Question

Distinguish between BOD and COD. 

Answer 1

BOD	COD
1.1t means the oxygen demand of bio-degradable pollutants only.	it measures the oxygen demand for bio-degradable pollutants along with non-biodegradable pollutants.
2.Less stable measurement method as it uses micro-organism which are susceptible to pH, temperature and other variable in the water.	More stable measurement method as it uses potassium dichromate which oxidises regardless of water condition.
3. Siow process. It takes 5 days.	Fast process. It takes 2-3 hours.
4.BOD values are generally less than COD values.	COD values are generally greater than BOD values.
5.`BOD =(DO_b DO_i)xx(" Volume of undiluted sample")/(" Volume of diluted sample.")`	`COD = ((V_1-V_2 ) xx N xx 8000) /Y`