Back-washing　time　is　one　of　the　most　critical　operational　parameters　for　biological　filter.　In　order　to　investigate　the　effect　of　backwashing　time　on　iron,　manganese,　ammonia　and　turbidity　removal,　three　backwashing　time　(5　min,　4　min　and　3　min)　were　adopted.　Results　showed　that　the　average　concentration　of　total　iron,　manganese　and　ammonia　in　effluent　was　0.025　mg/L,　0.007　mg/L,　and　0.022　mg/L;　0.012　mg/L,　0.001　mg/L　and　0.017　mg/L;　0.013　mg/L,　0.000　mg/L　and　0.016　mg/L,　respectively,　which　illustrated　varying　backwashing　time　had　little　influence　on　the　removal　efficiency　of　them.　The　turbidity　in　effluent　was　0.28　NTU,　0.38　NTU,　0.57　NTU,　respectively.　The　shorter　backwashing　time,　the　higher　turbidity　in　effluent.　Turbidity　was　almost　completely　removed　in　0　similar　to　0.4m　of　the　media.　After　backwashing,　the　turbidity　in　effluent　was　decreased　to　less　than　1　NTU　in　40　min,　droped　to　less　than　0.5　NTU　in　90　min.