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A long-term pilot-scale H 2 -based membrane biofilm reactor (MBfR) was tested for removal of nitrate from actual groundwater. A key feature of this secondgeneration pilot MBfR is that it employed lower cost polyester hollow fibers and still achieved high loading rate. The steady-state maximum nitrate surface loading at which the effluent nitrate and nitrite concentrations were below the Maximum Contaminant Level (MCL) was at least 5.9 g $N$(m 2 $d) -1 , which corresponds to a maximum volumetric loading of at least 7.7 kg$N$(m 3 $d) -1 . The steady-state maximum nitrate surface area loading was higher than the highest nitrate surface loading reported in the firstgeneration MBfRs using composite fibers (2.6 g$N $(m 2 $d) -1 ). This work also evaluated the H 2 -utilization efficiency in MBfR. The measured H 2 supply rate was only slightly higher than the stoichiometric H 2 -utilization rate. Thus, H 2 utilization was controlled by diffusion and was close to 100% efficiency, as long as biofilm accumulated on the polyester-fiber surface and the fibers had no leaks.

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Hydrogen release from solid-state ammonia borane (AB, NH 3 BH 3 ) exhibits a long induction period and requires a relatively high temperature. In the present work, D-mannitol (DM, C 6 H 8 (OH) 6 ) was used as an additive to enhance the hydrogen release properties of AB. At proton exchange membrane (PEM) fuel cell operating temperatures, the influence of various operating process parameters (temperature and heating rate) and AB−DM ratio has been investigated. In addition, the composition of gaseous products was analyzed to identify the reaction mechanism using mass spectrometry. In particular, the formation of ammonia, which poisons PEM fuel cells, was quantitatively analyzed. Using solid-state nuclear magnetic resonance, solid products were characterized to better understand the mechanism of AB thermolysis. In the presence of DM, the onset reaction temperature decreased to 80 °C, whereas dehydrogenation kinetics were significantly improved. With DM as an additive, we obtained a high hydrogen yield of 9.1 wt % (1.75 H 2 equivalent) at the PEM fuel cell operating temperature (90 °C).

This article tests the theory of using nitrate carrier surface loading (SL) as the primary design criterion for heterotrophic denitrification of drinking water. Two load‐increase tests (flow rate and nitrate concentration) with a pilot‐scale heterotrophic biofilm reactor identified that the maximum SL was approximately 6 g nitrogen/m2/d and was controlled by the effluent nitrite concentration. A comparison of SL values obtained from the literature also showed that the maximum SLs were similar for a wide range of heterotrophic denitrification processes. All of the SL values are consistent, even though the empty bed contact time and the nitrate volumetric loading varied widely. The experimental results confirm that the electron donor should be supplied at the stoichiometric requirement to achieve simultaneously low concentrations of nitrate, nitrite, and organic carbon.