3. Your engineering firm has been hired to design a secondary clarifier for an activated sludge process. Influent to the aeration tank has a flowrate of 10,000m3/h and there is no biomass in the influent. Under normal operating conditions, the secondary clarifier has an operating capacity of 5kg/m2/h and the return activated sludge concentration is 10g/L. The recycle ratio of the system is 2.0. Assume the sludge wasting stream flowrate is zero. (a) Calculate the area of the secondary clarifier (in m2 ). (15 points) (b) To enhance the density of the sludge, a chemical is added in the secondary clarifier (this is the only change). This successfully increased the operating capacity of the clarifier to 8kg/m2/h without having to modify the flowrate of the underflow stream. Calculate the biomass concentration (in g/L ) in the aeration tank with this new set up. (15 points) 3. Your engineering firm has been hired to design a secondary clarifier for an activated sludge process. Influent to the aeration tank has a flowrate of 10,000m3/h and there is no biomass in the influent. Under normal operating conditions, the secondary clarifier has an operating capacity of 5kg/m2/h and the return activated sludge concentration is 10g/L. The recycle ratio of the system is 2.0. Assume the sludge wasting stream flowrate is zero. (a) Calculate the area of the secondary clarifier (in m2 ). (15 points) (b) To enhance the density of the sludge, a chemical is added in the secondary clarifier (this is the only change). This successfully increased the operating capacity of the clarifier to 8kg/m2/h without having to modify the flowrate of the underflow stream. Calculate the biomass concentration (in g/L ) in the aeration tank with this new set up. (15 points)