sand bed filter 砂滤器

sand filter bed 砂滤床 ; 砂滤层

rapid sand filter bed 快速滤清器

moving-bed sand filter 移动床砂滤器

sand-bed d filter 砂滤器

sand-filter bed 沙滤层

slow sand filter bed 慢砂滤池

gravel and sand filter bed 砂砾滤床