Question 1 10 pts In the COD measurement of a raw wastewater

Question 1 (10 pts): In the COD measurement of a raw wastewater sample, initial K Cr:0- concentration added into the wastewater sample is 3.000 g/L. After the redox reaction has reached an equilibrium, the K Cr:O concentration has been reduced to 1.824 g/L. Assuming in the redox reaction, the Cr in K:Cr:O is reduced to Cr. What is the COD of the wastewater sample in mg/L.? Question 2 (10 pts): 1) What is the TOC (in mg/L) for an aqueous solution that only contains 5 mM acetic acid, CHsCOOH 2) What is the ThOD (in mg/L) of 46 mg/L ethanol (CH CH:OH) aqueous solution?

Solution

Initial concentration of K2Cr2O7 = 3.0 g/ L

After the redix reaction attaining equilibrium the conc. is = 1.824 g/ L

K2Cr2O7 consumed = 3.0 - 1.824 =. 1.176 g/ L

Or. = 1.176 * 1000/49.03 meq/ L

Now COD in terms of Oxygen can be calculated as

COD = ( 1.176*1000/49.03 = meq/ L ) * 8 mg O2 / 1 meq

= 191.88 mg/ L.