短语词组短語off -scum [環境]廢渣skim off the scum 撇去浮沫Blow -off and scum valves 下排汙閥;上fly ash industral off scum 粉煤灰工業廢渣scum off 除浮渣;撤渣scum blow off cock 浮滓吹泄鏇塞scum blow off valve 浮渣吹泄閥scum -off 除浮渣;排浮渣 返回 offscum