Hanna Instruments HI 4421 User Manual

Page 42

Biochemical oxygen demand (BOD) is an indicator for the concentration of biodegradable organic matter
present in a sample of water. It can be used to determine the general quality of the water and its degree of
pollution. BOD measures the rate of oxygen uptake by microorganisms in a sample of water at a fixed
temperature and over a given period of time. To ensure that all other conditions are equal, a very small
amount of microorganism seed is added to each sample being tested. This seed is typically generated by
diluting activated sludge with deionized water. The samples are kept at 20 ºC in the dark and tested for
dissolved oxygen (DO) after five days. The loss of dissolved oxygen in the sample, once correction have been
made for the degree of dilution, is called the BOD

Before running an BOD measurement remember to set the BOD method configuration from the BOD setup menu
and make sure the instrument has been calibrated on DO.

To take the BOD measurement:
• Press

and then

to select BOD measure

mode.

• Press

to access the BOD data management screen.

• Press

to add a new sample or a new seed. Select

between

and

• Press

to repeat the initial DO measurement.

• Press

to access the list of the samples and seeds

available. The seed records will have the symbol “*” dis-
played before the bottle ID.

BOD MEASURE

BOD MEASUREMENT

MENT