0-16 A water softener is used to treat well water that has a total hardness of 450mgL1. The design flow rate is 4.2m3 - 5 with a total hardness of 125mgL1. According to the manufacturer, the ion exchange resin used in the water softener has a leakage of 1.5% (which means that the effluent concentration from the sofiener is 1.5% ) of the influent concentration). What is the required flow rate through the softener to achieve the desired hardness? The design flow and overflow rates for a settling tank are 0.2m3sec1 and 25m. day 1, respectively. Determine the surface area of this tank. Determine the length of the tank, using conventional wisdom for length-to-width ratios. Determine the tank depth, assuming a detention time of 2 hours. (10 Marks)