Modeling Nitrogen Recovery and Water Transport in Gas-Permeable Membranes

This study presents a new modeling approach for nitrogen recovery for gas-permeable membrane (GPM) contactors, including both ammonia and water transport dynamics. A distinct feature of the model is its capacity to model water transport across the membrane, which has been overlooked in most publications. Osmotic pressure differences are used to predict the behavior of ammonia and water transport in the GPM. Experiments carried out to develop, test and calibrate the model examined the dynamics of ammonia and water transport through the GPM at various nitrogen concentrations. Specifically, the GPM contactor was tested for nitrogen recovery from high-strength synthetic wastewaters (2.4-10.6 g N/L) at 35°C and at pH 9. The initial volume of the trapping solution (diluted H₂SO₄) was 10 times lower than that of the synthetic wastewater, aiming to concentrate the recovered nitrogen. The estimated ammonia transport constant (K_m) ranged between (1.2 – 2.1)·10^-6 m/s and water transport constant K_w between (2.8 – 8.2)·10^-10 m/(s bar). Numerical determination of the model parameters revealed high R² values, demonstrating strong agreement with experimental data.