YSI BOD Analyst Pro - Manual (Page 29)

YSI BOD Analyst Pro ® User Manual 29
SECTION 3 SEEDING SAMPLES
3.1 WHY SEED?
Seeding is necessary when there are insufficient microbes present in the sample to adequately
deplete oxygen during the course of the test. Adding small amounts of microbes promotes the
depletion of oxygen to allow accurate quantification of the oxygen depletion.
Different samples need different levels of seed. Seeding is common with an effluent sample that
has been chlorinated. The seed material can come from the plant's influent, from some
intermediate point in the process, or from commercially available seed packets. Dilution blanks
should never be seeded and obviously the seed control sample is the seed and would not require
additional seeding.
If you do not seed in your application then ignore this section, but be sure that you do not fill in
the Seed Control Sample Name or Seed Quantity in ml fields on any Sample Setup Form.
3.2 SEED CONTROL SAMPLE
In a seeded sample both the sample and the seed contribute to the oxygen depletion. Since the
BOD of the sample is the value of interest the contribution of the seed material must be
subtracted.
To compensate for the
seed effect you must
run several dilutions of
the seed material itself.
This sample is called
the "Seed Control
Sample." You must
assign the seed control
sample in the Seed
Control Sample
Name field on the
Sample Setup Form.
NOTE: In the Sample
Setup Form shown
Influent has been
assigned as the seed
for Effluent.