At the Toormina (NSW) water treatment plant, raw water undergoes treatment by rapid sand filtration. Under normal circumstances, filtered water is then disinfected by chlorination to achieve a free hypochlorous acid (HOCI) CT of 45.0 mg.L-1.min at pH 6.0. The chlorine contact tank has a volume of 1550 m. Chlorination is normally achieved using 1-ton cylinders of compressed (liquified) chlorine. However, in emergency circumstances, the plant relies instead upon a supply of sodium hypochlorite solution, which can be dosed directly into the chlorine contact tank. Sodium hypochlorite solution has a concentration 12.5% available chlorine (by mass). The standard operating procedure stipulates that the sodium hypochlorite solution should be added to filtered water at a rate of 1 part in 25,000 (for example, 1 kg sodium hypochlorite solution in 25,000 kg of water). Following sodium hypochlorite dosing, online monitoring indicates a change in pH to pH 8.2 and no additional adjustments are made. Assume: Density of water is 1000 kg.m-3. HOCI HOCI pKa = 7.5 Hypchlorite ion has negligible (zero) disinfection strength, compared to hypochlorous acid. After dosing sodium hypochlorite solution in accordance with the standard operating procedure, determine: (a) The concentration of total available chlorine in the chlorine contact tank (mg/L) (5 marks) (b) The concentration of hypochlorous acid in the chlorine contact tank (5 marks) (c) The maximum treated water production rate (m.hour) to maintain satisfactory disinfection (5 marks)