Ammonia recovery from acidogenic fermentation effluents using a gas-permeable membrane contactor

Abstract

A gas-permeable membrane (GPM) contactor was used to recover ammoniacal nitrogen from a synthetic and a biowaste fermentation broth under different pH (from 6 to 11) and temperatures (35 and 55 ºC). Ammonia mass transfer constant (Km) increased as pH and temperature increased. For synthetic broth, pH 10 provided the best results, when considering the Km (9.2⋅10-7 m⋅s-1) and the reagents consumption (1.0 mol NaOH⋅mol-1 TAN and 0.6 mol H2SO4⋅mol-1 TAN). Biowaste fermentation generated a broth with a high concentration of ammoniacal nitrogen (4.9 g N⋅L-1) and volatile fatty acids (VFA) (41.1 g COD⋅L-1). Experiments using the biowaste broth showed a lower Km (5.0⋅10-7 m⋅s-1 at pH 10) than the synthetic broth, related to the solution matrix and other species interference. VFAs were not detected in the trapping solution. Overall, these results show that GPM is a suitable technology to efficiently separate ammoniacal nitrogen and VFA from fermentation broths.