$4.$ Activated Sludge Process $[15$ points$]$ You are hired by the army to retrofit an activated sludge plant $($open to the air with recycle$)$ to better treat TNT$.$ You discover an organism that degrades TNT and you decide to seed the activated sludge plant with the same organism. You run some laboratory experiments with the organism and find the following kinetic coefficients: $$max $=0\mathrm{.}1/$day; kd $=0\mathrm{.}01/$day; and Ks $=4$ mg$/$L$.$ Given: $[$TNT$]0$ is $500$ mg$/$L and Q$0$ is $1,000$ gallons$/$day a$.$ b$.(12$ pts$)$ Your permit states that you must achieve TNT effluent concentrations of $1$ mg$/$L$.$ What solids residence time $($SRT$)$ is needed to achieve this effluent concentration? $(3$ pts$)$ Based on what you know about wastewater treatment and typical SRT values, does this seem realistic? Why or why not?