A city is planning the installation of a new water treatment plant to supply a growing…

A city is planning the installation of a new water treatment plant to supply a growing population. There will be only one rapid mix tank basin and then the flow will be evenly split between two flocculator trains, each with three basins consisting of equal volumes for each stage. All basins will be square in the plan profile. The required water depth for all basins is 4.0 m. Determine the correct basin volumes in basin dimensions (in ), tank equivalent diameter (inm), required water power in W), required input power (in W), impeller diameter (use table below, in m) and rotational speed (in rpm). Be sure to check standard values for basin dimensions. The following parameters apply: Q= 11,500 m’/d Rapid mix HRT Total flocculation time = 30 min with tapered flocculation at G = 70·50. 30sec. Water temperature = 5°C Impeller depth = l/3 of water depth (ie, 2/3 of the tank is above impeller) * 2 min at G = 600/sec . The rapid mix basin will use radial flow impellers; the flocculator will use axial flow impellers (same size in each basin) Motor transfer efficiency * 75% Impeller T Im Diameter (m) Power Radial Axial 0.8 0.8 2.0 0.31