A rectangular primary sedimentation tank that is 40 m in length, 10 m in width and 3.5 m in height is used in a wastewater treatment plant. The overflow rate is 50 m/d. Influent wastewater contains 500 g/m of 10 um spherical particles of density 2.65 g/cm. (a) Calculate the removal efficiency (in %) for the particles. Assume Stokes' law holds but check the fluid property as part of your answer. (b) In order to improve removal efficiency, a flocculation and coagulation tank is added upstream of the primary sedimentation tank. After flocculation and coagulation, the particle diameter increases to 100 um. Calculate the removal efficiency (in %) for the larger particles in the sedimentation tank. Note: An iterative approach as shown in lecture notes is required