Provide answers to the following questions related to floatation, pH control, ion exchange and activated sludge process. (i) Briefly explain the main function and an operationai issue associated with each technology given below in the production of drinking water from surface water that has significant colloidal and suspended solids, a low pH and high conductivity: (3) (a) floatation: (4) (b) pH control; and (3) (c) ion exchange. (ii) A conventional activated sludge plant is used to treat 200,000m3/d of municipal wastewater. You have been asked to prepare the preliminary process design by calculating the following: (3) (a) The required aeration tank volume V in m3 and the aeration tank hydraulic retention time () in hours; (4) (b) the quantity of sludge to be wasted daily (Qw) in kg/d; and (3) (c) the sludge recycle ratio (Qr/QD). Use the following process information: - Influent BOD5 and TSS=240mg/L; - effluent BOD5 and TSS =25mg/L : - yield coefficient, Y=0.4 : - decay rate, kd=0.05d1; - average MLSS in the aeration tank, X=6,000mg/L : - waste MLSS from the clarifier, Xw=9,000mg/L; and - mean cell residence time, c=12 days