Asmall treatment plant with two filters operates at a filtration rate of 2 gpm/ft2 . the influent tss is 15 mg/l; the effluent tss is 0. (a) if each filter is square, 30 ft on a side, calculate the daily volume of water treated (in million gallons/d, mgd) assuming each filter is backwashed once per day in a process that takes 30 minutes. (b) if 3% of the treated flow is used for backwashing, calculate the backwash tss. (answers: 5.08 mgd, 500 mg/l)