The　municipal　water　supply　of　Songbei　District　in　Harbin,　Northeast　China,　relied　on　local　groundwater　which　contained　high　concentration　of　iron　(about　15　mg/L),　manganese　(about　1.5　mg/L)　and　ammonium　(about　1.1　mg/L).　The　waterworks　had　a　two-stage　filtration　process,　including　the　first　purification　filters　for　the　removal　of　iron　and　the　second　one　for　the　removal　of　manganese　and　ammonium.　The　total　treatment　capacity　was　10,000　m(3)/d.　In　order　to　double　it　to　meet　the　increasing　water-supply　demand,　the　upgrading　of　the　waterworks　from　operation　in　series　to　operation　in　parallel　by　the　simultaneous　removal　of　iron,　manganese　and　ammonium　in　single　biofilter　was　recommend.　After　inoculation　of　bacterial　solution,　aeration　was　enhanced　from　about　4.5　mg/L　to　almost　10　mg/L,　by　adding　of　cascaded　aeration　and　perforated　pipe　spargers,　to　meet　the　oxygen　demand　in　the　biofilter.　And　the　filter-layer　was　optimized,　by　adopting　the　dual-media　filter,　to　reduce　the　effect　of　ferrous　on　biofilter　for　manganese　removal.　Finally,　the　waterworks　was　successfully　transferred　into　the　one-stage　filtration　process　and　the　concentration　of　iron,　manganese　and　ammonium　in　the　treated　water　was　about　0.20,　0.05　and　0.17　mg/L,　superior　to　the　national　standards　for　drinking　water　(GB5749-2006).　Adequate　dissolved　oxygen　and　dual-media　filter　are　beneficial　to　biological　manganese　removal　from　groundwater,　in　the　condition　of　high　concentration　of　ammonia　nitrogen　and　ferrous　ion.