Evaluation of anionic surfactant removal by anaerobic degradation of commercial laundry wastewater and domestic sewage

An expanded granular sludge bed reactor was evaluated for the anaerobic digestion of commercial laundry wastewater and domestic sewage focused on the removal of linear alkylbenzene sulfonate (LAS). The reactor was operated in three stages, all under mesophilic conditions and with a hydraulic retention time of 36 h. At stage I, the laundry wastewater was diluted with tap water (influent: 15.3 ± 4.9 mg LAS/L); at stage II, 50% of the feed volume was domestic sewage and 50% was a mixture of tap water and laundry wastewater (influent: 15.8 ± 4.9 mg LAS/L); and at stage III, only domestic sewage was used as a diluent of the laundry wastewater (influent: 24.1 ± 4.1 mg LAS/L). Due to the addition of domestic sewage the organic compounds content and LAS in the influent increased. Under such conditions, it was observed that LAS removal rate decreased from 77.2 ± 14.9% (stage I) to 55.3 ± 18.4% (stage III). Statistical tests indicated that the decrease of the LAS removal rate was significant and indicated a correlation between the removal of LAS and specific organic loading rate. The analysis of 16S rRNA gene sequencing revealed genera similar to Geobacter, Desulfovibrio, Syntrophomonas, Syntrophus, Desulfobulbus, Desulfomonile, and Desulfomicrobium, which were related to the degradation of LAS.