As we have already discussed, when alum is added to water containing sufficient alkalinity aluminum hydroxide, Al(OH)3, precipitates. This assists greatly in removal of the very small (colloidal) particles that cause turbidity. The summary The reaction shown below is often used to make stoichiometric calculations related to this process. Al2(SO4)314.3H2O+3Ca(HCO3)22Al(OH)3(s)+3CaSO4+14.3H2O+6CO2 Suppose that an alum "dose" of 30mg/L is used to treat a total of eight million gallons of water per day ( 8MGD ) at a typical municipal surface water treatment plant. Note: Not all of the information supplied above is required for completing this assignment. Some of it will be pertinent to future assignments. 1. Suppose that one-half of the 8 MGD flow (i.e., 4 MGD) is directed to each of two parallel rapid mixing basins and that each of the basins has an average detention time of 30 seconds. Calculate the volume required for each basin and express your answer in cubic feet and also in gallons. 2. Assuming that the rapid mixing basins are 5.0 feet deep (actual water depth) and have a square shape when viewed from above, calculate the length (and width) of each basin. Express your answer in feet. 3. Calculate the horsepower required for mixing in each basin if the design mean velocity gradient, G, is 300sec1 and the mixing equipment has an overall efficiency (wire to water) of 75%. You may assume a design temperature of 50F