To study methods for nitrogen removal from Hanoi groundwater, the biological nitrificationdenitrification method was chosen using the newly developed swim-bed attached-growth methods with a novel acryl jiber biomass carrier called biofringe (BF). BF functions in a "swimming" mode and has demonstrated many advantages such as long sludge retention time, low effluent suspended solids, reduced sensitivity to toxic loads and high treatment capability. It can also eliminate head loss caused by clogging and channeling. For this study, synthetic influents were prepared similar in composition to Harioi groundwater with ammonium concentration up to 30 mg-N/L. NBF and DNBF reactors were used for biological nitrification and denitrification tests.