40 CFR 417.171 - Specialized definitions.
For the purpose of this subpart:
(c) The term surfactant shall mean those methylene blue active substances amenable to measurement by the method described in “Methods for Chemical Analysis of Water and Wastes,” 1971, Environmental Protection Agency, Analytical Quality Control Laboratory, page 131.
(d) The term BOD7 shall mean the biochemical oxygen demand as determined by incubation at 20 degrees C for a period of 7 days using an acclimated seed. Agitation employing a magnetic stirrer set at 200 to 500 rpm may be used.