1.During an epidemic of contagious diseases, why doesn’t everybody get infected ?and , Why are viruses difficult to remove from a water supply system?
2.Two rectangular primary sedimentation tanks each 27 m long, 5 m wide and 3.8m deep treat 6000 m3/day wastewater from a community. Total effluent weir length is 50m (both tanks). Calculate the detention time, surface overflow rate (in m3/m2.day), and weir loading rate (in m3/m.day).
3.What are the differences between airborne infectious diseases and diseases that are caused by air pollution? Give at least two examples for each category of diseases.
4.A sanitary sewer with a 450 mm diameter is constructed on the minimum allowable slope of 0.9 m/km. What is the full capacity of the sewer? At what depths of flow in the pipe are the velocities of flow equal to 0.6 m/s. Assume Mannings constant n = 0.013.