The following monthly effluent constituent concentrations have been obtained from four different existing activated sludge treatment plants. Each of these plants is to be replaced with a new plant to meet new and more stringent discharge requirements. For one of these plants (to be selected by the instructor), determine the mean design value assuming the following maximum monthly permit limits must be met: (a) BOD and TSS 5 15 mg/L at 99 and 99.9 percent reliability, (b) BOD and TSS 5 10 mg/L at 99 and 99.9 percent reliability, (c) BOD 5 5 mg/L and TSS 5 8 mg/L at 99 and 99.9 percent. On average, what percentage improvement would be required to meet the new discharge permit requirements? In your opinion, is the percentage improvement reasonable? Constituent concentration mg/L Month BOD TSS 5 456 5561 Jan Feb Mar 6 Apr 7.5 7 May 9 8 Jun 13 10 14 5 6 July 16 Aug 18 17 Sep 6.5 15 Oct 10 1.5 Nov 12 10 Dec 5.5 9