B.O.D (Biological Oxygen Demand): It shows the deficiency of oxygen in the water. Pollution in water due to presence of organic biodegradable waste causes increase in number of microbes. These microbes consumes maximum dissolved oxygen. This results in deficiency of dissolved oxygen for higher organisms.Increased BOD is an indicator of water pollution. Daphnia is the indicator of B.O.D.
BOD Stands for (Biological Oxygen Demand): It shows the deficiency of oxygen in the water.
COD means Chemical Oxygen Demand,it is define as amount of oxygen required to decompose organic compounds (biodegradable and non- biodegradable material)with the help of strong chemical like potassium dichromate.