± 7.8 gO₂ kWh⁻¹. Dimensionless analysis (Re ≈ 2 x 10⁴, Sc ≈ 500, Sh ≈ 682) confirms that oxygen transfer is governed by hydrodynamic-induced interfacial area generation rather than molecular diffusion. Biological validation demonstrated that fish (catfish) grown under nanobubble-assisted conditions achieved a 43% higher growth rate over 17 days compared to non-assisted groups. These findings demonstrate that hydrodynamically controlled nanobubble spray systems provide an energy-efficient and scalable solution for decentralized aquaculture aeration.