Activated sludge degradation of adipic acid esters.

The biodegradability of three aliphatic adipic acid diesters and a 1,3-butylene glycol adipic acid polyester was determined in acclimated, activated sludge systems. Rapid primary biodegradation from 67 to 99+% was observed at 3- and 13-mg/liter feed levels for di-n-hexyl adipate, di(2-ethylhexyl) adipate, and di(heptyl, nonyl) adipate in 24 h. When acclimated, activated sludge microorganisms were employed as the seed for two carbon dioxide evolution procedures, greater than 75% of the theoretical carbon dioxide was evolved for the three diesters and the polyester in a 35-day test period. The essentially complete biodegradation observed in these studies suggests that these esters would not persist when exposed to similar mixed microbial populations in the environment.

Tissue residues from subacute oral feeding of polychlorinated biphenyl dielectric fluids.

The results of this study can be summarized as follows: (1) Monochlorobiphenyl and the 30%-chlorinated biphenyl MCS 1043 did not accumulate in the lipid reservoir of the rats when fed at 25 ppm and 100 ppm in the diet. This result indicates that mono-, di-, and trichlorobiphenyls are readily metabolized and/or excreted under the conditions of this study. (2) Although a fraction of the ingested Aroclor 1242 and Aroclor 1016 was stored in the rats' lipid reservoir, most of this residue was depleted after the rats had been on the basal laboratory diet for several weeks. (3) Residues of Aroclor 1016 accumulated more slowly and to a significantly lesser extent than those of Aroclor 1242. During the recovery period these PCB residues decreased to lower values for Aroclor 1016. This result indicates that a product containing reduced amounts of the more highly chlorinated PCBs should have improved environmental compatibility.