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Sample point for biological growth?

P peteMember
Where is the best place to sample for biological growth?

Here is the situation:
Main turbine lube oil reservoir (18,000 gal cap).
Sampled one a month for usual test (from rep. sample point).
Sampled every 6 months for everything, including biological growth, from all our sample points.
Usual water content is appx. 30ppm.


Here is the million dollar question: Should we be sampling for biological growth from the bottom drain, instead of our rep. sample point?
Our thinking is any water we have in the system will separate to the bottom of the reservoir, in low turbulence locations, which is where any growth will take place.

Thanks for any input.
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O oiley1Member
From my experieince the best location will be, as you suggeted at the bottom of the tank. From my experieince sampling anywhere in the live part of the system, particularly when water is at a normal level such as 30ppm, rarely produces results even though there may be bacteria in the system. Treat fuel storage in the same manner.

Cheers
B billquesnelMember
You will certainly do better by sampling from the bottom of the reservoir, however, most likely any biological growth is going to stay relatively close to the interface between the water and the oil.

Any 'bugs' are going to live in the water phase, but will most likely be subsisting off something in the oil (e.g. sulphur), and therefore will stay close to the oil. Your best bet is to sample from the interface if possible, or to drain off all the water and have that analysed if practical.
H hussamadeniMember
Pete,

Your are right first time. And as Oiley 1 suggests bottom of the tank. Algae and bacteria proliferate in "still environment" where there is minimum movement or activity. Further, mulsifiers (phenolic compounds to bind water and oil molecules) attract bacteria. In this instance (Turbine oil) however has a very low or no additive package and not likely to attract bacteria.

Hussam Adeni
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