September 1, 1976



QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 76.25-T

Subject: WATER QUALITY: Analytical Methods--Microbiological

Attached is one copy each of the following provisional methods:


	1. Total coliform bacteria (membrane filter method), immediate
	incubation test.

	2. Fecal coliform bacteria (membrane filter method).

	3. Fecal streptococcal bacteria (membrane filter method).
	These provisional methods update and supersede the similar
	methods for indicator bacteria described in "Methods for
	Collection and Analysis of Aquatic Biological and
	Microbiological Samples" (Slack, K. V., and others, 1973,
	U.S. Geol. Survey Tech. Water-Resources Invest., Bk 5, Chap
	A4, p. 35-54). The methods are to become effective on
	October 1, 1976, with the provisions stated below.

Based on evidence published in the technical literature and on
studies conducted by the Water Resources Division, the Millipore
HC (0.7-um mean pore size), or equivalent, membrane filter will
become the endorsed filter for the determination of fecal coliform
bacteria. It has been shown that results obtained on 0.7-um
membrane filters are closer approximations of the true values for
bacterial concentrations in water than those results obtained on
0.45-um membrane filters. Continued use of the 0.45-um membrane
filter for the determination of fecal coliform bacteria after
October 1, 1976, is approved only for (1) incompleted
interpretive projects where consistency of methodology and results
are, required ln order to fulfill the project's objectives and (2)
programs required by public law to use the 0.45-um membrane
filter. STORET parameter code number 31625 has been assigned to
"Coliform, fecal, 0.7-um MF, M-FC media at 44.5 deg. C
(colonies/100 ml)."

The Quality of Water Branch has ordered a supply of Millipore HC
filters (catalog no. HCWG 047 S1) at a bulk discount rate. Each
District will receive automatically 600 of the filters following
delivery to the Branch from the manufacturer. Future orders for
Millipore HC filters should be submitted to the Atlanta Central
Laboratory after October 1, 1976.

It should be noted that option is given for the use of either the
Millipore HA (0.45-um mean pore size) or Millipore HC (0.7-um mean
pore size), or equivalent, membrane filter for the determination
of total coliform and fecal streptococcal bacteria. It should be
further noted that KF agar (rather than M-enterococcus agar) is
the endorsed medium for the determination of fecal streptococcal
bacteria. Continued use of M-enterococcus agar after October 1,
1976, is approved only for incompleted interpretive projects where
consistency of methodology and results are required in order to
fulfill the project's objectives. KF agar and the media for all
other indicator bacterial determinations should be ordered from
the Atlanta Central Laboratory.

Other noteworthy items are as follows: (1) All methods for the
determination of indicator bacteria call for the use of a
peptonephosphate buffer. (2) Dehydrated bacterial media should be
stored no longer than 6 months following receipt from the Atlanta
Central Laboratory. (3) Membrane filters should be stored no
longer than 1 year following receipt. (4) All media older than
6 months and all filters older than 1 year should be discarded.

It is recommended that the enclosed methods be read by all
personnel involved with the collection of water-quality data.
Questions or comments pertaining to the provisional methods should
be directed to the Chief, Quality of Water Branch (Mail Stop 412,
Reston, Virginia). Questions pertaining to the ordering of
Millipore HC filters and bacteriological media should be directed
to the Chief, Atlanta Central Laboratory (WRD, Doraville,
Georgia).




					R. J. Pickering

Attachments

WRD Distribution: A, B. FO, PO