CLAIR N. SAWYER, RICHARD H. BOGAN',
AND
JAMES R. SIMPSON
Massachuseffs lnsfifufe of Technology, Cambridge, M a s s .
The anionic and nonionic detergents used in commerce today appear to be subject to biological attack, but they vary greatly in their susceptibility even among a given class. This variation i s believed to be largely related to differences in chemical structure and molecular size. Adaptation or acclimation of biological forms i s important in evaluating their behavior. Tetrapropylene benzene sulfonate, the most important detergent in terms of current-day use, is extremely resistant to oxidation. A half life of about 16 days in river water under summer conditions is indicated.
DURING
the last few >-car$,jynthetic detergent.. hnve been suspect'ed of being a came of serious frothing in sewage treatment plants and in streams receiving sexage after having been subjected to primary or even complete treatment ( 8 , 18, 14, f7-19). Problems have been most intense at activated sludge plants and in rivers 174th extremely turbulent flow. In addition, there have been several report,s in the literature rlaiming interference in the purification of river n-aters for public or industrial mater supplies ( 4 5 , 1 0 , 1 $ ) . These problems have 1)een particularly challenging to ilariitary engineers because they consider one of their greatest responsibilities to be the protection of our water resources through applicat'ion of the principle of reasonable use as estsblished under Riparian lavi-. Fui tliermore, i t has been somewhat disconcerting to t,hem to find that their best methods of trcatmcnt are not adcquate to satisfactorily remove many modern products of technology, including cert,ain syndets, from doniest,ic and industrial wastes. There have been two schools of t,hought relative to the increased problem of frothing in tretttment~plants and rivers. One ha,s held that it is a natural corollary to the rapidly increasing use of synthetic detergents. The other hits contended t,ha.t t,!ie iritroduction of new and perhaps more biologically r is the cause. During the past f e v years several reports have ap~~e;irecI i n t.hr literature xyhich have helped t o clarify the issues coiiuitierably (3, 7 , 11, 12, .IC). Unfortunately, much of the early work ivas done on retail products sold under various tradc nmics without particular definition of the actual compositioii. I n gener:d i t may be stated t h a t the tendency to cause frothing w r i w gmatjly from product to product ( 13). Some limited evidence iiidicantes that mixtures of a foaming and nonfoaming syndet may result in a mixture with fortified foaming characteristics ( 1 2 ) . This may have particular significance in sewage where all forin,
