Modeling of fungal biofilter for the abatement of hydropic VOCs

[Abstract] This work describes the growth of filamentous fungi in biofilters for the degradation of hydrophobic VOCs. The study system was n-hexane and the fungus Fusarium solani B1. The system is mathematically described and the main physical, kinetic data and morphological parameters of aerial hyphae were obtained by independent experiments for model validation. The model proposed in this study describes the increase in the transport area by the growth of the filamentous cylindrical mycelia and its relation with n-hexane elimination in quasi -stationary state in a biofilter. The model describing fungal growth includes Monod-Haldane kinetic and hyphal elongation and ramification. The reduction in the permeability caused by mycelial growth was further related to pressure drop by Darcy’s equation. The model was verified with biofiltration experiments using perlite as support and gaseous n-hexane as substrate

Two-phase partitioning bioreactors: towards a new generation of high-performance biological processes for VOC and CH4 abatement.

The intense research and development conducted over the past 30 years in the field of air pollution control have increased the acceptance of biotechnologies as cost-efficient technological solutions to mitigate atmospheric pollution. Despite the low operating cost of biofilters and biotrickling filters, the limited mass transfer rates of certain key air contaminants from the gas phase to the microbial community and the perceived limited robustness of biotechnologies still make physical-chemical technologies the preferred methods for air pollution control. In this context, the addition of a non-aqueous phase to conventional bioreactors, in the so called two-phase partitioning bioreactors (TPPBs), can overcome the above mentioned limitations and trigger the consolidation of biotechnologies for the removal of odors, volatile organic contaminants (VOCs) or greenhouse gases. TPPBs have been successfully implemented in stirred tank, airlift, biofilter and biotrickling filter reactors for the removal of hydrophobic VOCs and CH4 at unprecedentedly high removal rates. The high affinity of the non-aqueous phase for the target gas pollutant creates a new and efficient mass transfer pathway and increases process robustness compared to conventional biotechnologies. Finally, recent studies have shown that the use of hydrophobic biomass can boost the abatement performance of TPPBs by one order of magnitude

Phenomenological model of fungal biofilters for the abatement of hydrophobic VOCs

This work describes the growth of filamentous fungi in biofilters for the degradation of hydrophobic VOCs. The study system was n-hexane and Fusarium solani B1. The system is mathematically described and the main physical, kinetic data and morphological parameters were obtained by independent experiments and validated with data from laboratory experiments. The model describes the increase in the transport area by the growth of the filamentous cylindrical mycelia and its relation with n-hexane elimination in quasi-stationary state in a biofilter. The model describing fungal growth includes Monod-Haldane kinetic and hyphal elongation and ramification. A specific surface area of transport (SSAT) of 1.91 × 105 m2 m-3 and a maximum elimination capacity (EC) of 248 g m-3 h-1 were obtained by the mathematical model simulation, with a 10% of error with respect to the experimental EC

Phase partition of gaseous hexane and surface hydrophobicity of Fusarium solani when grown in liquid and solid media with hexanol and hexane

The filamentous fungus, Fusarium solani, was grown in liquid and solid culture with glucose, glycerol, 1-hexanol and n-hexane. The partition coefficient with gaseous hexane (HPC) in the biomass was lower when grown in liquid medium with 1-hexanol (0.4) than with glycerol (0.8) or glucose (1) The HPC for surface growth were 0.2 for 1-hexanol, 0.5 for glycerol, 0.6 for glucose, and 0.2 for F. solani biomass obtained from a biofilter fed with gaseous n-hexane. These values show a 200-fold increase in n-hexane solubility when compared to water (HPC = 42). Lower HPC values can be partially explained by increased lipid accumulation with 1-hexanol, 10.5% (w/w) than with glycerol (8.5% w/w) or glucose (7.1% w/w). The diameter of the hyphae diminished from 3 μm to 2 μm when F. solani was grown on solid media with gaseous n-hexane thereby doubling the surface area for gaseous substrate exchange. The surface hydrophobicity of the mycelia increased consistently with more hydrophobic substrates and the contact angle of a drop of water on the mycelial mat was 113° when grown on n-hexane as compared to 75° with glucose. The fungus thus adapts to hydrophobic conditions and these changes may explain the higher uptake of gaseous hydrophobic substances by fungi in biofilters

A systematic comparison of two empirical gas-liquid mass transfer determination methodologies to characterize methane biodegradation in stirred tank bioreactors

Producción CientíficaThis study aimed at systematically comparing the potential of two empirical methods for the estimation of the volumetric CH4 mass transfer coefficient (klaCH4), namely gassing-out and oxygen transfer rate (OTR), to describe CH4 biodegradation in a fermenter operated with a methanotrophic consortium at 400, 600 and 800 rpm. The klaCH4 estimated from the OTR methodology accurately predicted the CH4 elimination capacity (EC) under CH4 mass transfer limiting conditions regardless of the stirring rate (∼9% of average error between empirical and estimated ECs). Thus, empirical CH4-ECs of 37.8 ± 5.8, 42.5 ± 5.4 and 62.3 ± 5.2 g CH4 m−3 h−1 vs predicted CH4-ECs of 35.6 ± 2.2, 50.1 ± 2.3 and 59.6 ± 3.4 g CH4 m−3 h−1 were recorded at 400, 600 and 800 rpm, respectively. The rapid Co2+-catalyzed reaction of O2 with SO3−2 in the vicinity of the gas-liquid interphase during OTR determinations, mimicking microbial CH4 uptake in the biotic experiments, was central to accurately describe the klaCH4.Ministerio de Economía, Industria y Competitividad - FEDER (Project CTM 2015–70442-R and Red NOVEDAR

Efficient dynamic simulation of pH in processes associated to biofiltration of volatile inorganic pollutants

This work proposes a generic methodology to include the pH as a state variable in mathematical models of bioreactors. An ordinary differential equation for pH is stated and introduced into the general model structure of a biotrickling filter. All chemical equilibriums were considered and included into the model framework. A preliminary evaluation was performed by comparing results predicted by the model with experimental data obtained from the oxidation of thiosulfate by sulfide-oxidizing bacteria under alkaline conditions. The model was able to describe adequately the evolution of the main state variables including the pH for the initial complete oxidation of thiosulfate. The methodology presented here can be easily adapted to other mathematical models dealing with biological waste treatment processes in which pH appears as a key factor.Postprint (published version

Caracterización morfológica de hifas aéras y simulación del crecimiento de Fusarium solani bajo diferentes fuentes de carbono para su aplicación en la biofiltración de COVs hidrofóbicos

Publicado por la Academia Mexicana de Investigación y Docencia en Ingeniería Química A.C.This work presents the e ect of di erent carbon sources (glycerol, 1-hexanol and n-hexane)over the morphology of the aerial hyphae of the filamentous fungus Fusarium solani for its application in the biofiltration of volatile organic compounds (VOCs). A mathematical model was developed and further verified that combines microscopic and macroscopic parameters describing the mycelial fungal growth. Image analysis of microcultures and culture in agar dishes was performed to determine the morphological parameters. The results show that the hydrophobic and volatile carbon sources modified the morphology of Fusarium solani, this is associated with the better utilization of the volatile carbon source. The main morphology changes observed with glycerol and n-hexane, were the reduction in both the hyphal diameter (from 2.99 um to 2.01 um) and the average hyphal length (from 603.8 um to 280.1 um). These results indicate an increase in the transport area for the same amount of biomass as an adaptation response to increase the uptake of volatile hydrophobic substrates.Este trabajo presenta el efecto de diferentes fuentes de carbono (glicerol, 1-hexanol y n-hexano) sobre la morfología de las hifas aéreas del hongo filamentoso Fusarium solani para su aplicación en la biofiltración de compuestos orgánicos volátiles (COVs). Un modelo matemático que combina parámetros microscópicos y macroscópicos que describen el crecimiento del micelio del hongo fue desarrollado y verificado. Análisis de imágenes de los microcultivos y cultivos en placas de agar fue realizado para determinar los parámetros morfológicos. Los resultados muestran que las fuentes de carbono hidrofóbicas y volátiles modifican la morfología de Fusarium solani, esto está asociado con la mejor utilización de la fuente de carbono volátil. Los principales cambios morfológicos observados con glicerol y n-hexano, fueron la reducción en ambos diámetros de las hifas (desde 2.99 um a 2.01 um) y la longitud promedio de la hifa (desde 603.8 um a 280.1 um). Estos resultados indican un aumento en el área de transporte para la misma cantidad de biomasa como una respuesta de adaptación para aumentar la captación de los sustratos hidrofóbicos volátiles

Elimination of hydrophobic volatile organic compounds in fungal biofilters: Reducing start-up time using different carbon sources

Fungal biofilters have been recently studied as an alternative to the bacterial systems for the elimination of hydrophobic volatile organic compounds (VOC). Fungi foster reduced transport limitation of hydrophobic VOCs due to their hydrophobic surface and extended gas exchange area associated to the hyphal growth. Nevertheless, one of their principal drawbacks is their slow growth, which is critical in the start-up of fungal biofilters. This work compares the use of different carbon sources (glycerol, 1-hexanol, wheat bran, and n-hexane) to reduce the start-up period and sustain high n-hexane elimination capacities (EC) in biofilters inoculated with Fusarium solani. Four parallel experiments were performed with the different media and the EC, the n-hexane partition coefficient, the biomass production and the specific consumption rate were evaluated. Biofilters were operated with a residence time of 1.3min and an inlet n-hexane load of 325gm-3reactorh-1. The time to attain maximum EC once gaseous n-hexane was fed was reduced in the three experiments with alternate substrates, as compared to the 36 days needed with the control where only n-hexane was added. The shortest adaptation period was 7 days when wheat bran was initially used obtaining a maximum EC of 160gm-3reactorh-1 and a critical load of 55gm-3reactorh-1. The results were also consistent with the pressure drop, the amount of biomass produced and its affinity for the gaseous n-hexane, as represented by its partition coefficient. © 2010 Wiley Periodicals, Inc

Simultaneous methane abatement and PHB production by Methylocystis hirsuta in a novel gas-recycling bubble column bioreactor

Producción CientíficaThe limited gas–liquid mass transfer represents the main challenge in the operation of cost-effective bioreactors devoted to the treatment of poorly soluble gas pollutants such as methane (CH4). This study evaluates the influence of internal gas-recycling strategies on the enhancement of CH4 abatement in a bubble column bioreactor inoculated with the methanotroph Methylocystis hirsuta. Maximum CH4 removal efficiencies of 72.9 ± 0.5% (corresponding to elimination capacities of 35.2 ± 0.4 g m−3 h−1) were recorded under process operation at an empty bed residence time of 30 min and 0.50 m3gas m−3reactor min−1 of internal gas-recycling rate. The accumulation of poly-3-hydroxybutyrate (PHB) in M. hirsuta was evaluated batchwise under limitations of potassium, manganese, nitrogen, and nitrogen with excess of iron. Nitrogen starvation resulted in the highest PHB content (28 ± 1%). Likewise, the implementation of sequential N starvation cycles in a continuous bubble column reactor operated at a gas residence time of 30 min and an internal gas-recycling rate of 0.50 m3gas m−3reactor min−1 supported a PHB content of up to 34.6 ± 2.5%, with a volumetric PHB productivity of 1.4 ± 0.4 kg m−3 d−1 and elimination capacities of 16.2 ± 9.5 g m−3 h−1.2019-12-122019-12-12Ministerio de Economía, Industria y Competitividad (Proyect CTM2015-7044 -R and Red NOVEDAR)Junta de Castilla y León (UIC71