Formaldehyde Removal from Airstreams Using a Biofilter with a Mixture of Compost and Woodchips Medium

Abstract

The performance of a laboratory-scale biofilter packed with a mixture of compost and woodchip on formaldehyde removal from polluted air streams was investigated. The reactor was inoculated with aerobic sludge as a source of bacteria, obtained from a municipal wastewater treatment plant. A nutrient solution was daily added to the reactor media. An airflow containing different concentrations of formaldehyde (from 20+/-2 to 276+/-5 mg m(-3)) was introduced into the reactor. In inlet formaldehyde concentration, an average removal efficiency and elimination capacity of 91 and 0.36 g m(-3) h(-1) were attained, respectively, at180 s empty bed residence time (EBRT). After acclimatization of the system for increased formaldehyde concentrations of up to 276+/-5 mg m(-3) and for EBRT of 180 s, those values were stabilized at around 72 and 3.98g(-3) h(-1), respectively. The experimental results showed that the system was effective for a high loading rate of formaldehyde with an acceptable EBRT. Compared to the application of compost alone as a media, a mixture of compost and woodchip (50/50v/v) enhanced the performance of the biofilter. The most predominant microorganism involved in the biodegradation of formaldehyde was a species of citrobacter called Citrobacter freundii, an aerobic gram-negative bacillus. Pressure drop of the reactor over the entire operations was about 1 mm(H2O)m(-1).