Environmental Engineering Reference
In-Depth Information
For compliance checks with organisms less than 50
ʼ
m in minimum dimension
and greater than or equal to 10
m in minimum dimension, and for indicator
microbes only small water quantities need to be sampled. This can be achieved
by using a pump or different water samplers. In case the pump is already chosen
to sample for organisms greater than or equal to 50
ʼ
m in minimum dimension,
where 100 l may be fi ltered, at the same time additional 5-6 l of a continuous
drip sample (see section “ Recommended Sample Quantity ”) may be collected in
a bucket for checking organisms less than 50
ʼ
ʼ
m in minimum dimension and
greater than or equal to 10
m in minimum dimension and for indicator microbes.
The recommended indicator microbes sample of 1 l may be subsampled from
this bucket.
ʼ
Plankton Net for In-Tank Sampling
For in-tank sampling D-2 standard compliance control sampling it is recommended
to lower the net to the maximum accessible tank depth, wait a minute and retrieve
the net by hand with an approximate speed of 0.5 m per second. The plankton net
cod-end should be emptied into a sample bottle and the process be repeated to meet
the desired water volume for sampling.
Pumps for In-Tank Sampling
A pump can be used to obtain an integrated sample from three different depths or
alternatively from the entire water column. The pump should be lowered to three
desired depths, i.e., the surface, somewhere in the middle of the water column, and
possibly close to the tank bottom or to the deepest point accessible. From each depth
water needs to be pumped up. Alternatively, when lowering the pump, water may
also be pumped out constantly from the surface water to the deepest point accessi-
ble. The limiting factor to be considered is the pumping head, which may not enable
to pump up water from greater depths. From each of the three desired depths or
constant pumping may be used when lowering the pump to the deepest point acces-
sible in the tank.
Water-Column Sampler for In-Tank Sampling
To obtain an integrated sample from the whole water column, the water column sampler
is lowered to the bottom of the tank or to the deepest point accessible. When lowering
the water column sampler, water will start entering the sampler from its top opening.
The water will be proportionally sampled from the entire water column provided (a) the
sampler is lowered with a constant speed, and (b) the time used to lower the sampler
from the surface to the deepest tank point accessible is the same as the time needed to
fi ll the sampler with water. The water column sampler may need to be lowered down
multiple times until the desired water volume is met.
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