Comparison of MBBR and SBAR in Treating Toxic Formaldehyde Wastewater

Formaldehyde is used in many industrial activities such as adhesives, resins, paper producing and pharmaceutics industries. Due to formaldehyde toxicity for microorganisms, aerobic biological methods were less studied for its treating. Chemical and anaerobic biological methods are often applied for treating wastewaters containing formaldehyde. Recently, some methods such as Fenton and photo-Fenton, photo catalytic degradation, combination of chemical-biological and anaerobic-aerobic biological have been investigated. In this research, formaldehyde removal efficiencies using aerobic biological treatment systems including moving bed biofilm reactor (MBBR) and sequencing batch airlift reactor (SBAR) were compared.Temperature, pH, and dissolved oxygen were adjusted every 6 hours for preparing suitable condition for microorganisms activity. Mixed liquor suspended solid and sludge volume index were measured daily. COD, BOD5, granular diameter, and velocity settling were used for illustrating reactors situation. All of the experiments were accomplished in accordance with the instructions presented in the "Standard Methods for the Examination of Water and Wastewater" [1]. After investigating all methods, the best one was selected regarding to the laboratory facilities. Removal efficiency was determined using COD results. COD removal efficiency The results showed both systems can be used for treating formaldehyde wastewater in low concentrations. The most removal efficiencies were 100% that occurred in concentration of 100 mg/L (Fig. 2). The results of this research in pilot scale showed both systems were capable in removing formaldehyde from wastewater in concentration of less than 300 mg/L with a 24-hour retention time. SBR and MBBR systems can be used as pretreatment units for the treatment of formaldehyde CODs more than 500 mg/L. 5.