A wastewater is to be treated with GAC to remove its COD. The following data were obtained from a lab study in which 0.5 g of GAC was added to a beaker containing 0.5 L of wastewater at selected COD values. Determine (1) the more suitable isotherm (Langmuir or Fruendlich) to describe the data (find the isotherm constants), and (2) how much GAC is needed to treat a flow of 5000 m3/d to a final COD concentration of 20 mg/L if the initial COD of the wastewater is 120 mg/L.