PROGRAMS AND PLANS- -Analytical Methods: Bateriology- Identification of coliform colonies; nutrient medium for the fecal coliform determination
  

                                       April 20, 1971

QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 71.07


Subject: PROGRAMS AND PLANS- -Analytical Methods: 
         Bateriology- Identification of coliform colonies; 
         nutrient medium for the fecal coliform determination

It has come to our attention that several Division offices have 
experienced difficulty identifying coliform colonies when using 
the membrane filter technique. The following definition from 
"Standard Methods for the Examination of Water and Wastewater, " 
12th edition, 1965, p. 613 should be used to identify coliform 
colonies when the membrane filter technique is employed:

"All organisms which produce a dark colony (generally purplish-
green) with a metallic sheen within 24 hr of incubation are 
considered members of the coliform group. The sheen may cover the 
entire colony or appear only in a central area or on the 
periphery."

If difficulty is encountered in differentiating between coliform 
and non-coliform colonies, it is recommended that a verified 
membrane filter test be completed. An abbreviated coliform 
verification procedure from a 1969 Dept. of Interior (FWPCA) 
Training Manual, "Current Practices in Water Microbiology," is 
attached.

This office has recently received requests from several districts 
for authorization to use commercially available nutrient ampoules 
for the fecal coliform determination. Current WRD policy prohibits 
use of ampoules of commercially prepared fecal coliform medium. 
The prepared ampoules of fecal coliform medium have been tested 
recently by the Environmental Protection Agenc, Division of Water 
Hygiene, and found to be unsatisfactory quality control of batches 
has proven to be poor and the medium has been found to be toxic. 
Therefore, for the fecal coliform determinations preparation of a 
nutrient medium using a commercially available dehydrated medium 
is required. Difco Laboratories BACTO-m-EC Broth Base (Code 0883) 
or equivalent is recommended. A simplified procedure for 
preparation of fecal coliform medium by Theodore A. Ehlke, WRD, 
Albany, New York, is presented on p. 6-7 of the Oct.-Dec. 1970; 
Jan.-Mar. 1971 WRD Bulletin.

If you have questions concerning these items, please feel free to 
call this office.


                                    W. H. Durum

Attachment

WRD Distribution:
A, B, FO, PO