Treatment of Propylene Glycol Monomethyl Ether Acetate in Air Streams by a Biofilter Packed with Fern Chips

Abstract

This study aimed to develop a biofilter packed only with fern chips for the removal of airborne propylene glycol monomethyl ether acetate (PGMEA). Fern chips could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. In addition, the fern chip medium has the following merits: (1) simplicity in composition; (2) low pressure drop for gas flow (<20 mmH₂O∙m^-1); (3) simple in humidification, nutrient addition, pH control, and metabolite removal; (4) economical (US$174–385∙m^-3), and (5) low weight (wet basis around 290 kg∙m^-3). A two-stage downflow biofilter (2.18 m in height and 0.4×0.4 m in cross-sectional area) was constructed for the performance test. Both stages were packed with fern chips of 0.30 m in height and 0.40×0.40 m in cross-section. Results indicate that with operation conditions of media moisture content controlled in the range of 50–74%, media pH of 6.5–8.3, empty bed retention time (EBRT) of 0.27–0.4 min, influent PGMEA concentrations of 100–750 mg∙m^-3, volu-metric organic loading of <170 ∙m^-3 ∙hr^-1, and nutrition rates of Urea-nitrogen 66 g∙m^-3 ∙day^-3, potassium dihydrogen phosphate (KH₂PO₄)-phosphorus 13.3 g ∙m^-3 ∙day^-3, and milk powder 1.00 g∙m^-3∙day^-1, the fern-chip-packed biofilter could achieve an overall PGMEA removal efficacy of around 94%. Instant milk powder or liquid milk was essential to the good and stable performance of the biofilter for PGMEA removal.