短语词组短语off -scum [环境]废渣skim off the scum 撇去浮沫Blow -off and scum valves 下排污阀;上fly ash industral off scum 粉煤灰工业废渣scum off 除浮渣;撤渣scum blow off cock 浮滓吹泄旋塞scum blow off valve 浮渣吹泄阀scum -off 除浮渣;排浮渣 返回 offscum