BODTrak II Respirometric BOD Apparatus

Respirometric Biological Oxygen Demand (BOD) is a test that measures the quantity of oxygen consumed by bacteria that oxidize organic matter in a water sample. 

The test is used to measure waste loadings at wastewater treatment plants and to examine the efficiency of wastewater treatment.The instrument is sealed to prevent external atmospheric pressure changes in the test bottle. The pressure in the sample bottles is monitored. 

Bacteria in the sample use oxygen when they consume organic matter. This oxygen consumption causes the pressure in the

bottle head space to drop. The pressure drop correlates directly to BOD.

During a test period, stir bars mix the sample and cause oxygen to move from the air in the bottle to the sample. This helps simulate natural conditions.

Carbon dioxide is a result of the oxidation process and can interfere with a measurement. The instrument continuously removes carbon dioxide from the system so that the monitored pressure difference stays proportional to the quantity of oxygen used. Pressure changes in theclosed system are shown graphically in milligrams per liter (mg/L) on a liquid crystal display. The instrument gives 360 uniform data points over the selected time period.

The instrument adjusts for any negative errors produced when heat is applied to a sample. The instrument does not start the test until the temperature gets to equilibrium.