6.Factors of settling velocity in laminar region include (1) particle density, (2) water density, (3) particle diameter, (4) particle mass. 7.Suspended solids are removed from water through sedimentation by gravity, according to their (1) density, (2) mass, (3) volume, (4) buoyancy, difference to the water's. 8. Sedimentation can remove suspended solids with diameter larger than 9. Grit chanmber is to remove : Primary sedimentation tank is to remove Secondary sedimentation tank is to (1) inorganic matter, (2) suspended organic matter, (3) dissolved organic matter, (4) separate active sludge.