Background and objectives: Formaldehyde is one of the compounds widely used in various industries hence, its discharge into the effluent is unavoidable. Exposure to formaldehyde has a significant health effects. To prevent these issues, treatment of wastewater containing formaldehyde is necessary. The purpose of this study was to determine the performance of aerobic sequencing batch reactor (SBR) in removing formaldehyde from wastewater. Methods: We used a SBR having a total volume of 6.15 liters and an effective volume of 4 liters. The formaldehyde and COD removal efficiency of SBR was evaluated by applying loading rate of 0.031 to 0.156 kgCOD/m3.h. Four cycles of 6, 8, 10, and 12 hours were considered to investigate retention time effect onto the reactor efficiency. Results: Acclimation of microorganism with formaldehyde was achieved after about 30 days. We found that a retention time lower than an hour is not enough for achieving an acceptable efficiency. The maximum removal efficiency (90.52% for COD and 95.32% for formaldehyde) was observed at organic loading rate of 0.031 kg COD/m3.h and 12 hour retention time. The removal efficiency decreased to 46.44% for COD and 69.12%, for formaldehyde with increasing the organic loading rate to 0.156 kg COD/m3.h. The maximum concentration of MLSS was measured 2863 mg / L at organic loading rate of 0.091 kg COD/m3.h. Conclusion: The results showed that SBR could be applied as a practical, effective, and reliable technology for treatment of wastewater containing formaldehyde.
