Start-up　experiments　were　carried　out　using　a　constructed　a　pilot-scale　biofilter　in　a　water　supply　plant　to　purify　iron　(Fe),　manganese　(Mn),　and　ammonia　(NH3-N)　from　low-temperature　groundwater　(3-4　degrees　C　throughout　the　year).　The　results　of　the　biofilter　operation　indicated　that　the　simultaneous　removal　of　these　contaminants　could　be　obtained　with　a　one-stage　biofilter,　while　the　operational　parameters　such　as　aeration　and　backwashing　strength　(BWS)　should　be　optimized　during　the　start-up　operation　period.　Removal　of　Fe　was　most　likely　dominated　by　chemical　oxygen　oxidation　since　the　biofilter　exhibited　high　removal　efficiency　at　the　initial　running　period　and　the　start-up　time　was　not　required.　Higher　levels　of　aeration　(that　corresponds　to　higher　dissolved　oxygen　concentration)　helped　to　transform　the　water　redox　environment　and　increase　Mn　removal.　Nitrification　effects　were　irrelevant　with　the　extra　aeration.　A　weaker　BWS　was　helpful　in　avoiding　biomass　loss　during　the　initial　operation　of　the　biofilter;　however,　the　BWS　should　be　improved　to　eliminate　excess　amounts　of　metal　oxide　accumulation　after　a　long　operation　time,　since　it　could　enhance　the　overall　removal.　Using　high-throughput　sequencing　technology,　the　functional　bacteria　genera　were　identified.　It　was　demonstrated　that　the　corresponding　functional　oxidizing　bacteria　could　be　acclimated　sufficiently　in　low-temperature　water.