4. An activated sludge process with recycle can process 1500 m/d of wastewater containing an influent BOD concentration of 250 g/m. The hydraulic retention time is 8 hours. The return activated sludge stream recycles 50% of the solids in terms of mass exiting the bottom of the secondary clarifier each day and the other 50% is disposed of in the wasting stream. There is no solid in the effluent from the secondary clarifier. The recycle ratio is 0.1 and the BOD removal efficiency of the system is 99%. The properties of the biomass are shown in the table. Coefficients Y = 0.6 g VSS/g BOD k= 2 g BOD/g VSS/ ka = 0.1 g VSS/g VSS/ Ks = 4 g BOD/m Calculate the following: (20 points) (a) The solids retention time (SRT) in day). (b) The waste sludge flowrate (Qw) (in m/d)