Refractory waterborne organics resist biodegradation, accumulate in the environment and can inhibit life forms. This research develops laboratory techniques for, and interpretations of, a Refractory Index (R.I.) to quantitatively assess the persistency of refractory organics and uses R.I. to evaluate some 38 industrial, natural and combined organics. R.I. values close to 1.0 characterize readily biodegradation; R.I. values near zero indicate refractory organics; negative R.I. values indicate inhibitors. The coefficient of variation for R.I. values is 13%. Since negative R.I. values are of qualitative significance only, a Biological Inhibition Value (B.I.V.) is developed and used to quantitatively assess those organics found to interfere with the biochemical tests used, long-term ultimate Warburg Respirometer determinations. In a few cases, confirmation of the R.I. interpretation was performed using a model activated sludge unit and by specific analysis. Correlations between oxygen demand tests (BOD5, BODu, TOD) and organic parameters (TOC, TN) are presented. Suggestions for required pretreatments of industrial wastewaters before allowing discharge into municipal sewage treatment plants are included as an application of the Refractory Index criterion. The bibliography contains 49 references.

"Prepared by Environmental Engineering Program, Civil Engineering Department, University of Connecticut, Storrs, Connecticut under Grant No. R803231-01-05." "Includes appendix." "August 1977." Includes bibliographical references (pages 40-44).