Effect of bimetallic and polymer-coated Fe nanoparticles on biological denitrification.

Bimetallic nanoparticles (nano Fe-Ni, nano Fe-Cu) and coated iron nanoparticles (chitosan-Fe(0), sodium oleate-Fe(0)) were utilized to support autotrophic denitrification. In comparison to nanoscale zero-valent iron (NZVI) particles, Ni-containing nanoparticles resulted in faster nitrate removal, but generated 17% more ammonium. The nano Fe-Cu integrated system, required two days less than the unmodified NZVI integrated system to remove all the nitrate and decrease ammonium by 13%, but a large amount of nitrite remained in the system.

Decreasing ammonium generation using hydrogenotrophic bacteria in the process of nitrate reduction by nanoscale zero-valent iron.

An integrated nitrate treatment using nanoscale zero-valent iron (NZVI) and Alcaligenes eutrophus, which is a kind of hydrogenotrophic denitrifying bacteria, was conducted to remove nitrate and decrease ammonium generation. Within 8 days, nitrate was removed completely in the reactors containing NZVI particles plus bacteria while the proportion of ammonium generated was only 33%. That is a lower reduction rate but a smaller proportion of ammonium relative to that in abiotic reactors.