Characteristics of MEG Removal from Industrial Wastewater by Sequencing Batch Reactor (SBR)

Background: MEG is extensively applied in the sour gas industry as hydrate inhibitor. It is toxic in oral drinking and serious injury or death may result from swallowing of pure ethylene glycol and poses a potential hazard to the environment through impact soil. Glycols are harmful to aquatic life. There is a little information about digestion of MEG in aerobic reactor. Therefore, the feasibility of MEG removal in aerobic reactor was investigated. Materials and method: Biodegradation of MEG was done in an aerobic SBR reactor with the capacity of 2000 mL and sanitary wastewater as primary required microorganism. The experiments were done in the three stages. In stages 1 and 2, 500 mL of reactor content was drawn-off and solutions contain 500 mL of 0.073 (wt %) of MEG (for first stage) and 0.201 (wt %) of MEG (for second stage) were added to reactor. In stage 3, 500 mL of wastewater of MEG removal unit in the 2nd refinery of South Pars Gas Company, Iran with the concentration of 4.021 (wt %) of MEG was added to 1500 mL of reactor content. Feed of stage 1 was pure MEG that was diluted in de-mineralized water but Feed of stage 2 was a dilution of industrial feed of stage 3. Results: In stage 1, after four days, removal efficiency more than 80% was obtained. In stage 2 after six days, efficiency of 20% was obtained. In stage 3, after seven days, more than 70 percent of MEG removal was obtained. Conclusion: by increasing residence time, the removal efficiency of the reactor could be increased acceptably. Therefore, the MEG solution of more than 4 (wt %) of MEG can be treated biologically.