The current invention provides for a microbial consortium comprising one or more ammonium-oxidizing strains which are generally recognized as safe (GRAS) and which are selected from the group of Nitrosomonas, Nitrosospira, Nitrosopumilus, Cenarchaeum, Nitrosoarchaeum, Nitrosocaldus, Caldiarchaeum； and one or more GRAS strains which are commensal to the one or more ammonium-oxidizing strains, and which are selected from the group of Acinetobacter, Alcaligenes, Arthrobacter, Azospirillum, Azotobacter, Bacillus, Beijerinckia, Enterobacter, Erwinia, Flavobacterium, Rhizobium, Serratia and Deinococcus.
