Efficiency of Activated Sludge Process (Extended Aeration) in Removal of Linear Alkyl Benzene Sulfonate (LAS) from Municipal Wastewater - Case Study: Wastewater Treatment of Paveh City.

Background & Objectives: Surfactants are organic chemical compounds that increase cleaning power of water through reducing surface tension. Linear alkyl benzene sulfonate (LAS) as an anionic surfactant may cause environmental problems especially eutrophication phenomenon in surface waters. The purpose of this study is to evaluate efficiency of extended aeration process in removal of LAS in Paveh city. Methods: This descriptive cross-sectional study was carried out for 12 months in 2008. Sampling was done at 8:00 am, 10:00 am, and 12:30 pm. Methylene blue method was used to determine LAS. In total, 108 samples were taken from inlet, outlet, and return sludge during the study. All the sampling and testing methods were performed according to standard method guidelines. Results: The results showed that efficiency of the system in removal of LAS, COD, and TSS in the warm seasons (i.e. April to September) were significantly higher than the cold seasons (p