Biological H2S Removal Research Articles

New microbial electrosynthesis system for methane production from carbon dioxide coupled with oxidation of sulfide to sulfate

Microbial electrosynthesis system (MES) is a promising method that can use carbon dioxide, which is a greenhouse gas, to produce methane which acts as an energy source, without using organic substances. However, this bioelectrical reduction reaction can proceed at a certain high applied voltage when coupled with water oxidation in the anode coated with metallic catalyst. When coupled with the oxidation of HS– to SO42−, methane production is thermodynamically more feasible, thus implying its production at a considerably lower applied voltage. In this study, we demonstrated the possibility of electrotrophic methane production coupled with HS– oxidation in a cost-effective bioanode chamber in the MES without organic substrates at a low applied voltage of 0.2 V. In addition, microbial community analyses of biomass enriched in the bioanode and biocathode were used to reveal the most probable pathway for methane production from HS– oxidation. In the bioanode, electroautotrophic SO42− production accompanied with electron donation to the electrode is performed mainly by the following two steps: first, incomplete sulfide oxidation to sulfur cycle intermediates (SCI) is performed; then the produced SCI are disproportionated to HS– and SO42−. In the biocathode, methane is produced mainly via H2 and acetate by electron-accepting syntrophic bacteria, homoacetogens, and acetoclastic archaea. Here, a new eco-friendly MES with biological H2S removal is established.

Biological removal of gas‐phase H2S in hollow fibre membrane bioreactors

AbstractBACKGROUNDHydrogen sulphide (H2S) must be treated at its emission source to avoid health risks, odour, and corrosion. Conventional physico‐chemical H2S removal technologies (for example, membrane contactors or chemical scrubbers) have several limitations, such as requiring high amounts of absorption chemicals and energy. In contrast, biological H2S removal technologies are environment friendly, easy to operate, and less expensive due to their low energy requirements. In this study, the feasibility of a porous hydrophilic polyethersulfone hollow fibre membrane bioreactor (HFMB) was tested for the biological removal of gas‐phase H2S by employing three lab‐scale reactors (two biotic and one abiotic). The HFMBs were operated at ~20 °C for ~3 months, employing different H2S inlet loading rates (ILR) and an empty bed residence time of 187 s.RESULTSBiotic performance of the HFMBs demonstrated that the removal efficiency (RE) varied between the different inocula and was in the range of 80–100% for the applied H2S ILR of ~5.0–7.5 g m−3 h−1. The RE reached a constant value of ~100% in both biotic reactors at an ILR of ~17.0 g m−3 h−1 when using acclimatized inoculum. The biotic HFMBs demonstrated ~5–9 times higher H2S flux and ~ 20–26 times higher mass transfer compared to the abiotic control. Surface morphology revealed attached microbial growth on the outer surface of the membranes, while the high throughput sequencing confirmed the richness of H2S oxidizing microbial communities on the shell side.CONCLUSIONThe obtained results confirm that the HFMB configuration is suitable for biological treatment of H2S laden waste gas. © 2021 Society of Chemical Industry (SCI).

Model-Based Analysis of Feedback Control Strategies in Aerobic Biotrickling Filters for Biogas Desulfurization

Biotrickling filters are one of the most widely used biological technologies to perform biogas desulfurization. Their industrial application has been hampered due to the difficulty to achieve a robust and reliable operation of this bioreactor. Specifically, biotrickling filters process performance is affected mostly by fluctuations in the hydrogen sulfide (H2S) loading rate due to changes in the gas inlet concentration or in the volumetric gas flowrate. The process can be controlled by means of the regulation of the air flowrate (AFR) to control the oxygen (O2) gas outlet concentration ([O2]out) and the trickling liquid velocity (TLV) to control the H2S gas outlet concentration ([H2S]out). In this work, efforts were placed towards the understanding and development of control strategies in biological H2S removal in a biotrickling filter under aerobic conditions. Classical proportional and proportional-integral feedback controllers were applied in a model of an aerobic biotrickling filter for biogas desulfurization. Two different control loops were studied: (i) AFR Closed-Loop based on AFR regulation to control the [O2]out, and (ii) TLV Closed-Loop based on TLV regulation to control the [H2S]out. AFR regulation span was limited to values so that corresponds to biogas dilution factors that would give a biogas mixture with a minimum methane content in air, far from those values required to obtain an explosive mixture. A minimum TLV of 5.9 m h−1 was applied to provide the nutrients and moisture to the packed bed and a maximum TLV of 28.3 m h−1 was set to prevent biotrickling filter (BTF) flooding. Control loops were evaluated with a stepwise increase from 2000 ppmv until 6000 ppmv and with changes in the biogas flowrate using stepwise increments from 61.5 L h−1 (EBRT = 118 s) to 184.5 L h−1 (EBRT = 48.4 s). Controller parameters were determined based on time-integral criteria and simple criteria such as stability and oscillatory controller response. Before implementing the control strategies, two different mass transfer correlations were evaluated to study the effect of the manipulable variables. Open-loop behavior was also studied to determine the impact of control strategies on process performance variables such as removal efficiency, sulfate and sulfur selectivity, and oxygen consumption. AFR regulation efficiently controlled [O2]out; however, the impact on process performance parameters was not as great as when TLV was regulated to control [H2S]out. This model-based analysis provided valuable information about the controllability limits of each strategy and the impact that each strategy can have on the process performance.

Use of compost as biological filter to remove gaseous hydrogen sulfide

Odor pollution is very popular in developing countries. Odors can arise from many different sources, cause discomfort to expose, and also have certain effects on health. Odors can come from the anaerobic digestion of waste, from a factory's wastewater treatment system, or from manufacturing operations in industries such as seafood processing or animal feed production, tanning, and rubber processing. The composition of the odor is often diverse with many gases, mainly in low concentrations. Because it is gaseous pollution, the odor has the risk of spreading widely, the collection must be carried out in a wide range, the flow of gas to be treated is often large. In this study, one of the basic components of odors, H2S, was of interest to be treated because of its prevalence and toxic nature. Currently, although there are many technologies to handle H2S, the application in odor treatment still has many shortcomings. The current technologies such as adsorption and absorption are not suitable for the removal of H2S in odor because of the low efficiency but high cost. In this study, a cheap and available commercial compost fertilizer was used for the removal of gaseous H2S in a lab-scale biofilter. Results showed that microorganisms had an avital role in H2S removal. The factors affecting the biological removal of H2S were determined to be relative humidity (RH), operation time, presence of mixing/turning, and height of compost column. The high H2S removal efficiency of 94.2% was obtained at RH of 50% and compost height of 400 mm, which is suggested for full-scale biofilter design. Under turning condition of once per two days for compost column, the biofilter system was stable at removal efficiency of over 80% during at least 12 days of operation.

Autotrophic sulfide removal by mixed culture purple phototrophic bacteria

Current H2S treatment methods for sour gases require considerable amounts of chemicals and energy, or in case of biological treatment, unwanted diluents such as oxygen or nitrogen may be introduced. In order to reduce those requirements, the viability of an anaerobic biological H2S removal process using purple phototrophic bacteria (PPB) was investigated in this study. PPB can use sunlight, and centrate as nutrient source, thus potentially reducing energy and chemical requirements. An added benefit is the production of biomass with potential uses, such as single cell protein. An inoculum of PPB enriched from domestic wastewater was grown photoautotrophically with sulfide as the electron donor and inorganic carbon in a mixed culture. Additionally, synthetic medium and centrate as well as high (56 ± 11 Wm-2) and low (27 ± 3 Wm-2) IR irradiation were trialled. Finally, a process model was developed to study biomass specific removal rates and yield. The results showed that a mixed culture of PPB removed sulfide completely in synthetic media (121 ± 9 mg-S.L−1) at a maximum rate of 1.79 ± 0.16 mg-S(Lh)−1 (low irradiance) and 2.9 mg-S(Lh)−1 (high irradiance). The pH increased in both experiments from about 8.5 to 9. Sulfide removal rates using centrate and low irradiance were similar. However Fe and Mn were found to be limiting growth and sulfide removal. In all experiments, Chromatiaceae (purple sulfur bacteria) were most abundant at the end of the experiment, while at the start purple non-sulfur bacteria were most abundant (from the inoculum). Process modelling and experimental work identified the sulfide oxidation to be a multi-step process with accumulation of intermediates. Specific rates were directly dependent on light input, doubling at high irradiance. Sulfide oxidation was estimated at 0.100 ± 0.014 h−1 (0.085 ± 0.012 g-S(g-VS.h)−1) at low irradiance, and the biomass yield at 0.86 ± 0.05 mg-COD.mg-COD−1. This process model enables the virtual evaluation of autotrophic sulfide removal by PPB in a continuous scaled-up process. Overall, the photoautotrophic removal of sulfide seems to be a viable option, especially because of the possibility of using sunlight as an energy source and centrate as a nutrient source.

Effect of dimethyl disulfide on the sulfur formation and microbial community composition during the biological H2S removal from sour gas streams

Effect of dimethyl disulfide on the sulfur formation and microbial community composition during the biological H2S removal from sour gas streams

H2S removal from sour water in a combination system of trickling biofilter and biofilter

Desulfurization of sour water was investigated in a combination system of trickling biofilter (BTF) and biofilter (BF) filled with ceramic packing materials. A critical elimination capacity (EC) of 251.93 g S m−3 h−1 was obtained for the BTF/BF system during a stepwise increase of sulfide concentration from 10 to 60 g S m−3. This stepwise increment of loading rate also led to critical ECs of 176.21 and 478.88 g S m−3 h−1 for BTF and BF, respectively. A dynamic model describing biological H2S removal from sour water in the BTF/BF was developed and calibrated by a set of experimental data. The model includes the main processes occurring in the BTF/BF such as mass transfer between phases, diffusion and biological reaction inside the biofilm. The model also considers the intermediate (elemental sulfur) production/consumption and sulfate formation through the different oxidation pathways. The model validation was performed under a starvation period and a dynamic H2S loading period. A sensitivity analysis was carried out to evaluate the relative importance of the key parameters on the performance of the BTF/BF system. Sensitivity analysis showed that the BTF performance is more affected by the parameters related to H2S mass transfer.

Simultaneous removal of siloxanes and H2S from biogas using an aerobic biotrickling filter

The feasibility of simultaneous removal of siloxane and H2S from biogas was investigated using an aerobic biotrickling filter (BTF). The biodegradation of H2S in the BTF followed a first-order kinetic model and more than 95 % H2S was eliminated within a residence time of 0.3 min. The removal of decamethylcyclopentasiloxane (D5) increased with longer empty bed residence time (EBRT). The partition test and microbial community analysis further reveals that up to 52 % removal of D5 was reached mainly by the chemical-absorption in acid recycling liquid. Finally, D5 was converted into mixtures of dimethylsilanediol (DMSD) and hexamethyldisiloxane (L2) via ring-opening hydrolysis in acid liquid and ring-shrinking polyreaction using CH4 derived from biogas. These operational characteristics demonstrate that the abiotic removal of D5, in addition to biological removal of H2S in an aerobic BTF can significantly decrease the siloxane loading to the downstream siloxane removing units.

Effect of dimethyl disulfide on the sulfur formation and microbial community composition during the biological H2S removal from sour gas streams

Removal of organic and inorganic sulfur compounds from sour gases is required because of their toxicity and atmospheric pollution. The most common are hydrogen sulfide (H2S) and methanethiol (MT). Under oxygen-limiting conditions about 92 mol% of sulfide is oxidized to sulfur by haloalkaliphilic sulfur-oxidizing bacteria (SOB), whilst the remainder is oxidized either biologically to sulfate or chemically to thiosulfate. MT is spontaneously oxidized to dimethyl disulfide (DMDS), which was found to inhibit the oxidation of sulfide to sulfate. Hence, we assessed the effect of DMDS on product formation in a lab-scale biodesulfurization setup. DMDS was quantified using a newly, in-house developed analytical method. Subsequently, a chemical reaction mechanism was proposed for the formation of methanethiol and dimethyl trisulfide from the reaction between sulfide and DMDS. Addition of DMDS resulted in significant inhibition of sulfate formation, leading to 96 mol% of sulfur formation. In addition, a reduction in the dominating haloalkaliphilic SOB species, Thioalkalivibrio sulfidiphilus, was observed in favor of Thioalkaibacter halophilus as a more DMDS-tolerant with the 50 % inhibition coefficient at 2.37 mM DMDS.

A review on prospects and challenges of biological H2S removal from biogas with focus on biotrickling filtration and microaerobic desulfurization

The production of biogas from sulfate-rich materials under anaerobic digestion results in the formation of hydrogen sulfide (H2S). The recommended level of H2S in the produced biogas for direct combustion purposes is in the range of 0.02 to 0.05% w/w (200 to 500 ppm), therefore, desulfurization is required to avoid damages to combustion equipment and prevent the formation of sulfur dioxide (SO2) which is an acid rain precursor. It has been well documented that physical, thermal, and chemical desulfurization approaches suffer from high operation costs as well as waste production needing to be disposed of. Accordingly, a great deal of efforts has been put into biological methods because of being more environmentally friendly and more economically advantageous in comparison with the other techniques. Biotrickling filtration (BTF) and microaerobic desulfurization have shown a high potential for H2S removal at pilot- and large-scale plants. Despite all the progress made and the promising aspects keeping these methods at the core of interest, there are still challenges to be addressed. The present article attempts to briefly review and discuss the challenges and future prospects of BTF and microaerobic desulfurization.

Comparison of biological H2S removal characteristics between a composite packing material with and without functional microorganisms

The performances of two identical biofilters, filled with a new composite packing material (named CM-5) embedded with functional microorganisms or sterilized CM-5 without microorganisms, were investigated for H2S treatment. Running parameters in terms of microbial counts, pressure drops, and inlet and outlet H2S concentrations were measured. The results show that the microbial count of the CM-5 was approximately ×105 CFU/g before being filled into the biofilter, while that of the sterilized CM-5 was negligible. The functional microorganisms embedded in CM-5 adapted to the environment containing H2S quickly. In most cases, pressure drops of the CM-5 biofilter were slightly higher than those of the sterilized CM-5 biofilter when the gas flow rate was 0.6–2.5 m3/h. The maximum elimination capacity (EC) of the CM-5 biofilter in treating H2S could reach up to 65 g/(m3·h) when the loading rate (LR) was approximately 80 g/(m3·h). If the LR was much higher, the measured EC showed a slight downward trend. The experimental ECs of biofilters were fitted by two typical dynamic models: the Michaelis-Menten model and the Haldane model. Compared with the Michaelis-Menten model, the Haldane model fit the experimental ECs better for the two biofilters because of the presence of the substrate inhibition behaviour.

Low-cost filter media for removal of hydrogen sulphide from piggery biogas

The presence of elevated concentrations of hydrogen sulphide (H2S) in piggery biogas is problematic due to its corrosiveness and toxicity. At small scale, the cost of using iron or carbon-based commercial filter media to remove H2S can act as a barrier to the uptake of on-farm biogas technology. To identify cost-effective, alternative options, this study tested and compared H2S removal by the commercial iron-oxide H2S scavenger (cg5) with the alternative solid media: granulated steel furnace slag (GSFS), red soil, compost, composted beef feedlot manure, granular activated carbon (GAC) and biochar. Experiments measured single-pass H2S removal from a pre-humidified standard gas (2000ppm H2S in nitrogen) onto solid media contained in a cylindrical plastic column (DN 25mm, depth 110–147mm). The commercial medium (cg5) performed considerably better than the other media, achieving sulphur removal of 143gS/kg medium at breakthrough (>10ppm outlet H2S). A red soil was the most promising alternative medium (2–12gS/kg medium at breakthrough). The crystalline structure of the iron-oxide minerals appeared to strongly influence the H2S removal capacity of the red soils, and pressure drop was generally high. Bulking with ground sugar cane mulch (SCM) was effective at reducing pressure drop. Interestingly, H2S removal with red soil improved when the soil was regenerated by exposure to air, followed by reuse in the column. Overall, red soil may be a suitable low-cost option, especially for polishing biogas after initial biological H2S removal.

Biological removal of H2S from the livestock manure using a biofilter

In this paper, the biological removal of H2S from air had been investigated using a self-made biofilter with efficient bioceramics and a polyhedral hollow ball. The biological removal efficiency of H2S had been analyzed at different experimental conditions, such as inlet H2S concentration, residence time, initial pH value, and reaction temperature etc. The results showed that the initial pH value had a slight effect on H2S removal efficiency from pH 3 to 9. The optimal initial pH value was 5.5, while the H2S removal efficiency was 100%. The H2S removal efficiency increased with increases in the nutrient solution spraying rate. The appropriate temperature was 25°C in the temperature range from 15 to 30°C. The H2S removal efficiency dropped with the increase of air input and inlet H2S concentration. After being isolated and screened, six strains of heterotrophic sulfide oxidizing bacteria and one strain autotrophic sulfide oxidizing bacteria were determined to be involved in the removal of H2S within the biofilter. The reaction kinetics of H2S was in accordance with first order reaction kinetics.

Microbial Removal of Hydrogen Sulfide from Biogas

Biogas can contain 50–300 ppm of hydrogen sulfide, which is a highly corrosive and malodorous gas. It can be separated by several chemical techniques which are cost effective but the disposal of byproducts is another problem. Biological removal of H2S from biogas is a low-cost technique and environmentally safe. For the removal of H2S from biogas a packed bed biofilter is developed having wooden pellets as packing material for adhering each one of the microbial cultures such as T. thioparus, T. thioxidans, and T. novellus. Biogas passed through this biofilter column at different flow rates (0.003, 0.006, 0.075, 0.012, and 0.015 m3h−1) with a spray of liquid medium of different microbial cultures (flow rate 12 Lh−1) at different temperatures (25, 30, 35, and 40°C) separately in counter current action. It is observed that at a low flow rate 0.003 to 0.006 m3h−1 100% removal efficiency was observed for each of the mentioned microbial cultures. However, H2S removal efficiency by T. thioparus is higher (47, 66.6, and 76.7%) at a high flow rate (0.003 and 0.006 ml/min−1) as compared to the other two microbial cultures.

Removal study of hydrogen sulfide using natural second metabolites

This paper reports on the experimental investigation carried out to evaluate the physical optimal conditions in a packed absorption column to remove odorous chemical of hydrogen sulfide gas (H2S). H2S is a highly undesirable contaminant that is most commonly from environmental treatment facilities. Natural second metabolites extracted from conifer trees were used to remove H2S via chemical neutralization. The absorbent of natural second metabolites achieved a removal efficiency of 62% by itself. However, the removal efficiency was increased to 96% using complex absorbent mixed with 1.0% of an amine chemical. The liquid mass transfer coefficient was used to determine the conditions for the optimal removal efficiency using the convective flow rate, temperature, and pH. The results show that an aqueous solution containing natural second metabolites might be a good absorbent in a column packed with Raschig rings for the biological removal of H2S.

Laboratory pilot scale study for H2S removal from biogas in an anoxic biotrickling filter

The purpose of this laboratory pilot scale study at the Wastewater Technology Centre (WTC), Environment Canada, Burlington, ON was to investigate the anaerobic biological removal of H2S from biogas under real-time operating conditions. Biogas produced in a 538 litre pilot anaerobic digester was continuously fed into a 12 litre biotrickling filter containing plastic fibres as packing bed media. The process was monitored for several months. The biogas flowrate and H2S concentration ranged between 10 to 70 L/h and 1,000 to 4,000 ppmv respectively over the course of the test period. Nitrate-rich wastewater from a pilot scale sequencing batch reactor effluent was used as the nutritive solution for the biotrickling filter. The paper presents the influence of several operational parameters such as biogas flowrate, hydrogen sulphide concentration and composition of nutrient solution on process performance. To date, our results show H2S removal rates up to 100% without adverse effects on the methane concentration of the biogas. No system deterioration was observed over long term operation. This non-conventional technology is very promising and could be considered for full scale applications.

Comparison of the Biological H2S Removal Characteristics among Four Inorganic Packing Materials.

Four inorganic packing materials were evaluated in terms of their availability as packing materials of a packed tower deodorization apparatus (biofilter) from the viewpoints of biological H2S removal characteristics and some physical properties. Among porous ceramics (A), calcinated cristobalite (B), calcinated and formed obsidian (C), granulated and calcinated soil (D), the superiority of these packing materials determined based on the values of non-biological removal per unit weight or unit volume of packing material, complete removal capacity of H2S per unit weight of packing material per day or unit volume of packing material per day and pressure drop of the packed bed was in the order of A approximately equal to C > D approximately equal to B, which is correlated with the maximum water content, porosity, and mean pore diameter.