Classification of the Biodegradation Factors of Linear Alkylbenzene Sulfonate.

The conditions that significantly affect the biodegradability of linear alkylbenzene sulfonate (LAS) based on previous studies were categorized. Among these previous studies, we focused on those that used activated sludge and river water as inocula in biodegradation studies. Analyzing the results of these studies revealed two types of methylene blue active substances (MBAS) removal curves in primary biodegradation, and the study conditions that differentiated the two types were analyzed, along with verification studies. The effects of the LAS concentration and interfacial activity during biodegradation were analyzed to set the concentration of LAS in this study. Surface tension was measured as an indicator of interfacial activity and biodegradation was measured by oxygen demand. Two widely used surfactants, alcohol ethoxylate and sodium dodecyl sulfate, were evaluated to clarify the significance of the effective concentration range of LAS. The concentration of LAS was set at 10 or 20 mg/L in the verification study. Acclimatization and the concentration balance of LAS and river water were the strongest factors in studies using activated sludge and river water, respectively. Our classification chart may be helpful in analyzing and comparing the conditions of previous and current studies. Such understanding of the study conditions and practical evaluation may aid in avoiding misleading environmental impact assessments of LAS.