L1 /
15
CH3041
WATER QUALITY II
• Chemical Oxygen Demand (COD) mg /L
(i)
chemically degrade the organic material in water by reacting with excess oxidising agent (eg. H+ / Cr2O72-) leave
for 2h,
(ii) back
titrate with Fe(II) to find the excess of Cr2O72-. 1 mol of Cr2O72- = 1.5 mol of O2.
»2 mg /L
unpolluted 10000 mg /L wool scouring
• Biochemical Oxygen Demand (BOD) mg
/L
amount of O2 used when organic matter in a
set volume of water is degraded biologically
xxx mg /L , used for monitoring , 5 day test
set volume of water is degraded biologically
xxx mg /L , used for monitoring , 5 day test
