Performance Of Biotrickling Filter Research Articles

Removal Characteristics of Gas-Phase D-Limonene in Biotrickling Filter and Stoichiometric Analysis of Biological Reaction using Carbon Mass Balance

Volatile organic compounds (VOCs) pose significant risks to human health and environmental quality, prompting stringent regulations on their emissions from various industrial processes. Among VOCs, d-limonene stands out due to its low threshold and contribution to malodorous emissions. While biofiltration presents a promising approach for VOC removal, including d-limonene, a comprehensive understanding of its performance and kinetics is lacking. This study aims to comprehensively assess the performance of a lab-scale biotrickling filter in treating gas-phase d-limonene. The experimental results indicate that the biotrickling filter efficiently removed d-limonene, achieving a critical loading rate of 19.4 g m−3 h−1 and a maximum elimination capacity of 31.8 g m−3 h−1 (correspondingly, up to 85% removal) at the condition of 94.2 s of EBRT. Microbial activity played a significant role in biotrickling filter performance, with a strong linear correlation being observed between CO2 production and substrate consumption. The Michaelis–Menten model was employed to represent enzyme-catalyzed reactions, suggesting no inhibition during biotrickling filter operation.

Impact of p-cresol on hydrogen sulfide and ammonia treatment by biotrickling filter and the production of nitrous oxide

Biotrickling filter (BTF) is often used for purification of waste gas from swine houses, with vital information still needed regarding interaction effects among multiple gas pollutants removal and also the formation of byproducts especially nitrous oxide (N2O, a strong greenhouse gas) due to the relative high NH3 concentration level compared to other gases. In this study, gas removal and N2O production were compared between two BTFs, where the inlet gas of BTF-1 contained NH3 and H2S while p-cresol was additionally supplied to BTF-2. At inlet load (IL) between 3.67 and 18.91 g m−3 h−1, removal efficiencies of NH3 exceeded 95% for both BTFs. As alternative strategy, adding thiosulfate improved H2S removal. Interestingly, presence of p-cresol to some extent promoted H2S removal at IL of 0.56 g m−3 h−1possibly due to effect on pH value of circulating solution. Similar to NH3, removal efficiencies of p-cresol were higher than 95% at an average IL of 2.98 g m−3 h−1. Gas residence time, pH of circulating solution and inlet loading were identified as key factors affecting BTF performance, but the response of individual gas compound to these factors was not consistent. Overall, p-cresol enhanced N2O generation although the effects were not always significant. High-throughput sequencing results showed that Proteobacteria accounted for the largest proportion of relative abundance and BTF-2 had much richer microbial diversity compared to BTF-1. Thermomonas, Comamonas, Rhodanobacter and other bacterial genus capable of denitrification were detected in both BTFs, and their corresponding abundances in BTF-2 (10.9%, 8.7% and 5.2%) were all greater than those in BTF-1 (0.4%, 0.3% and 2.0%), indicating that more denitrification may occur within BTF-2 and higher N2O could have been generated. This study provided evidence that organic gas components, served as carbon source, may increase the N2O production from BTF when treating waste gases containing NH3.

Effect of nitrogen source and spray conditions on the integral biotrickling filter operation for hydrophobic volatile organic compounds

A nutrient solution containing major and trace elements plays a crucial role in biotrickling filter (BTF) operation in practical applications. This study conducted a series of experiments on the BTF packed with integral filters using two types of nitrogen sources under different spray conditions. The rapid start-up was observed in the BTF feeding with ammonium tartrate-N (AT-N) nutrient solution. Heterotrophic nitrification and denitrification were observed by monitoring the concentration of ammonia-N, nitrite-N, nitrate-N, PO43− and SO42− in the nutrient solution. The BTF performance under two different types of the nutrient solutions were detected up to ∼90% at the inlet toluene concentration of 300–700 mg∙m−3. The BTF packed with integral filters exhibited the stable performance with the change of nitrogen source and could be steadily operated at a wide pH range of 5.5–8.5. To illustrate the effect of the two types of nitrogen sources on the biofilm, metagenomic sequencing was used to assess the microbial diversity and functional genes of biofilm on the integral filters. The results showed that the application of AT-N nutrient solution increased the functional genes of denitrification in the microorganisms on the filters. Furthermore, the more stable performance of BTF was achieved by using the AT-N nutrient solutions, which might be beneficial to the long-term operation of BTF packed with honeycomb integral packing.

Performance evaluation of fungal biotrickling filter for styrene destruction: Experimental and artificial neural networks modeling

Removal of styrene vapors was investigated using a fungi-cultured biotrickling filter (BTF) in the presence of rhamnolipid. Evaluations at empty bed residence times (EBRTs) of 90, 60, and 30 s and inlet loading rates (LRs) ranging from 25.5 to 186.1 g m−3 h−1 were conducted. The maximum elimination capacity (EC) of 173.7 g m−3 h−1 was obtained at an inlet LR of 186.1 g m−3 h−1 at 90 s EBRT. Reducing the EBRT to 60 and 30 s resulted in decline of removal efficiency (RE). The performance of BTF was modeled using artificial neural network (ANN) to predict styrene RE using measurable inputs, inlet LR, EBRT, and pressure drop. The model performance was assessed by mean square error and overall coefficient of correlation. The influence of different input parameters on the output was analyzed using casual index. Styrene removal was positively influenced by the increase in EBRTs, negatively impacted by its inlet LRs, while pressure drop had a negligible effect. The BTF was then exposed to intermittent loading phases by varying operational conditions during the non-loading periods. The results from this study confirmed that rhamnolipids could enhance the BTF performance for handling transient load variations at unsteady-state conditions.

Extremely acidic condition (pH

Extremely acidic conditions (pH < 1.0) during hydrogen sulfide (H2S) biotreatment significantly reduce the cost of pH regulation; however, there remain challenges to its applications. The present study investigated the H2S removal and biomass variations in biotrickling filter (BTF) under long-term highly acidic conditions. A BTF operated for 144 days at pH 0.5–1.0 achieved an H2S elimination capacity (EC) of 109.9 g/(m3·h) (removal efficiency = 97.0%) at an empty bed retention time of 20 s, with an average biomass concentration at 20.6 g/L-BTF. The biomass concentration at neutral pH increased from 22.3 to 49.5 g/L-BTF within 28 days. In this case, elemental sulfur (S0) accumulated due to insufficient oxygen transfer in biofilm, which aggravated the BTF blockage problem. After long-term domestication under extremely acidic conditions, a mixotrophic acidophilic sulfur-oxidizing bacteria (SOB) Alicyclobacillus (abundance 55.4%) were enriched in the extremely acidic biofilm, while non-aciduric bacteria were eliminated, which maintained the balance of biofilm thickness. Biofilm with optimum thickness ensured oxygen transfer and H2S oxidation, avoiding the accumulation of S0. The BTF performance improved due to the enrichment of active mixotrophic SOB with high abundance under extremely acidic conditions. The mixotrophic SOB is expected to be further enriched under extremely acidic conditions by adding carbohydrates to enhance H2S removal.

Co-Treatment with Single and Ternary Mixture Gas of Dimethyl Sulfide, Propanethiol, and Toluene by a Macrokinetic Analysis in a Biotrickling Filter Seeded with Alcaligenes sp. SY1 and Pseudomonas Putida S1

The biotrickling filter (BTF) treatment is an effective way of dealing with air pollution caused by volatile organic compounds (VOCs). However, this approach is typically used for single VOCs treatment but not for the mixtures of VOC and volatile organic sulfur compounds (VOSCs), even if they are often encountered in industrial applications. Therefore, we investigated the performance of BTF for single and ternary mixture gas of dimethyl sulfide (DMS), propanethiol, and toluene, respectively. Results showed that the co-treatment enhanced the removal efficiency of toluene, but not of dimethyl sulfide or propanethiol. Maximum removal rates (rmax) of DMS, propanethiol and toluene were calculated to be 256.41 g·m−3·h−1, 204.08 g·m−3·h−1 and 90.91 g·m−3·h−1, respectively. For a gas mixture of these three constituents, rmax was measured to be 114.94 g·m−3·h−1, 104.17 g·m−3·h−1 and 99.01 g·m−3·h−1, separately. Illumina MiSeq sequencing analysis further indicated that Proteobacteria and Bacteroidetes were the major bacterial groups in BTF packing materials. A shift of bacterial community structure was observed during the biodegradation process.

Enhancing the environmental performance of biotrickling filters treating volatile organic compounds in air

The actual biotrickling filtration technology addresses volatile organic compounds (VOCs) removal from air, by their conversion into less harmful gaseous compounds (e.g. carbon dioxide). The actual study extends this capability towards not only VOCs removal, but also removal of carbon dioxide issued from biodegradation, in the same biotrickling filter (BTF). This upgrade results in higher C-capture and the reduction of greenhouses gases associated with this process, thus increasing the environmental performance of such BTFs. The model pollutant used in this study is ethanol, while a co-immobilised microalgae and compost-derived microorganisms is used for the first time accomplishing the above mentioned desiderate (simultaneously removal of VOC and carbon dioxide in the same BTF), under continuous regime and illumination provided by an array of light-emitting diodes (LED)). Very promising performances are obtained, revealing new competitive alternatives with high potential for further development, in the light of atmospheric protection and climate change issues.

The core microbiome is responsible for volatile silicon and organic compounds degradation during anoxic lab scale biotrickling filter performance

Volatile silicon compounds present in the biogas of anaerobic digesters can cause severe problems in the energy recovery systems, inducing costly damages. Herein, the microbial community of a lab-scale biotrickling filter (BTF) was studied while testing its biodegradation capacity on octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5), in the presence of toluene, limonene and hexane. The reactor performance was tested at different empty bed residence times (EBRT) and packing materials. Community structure was analysed by bar-coded amplicon sequencing of the 16S rRNA gene. Microbial diversity and richness were higher in the inoculum and progressively decreased during BTF operation (Simpson's diversity index changing from 0.98–0.90 and Richness from 900 to 200 OTUs). Minimum diversity was found when reactor was operated at relatively low EBRT (7.3 min) using a multicomponent feed. The core community was composed of 36 OTUs (accounting for 55% of total sequences). Packing material played a key role in the community structure. Betaproteobacteriales were dominant in the presence of lava rock and were partially substituted by Corynebacteriales and Rhizobiales when activated carbon was added to the BTF. Despite these changes, a stable and resilient core microbiome was selected defining a set of potentially degrading bacteria for siloxane bioremoval as a complementary alternative to non-regenerative adsorption onto activated carbon.

Odorous Compound Removal Performance and Water Properties of a Biotrickling Filter Installed in a Piggery

Highlights We evaluated the performance of a two-stage biotrickling filter in a pig facility. A short empty bed residence time lowered the secondary filter removal efficiency for many odorous compounds. The removal efficiency of some compounds increased when the pH in the secondary water tank decreased. Low-odor-threshold compounds such as MT, n-BA, n-PA, and p-cresol were indicated as targets for optimization. Abstract . Odor is a major problem in pig production, and it is important to minimize odor emissions. To determine the factors influencing variations in odor removal efficiency, we analyzed the performance of a biotrickling filter installed in growing-finishing pig rooms on a commercial farm. Over 16 months, we conducted measurements of representative odorous compounds, namely sulfur compounds (hydrogen sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide), volatile fatty acids (propanoic acid, 2-methylpropanoic acid, butanoic acid, 3-methylbutanoic acid, and pentanoic acid), and ammonia. The average removal efficiencies of methanethiol, dimethyl disulfide, volatile fatty acids, and ammonia were 83% to 89%, with 50% for hydrogen sulfide and 18% for dimethyl sulfide. For many, but not all, odorous compounds, removal efficiency declined significantly with decreasing empty bed residence time (EBRT). From an analysis of the correlations of odorous compounds’ removal efficiency with the properties of the trickling water, we hypothesized that water properties such as pH, free ammonia, free nitrous acid, ionic species (Na+, Ca2+) concentrations, temperature, electrical conductivity, and biological oxygen demand, in addition to EBRT, were associated with fluctuations in removal efficiency during full-scale operation. The pH in the secondary water tank was negatively correlated with the removal efficiencies of methanethiol, dimethyl sulfide, butanoic acid, 3-methylbutanoic acid, pentanoic acid, and ammonia. Our identification of key odorous compounds indicates the importance of the secondary filter in odor treatment. Biotrickling filters for air in pig facilities could be further optimized by targeting low-odor-threshold compounds such as methanethiol, butanoic acid, pentanoic acid, and p-cresol, in addition to ammonia. Keywords: Ammonia, Biotrickling filter, Pig facility odor, Sulfur compound, Trickling water, Volatile fatty acid.

Effect of surfactin on removal of semi-volatile organic compound: Emphasis on enhanced biofiltration performance

The performance of a lab-scale biotrickling filter (BTF) inoculated with a mixed fungal consortium was investigated for the simultaneous abatement of 2-ethylhexanol; a hydrophobic semi-volatile organic compound (SVOC), and propylene glycol monomethyl ether (PGME). The BTF performance was investigated in the presence of lipopeptide-type biosurfactant, surfactin. The effect of surfactin on the removal efficiency and elimination capacity was examined at stretched inlet loading rates (LR): 1.04 to 15.7 and 3.2–48 g m−3 h−1 of PGME and 2-ethylhexanol, respectively. Seeding the BTF with 50 mg L−1 of surfactin maintained high and consistent removal efficiencies of PGME and 2-ethylhexanol up to LRs of 15.7 and 32 g m−3 h−1, with removal efficiencies of 98.5 and 99%, respectively. Once the LR of 2-ethylhexanol increased to 48 g m−3 h−1, a substrate inhibition was observed, accompanied by a sudden decrease in removal efficiency from 99.2 to 62.3%. At the same LR, the BTF performance was improved by reseeding 100 mg L−1 of surfactin, hence, reinstated the removal efficiency of 2-ethylhexanol to 92.7% and achieving a maximum elimination capacity of 44.5 g m−3 h−1. This enhanced SVOC uptake rate was further confirmed by a considerable increase in reaction rate constant from 0.005 to 0.017 s−1. A batch study was also conducted at the end of the experimental run to better understand the correlation between surfactin concentrations and the time-dependent partition coefficient of 2-ethylhexanol. Biofilm microbial community structure revealed relative abundancy of 72 and 28% of Trichoderma asperellum and Fusarium solani, respectively. The findings of this study show for the first time that the removal of a semi-VOC such as 2-ethylhexanol is feasible in the presence of surfactin and hence improving the bioavailability of hydrophobic semi-VOC.

Effect of liquid supply on the performance of a fungal bio-trickling filter treating hydrophobic VOC

Fungi can be used in a bio-trickling filter (BTF) to treat volatile organic compound pollutants. To explore the effect of liquid supply on the performance of a fungal BTF, a three-layer BTF filled with ceramsite and inoculated with Fusarium oxysporum to treat toluene was constructed. The BTF started rapidly (<10 days) and could be restarted within 4 days after 24 day’ stagnation. High-throughput sequencing showed that Fusarium evolved into a complex microbial system. The middle layer had the most even proportions of dominant fungi and the highest coexistence of various genera. The effect of liquid supply on the performance of microorganism in the BTF was investigated in detail. The pH of the nutrient liquid fluctuated between 5.6 and 8.1. Small amounts of nutrient sprayed at frequent intervals (49 mL every 2 h) and a minimum humidity of 40 % provided optimal conditions for fungal survival. Nutrient replacement cycle can be extended from one week to two weeks, and timely removal of microelements can enhance the microbial activity. Moreover, fungi can grow well at ambient temperatures of 16 to 28℃.

Biodegradation of o-dichlorobenzene by Bacillus cereus DL-1：kinetics, degradation pathway, biodegradability and performance in biotrickling filter

ABSTRACT o -Dichlorobenzene could be mineralized as the sole carbon and energy source by Bacillus cereus DL-1. In this work, Haldane–Andrews and pseudo-first-order models were used to simulate the growth and degradation abilities of the strain. Two possible degradation pathways were identified by GC/MS intermediate and open-loop analysis. The removal efficiency (RE) of biotrickling filter (BTF) could reach 57.86% at the start phase. At the steady phase, the effects of empty bed residence time (EBRT), inlet gas concentration and intake load rate (ILR) on the performance of BTF have highlighted the potential of strain DL-1 for the treatment of o-dichlorobenzene.

Effects of n-butanol presence, inlet loading, empty bed residence time and starvation periods on the performance of a biotrickling filter removing cyclohexane vapors from air

This paper presents the results of investigations on the removal of cyclohexane vapors from air using a peat-perlite packed biotrickling filter. Effects of basic process parameters i.e. inlet loading and empty bed residence time as well as introduction of n-butanol to the treated air stream and starvation periods on the process performance were evaluated. The results show that the introduction of hydrophilic n-butanol results in an enhanced removal of hydrophobic cyclohexane comparing to the experiments where only cyclohexane was treated. Additionally, the biotrickling filter performance after the starvation events is regained to more extent for mixed system than for the single cyclohexane. A novel and interesting element of the paper is the application of an electronic nose for the process monitoring. Obtained results are discussed in the perspective of an influence of the presence of a compound with different affinity to aqueous phase on the removal efficiency of the compound with opposite chemical properties.

A high performance biological degradation of trimethylamine: Experimental study and mathematical modeling

A bench scale Biotrickling filter (BTF) packed with polyurethane foam seeded with potential TMA degrading bacterial strains (Agromyces and Ochrobactrum sp.) was tested to eliminate TMA from ambient air. BTF was functioned constantly for a period of 125 days at retention time of 180 s and 90 s corresponding to the different loading rate of 14.4–232 g m−3 h-1. The maximum elimination capacity attained in the study was 160 g m−3 h-1 with the removal efficiency above 95%. Low, medium and high shock loads of higher concentration were applied to the BTF during the operational period. The BTF has recuperated its performance after each shock loads which shows its good resilience capacity. The performance of the BTF was modeled first time using RSM and ANN algorithm to predict the outlet concentration, elimination capacity and removal efficiency of TMA. Both the algorithm can efficiently be employed to model the BTF performance for degrading TMA.

The styrene purification performance of biotrickling filter with toluene-styrene acclimatization under acidic conditions

ABSTRACT The obvious disadvantages of biotrickling filters (BTFs) are the long start-up time and low removal efficiency (RE) when treating refractory hydrophobic volatile organic compounds (VOCs), which limits its industrial application. It is worthwhile to investigate how to reduce the start-up period of the BTF for treating hydrophobic VOCs. Here, we present the first study to evaluate the strategy of toluene induction combined with toluene-styrene synchronous acclimatization during start-up in a laboratory-scale BTF inoculated with activated sludge for styrene removal, as well as the effects of styrene inlet concentration (0.279 to 2.659 g·m−3), empty bed residence time (EBRT) (i.e., 136, 90, 68, 45, 34 sec), humidity (7.7% to 88.9%), and pH (i.e., 4, 3, 2.5, 2) on the performance of the BTF system. The experiments were carried out under acidic conditions (pH 4.5) to make fungi dominant in the BTF. The start-up period for styrene in the BTF was shortened to about 28 days. A maximum elimination capacity (ECmax) of 126 g·m−3·hr−1 with an RE of 80% was attained when styrene inlet loading rate (ILR) was below 180 g·m−3·hr−1. The highest styrene RE(s) [of BTF] that could be achieved were 95% and 93.4%, respectively, for humidity of 7.7% and at pH 2. A single dominant fungal strain was isolated and identified as Candida palmioleophila strain MA-M11 based on the 26S ribosomal RNA gene. Overall, the styrene induction with the toluene-styrene synchronous acclimatization could markedly reduce the start-up period and enhance the RE of styrene. The BTF dominated by fungi exhibited good performance under low pH and humidity and great potential in treating styrene with higher inlet concentrations. Implications: The application of the toluene induction combined with toluene-styrene synchronous acclimatization demonstrated to be a promising approach for the highly efficient removal of styrene. The toluene induction can accelerate biofilm formation, and the adaptability of microorganisms to styrene can be improved rapidly by the toluene-styrene synchronous acclimatization. The integrated application of two technologies can shorten the start-up period of biotrickling filters markedly and promote its industrial application.

Transient-state operation of an anoxic biotrickling filter for H2S removal.

The application of an anoxic biotrickling filter (BTF) for H2S removal from contaminated gas streams is a promising technology for simultaneous H2S and NO3- removal. Three transient-state conditions, i.e. different liquid flow rates, wet-dry bed operations and H2S shock loads, were applied to a laboratory-scale anoxic BTF. In addition, bioaugmentation of the BTF with a H2S removing-strain, Paracoccus MAL 1HM19, to enhance the biomass stability was investigated. Liquid flow rates (120, 60 and 30 L d-1) affected the pH and NO3- removal efficiency (RE) in the liquid phase. Wet-dry bed operations at 2-2 h and 24-24 h reduced the H2S elimination capacity (EC) by 60-80%, while the operations at 1-1 h and 12-12 h had a lower effect on the BTF performance. When the BTF was subjected to H2S shock loads by instantly increasing the gas flow rate (from 60 to 200 L h-1) and H2S inlet concentration (from 112 (± 15) to 947 (± 151) ppmv), the BTF still showed a good H2S RE (>93%, EC of 37.8 g S m-3 h-1). Bioaugmentation with Paracoccus MAL 1HM19 enhanced the oxidation of the accumulated S0 to sulfate in the anoxic BTF.

Long-term microbial community dynamics at two full-scale biotrickling filters treating pig house exhaust air.

SummaryIn this study, the microbial community structure of two full‐scale biotrickling filters treating exhaust air from a pig housing facility were evaluated using 16S metabarcoding. The effect of inoculation with activated sludge of a nearby domestic waste water treatment plant was investigated, which is a cheap procedure and easy to apply in practice. The study was performed at a three‐stage and a two‐stage full‐scale biotrickling filter; of which, only the latter was inoculated. Both biotrickling filters evolved towards a rather similar community over time, which differed from the one in the activated sludge used for inoculation. However, the bacterial population at both biotrickling filters showed small differences on the family level. A large population of heterotrophic bacteria, including denitrifying bacteria, was present in both biotrickling filters. In the non‐inoculated biotrickling filter, nitrite‐oxidizing bacteria (NOB) could not be detected, which corresponded with the incomplete nitrification leading to high nitrite accumulation observed in this system. Inoculation with the wide spectrum inoculum activated sludge had in this study a positive effect on the biotrickling filter performance (higher ammonia removal and lower nitrous oxide production). It could thus be beneficial to inoculate biotrickling filters in order to enrich NOB at the start‐up, making it easier to keep the free nitrous acid concentration low enough to not be inhibited by it.

Pilot-scale study using biotrickling filter to remove H2S from sewage lift station: Experiment and CFD simulation

In this study, a pilot-scale biotrickling filter (BTF) was developed to remove poisonous gas contaminated by hydrogen sulfide (H2S) from a sewage lift station. The BTF provided a smooth start-up with an increase in the inlet H2S concentration and delivered a stable operation for more than 300 days. The biomass concentration and microbial community structures were analyzed to determine the biodegradation kinetics, and some key operating variables, the inlet H2S concentration and empty bed retention time (EBRT), were investigated to explore the deodorization performance of the pilot-scale BTF. When the EBRT was 10.9–28.9 s and the inlet H2S concentration was 5–20 ppmv, an H2S removal efficiency of no less than 99% was observed. The elimination capacity (EC) reached 6.58 g H2S/m3/h (removal efficiency of 99.8%) for an EBRT of 10.9 s. In addition, a computational fluid dynamics (CFD) model was integrated with a biodegradation kinetic model and a porous medium model to simulate the deodorization performance of the pilot-scale BTF. Under different operating conditions, the simulated results agreed well with experimental data for H2S concentration profiles and the pressure drop (R2>0.985), which indicates that the established CFD model can be used as a reference for optimizing the design and scale-up of the BTF.

Research on pressure drop solution and pilot-scale application of bio-trickling filter for the treatment of butan-2-yl ethanoate

A pilot-scale bio-trickling filter (BTF) packed with ceramsite was investigated to treat butan-2-yl ethanoate (BE), which is discharged from the pharmaceutical industry. To choose an appropriate operation technology, the performance of twin bench-scale BTFs, vertical (BTF1) and horizontal (BTF2) towers, to purify BE were tested. The BTF1 had superior degradation capabilities when compared to BTF2, a quick start up of three days, a maximum elimination capacity of 548.5 g/(m3h) and an average removal efficiency of approximately 95% with an empty bed residence time (EBRT) of 17 s. Therefore, in a subsequent pilot test, a vertical BTF with a high-temperature shade net was setup, which demonstrated effective BE degradation performance. The pressure drop of the vertical BTFs could be addressed effectively by commutation and optimizing the nutrient supply. A high-throughput sequencing comparison of the three towers indicated similarity in the microorganisms between the two vertical BTFs, indicating that the flow patterns within the tower could affect microorganisms cultivation.

Performance of a biotrickling filter for the anaerobic utilization of gas-phase methanol coupled to thiosulphate reduction and resource recovery through volatile fatty acids production

The anaerobic removal of continuously fed gas-phase methanol (2.5–30 g/m3.h) and the reduction of step-fed thiosulphate (1000 mg/L) was investigated in a biotrickling filter (BTF) operated for 123 d at an empty bed residence time (EBRT) of 4.6 and 2.3 min. The BTF performance during steady step-feed and special operational phases like intermittent liquid trickling in 6 and 24 h cycles and operation without pH regulation were evaluated. Performance of the BTF was not affected and nearly 100% removal of gas-phase methanol was achieved with an ECmax of 21 g/m3.h. Besides, >99% thiosulphate reduction was achieved, in all the phases of operation. The production of sulphate, H2S and volatile fatty acids (VFA) was monitored and a maximum of 2500 mg/L of acetate, 200 mg/L of propionate, 150 mg/L of isovalerate and 100 mg/L isobutyrate was produced.