Relationship between co-substrate and microbial composition in the degradation of anionic surfactant

Different carbon sources were used as co-substrate to evaluate the removal of linear alkylbenzene sulfonate (LAS) from laundry wastewater, as well as the related microbial community. An anaerobic fluidized bed reactor (AFBR) was operated in three stages, after the biomass adaptation without LAS (stage I). Those stages were differentiated by the co-substrate supplementation: stage II, sucrose plus ethanol, stage III, only ethanol, stage IV, no co-substrate. Laundry wastewater was diluted to obtain approximately 20 mg.L-1 of LAS in the AFBR influent. The replacement of sucrose plus ethanol in the substrate composition with only ethanol favored the removal efficiency of LAS, and that removal remained high after the co-substrate was removed (Stage II: 52%; Stage III: 73%; Stage IV: 77%). Those results suggest that the microbial community favored by only ethanol was more capable of degrading LAS than the community favored by sucrose plus ethanol. The presence of sucrose favored the Comamonadaceae family (stage II). After the sucrose was removed (stage III), the Comamonadaceae family decreased and the Rhodocyclaceae family increased. Some genera from the Rhodocyclaceae family are possibly related to LAS degradation. The relative abundance of these genera increased in stage IV in the absence of the co-substrate. Therefore, only ethanol is suggested as a more suitable co-substrate than sucrose plus ethanol in the co-metabolic process of LAS removal.