MIL-HDBK-1005/16
e)
Grab samples are necessary to meet permit
requirements.
f)
Information on maximum, minimum or variability is
desired.
11.5.3.2
Composite Samples.
Use composite samples when:
a)
Determining average concentrations
b)
Calculating mass per unit time loading
11.6
Methods of Sample Collection. Samples can be collected
manually or with automatic samplers. Whichever technique is
adopted, the quality of laboratory data is a function of the care
exercised in sample collection. Optimum performance will be
obtained by using trained personnel.
11.6.1
Manual Sampling. There is minimal initial cost
involved in manual sampling and a certain amount of manual
sampling is unavoidable. But the technique can become costly and
time consuming for collection of routine composite samples.
Table 19 lists some of the advantages and disadvantages of manual
and automatic sampling.
11.6.2
Automatic Samplers. Automatic samplers are used
because of their cost effectiveness, reliability, and improved
capabilities (i.e., they permit greater sampling frequency). In
some cases, the increased sampling requirements of NPDES and
other regulatory permit programs virtually mandate automatic
samplers. Automatic samplers are available with widely varying
levels of sophistication, performance, mechanical reliability,
and cost. No single automatic sampling device is ideally suited
for all situations. For each application, the following
variables should be considered in selecting an automatic sampler:
a)
Variation of wastewater characteristics with time
b)
Variation of flow rate with time
c)
Specific gravity of liquid and concentrations of
suspended solids
d)
Presence of floating materials
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