(Solved): WASTEWATER 2. a. Chemical oxygen demand (COD) is measured through the reaction of organic compound ...

WASTEWATER

2. a. Chemical oxygen demand (COD) is measured through the reaction of organic compounds with potassium dichromate forming chromium (III) ion. The computation of COD is in the following: - COD 8000 (a - b) -x NormalityofFAS Where: COD= chemical oxygen demand, mg/L a = amount of ferrous ammonium sulphate titrant added to blank, mL b = amount of titrant added to sample, mL V =volume of sample, mL 8000 = multiplier to express COD in mg/L of oxygen An influent of domestic wastewater sample was collected from Taman Universiti oxidation pond treatment system. The amount of the FAS titrant of 0.545 N added was 37.8 mL and 10.7 mL for blank and sample, respectively. Determine the COD of the wastewater when the volume used for the titration is 200 mL but was diluted 5 times before conducting the COD test. (2 marks) b. COD for a domestic wastewater normally ranged between 200 mg/L and 70 mg/L. Based on (a), does the COD of this wastewater falls under this range? Explain your observation. (2 marks) c. Then, you were asked to find out the biodegradability of this wastewater by conducting a 5-day biochemical oxygen demand (BOD5). A good indication for a biodegradable wastewater would have a COD/BOD ratio of 2 and above. Here, 55 mL of sample was employed for the test where the measured dissolved of oxygen at day 0 was 7.7 mg/L and 2.3 mg/L, respectively. Assess if the wastewater is biodegradable. (3 marks)