Formaldehyde biodegradation using an immobilized bed aerobic bioreactor with pumice stone as a support

The objective of this study is the investigation of formaldehyde degradation in a bioreactor with pumice stone as a support. The reactor was tested at different synthetic wastewater concentrations with total COD of 500, 1000 and 1500 mg/L, respectively, at 24 h hydraulic retention time. The effect of feed composition was tested by changing the CODT/CODFA ratio in order to analyze the impact of formaldehyde concentration. The average formaldehyde and COD removal efficiencies obtained in the reactor were 97.1% and 88%, respectively. The maximum COD and formaldehyde removal efficiencies occurred at the CODT/CODF of 4/1 at CODT=1000mg/L. The effect of toxic shock on reactor performance was examined; the reactor has good resistance against a sudden increase in formaldehyde concentration. The formaldehyde concentration threshold at which toxic effects severely inhibited the biological process was 1370 ppm. So a fixed film bioreactor packed with pumice stone could be recommended for the treatment of formaldehyde-containing wastewater.