A industrial waste treatment facility receiving 1 MGD of flow needs to build a new reactor to treat chromium(VI) waste from an electroplating operation. Cr(VI), present in water as HCrO4- can be treated by chemical reduction with bisulfite, HSO3- , yielding Cr(OH)3(s) that can be removed by gravity sand filtration and sulfate (SO42-), an inert anion species. 3 HSO3- + 2 HCrO4 + H2O 2 Cr(OH)3(s) + 3 SO42- + H+ Information from the literature shows that HCrO4- reduction by this reaction follows a pseudo-first-order rate with k1'= 0.1 s-1 at pH 7.5 when treating with 1 mM HSO3- . If the wastewater initially has a HCrO4- concentration of 100 M, determine the minimum reactor volume (in gallons) needed to ensure that the HCrO4- concentration drops to 0.1 M if (a) reaction is conducted in an ideal CSTR, (b) reaction is conducted in an ideal PFR, or (c) reaction is conducted in a PRF with dispersion that can be modeled as 5 CSTR reactors-in-series.