Bio-desulfurization of biogas using acidic biotrickling filter with dissolved oxygen in step feed recirculation

Assessing the efficiency and microbial diversity of H2S-removing biotrickling filters at various pH conditions

This study aimed to investigate the operation of three parallel biotrickling filters (BTFs) in removing H2S at different pH conditions (haloalkaliphilic, neutrophilic, and acidophilic) and their associated microbial population in the biodesulfurization process. BTF columns were inoculated with enriched inoculum and experiments were performed by gradually reducing Empty Bed Retention Time (EBRT) and increasing inlet concentration in which the maximum removal efficiency and maximum elimination capacity in EBRT 60 s reached their maximum level in haloalkaline condition (91% and 179.5 g S-H2S m-3 h-1). For visualizing the attached microbial biofilms on pall rings, Scanning Electron Microscopy (SEM) was used and microbial community structure analysis by NGS showed that the most abundant phyla in haBTF, nBTF, and aBTF belong to Gammaproteobacteria, Betaproteobacteria, and Acidithiobacillia, respectively. Shannon and Simpson indexes evaluation showed a lower diversity of bacteria in the aBTF reactor than that of nBTF and haBTF and beta analysis indicated a different composition of bacteria in haBTF compared to the other two filters. These results indicated that the proper performance of BTF under haloalkaliphilic conditions is the most effective way for H2S removal from air pollutants of different industries.

Biodesulfurization of landfill biogas by a pilot-scale bioscrubber: Operational limits and microbial analysis

Biogas serves as a crucial renewable energy vector to ensure a more sustainable energy future. However, the presence of hydrogen sulfide (H2S) limits its application in various sectors, emphasizing the importance of effective H2S removal techniques for maximizing its potential. In the present study, the limits of a pilot-scale bioscrubber for biogas desulfurization was study in a real scenario. An increase in the superficial liquid velocity resulted in significant improvements in the H2S removal efficiency, increasing from 76 ± 8% (elimination capacity of 6.2 ± 0.5 gS-H2S m-3 h-1) to 97.7 ± 0.5% (elimination capacity of 8 ± 1 gS-H2S m-3 h-1) as the superficial liquid velocity increased from 50 ± 3 m h-1 to 200 ± 8 m h-1. A USL of 161.4 ± 0.5 m h-1 was able to achieve outlet H2S concentrations as low as 3 ± 1 ppmv (H2S removal efficiency of 97 ± 1%) for 7 days. High superficial liquid velocity favoured the aerobic H2S oxidation reducing the nitrate demand. The maximum EC reached throughout the operation was 50.8 ± 0.6 gS-H2S m-3 h-1 (H2S removal efficiency of 96 ± 1%) and a sulfur production of 60%. Studies in batch flocculation experiments showed sulfur removal rates up to 97.6 ± 0.9% with a cationic flocculant dose of 75 mg L-1. Microbial analysis revealed that the predominant genus with sulfo-oxidant capacity during periods of low H2S inlet load was Thioalkalispira-sulfurivermis (61-69%), while in periods of higher H2S inlet load, family Arcobacteraceae was the most prevalent (11%).

Biochemical engineering for elemental sulfur from flue gases through multi-enzymatic based approaches - A review

Flue gases are the gases which are produced from industries related to chemical manufacturing, petrol refineries, power plants and ore processing plants. Along with other pollutants, sulfur present in the flue gas is detrimental to the environment. Therefore, environmentalists are concerned about its removal and recovery of resources from flue gases due to its activation ability in the atmosphere to transform into toxic substances. This review is aimed at a critical assessment of the techniques developed for resource recovery from flue gases. The manuscript discusses various bioreactors used in resource recovery such as hollow fibre membrane reactor, rotating biological contractor, sequential batch reactor, fluidized bed reactor, entrapped cell bioreactor and hybrid reactors. In conclusion, this manuscript provides a comprehensive analysis of the potential of thermotolerant and thermophilic microbes in sulfur removal. Additionally, it evaluates the efficacy of a multi-enzyme engineered bioreactor in this process. Furthermore, the study introduces a groundbreaking sustainable model for elemental sulfur recovery, offering promising prospects for environmentally-friendly and economically viable sulfur removal techniques in various industrial applications.

Mechanisms of N, N-dimethylacetamide-facilitated n-hexane removal in a rotating drum biofilter packed with bamboo charcoal-polyurethane composite

n-Hexane and N, N-dimethylacetamide (DMAC) are two major volatile organic compounds (VOCs) discharged from the pharmaceutical industry. To enhance DMAC-facilitated n-hexane removal, we investigated the simultaneous removal of multiple pollutants in a rotating drum biofilter packed with bamboo charcoal-polyurethane composite. After adding 800 mg·L^-1 DMAC, the n-hexane removal efficiency increased from 59.4 % to 83.1 % under the optimized conditions. The maximum elimination capacity of 10.0 g·m^-3·h^-1n-hexane and 157 g·m^-3·h^-1 DMAC were obtained. The biomass of bamboo charcoal-polyurethane and the ratio of protein-to-polysaccharide in extracellular polymeric substances were significantly increased compared with the non-DMAC stage, which is attributed to increased carbon utilization. In addition, Na⁺ K⁺-ATPase was positively correlated with increasing electron transport system activity, which was 1.98 and 1.36 times greater. Hydrophilic DMAC improved the bioavailability of hydrophobic n-hexane and benefited bacterial metabolism. Co-degradation of n-hexane and DMAC system can be used for other volatile organic pollutants.

Low H2S content biogas biodesulfurization from high solid sludge anaerobic digestion using limited external aeration biotrickling filter: Effect of gas-liquid pattern on oxygen utilization performance

An efficient and precise method is needed for low H₂S content biogas biodesulfurization, produced during high solid sludge anaerobic digestion. Continuous experiments were conducted to evaluate the performance of a lab-scale biotrickling filter (BTF) in H₂S removal and oxygen utilization. The results show that the sulfur loading rate decreased by 66% compared to conventional H₂S content, thus achieving a sufficient removal efficiency (>0.9). With a limited external aeration (0.5-2.0 molO₂·molS^-1), the oxygen consumption (O/S_re) to its supplement (O/S_in) ratios increased from 50-71% (conventional H₂S) to 83-92% (low H₂S), indicating that low H₂S flux promotes a sufficient oxygen utilization. Furthermore, the difference in oxygen utilization between co-current and counter-current flow patterns decreased under limited external aeration as the H₂S content sharply decreased. These results indicate that a dynamic oxygen-sulfur (O-S) balanced multistage BTF is expected to achieve a more precise vertical O-S distribution for sulfur resource recovery.

Sulfur recycle in biogas production: Novel Higee desulfurization process using natural amino acid salts

In this work, a desulfurization method using natural amino acid salts (AAS), which can be green prepared by biological fermentation, is proposed to remove H₂S from raw biogas. Biogas purification and fertilizer production can be simultaneously achieved to close sulfur recycle. The reaction kinetic characteristics of H₂S absorption with three kinds of AAS, including potassium β-alaninate (PA), potassium sarcosinate (PS) and potassium l-prolinate (PP) are first studied. Kinetic parameters including orders of reaction, rate constants, pre-exponential factors and activation energies are given. AAS absorbent exhibits good potential for biogas desulfurization. Higee (high gravity) technology is utilized to intensify H₂S removal. The effects of operating conditions on H₂S removal efficiency are investigated and PP shows the best desulfurization performance. The phytotoxicity of AAS and amino acid salt sulfide (AASS) is assessed by the germination index of mungbean seeds. PP and its salt sulfide (PPS) show relatively low phytotoxicity and their allowable agricultural feeding concentrations are below 0.08 M and 0.04 M, respectively. The desulfurization method demonstrates a green route for biogas purification to achieve sulfur recycle.

Bamboo charcoal powder-based polyurethane as packing material in biotrickling filter for simultaneous removal of n-hexane and dichloromethane

Bamboo charcoal powder-based polyurethane (BC-PU) was firstly applied in biotrickling filter to treat n-hexane and dichloromethane (DCM) simultaneously. Maximum elimination capacity of 12.68 g m^-3h^-1 n-hexane was achieved and exceed 30.28 g m^-3h^-1 DCM could be degraded. BTF respond quickly to the mixed shock loadings, and recovered to 76% and 100% respectively in less than 1 h. By increasing inlet loading (IL) of DCM from 6.20 g m^-3h^-1 to 28.36 g m^-3h^-1, the removal efficiency of n-hexane decreased from 73.4% to 55.9% corresponding to the IL of 19.96 g m^-3h^-1. N-hexane degradation was inhibited by high IL of DCM due to enzymes competition for active sites. The growth of key microorganisms Mycobacterium sp., Hyphomicrobium sp. was stimulated and colonized. BC-PU is an innovative and applicable bio-based material in the process of biological purification, which could be widely applied to treat hydrophobic pollutants in the pharmaceutical industry.

Analyses of deodorization performance of mixotrophic biotrickling filter reactor using different industrial and agricultural wastes as packing material

In this study, to efficiently remove malodorous gas and reduce secondary pollution under mixotrophic conditions, pine bark, coal cinder, straw and mobile bed biofilm reactor (MBBR) fillers were used as packing materials in a biological trickling filter (BTF) to simultaneously treat high-concentration H₂S and NH₃. The results showed that the removal rate of BTF-A filled with pine bark was the highest, which was 86.31% and 94.06% under the H₂S and NH₃ loading rates of 53.59 g/m³·h while the empty bed residence time (EBRT) was 40.5 s. The theoretical maximum load was obtained by fitting the kinetic curve, and the value were 90.09 g H₂S m^-³·h^-1 and 172.41 g NH₃ m^-³·h^-1. Meanwhile, after treating with 720 ppm of NH₃, the average concentration of NO₃^- in the BTF circulating fluid was only 127.58 mg/L, indicating the better performance of secondary pollutants control. Microbiological analysis showed that Dokdonella, Micropruina, Candidatus_Alysiosphaera, Nakamurella and Thiobacillus possessed high abundance at the genus level, and their entire percentage in four BTF reactors were 62.87%, 46.32%, 47.98%, and 57.35% respectively. It is worthwhile that the genera Comamonas and Trichococcus with heterotrophic nitrification and aerobic denitrification capabilities and proportion of 3.66%, 1.45%, 5.43%, and 3.23% were observed in four reactors.

The performance and microbial community in a slightly alkaline biotrickling filter for the removal of high concentration H2S from biogas

In this study, high concentration of H₂S (i.e., 5000 ppmv) in biogas was effectively removed by a slightly alkaline biotricking filter (BTF) with Polypropylene rings as packing material and oxygen from air as the electron acceptor. The results showed that when the inlet loading of H₂S increased from 101.7 to 422.0 g/m³/h, the removal efficiency of H₂S decreased from 100.0% to 91.4%, and the maximum elimination capacity (EC) was 386.0 ± 10.5 gH₂S/m³/h when empty bed retention time (EBRT) was 1.0 min. The slightly alkaline condition could increase the mass transfer of H₂S from gas to liquid phase and avoid the toxic effect of high concentration of H₂S, resulting in high removal performance of H₂S in the system. With the increase of H₂S inlet loading, the ratio of SO₄^2- in bio-desulfurization products gradually decreased, while that of S⁰ increased. At 101.7-210.7 gH₂S/m³/h of inlet loading, SO₄^2- was the dominant product with the ratio of above 50.00%, while S⁰ became the dominant product with 62.96% at 422.0 gH₂S/m³/h of inlet loading. The 16S rDNA sequencing results showed that the dominant genus in the BTF was sulfide-oxidizing bacteria (SOB), with the abundance of SOB decreased with the increase of inlet loading. The dominant genus were Pseudomonas, Halothiobacillus and Sulfurimonas in the BTF at 101.7, 139.8 and 210.7 gH₂S/m³/h of inlet loading, respectively. The SOB Sulfurimonas might play an important role for bio-desulfurization of high concentration of H₂S in a slightly alkaline BTF under high inlet loading of H₂S.

Single-/triple-stage biotrickling filter treating a H2S-rich biogas stream: Statistical analysis of the effect of empty bed retention time and liquid recirculation velocity

Biogas containing H₂S has limited use in electricity and heat production as H₂S can be corrosive to metal equipment. Bio-filtration has proved to be a suitable technology for biogas desulfurization because of economical and environmental benefits over physicochemical techniques. In the present study, a response surface methodology using 3² full factorial design was employed to determine the effects of two operating parameters, namely empty bed retention time (EBRT: 100-180 sec) and liquid recirculation velocity (LRV: 2.4-7.1 m³ m^-2 h^-1) on H₂S removal efficiency (%) in single-stage and triple-stage bio-trickling filters (SBTF and TBTF) treating an H₂S-rich biogas. Quadratic model was found to be the best predictive model for H₂S removal efficiency. The results indicated that H₂S removal efficiency was significantly influenced by the synergistic effect of linear terms of EBRT and LRV with a greater effect associated with EBRT. However, the quadratic term of LRV had an antagonistic effect. The quadratic term of EBRT and cross-product term between EBRT and LRV did not exhibit a significant effect on H₂S removal efficiency. The predicted values from the established models showed a close agreement with the experimental data with the coefficient of determination (R²) of 0.99 for H₂S removal efficiency in both SBTF and TBTF. Response analysis demonstrated that the performance of TBTF was superior compared to SBTF.Implications: Bio-trickling filter technology has gained a lot of attention for biogas desulfurization because it is economically and environmentally superior over chemical methods. Empty bed retention time (EBRT) and liquid recirculation velocity (LRV) are crucial variables influencing the performance of bio-trickling filters. In this work, the authors established a model that can properly predict H₂S removal efficiency in a single/triple bio-trickling filter (SBTF and TBTF) treating H₂S-rich biogas with regard to the individual and interaction effects between EBRT and LRV. Analysis with the help of response surface methodology indicated that TBTF was more efficient compared to SBTF for H₂S removal.

Desulphurisation of Biogas: A Systematic Qualitative and Economic-Based Quantitative Review of Alternative Strategies

The desulphurisation of biogas for hydrogen sulphide (H2S) removal constitutes a significant challenge in the area of biogas research. This is because the retention of H2S in biogas presents negative consequences on human health and equipment durability. The negative impacts are reflective of the potentially fatal and corrosive consequences reported when biogas containing H2S is inhaled and employed as a boiler biofuel, respectively. Recognising the importance of producing H2S-free biogas, this paper explores the current state of research in the area of desulphurisation of biogas. In the present paper, physical–chemical, biological, in-situ, and post-biogas desulphurisation strategies were extensively reviewed as the basis for providing a qualitative comparison of the strategies. Additionally, a review of the costing data combined with an analysis of the inherent data uncertainties due underlying estimation assumptions have also been undertaken to provide a basis for quantitative comparison of the desulphurisation strategies. It is anticipated that the combination of the qualitative and quantitative comparison approaches employed in assessing the desulphurisation strategies reviewed in the present paper will aid in future decisions involving the selection of the preferred biogas desulphurisation strategy to satisfy specific economic and performance-related targets.

Characteristics of low H2S concentration biogas desulfurization using a biotrickling filter: Performance and modeling analysis

This study investigated the characteristics of low H₂S concentration biogas biodesulfurization using a lab-scale biotrickling filter (BTF). The influence of operational parameters on H₂S removal efficiency and H₂S distributions in packed bed was evaluated by establishing a counter-current one-dimensional multi-layer BTF model and statistical analysis of the simulation results. The overall biodesulfurization efficiency of counter-current BTF on treating low H₂S concentration was 92.27 ± 10.30%. The H₂S distribution of the BTF packed bed could be predicted by the calibrated BTF model. The influence of the operational parameters on the H₂S distribution of the packed bed was following the sequence of pH > empty bed retention time (EBRT) > gas-to-liquid flow ratio (G/L). The biogas biodesulfurization process was strongly related to the sulphide affinity constant. Moreover, a high substrate concentration of the SOB could further accelerate the biodesulfurization process of the biogas with low H₂S concentration.

Synthesis of novel magnetic ionic liquids as high efficiency catalysts for extraction-catalytic oxidative desulfurization in fuel oil

Deep desulfurization of magnetic ionic liquids [C₄(mim)₂]Cl₂/2FeCl₃.

Performance of a monolith biotrickling filter treating high concentrations of H2S from mimic biogas and elemental sulfur plugging control using pigging

A novel biotrickling filter using a 3D-printed honeycomb-monolith as its filter bed has been proposed and studied in this work and a solution to bed-clogging problems using pigging was demonstrated. The inlet H₂S concentration in the mimic biogas was controlled around 1000 ppm_v and the empty bed gas residence time (EBRT) was 41 s corresponding to a loading rate of 127 g S-H₂S m^-3 h^-1. The influence of different H₂S/O₂ ratios on the removal performance and fate of sulfur end-products was investigated. The results indicated that at a H₂S/O₂ molar ratio of 1:2, an average removal efficiency of 95% and an elimination capacity of 122 g H₂S m^-3 h^-1 was obtained. Under all conditions investigated, elemental sulfur (rather than sulfate) was the dominant end-product which mostly accumulated in the bed. However, the monolith bed design reduced the risk of clogging by elemental sulfur, while bed pigging was shown to be an effective means to remove excess biomass and elemental sulfur accumulated inside the bed and extend the life of the system indefinitely. Altogether, these findings could lead to significant process improvement for biological sweetening of biogas or for removing biomass in biotrickling filters at risk of plugging.

Comparison of Removal Behavior of Two Biotrickling Filters under Transient Condition and Effect of pH on the Bacterial Communities

Although biotrickling filters (BTFs) applied under acidic condition to remove H₂S from waste gases have been reported, the removal behavior of the acidic BTF under transient condition which was normal in most industry processes, and corresponding bacterial community have not been thoroughly studied. In the present study, two BTFs were run under neutral (BTFn) and acidic (BTFa) conditions, respectively. The results revealed that the removal performance of BTFa under transient condition was superior to that of BTFn; the maximum H₂S eliminating capacities (ECs) achieved by BTFa and BTFn were 489.9 g/m³ h and 443.6 g/m³ h, respectively. High-throughput sequencing suggested that pH was the critical factor and several other factors including nutrient and the inlet loadings also had roles in shaping bacterial community structure. Acidithiobacillus was the most abundant bacterial group. The results indicated that BTF acclimation under acidic condition may facilitate generating microbial community with high H₂S-degrading capability.

Theoretical study on the mechanism of oxidative–extractive desulfurization in imidazolium-based ionic liquid

The oxidation of TH to SP by H₂O₂ with the assistance of IL experiences two steps via two transition states.

An efficient and recyclable polyoxometalate-based hybrid catalyst for heterogeneous deep oxidative desulfurization of dibenzothiophene derivatives with oxygen

The possible reaction mechanism.