Background and Objective: This study investigated the efficiency of an anoxic baffled reactor (AnBR) system for the biological treatment of synthetic wastewater containing sodium dodecyl sulfate (SDS) as a representative anionic surfactant, with the goal of enabling safe discharge into the environment.
Materials and Methods: The research aimed to examine the effects of SDS concentration as a substrate, hydraulic retention time (HRT), and the type of electron acceptor (nitrate or organic materials) in the AnBR reactor. Daily measurements of influent and effluent wastewater were conducted to assess surfactant, chemical oxygen demand (COD), and nitrate levels.
Results: The average COD removal efficiencies at SDS concentrations of 200, 250, 350, and 500 mg/L were 99.6%, 99.8%, 99.6%, and 99.3%, respectively, under steady-state conditions. The SDS removal efficiency for all concentrations was 99.8 ± 0.2%. As the HRT decreased from 24 to 4 hours, the COD removal efficiency dropped from 99.4% to 90.9%. At an SDS concentration of 250 mg/L and an HRT of 4 hours, the effluent SDS concentration was 11 mg/L, which meets the discharge standards for surface water (1.5 mg/L). The removal of nitrate from the influent indicated a significant decrease in system efficiency, demonstrating that nitrate was consumed as an electron acceptor and SDS was degraded under anoxic conditions. PCR testing revealed that Bacillus species were the dominant bacteria in the AnBR.
Conclusion: Given the high removal efficiencies of SDS and COD, this process can be recommended for the degradation of anionic surfactants in wastewater from industries producing such pollutants.
