Hydrogen sulfide oxidation under anoxic conditions by a nitrate-reducing, sulfide-oxidizing bacterium isolated from the Mae Um Long Luang hot spring, Thailand (2023)

Volatile reduced sulfur compounds were odor and irritating toxic gas, which were commonly produced during waste and wastewater treatment. The autotrophic sulfide denitrifiers converted sulfide as alternative electron acceptor to reduce nitrate, which achieved simultaneous denitrification and sulfur oxidation. In this study, to investigate the effect of sulfur compounds solubility, S/N and oxygen on sulfur and nitrogen removal, a bioscrubber was studied for treatment of hydrophilic H₂S and hydrophobic CS₂. Both H₂S and CS₂ could be efficiently removed (99%), with the highest sulfide loading of 46.9 gS/m³·d. The elemental sulfur production was strongly correlated to S/N ratio (r=0.969, p=0.03), the highest elemental sulfur production efficiency achieved 92.0% under S/N ratio of 2.0 for treatment of H₂S. Thiobacillus sp. bacteria was the pre-dominated sulfide-dependent denitrifiers (78.2%) before exposing to oxygen, while abundance of Cryseobacterium and unclassified Xanthomonadaceae aerobic sulfide oxidizer dramatically increased up to 40% and 7.3% after aeration. Remarkably increasing production of extracellular polymeric substance (197%) was observed after treatment of CS₂, which might promote the hydrolysis of CS₂ and stabilization of elemental sulfur. This study demonstrated the possibility to apply sulfide-dependent denitrification process for treatment of both hydrophilic and hydrophobic volatile reduced sulfur waste gas with elemental sulfur recovery.

Biogas as a renewable energy resource can be broadly recognised as a carbon–neutral fuel which reduces anthropogenic greenhouse gas emissions, mitigates global warming, and diversifies energy supply. However, the biogas share in the global renewable energy supply chain and technology deployment and maturity are not commensurate with the potential. The first half of this study critically reviews state of the art developments in biogas cleaning and upgrading technologies by considering their present status, current challenges, and barriers associated with their future development. The second part of this paper aims to address critical gaps in converting biogas to biomethane, proposing required pre-treatment steps for different technologies. The third part focuses on current policies concerning the strict regulations implemented for flaring consent applications. In this section, biogas upgrading technologies were compared by estimating the global warming potential (GWP) resulting from waste gases (WG). It was observed that due to high methane losses, WGs from membrane technologies have the highest GWP, but with flaring have the lowest GWP. In the last part of this review, the recent applications of biogas in cogeneration (CHP), tri-generation (CCHP), quad-generation systems, heat, and vehicles are discussed. The use of biogas by different technologies, and their resulting efficiencies were analysed in CHP applications, including microturbines, micro humid air turbine (mHAT), solid oxide fuel cells (SOFC) and hybrid systems of SOFC-microturbines.

Hydrogen sulfide (H₂S) is considered one of the serious toxic pollutants in mariculture environment. Consequently, it is necessary to develop an effective strategy to prevent the production of sulfide. In this study, we modified the ceramsite with iron (ICC) and prepared a microbial agent, i.e., the immobilized sulfur-oxidizing-bacterium on the ICC (SICC), the microbial agent was following dosed in the simulated mariculture systems to control the sulfide pollutant. Results showed that the sulfide removal capacity of the new material ICC reached to 3.42 mg S g⁻¹ in 24 h. Comparably, the microbial agent SICC presented a stable capability in oxidizing sulfide and the sulfide removal was above 65% in test media feeding with 600 mg L⁻¹ sulfide even after five times of recycling. The microcosm experiments conducted in the simulated mariculture systems showed that the application of the ICC together with the SICC was able to quickly remove the existing sulfide and persistently inhibit the production of sulfide, the immobilized sulfur-oxidizing-bacterium survived stably in the new environment accounting for 1.22% of total microbial community. Therefore, dosing the ICC and SICC simultaneously might be a preferable strategy and presented a promising perspective in remediating the deteriorated mariculture environment.

The present study deals with the biotransformation of virulent petroleum refinery concoction with phenol (750mg/L), emulsified crude oil (300mg/L), S²⁻ (750mg/L), NH₄⁺-N (350mg/L) and NO₃⁻-N (1000mg/L) in anoxic (A1) - aerobic (A2) moving bed reactors operated in series. The efficacy of the system was analysed through measurement of pollutant concentrations, GC-MS and FTIR peaks of the influent and effluent, and biomass activity studies. The system was able to eliminate the organics and inorganics with more than 99% efficiency at 80h HRT and 64h cycle time. GC-MS results revealed breakage of high molecular weight organics to smaller compounds after anoxic treatment. Further treatment of anoxic effluent by aerobic biomass reduced the number of peaks in the final effluent significantly. FTIR results were in accord with the GC-MS results. Heterotrophic activity (HA) of the aerobic biomass was higher than anoxic biomass due to its higher free energy change. Anoxic biomass showed chemolithotrophic activity (CA), suggesting survival in the absence of organics. Gas generated from anoxic reactor consisted of 91% nitrogen, 1% CO₂, 1% H₂S and rest was unaccounted.

Biological hydrogen sulphide (H₂S) removal from a biogas mimic (pH=∼7.0) was tested for 189 days in an anoxic biotrickling filter (BTF) inoculated with a pure culture of Paracoccus versutus strain MAL 1HM19. The BTF was packed with polyurethane foam cubes and operated in both fed-batch and continuous modes. The H₂S inlet concentration to the BTF was varied between ∼100 and ∼500 ppm_v during steady-state tests, and thereafter to ∼1000, ∼2000, ∼3000 and ∼4000 ppm_v during shock-load (i.e. transient state) tests. The H₂S removal efficiency (RE) ranged between 17 and 100% depending on the operational mode of the BTF and the presence of acetate as a carbon source. The maximum elimination capacity (EC_max) of the BTF reached 113.5 (±6.4) g S/m³ h with 97% RE during H₂S shock-load experiments at ∼4000 ppm_v which showed the robustness and resilient capacity of BTF for the large fluctuations of H₂S concentrations. The results from polymerase chain reaction denaturing gradient gel electrophoresis (PCR–DGGE) revealed that P.versutus remained dominant throughout the 189 days of BTF operation which can imply the crucial role of this bacterium to remove H₂S and upgrade to clean biogas. The analysis using artificial neural networks (ANNs) predicted the H₂S and NO₃⁻-N REs and SO₄²⁻ production in the anoxic BTF. Consequently, this study revealed that a BTF can be used to treat H₂S contamination of biogas under anoxic conditions.

The pore distribution in activated carbon is crucial for its performance on adsorption processes. In desulfurization applications, the literature highlights the importance of pores from 5 to 10 Å. However, little is known and reported about the range of ultramicropores smaller than 4 Å, which has been found in commercial samples used for H₂S retention. In order to clarify the influence of this fraction of pores on the H₂S retention of typical biogas mixtures, measurements of multicomponent adsorption of hydrogen sulfide in the presence of carbon dioxide for activated carbon samples further impregnated with potassium hydroxide have been performed in column dynamics. Molecular simulation, XRF analysis and textural characterization were applied to aid the study. Results have shown that the H₂S retention capacity in the presence of CO₂ decreased significantly mainly in the impregnated samples. The degree of reduction in H₂S retention indicates that ultramicropores can be of substantial importance through a synergistic immobilizing effect of H₂S molecules. The better understanding of such an effect could improve the development of more efficient adsorbents for chemical industries.

Chemical Engineering Journal, Volume 285, 2016, pp. 83-91

A real biogas effluent was desulfurized using an anoxic biotrickling filter at pilot scale. Guidelines and recommendations have been proposed to achieve the correct inoculation and biofilm development. The hydrogen sulfide inlet concentration (4100–7900ppm_V) was not controlled. The operational variables studied were the hydrogen sulfide inlet load (37–149gSm⁻³h⁻¹), biogas flow rate (1–3.4Nm³h⁻¹) and pH (6.8–7.4). Moreover, three nitrate-feeding modes were studied: manual, continuous and automated. Without the addition of nutrients to the nitrate solution, a removal efficiency greater than 95% was obtained for loads in the range 33–55gSm⁻³h⁻¹ along with an elemental sulfur percentage of 85±5%. The nitrate solution was mainly composed of NaNO₃ (500gL⁻¹), the macronutrients KH₂PO₄ (10gL⁻¹), NH₄Cl (5gL⁻¹) and MgSO₄·7H₂O (4gL⁻¹), and trace elements. The critical elimination capacity was 94.7gSm⁻³h⁻¹ (RE>99%) on day 119 and the maximum elimination capacity was 127.3gSm⁻³h⁻¹ (RE=92.6%) on day 122. The recommended operational conditions for start-up are an inlet load of 100gSm⁻³h⁻¹, a pH set-point of 6.8 to reduce sulfide accumulation and nitrate-feeding automated by oxide reduction potential.

International Journal of Hydrogen Energy, Volume 42, Issue 29, 2017, pp. 18425-18433

Hydrogen sulfide (H₂S), a highly corrosive gas, is found in biogas due to the biodegradation of proteins and other sulfur containing organic compounds present in feed stock during anaerobic digestion. The presence of H₂S is one of the biggest factors limiting the use of biogas. It should be removed prior to application of biogas in an electric generator or industrial boiler. The present research evaluated the performance of biotrickling filter inoculated with Halothiobacillus neapolitanus NTV01 (HTN) on the H₂S removal from synthetic biogas. HTN, isolated and purified from activated sludge, is a sulfur oxidizing bacteria able to degrade H₂S and thiosulfate to elemental sulfur and sulfate, respectively. Operational parameters in a short term operation were varied as following; gas flow rate (0.5–0.75LPM); EBRT (40–120s); the inlet H₂S concentrations (0–1500ppmv); liquid recirculation rate (3.6–4.8L/h). EBRT showed a greater effect to the removal efficiency than increasing H₂S concentration. Longer EBRT resulted higher removal efficiency. The changes of liquid recirculation rates did not significantly affect the removal efficiency. In long term operation, the gas flow rate and liquid recirculation rate were fixed at 0.5 LPM (120s EBRT) and 3.6L/h; and H₂S concentrations were varied (0–2040ppmv). The maximum elimination capacity was found as 78.57gH₂S/m³h, which had greater performance than the previous studies.

Journal of Environmental Chemical Engineering, Volume 5, Issue 6, 2017, pp. 5617-5623

The biofiltration of hydrogen sulfide present in a biogas mimic under anoxic conditions was performed using expanded schist and cellular concrete waste as packing materials. The impact of various parameters, such as H₂S concentrations, Empty Bed Residence Time (EBRT) and molar ratio N/S, on the performances of biofilters was evaluated. At an EBRT of 300s, expanded schist efficiently treated H₂S concentrations up to 1100 ppmv (maximum elimination capacity EC_max=30.3gm⁻³h⁻¹). At an EBRT of 240s, cellular concrete waste was an effective material for the treatment of concentrations of H₂S up to 900ppmv (EC_max=25.2gm⁻³h⁻¹). Whatever the molar ratio N/S selected, sulfate and elemental sulfur were produced in the biofilters. Both materials presented a satisfactory mechanical behavior with low pressure drops. Therefore, this study showed that biofilters could be used to treat moderate concentrations of H₂S in biogas under anoxic conditions.

Journal of Environmental Chemical Engineering, Volume 4, Issue 2, 2016, pp. 2370-2377

International Journal of Hydrogen Energy, Volume 41, Issue 35, 2016, pp. 15682-15687

Hydrogen sulfide (H₂S) in biogas, is both toxic and damaging to the environment, to the human health, and also damages machines and engines by contributing substantially towards corrosion. It can be removed from the biogas before being used by utilizing biological or physiochemical processes. A new bacterial strain of obligately chemolithoautotroph, Halothiobacillus neapolitanus NTV01 (HTN) with ability to remove H₂S from gas stream was screened, purified, and inoculated in a biotrickling filter system with counter current gas/liquid flows. Maximum sulfur oxidation activity and cell growth were found in the culture medium consisting of 10g/L of thiosulfate and 52mM phosphate buffer pH 7. HTN is able to tolerate higher sulfate concentrations (8.35g/L) than reported previously. In the biotrickling filter operation with biogas fed to the system, pH appeared to be a highly important factor to affect the H₂S removal. Liquid recirculation required a fresh replacement every 48h and controlled pH 7 to achieve the optimum performance of H₂S removal. H₂S was efficiently removed 95–100% when the initial concentration in the range of 45–255 ppmv.

International Biodeterioration & Biodegradation, Volume 105, 2015, pp. 185-191

In this work, a sulfur-oxidizing bacteria, Thiobacillus thioparus (immobilized on Mavicell B support) was employed to develop a microaerobic, biotrickling filter reactor for the efficient elimination of H₂S from synthetic (bio)gas. To test the capability of this particular strain in oxygen-limited atmosphere, fixed bed reactor was operated under 0.25–5 vol.% O₂ concentrations and its H₂S decomposing ability was statistically evaluated. It was found that the system achieved 100% H₂S elimination efficiency when at least 2.5 vol.% oxygen was provided. Further decrease of O₂ levels to 0.25–1 vol.% cut the reliability and caused the loss of H₂S biodegradation performance. The results of this study contributed to understand the behavior of T.thioparus under microaerobic conditions and thus may help to design efficient gas purification processes for biogas technology.