Because the initial DO is determined shortly after the dilution is made, all oxygen uptake occurring after this measurement is included in the BOD measurement. Minimize reduction of BOD by analyzing the sample promptly or by cooling it to near freezing temperature during storage. However, even at low temperature, keep holding time to a minimum. Continuous stirring replenishes oxygen to the sample. The BOD rate can be observed daily without disturbing the sample.
Carbon dioxide is produced when microorganisms oxidize organic matter within the sample.
The CO 2 must be removed from the system so the measured pressure difference is proportional only to the amount of O 2 consumed. Lithium hydroxide crystals, placed on the seal cup of each sample bottle prior to testing, remove the CO 2 . Place the bottles on the chassis of the BODTrak and connect the appropriate tube to the sample bottle. Firmly tighten the cap. Each tube is tagged with the channel number and the channel number setup will be reflected on the control panel.