28. Determination of Oxygen Demand

Oxygen demand is a commonly used parameter to evaluate the potential effect of organic pollutants (e.g., from a food processing facility) on either a wastewater treatment process or a receiving water body. Because microorganisms utilize these organic materials, the dissolved oxygen is greatly depleted from the water, which can have a detrimental effect on fish and plant life. This chapter focuses on the two main methods used to measure the oxygen demand of water and wastewater: biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Described in the chapter are the principles, procedures, applications, and limitations of each method. The BOD test measures the amount of oxygen required by microorganisms to oxidize the biodegradable organic matter present in water and wastewater. The COD method determines the quantity of oxygen consumed during the oxidation of organic matter in water and wastewater by potassium dichromate. The COD test can be used to monitor routinely the biodegradability of organic matter in water and wastewater if a relationship between COD and BOD has been established.