Effect of Operational Conditions on Ammonia Recovery from Simulated Livestock Wastewater Using Gas-Permeable Membrane Technology

Gas-permeable membrane (GPM) technology is a novel alternative to reduce N content in wastewater while recovering N in the form of an ammonium salt solution that can be used as fertilizer. This work aims to elucidate the effects of three operational conditions on the performance of GPM technology for ammonia recovery in batch conditions using synthetic wastewater that simulates livestock wastewater. Firstly, the effect of the ratio of the initial mass of total ammonia nitrogen (TAN) per membrane surface from 197 to 936 g N per m(2) of membrane was investigated. The highest ratio presented the highest TAN recovery rate (90 g N m(-2) d(-1)). Secondly, the influence of the ratio of the volume of wastewater per volume of acidic trapping solution in the range from 7.8 to 33.3 L L-1 was studied. In this case, the higher the ratio, the higher the N concentration in the trapping solution, achieving a N concentration of 43,773 mg N L-1 with a ratio of 33.3 L L-1. Finally, two different TAN concentrations (<0.1 and 30 g N L-1) in the acidic trapping solution were evaluated. The use of a trapping solution with a TAN concentration of 30 g N L-1 led to a reduction in the TAN recovery rate, which meant that the diffusion of ammonia through the membrane was more difficult as the trapping solution became saturated with TAN. Overall, the tested conditions highly influence the performance of GPM technology, and therefore, these conditions should be set to optimize the ammonia recovery and reduce nitrogen losses.