Biodegradation of LAS benzene rings in activated sludge

Effluents from continuous flow and from fill and draw activated sludge cultures were analyzed quantitatively for benzene ring content by ultraviolet spectroscopy, with appropriate correction for interference by nitrate ion. C 12 LAS mixture and two of its components in pure form, 3‐phenyl‐ and 6‐phenyldodecane‐ p ‐sulfonates, all showed approximately 90% ring biodegradation under a variety of conditions once acclimation had occurred. When feeds to 3‐phenyl and 6‐phenyl acclimated cultures were interchanged, the characteristics 100% primary biodegradation (methylene blue analysis) proceeded without interruption. However, ring degradation was impaired for 4–7 days until reacclimation was accomplished. Biochemical implications are discussed.