Appendix E to Part 403 - Sampling Procedures
40:31.0.1.1.4.0.1.21.3 : Appendix E
Appendix E to Part 403 - Sampling Procedures I. Composite Method
A. It is recommended that influent and effluent operational data
be obtained through 24-hour flow proportional composite samples.
Sampling may be done manually or automatically, and discretely or
continuously. If discrete sampling is employed, at least 12
aliquots should be composited. Discrete sampling may be flow
proportioned either by varying the time interval between each
aliquot or the volume of each aliquot. All composites should be
flow proportional to either the stream flow at the time of
collection of the influent aliquot or to the total influent flow
since the previous influent aliquot. Volatile pollutant aliquots
must be combined in the laboratory immediately before analysis.
B. Effluent sample collection need not be delayed to compensate
for hydraulic detention unless the POTW elects to include detention
time compensation or unless the Approval Authority requires
detention time compensation. The Approval Authority may require
that each effluent sample is taken approximately one detention time
later than the corresponding influent sample when failure to do so
would result in an unrepresentative portrayal of actual POTW
operation. The detention period should be based on a 24-hour
average daily flow value. The average daily flow should in turn be
based on the average of the daily flows during the same month of
the previous year.
II. Grab Method
If composite sampling is not an appropriate technique, grab
samples should be taken to obtain influent and effluent operational
data. A grab sample is an individual sample collected over a period
of time not exceeding 15 minutes. The collection of influent grab
samples should precede the collection of effluent samples by
approximately one detention period except that where the detention
period is greater than 24 hours such staggering of the sample
collection may not be necessary or appropriate. The detention
period should be based on a 24-hour average daily flow value. The
average daily flow should in turn be based upon the average of the
daily flows during the same month of the previous year. Grab
sampling should be employed where the pollutants being evaluated
are those, such as cyanide and phenol, which may not be held for an
extended period because of biological, chemical or physical
interaction which take place after sample collection and affect the
results.
[49 FR 31225, Aug. 3, 1984]