Biological oxygen demand (BOD5)
The BOD55 indicates the amount of oxygen which bacteria and other micro organisms consume in a water sample during the period of 5 days at a temperature of 20 °C to degrade the water contents aerobically. BOD5 is thus an indirect measure of the sum of all biodegradable organic substances in the water. The BOD5 indicates how much dissolved oxygen (mg / l) is needed in a given time for the biological degradation of the organic wastewater constituents. This value is an important parameter for the assessment of the degree of pollution that wastewater represents for the environment (receiving water). Since the wastewater contents in the receiving water are degraded by the bacteria therein, the oxygen is completely or partly drawn from the water. If the limit values are exceeded, creatures breathing oxygen (crabs, fish, etc.) may die.