A sewage disposal plant has a big concrete holding tank of 100,000-gal capacity. It is % full of liquid to start with and contains 60,000 Ib of organic material in suspension. Water runs into the holding tank at the rate of 20,000 gal/hr and the solution leaves at the rate of 15,000 gal/hr. How much organic material is in the tank at the end of 3 hours?

Experiments conducted for a dilute system under laboratory conditions approximating plug flow give HTUOx= 3 ft. If a commercial column is to be designed for NTUOx = 4, with NPex and NPey estimated to be 19 and 50, respectively, determine the necessary column height if E = 0.5.

plz answer both 2 questions

on problem B    equation 1) what symbol is that? it looks like a N or an X , can you tell me the symbols for transport velocities and mass transfer   thanks  can you clarify more on what the symbolism is for that equation