Fungal removal of gaseous hexane in biofilters packed with poly(ethylene carbonate) pine sawdust or peat composites

Abstract

The removal of volatile organic compounds (VOC) in biofilters packed with organic filter beds, such as peat moss (PM) and pine sawdust (PS), frequently presents drawbacks associated to the collapse of internal structures affecting the long-term operation. Poly(ethylene ether carbonate) (PEEC) groups grafted to these organic carriers cross linked with 4,4'-methylenebis(phenylisocyanate) (MDI) permitted fiber aggregation into specific shapes and with excellent hexane sorption performance. Modified peat moss (IPM) showed very favorable characteristics for rapid microbial development. Water-holding capacity in addition to hexane adsorption almost equal to the dry samples was obtained. Pilot scale hexane biofiltration experiments were performed with the composites after inoculation with the filamentous fungus Fusarium solani. During the operation of the biofilter under non-aseptic conditions, the addition of bacterial antibiotics did not have a relevant effect on hexane removal, confirming the role of fungi in the uptake of hexane and that bacterial growth was intrinsically limited by an adequate performance of the composites. IPM biofilter had a start-up period of 8-13 days with concurrent CO(2) production of approximately 90 g m(-3) h(-1) at day 11. The final pressure drop after 70 days of operation was 5.3 mmH(2)O m(-1) reactor. For modified pine sawdust (IPS) packed biofilter, 5 days were required to develop an EC of about 100 g m(-3) h(-1) with an inlet hexane load of approximately 190 g m(-3) h(-1). Under similar conditions, 12-17 days were required to observe a significant start-up in the reference perlite biofilter to reach gradually an EC of approximately 100 g m(-3) h(-1) at day 32. Under typical biofiltration conditions, the physical-chemical properties of the modified supports maintained a minimum water activity (a(w)) of 0.925 and a pH between 4 and 5.5, which allowed the preferential fungal development and limited bacterial growth.

Degradation of hexane and other recalcitrant hydrocarbons by a novel isolate, Rhodococcus sp. EH831

“…This was similar to the results of Arriaga and Revah (2005), who reported 59% mineralization of hexane in a microcosm experiment using a bacterial consortium. Hernández-Meléndez et al (2008) also reported that 50% of the inlet hexane was completely transformed into CO 2 in a hexane removal biofilter system. The lack of non-14 CO 2 in the air phase indicated that all of the intermediates were nonvolatile, and the lower proportion of metabolites in the EH831 culture suggests they were more quickly degraded or taken up than by the consortium culture.…”

“…Because of its lower solubility, hexane is degraded relatively slowly by bacteria compared with benzene, toluene, and methyl ethyl ketone probably due to its slow transfer from the gaseous to the liquid phase Hernández-Meléndez et al 2008). Therefore, to improve the degradation of hexane, surfactants have been added to the aqueous phase (Kastner et al 1999).…”

“…Amouric et al (2006) studied the biodegradation of hexane using a consortium and Garnier et al (1999) researched the characteristics of hexane degradation using Pseudomonas aeruginosa. Yang et al (2008) investigated the rate of hexane degradation using an activated sludgeinoculated rotating drum biofilter, and Hernández-Meléndez et al (2008) studied the nature of hexane degradation using a biofilter inoculated with Fusarium solani. In addition, Wilkes et al (2002) reported the biodegradation pathway of hexane using denitrifying bacteria under anaerobic conditions.…”

Treatment of hydrophobic VOCs in trickling bed air biofilter: Emphasis on long-term effect of initial alternate use of hydrophilic VOCs and microbial species evolution

“…Many processes were tested for addressing the bioavailability of hydrophobic contaminants. One is the introduction of surfactants (Aly Hassan and Sorial, 2008;Woertz and Kinney, 2004), providing favorable conditions for fungi (Aly Hassan and Sorial, 2008;Arriaga and Revah, 2005a;Hernández-Meléndez et al, 2008;Spigno and De Faveri, 2005;Van Groenestijn et al, 2001); others include mixture of n-hexane with other less hydrophobic compound such as benzene (Aly Hassan and Sorial, 2010a), introduction of more hydrophilic contaminants in mixture with n-hexane, such methanol (Zehraoui et al, 2012(Zehraoui et al, , 2013, and most recently the alternate use of methanol with n-hexane (Zehraoui et al, 2014).…”

“…Current literature shows a very great interest in using molecular biology techniques for microbial species identification from environmental samples (García-Peña et al, 2008;Vigueras et al, 2009). Most reported species for n-hexane biodegradation were Fusarium solani (Arriaga and Revah, 2005b;Hernández-Meléndez et al, 2008), Rhinocladiella similis (Vigueras et al, 2009), and Aspergillus niger (Spigno et al, 2003). Combination of Fusarium solani, Aspergillus niger, and Dothioraceae.…”