Anammox - A novel microbial process for ammonium removal

摘要

Anammox, a process of anaerobic ammonium oxidation, is an innovative technological advancement in the removal of ammonia nitrogen in waste water. This new process combines ammonia and nitrite directly into dinitrogen gas. The anammox reaction can be represented as NH_4~+ + NO_2 = N_2 + 2H_2O. This reaction is carried out by anammox bacteria belonging to the planctomycete group. Bacteria capable of anaerobically oxidizing ammonia were not identified earlier and were known as 'lithotrophs missing from nature'. Subsequently, this missing lithotroph was discovered and identified as a new autotrophic member of the order Planctomycetales. It appears that they might be the most primitive group of bacteria, at the very root of the bacterial tree. Two of the anammox bacteria have been named provisionally: Candidatus 'Brocadia anammoxidans' and Candidatus 'Kuenenia stuttgartiensis'. The former bacterium was responsible for anaerobic oxidation of ammonia observed in the Netherlands, while the latter organism has been shown to be responsible for ammonia oxidation anaerobically in several wastewater treatment plants in Germany and Switzerland. Interestingly the two species of the anammox bacteria which have been characterized are rarely found together in a single anammox reactor, they must have different, as-yet unknown, ecological niches.