9.1 A “slop" tank in an oil refinery is used to collect various intermittent aqueous flows containing tank bottom residues, floor and pad wash downs,reactor blow downs, organic lab wastes,

and rejected product streams.When the tank is filled, mixers are activated and its contents are vigorously mixed. While mixing continues, a strong oxidant is added in excess to reduce the TOC of the tank contents to less than 100 mg/L. The tank contents are then discharged to a central biological treatment facility. The oxidation process is known to be first-order in TOC, with an empirically correlated rate coefficient of k = 2.5 x 10-3(TOC), per day. For a starting concentration of 12,500 mg TOC/L, determine the minimum reaction time interval required to meet the pre treatment objective. Comment on why in this type of situation k might in fact be found to correlate with the initial TOC concentration.