The effect of ammonia initial concentration in membrane distillation process for high ammonia concentration wastewater treatment

Direct contact membrane distillation process was used for high ammonia concentration wastewater treatment in this study. Through the regulation of raw water pH value, the ammonia transferred from feed side to permeate side in the form of gaseous NH₃ molecules. In the experiment we used raw water with different ammonia concentration to investigate the ammonia removal rate, total transmembrane flux, mass transfer coefficient and selectivity. It was found that, during the reaction process, ammonia in feed side rapidly transferred to permeate side. As the ammonia concentration in raw water increased, the removal rate, mass transfer coefficient and selectivity increased respectively. While the ammonia concentration was above 400 mg/L, the removal rate achieved more than 85% in 20~30 minutes. But when the ammonia concentration was above 1200 mg/L, the mass transfer coefficient decreased. And the selectivity also decreased when ammonia concentration achieved 1800 mg/L.