The Biochemical Treatability Index
(BTI) Concept
C. HUGH THOMPSON, Sanitary Engineering Specialist
Technical Service and Development
The Dow Chemical Co.
Midland, Michigan
D. W. RYCKMAN, Professor
JAMES C. BUZZELL, JR., Assistant Professor
Department of Civil and Environmental Engineering
Washington Universtiy
St. Louis, Missouri
INTRODUCTION
The need for the development of an index of the treatability of organic
chemicals was documented by a President's Science Advisory Committee. The
Committee's report states that the, ". . . development of a method for assigning a
numerical index of chemical pollution to water samples" be initiated (1). Such an
index would aid engineers, scientists, lawyers, management, as well as others, in the
decision making and the communication of information with regard to the relative
behavior of organic chemicals. Industry has indicated support of a concept of indexing as a fair basis of comparison (2).
The index concept reported in this study is designed to be useful as a
common yardstick of the degree of treatment feasible. It is conceivable that this
concept, using the technique developed in this study or a modification of it, would
be useful as a basis of decision in either industrial or municipal waste treatment
operation. At present, many reported results vary widely (3) depending on the
techniques used. The need for uniform, standardized techniques of measuring bio-
degradability is clear.
Conceptually, Figure 1 demonstrates that parameters were measured for each
organic chemical exposed to lyophilized activated sludge which had been revived
and the responses evaluated relative to a primary standard into a ranking index
(BTI) of biodegradability.
PURPOSE OF STUDY
The initial purpose of this investigation was to develop an index to predict
the relative biological treatability of organic chemicals under well-defined conditions.
The purpose of this paper is to submit this concept of indexing for discussion and
evaluation by the profession. The biochemical treatability index (BTI) was designed
with the following five criteria in mind: 1) The technique should be amenable to
most organic chemicals; 2) The treatment system should be well-defined and simulate
a secondary aerobic biological process; 3) The results should be reproducible and
reliable;4) The tests should be economically feasible; and 5) The technique should be
usable by individuals of varied backgrounds.
-413-