[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Testing B.O.D.

A question for the Chemists....

Tests for Biological (Biochemical?) Oxygen Demand, B.O.D., call for
measuring and comparing the dissolved Oxygen levels before and after (5
days) incubation of a sample of water. From the LaMotte Website I obtained
the following:

BIOCHEMICAL OXYGEN DEMAND (BOD)  This is a determination of the amount of
organic material in  wastewater by measuring  and comparing the dissolved
oxygen content before and after incubating the sample for 5  days at 20C.
All reagents, including seed  capsules and glassware needed to perform this
test are included in the kit. Incubator and DO meter are not included. See
p. 52 for BOD  accessories.

LaMotte sells test kits for both Dissolved Oxygen and B.O.D. - I have the
Dissolved Oxygen Test Kit but not the one specifically designed to measure

My question is: how close an approximation of the B.O.D. can I get without
using LaMotte's special test kit (which contains "seed capsules") if I
merely use their Dissolved Oxygen Test Kit and maintain a sample of water
(in the dark) at 20C for 5 days, i.e. - If I measure the D.O. in an aquarium
on Day 1 and then take another sample and keep it in the dark at 20C for 5
days and then measure the D.O. in that sample on Day 5? Is there something
special in the "seed capsules" that are used in the B.O.D. kit or would the
organics and bacteria naturally in the aquarium water be sufficient to
provide at least a ballpark figure for B.O.D. in the tank?

Last Sunday, the D.O. level in one of my tanks was measured at 7.0 ppm O2. I
took another water sample and kept it in the dark at 20C for 5 days. Today
(Day 5), I measured the D.O. in that sample and recorded the D.O. at 6.2 ppm
O2. Am I correct in assuming that the B.O.D. in the aquarium is 0.8 ppm O2?
If this is an accurate measurement of the B.O.D., how would this rate as an
indicator of the health of the aquarium (the 0.8 ppm reading)?


James Purchase
Toronto, Ontario
jpurch at interlog_com