Problem $3.$ Effluents from a metal$-$finishing plant has the potential of discharging undesirable quantities of metals, such as zinc, cadmium, nickel, lead, manganese, and chromium in forms that are detrimental to water and air quality. A local metal$-$finishing plant has identified a wastewater stream that contains $5\mathrm{.}15wt\%$ nickel $($Ni$)$ and devised the following approach to lowering risk and recovering the valuable metal. The wastewater stream is fed to a treatment unit that removes $95\%$ of the nickel in the feed $($to the unit$)$ and recycles it to the plant. The residual liquid stream leaving the treatment unit is sent to a waste lagoon. The treatment unit has a maximum capacity of $4500kg$ wastewater$/$h$.$ If wastewater leaves the finishing plant in a rate higher than the capacity of the treatment unit, the excess $($anything above $4500k\frac{g}{h})$ bypasses the unit and combines with the residual liquid leaving the unit, and the combined stream goes to the waste lagoon.

A$.$ Draw and label a more detailed flowchart for the process. Do not assume a basis of calculation at this point. ${?}^{****}$ Note: Assume ${?}_4$ is pure Nickel.

B$.$ Assuming the wastewater leaves the finishing plant at a rate of $1=1000k\frac{g}{h},$ calculate the flow rate of liquid to the waste lagoon, $6(k\frac{g}{h}),$ and the mass fraction of $Ni$ in this liquid, $x_6(kgN\frac{i}{k}g).$

Answers: $m_6=951\mathrm{.}1k\frac{g}{h}$;$x_{6,Ni}=0\mathrm{.}0027$

C$.$ In this case, assume the wastewater leaves the finishing plant at a rate of ${?}_1=7500k\frac{g}{h}.$ Calculate the flow rate of liquid to the waste lagoon, $6(k\frac{g}{h}),$ and the mass fraction of $Ni$ in this liquid, $N\frac{i}{k}g.$