An effluent at a flow rate of 2670 m³/d from a sewage treatment plant is to be disinfected. The laboratory data of disinfection studies with a chlorine dosage of 15 mg/l yield the model Nt = No e–0.145t where Nt = number of microorganisms surviving at time t (in min.) and No = number of micro-organisms present initially (at t = 0). The volume of disinfection unit (in m³) required to achieve a 98% kill of micro-organisms is _______