You have been asked to design a primary clarifier that will treat $2\mathrm{.}5$ MGD of wastewater from a proposed Disney theme park. You have conducted a batch settling test with an initial suspended solid concentration of $320m\frac{g}{L}$ to develop criteria for the design of the primary clarifier. The test column was $8in.(203mm)$ in diameter and $10ft(3\mathrm{.}08m)$ high, and sampling ports were located at $2,4,6,8,$ and $,1\mathrm{.}83,2\mathrm{.}44,3\mathrm{.}05m)$ from the water surface in the column. The percent removals after the various sampling times are given in the following Table $($Table $2).$

The isoremoval lines are plotted in the following figure $($Figure $3).$ The $20\%$ removal line intersects the $x$ axis at $16$ min $.$

Table $2.$ Percent removal affer varions sqmpling cimes at differeat sampling por

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