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 differ- ent concentrations of formaldehyde (from 20±2 to 276± 5m g m �3 ) was introduced into the reactor. In inlet formaldehyde concentration, an average removal effi- ciency 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 formalde- hyde with an acceptable EBRT. Compared to the appli- cation 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 in- volved in the biodegradation of formaldehyde was a species of citrobacter called Citrobacter freundii ,a n aerobic gram-negative bacillus. Pressure drop of the re- actor over the entire operations was about 1 mmH2Om �1 .