Things to remember during Biochemical Oxygen Demand Determination

Things to Remember during Biochemical Oxygen Demand Determination

Things to remember during Biochemical Oxygen Demand Determination
All samples must be kept at or below 4°C until the sample is ready to be tested.

Because microbes are most active between pH values of 6.5 and 7.5 all samples must be neutralised to a pH within this range.

It is also important to remove any residual chlorine from the sample before running the experiment. Failure to do so would kill the valuable bacterial source.

A seed source (bacterial control) must be prepared from a commercial product, or from a diluted portion of waste water. This seed source will be the source of bacteria added to the sample. The bacteria are added to oxidise the biodegradable organic matter in the sample. This is the backbone of the experiment. If bacteria fail to oxidise the organic matter, then the test will not work. It is also important to run a seed control to account for any BOD in the seed material.

Because the BOD concentration in most waste water exceeds the concentration of DO available in air saturated samples, it is necessary to dilute the samples being tested. This is done by using properly prepared dilution water. This dilution water contains nutrients such as nitrogen, phosphorus, and other trace metals necessary for microbial growth. The dilution water is also buffered to ensure that the pH of the sample remains in a suitable range for microbial activity.

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