How should effluent samples for BOD measurement be handled?
If analysis begins within 2 hours of sample collection, the sample does not need to be cooled. Otherwise, the sample must be cooled to <4°Cimmediately after it has been taken.
The time to analysis must not exceed 6 hours. If this is not possible, the duration and temperature of storage must be noted. The sample must not be stored for more than 24 hours.
The sampling volume is at least one liter.
If possible, the sample should not be frozen. Deep-frozen samples result in lower measured values (up to 10% lower). The reason for this is again due to the fact that a biological process is being analyzed: Deep-frozen cells can burst and, thus, damage the microorganisms. This inevitably causes the BOD value to fall.