Anoxic Biotrickling Filter Research Articles

Implementation of a Pilot-Scale Biotrickling Filtration Process for Biogas Desulfurization under Anoxic Conditions Using Agricultural Digestate as Trickling Liquid.

A pilot-scale biotrickling filter (BTF) was operated in counter-current flow mode under anoxic conditions, using diluted agricultural digestate as inoculum and as the recirculation medium for the nutrient source. The process was tested on-site at an agricultural fermentation plant, where real biogas was used. The pilot plant was therefore exposed to real process-related fluctuations. The purpose of this research was to attest the validity of the filtration process for use at an industrial-scale by operating the pilot plant under realistic conditions. Neither the use of agricultural digestate as trickling liquid and nor a BTF of this scale have previously been reported in the literature. The pilot plant was operated for 149 days. The highest inlet load was 8.5 gS-H2Sm-3h-1 with a corresponding removal efficiency of 99.2%. The pH remained between 7.5 and 4.6 without any regulation throughout the complete experimental phase. The analysis of the microbial community showed that both anaerobic and anoxic bacteria can adapt to the fluctuating operating conditions and coexist simultaneously, thus contributing to the robustness of the process. The operation of an anoxic BTF with agricultural digestate as the trickling liquid proved to be viable for industrial-scale use.

A Two-Stage Biogas Desulfurization Process Using Cellular Concrete Filtration and an Anoxic Biotrickling Filter

A two-stage desulfurization process including an abiotic filtration using cellular concrete waste (first stage) and an anoxic biotrickling filter filling with an inoculated expanded schist material (second stage) was investigated to remove H2S in mimic biogas with limited O2 amount (ranged from 0.5 to 0.8%). The two-stage process was able to satisfactorily remove H2S for all experimental conditions (RE > 97%; H2S concentration = 1500 mg m−3; total Empty Bed Residence Time (EBRT) = 200 s; removal capacity (RC) = 26 g m−3 h−1). Moreover, at a total EBRT = 360 s (i.e., 180 s for each stage), the H2S loading rate (LR) was almost treated by the bed of cellular concrete alone, indicating that abiotic filtration could be applied to satisfactorily remove H2S contained in the gas. According to the H2S concentration entering the biotrickling filter, the majority end-product was either elemental sulfur (S0) or sulfate (SO42−). Thus, the ability of the abiotic filter to remove a significant part of H2S would avoid the clogging of the biotrickling filter due to the deposit of S0. Consequently, this two-stage desulfurization process is a promising technology for efficient and economical biogas cleaning adapted to biogas containing limited O2 amounts, such as landfill biogas.

Integration of a nitrification bioreactor and an anoxic biotrickling filter for simultaneous ammonium-rich water treatment and biogas desulfurization

A preliminary assessment has been carried out on the integration of an anoxic biotrickling filter and a nitrification bioreactor for the simultaneous treatment of ammonium-rich water and H2S contained in a biogas stream. The nutrient consumption in the biotrickling filter was as follows (mol−1 NO3−-N): 6.3·10−4 ± 1.2·10−4 mol PO43−-P, 0.04 ± 0.05 mol NH4+-N and 0.04 ± 0.03 mol K+-K. Furthermore, it was possible to supply a mixture of biogenic NO3− and NO2− into the biotrickling filter from the nitrification bioreactor to obtain a maximum elimination capacity of 152 gH2S–S m−3 h−1. The equivalence between the two compounds was 1 mol NO3−-N equal to 1.6 mol NO2−-N. The biotrickling filter was also operated under a stepped variable inlet load (30–100 gH2S–S m−3 h−1) and outlet H2S concentrations of less than 150 ppmV were obtained. It was also possible to maintain the outlet H2S concentration close to 15 ppmV with a feedback controller by manipulating the feed flow (in the nitrification bioreactor). Two stepped variable inlet loads were tested (60–111 and 16–102 gH2S–S m−3 h−1) under this type of control. The implementation of feedback control could enable the exploitation of biogas in a fuel cell, since the H2S concentrations were 15.1 ± 4.3 and 15.0 ± 3.4 ppmV. Finally, the anoxic biotrickling filter experienced partial denitrification and this implied a loss of the desulfurization effectiveness related to SO42− production.

Markers for the Comparison of the Performances of Anoxic Biotrickling Filters in Biogas Desulphurisation: A Critical Review

The agriculture and livestock industry generate waste used in anaerobic digestion to produce biogas containing methane (CH4), useful in the generation of electricity and heat. However, although biogas is mainly composed of CH4 (~65%) and CO2 (~34%), among the 1% of other compounds present is hydrogen sulphide (H2S) which deteriorates engines and power generation fuel cells that use biogas, generating a foul smell and contaminating the environment. As a solution to this, anoxic biofiltration, specifically with biotrickling filters (BTFs), stands out in terms of the elimination of H2S as it is cost-effective, efficient, and more environmentally friendly than chemical solutions. Research on the topic is uneven in terms of presenting performance markers, underestimating many microbiological indicators. Research from the last decade was analyzed (2010–2020), demonstrating that only 56% of the reviewed publications did not report microbiological analysis related to sulphur oxidising bacteria (SOB), the most important microbial group in desulphurisation BTFs. This exposes fundamental deficiencies within this type of research and difficulties in comparing performance between research works. In this review, traditional and microbiological performance markers of anoxic biofiltration to remove H2S are described. Additionally, an analysis to assess the efficiency of anoxic BTFs for biogas desulphurisation is proposed in order to have a complete and uniform assessment for research in this field.

Characterization of eubacterial communities by Denaturing Gradient Gel Electrophoresis (DGGE) and Next Generation Sequencing (NGS) in a desulfurization biotrickling filter using progressive changes of nitrate and nitrite as final electron acceptors

Anoxic biotrickling filters (BTFs) represent a technology with high H2S elimination capacity and removal efficiencies widely studied for biogas desulfurization. Three changes in the final electron acceptors were made using nitrate and nitrite during an operating period of 520 days. The stability and performance of the anoxic BTF were maintained when a significant perturbation was applied to the system that involved the progressive change of nitrate to nitrite and vice versa. Here the impact of electron acceptor changes on the microbial community was characterized by denaturing gel gradient electrophoresis (DGGE) and next generation sequencing (NGS). Both platforms revealed that the community underwent changes during the perturbations but was resilient because the removal capacity did not significantly change. Proteobacteria and Bacteroidetes were the main Phyla and Sulfurimonas and Thiobacillus the main nitrate-reducing sulfide-oxidizing bacteria (NR-SOB) genera involved in the biodesulfurization process.

Special Issue “Advances in Biogas Desulfurization”

This Special Issue contains three articles and two reviews. The biological reactors used in the studies were fed with real biogas from Landfill or STPs. One research article concerns the use of a pilot scale plant with a combined process with a chemical and biological system. The other two studies concern anoxic biotrickling filters, with one study focused on the study of variable operation and its optimization through the response surface methodology, and the other focused on the selection of packing material. The reviews concern the current state of biogas desulfurization technologies, including an economic analysis, and the microbial ecology in biofiltration units. This Issue highlights some of the most relevant aspects about biogas desulfurization.

Resilient performance of an anoxic biotrickling filter for hydrogen sulphide removal from a biogas mimic: Steady, transient state and neural network evaluation

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 ppmv during steady-state tests, and thereafter to ∼1000, ∼2000, ∼3000 and ∼4000 ppmv 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 (ECmax) of the BTF reached 113.5 (±6.4) g S/m3 h with 97% RE during H2S shock-load experiments at ∼4000 ppmv 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.

Efficient removal of siloxanes and volatile organic compounds from sewage biogas by an anoxic biotrickling filter supplemented with activated carbon

The removal of siloxanes (D4 and D5) and volatile organic contaminants (hexane, toluene and limonene) typically found in sewage biogas was investigated in a lab-scale biotrickling filter (BTF) packed with lava rock under anoxic conditions. Complete removal efficiencies for toluene and limonene were recorded at all empty bed residence time (EBRT) tested. The influence of EBRT was remarkable on the abatement of D5, whose removal decreased from 37% at 14.5 min to 16% at 4 min, while the removal of D4 and hexane remained below 16%. The packing material was supplemented with 20% of activated carbon aiming at increasing the mass transfer of the most hydrophobic pollutants. This strategy supported high removal efficiencies of 43 and 45% for hexane and D5 at the lowest EBRT. CO2 and silica were identified as mineralization products along with the presence of metabolites in the trickling solution such as dimethylsilanediol, 2-carene and α-terpinene.

Application of Response Surface Methodology for H2S Removal from Biogas by a Pilot Anoxic Biotrickling Filter

In this study, a pilot biotrickling filter (BTF) was installed in a wastewater treatment plant to treat real biogas. The biogas flow rate was between 1 and 5 m3·h−1 with an H2S inlet load (IL) between 35.1 and 172.4 gS·m−3·h−1. The effects of the biogas flow rate, trickling liquid velocity (TLV) and nitrate concentration on the outlet H2S concentration and elimination capacity (EC) were studied using a full factorial design (33). Moreover, the results were adjusted using Ottengraf’s model. The most influential factors in the empirical model were the TLV and H2S IL, whereas the nitrate concentration had less influence. The statistical results showed high predictability and good correlation between models and the experimental results. The R-squared was 95.77% and 99.63% for the ‘C model’ and the ‘EC model’, respectively. The models allowed the maximum H2S IL (between 66.72 and 119.75 gS·m−3·h−1) to be determined for biogas use in a combustion engine (inlet H2S concentration between 72 and 359 ppmV). The ‘C model’ was more sensitive to TLV (–0.1579 (gS·m−3)/(m·h−1)) in the same way the ‘EC model’ was also more sensitive to TLV (4.3303 (gS·m−3)/(m·h−1)). The results were successfully fitted to Ottengraf’s model with a first-order kinetic limitation (R-squared above 0.92).

Feedback and Feedforward Control of a Biotrickling Filter for H2S Desulfurization with Nitrite as Electron Acceptor

Biotrickling filters’ control for H2S removal has special challenges because of complexity of the systems. Feedback and feedforward control were implemented in an anoxic biotrickling filter, operated in co-current flow mode and using nitrite as an electron acceptor. The feedback controller was tuned by three methods—two based on Ziegler-Nichols’ rules (step-response and maintained oscillation) and the third using the Approximate M-constrained Integral Gain Optimization (AMIGO). Inlet H2S staircase step perturbations were studied using a feedforward control and the effect of EBRT considered by feedback control. The tuning method by maintained oscillation shows the lower errors. The selected controller was a PI, because unstable behavior at the lowest H2S inlet loading was found under a PID controller. The PI control was able to maintain an outlet H2S concentration of 14.7 ± 0.45 ppmV at three EBRT, studied at 117 s, 92 s and 67 s. Therefore, desulfurized biogas could be used to feed a fuel cell. Feedforward control enhances BTF performance compared to the system without control. The maximum outlet H2S concentration was reduced by 26.18%, although sulfur selectivity did not exceed 55%, as elemental sulfur was the main oxidation product.

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.

Influence of trickling liquid velocity, low molar ratio of nitrogen/sulfur and gas-liquid flow pattern in anoxic biotrickling filters for biogas desulfurization

Hydrogen sulfide has been successfully removed from biogas using anoxic biotrickling filters but an in-depth study of the main operational variables has not yet been carried out. The effect of (i) the empty bed residence time (32–164 s) at a hydrogen sulfide concentration of 2,000 ppmv, (ii) the inlet hydrogen sulfide concentration (2,000–10,000 ppmv), (iii) the trickling liquid velocity (4.8–20.9 m h−1) and (iv) the feed of low nitrogen/sulfur molar ratio (0.334–0.409 mol N-NO3– mol−1 S-H2S) on the hydrogen sulfide removal efficiency have been studied. The BTF (total packed volume of 2.8 L, height/diameter ratio of 9.8) was filled with polypropylene Pall rings (5/8″) and fed continuously with nitrate and a biogas mimic operating in counter-current and co-current flow modes.The maximum elimination capacity was 282.0 gS-H2S m–3 h–1 (RE 97 ± 0.5%) for counter-current flow and 287.5 gS-H2S m–3 h–1 (RE 99 ± 0.4%) for co-current flow mode for an EBRT of 164 s. In addition, in terms of the nitrogen/sulfur molar ratio a higher elemental sulfur production was found in counter-current flow (97.6 ± 2.0%) when compared to co-current flow (87.6±2.8%) since a better depletion of nitrate occurred in co-current flow mode.Finally, three different nitrogen/sulfur molar ratios (0.4, 1.0 and 1.6 mol N-NO3– mol–1 S-H2S) were compared economically. The low and high ratios would involve a nitrate cost of 0.54 and 2.15 € per kg of treated of S-H2S and an elemental sulfur production of 21.5 metric tons and zero production, respectively.

Abatement of dimethyl sulfide using anoxic biotrickling filter

AbstractBACKGROUNDThis study aimed to use a lab‐scale anoxic biotrickling filter (ABTF) for the bioconversion of dimethyl sulfide (DMS) gas to produce less harmful byproducts, i.e. elemental sulfur and/or sulfate. It examined the exploitation of nitrate as an electron acceptor in the oxidation of malodorous DMS‐containing gas in combination with other parameters: gas/liquid (G/L) ratio (40, 60, 80, 100, 150), empty bed residence time (EBRT) (10, 30, 60, 90, 120 s) and inlet loading (IL) (9, 18, 48, 90 g m−3 h−1).RESULTSThermodynamic analysis and half‐reactions showed that at DMS/NO3− molar yield ratios 0.75 and 0.34, elemental sulfur and sulfate were the main metabolic products respectively. Overall, 58% of the sulfur element in DMS was bioconverted to elemental sulfur. Mass balance calculations revealed high denitrification efficiency, i.e. 52.7% of inlet NO3− was converted to N2. The optimal EBRT was found as 30 s (corresponding to removal efficiency (RE) 89%) for inlet concentration 150 mg m−3 and as 60 s (corresponding to RE 78%) for inlet concentration 1500 mg m−3. However, the maximum elimination capacity (EC) was 70.3 g m−3 h−1 at EBRT 60 s and G/L ratio 80. The relative abundance of bacterial communities was dominated by Proteobacteria (56.1%) and Alphaproteobacteria (27.3%) at phylum and class levels respectively.CONCLUSIONThe study revealed that ABTF has a reliable biodegradation capacity in DMS oxidation under anoxic conditions; however, process improvement on mass transfer enhancement for low waste gas concentrations is still required. © 2019 Society of Chemical Industry

H2S removal and microbial community composition in an anoxic biotrickling filter under autotrophic and mixotrophic conditions.

Removal of H2S from gas streams using NO3--containing synthetic wastewater was investigated in an anoxic biotrickling filter (BTF) at feed N/S ratios of 1.2-1.7 mol mol-1 with an empty bed residence time of 3.5 min and a hydraulic retention time of 115 min. During 108 days of operation under autotrophic conditions, the BTF showed a maximum elimination capacity (EC) of 19.2 g S m-3 h-1 and H2S removal efficiency (RE) >99%. When the BTF was operated under mixotrophic conditions by adding organic carbon (10.2 g acetate m-3 h-1) to the synthetic wastewater, the H2S EC decreased from 16.4 to 13.1 g S m-3 h-1, while the NO3- EC increased from 9.9 to 11.1 g NO3--N m-3 h-1, respectively. Thiobacillus sp. (98-100% similarity) was the only sulfur-oxidizing nitrate-reducing bacterium detected in the BTF biofilm, while the increased abundance of heterotrophic denitrifiers, i.e. Brevundimonas sp. and Rhodocyclales, increased the N/S ratio during BTF operation. Residence time distribution tests showed that biomass accumulation during BTF operation reduced gas and liquid retention times by 17.1% and 83.5%, respectively.

Removal of ethanethiol using a biotrickling filter with nitrate as an electron acceptor

ABSTRACTMany studies have discussed the biotreatment of ethanethiol (ET) under aerobic conditions. However, O2 free conditions offer bio-conversion of ET gas into elemental sulphur and/or sulphate using as electron acceptor, and this has been not studied. In this study, an anoxic biotrickling filter was tested in lab-scale conditions with ET/ ratio 0.74 and 0.34 mole/mole to remove malodorous ET waste gas. The study examined the effect of three operational parameters: ET inlet concentrations (150, 300, 800, and 1500 mg/m3), trickling velocities (0.12, 0.18, 0.24, 0.3, and 0.45 m/h), and empty bed residence times (30, 60, 90, and 120 s). It found that the effect of trickling velocity on removal efficiency depended on inlet concentrations; 0.24 m/h trickling velocity resulted in efficient ET removal (higher than 90.8% for 150 mg/m3 of inlet concentration) while 0.45 m/h trickling velocity could only achieve a removal of 80.6% for 1500 mg/m3 of inlet concentration at fixed EBRT 60 s. Increasing the EBRT up to 60 s was adequate to achieve removal efficiency, i.e. 92 and 80% for ET inlet concentrations 150 and 1500 mg/m3 respectively, and the maximum elimination capacity was 75.18 g/m3/h at 0.45 m/h. Overall, the anoxic conditions enhanced the low oxidation rates of ET in an anoxic biotrickling filter despite mass transfer limitations and poor solubility of ET.

Progressive change from nitrate to nitrite as the electron acceptor for the oxidation of H2S under feedback control in an anoxic biotrickling filter

Nitrate has been progressively replaced by nitrite as the electron acceptor in the oxidation of H2S from biogas mimic by an anoxic biotrickling filter. Perturbations in the inlet H2S concentration with and without the implementation of feedback controllers have been evaluated. Nitrite was successfully used without decreasing the H2S removal efficiency (94.74 ± 0.01%). Moreover, a PID controller allowed the sulfate selectivity to be maintained and reduced the maximum outlet H2S concentration when compared to the system without control (54.4–64.4%), although elemental sulfur was the main oxidation product. On using ORP control the main disadvantage was the production of peaks in the outlet H2S concentration. The stability and resilience of the biological system were assessed by analyzing the microbial community profiles by 16S rDNA-denaturing gradient gel electrophoresis (DDGE). The modification of the electron acceptor led to a reduction in the diversity and increased the dominance of the microbial populations.

Feedforward control application in aerobic and anoxic biotrickling filters for H2S removal from biogas

AbstractBACKGROUNDFeedforward control was implemented at laboratory scale in an aerobic and an anoxic biotrickling filter (BTF) operating under fluctuating H2S loading rate (LR) conditions in order to show the capabilities and added value of this control strategy. Dynamic, long‐term tests with variable H2S LR were performed to simulate disturbances in the inlet gas concentration with and without the implementation of a feedforward control loop based on trickling liquid velocity (TLV) and nitrate feeding rate manipulation for the aerobic and anoxic BTFs, respectively.RESULTSAn average LR of 80 g S‐H2S m–3 h–1 with peaks and valleys of 141 and 28 gS‐H2S m–3 h–1 were tested. At the highest H2S LR, a 68.4% and 62.6% reduction of maximum outlet H2S concentration, and 50.0% and 26.6% reduction of H2S cumulative mass emitted were reached in the aerobic and anoxic BTFs, respectively, thanks to the application of feedforward control strategies. The sulfate selectivity in the aerobic BTF was enhanced up to 100.6 ± 5.0% under controlled conditions. In the anoxic BTF the sulfate selectivity was kept constant at 32.8% ± 0.8%.CONCLUSIONDespite demonstrating that the feedforward controller significantly reduced the impact of disturbances, the utilization of TLV as manipulated variable in the aerobic reactor showed performance problems. However, the feedforward control through nitrate addition was shown to be an adequate, robust strategy for reducing the impact of load perturbation in anoxic BTFs. © 2018 Society of Chemical Industry

PID control system for biogas desulfurization under anoxic conditions

AbstractBACKGROUNDA high H2S elimination capacity has been achieved by anoxic biotrickling filters but accurate control of the nitrate dosage is required. Different control strategies have been used in biotrickling filters but proportional‐integral‐derivative (PID) control studies have not been reported to date. The aim of this study was to demonstrate the stability and robustness of PID control in an anoxic biotrickling filter.RESULTSThree PID tuning methods were tested: Ziegler–Nichols, Approximate M‐constrained integral gain optimization (AMIGO), and maintained oscillation. The best results were obtained using PID control by the maintained oscillation method, where the system reached stabilization 0.41 h after the H2S inlet step. Moreover, the nitrate consumption was 15.4% lower than that without control.CONCLUSIONThe biotrickling filter operated with a PID control strategy proved to be highly stable and robust against the perturbations and disturbances evaluated. The control system was able to operate satisfactorily to a change in the set‐point of the outlet H2S concentrations from 25 to 200 ppmV. The desulfurized biogas could be fed directly to an internal combustion engine or solid oxide fuel cell (SOFC) equipped with a zeolite clean unit. © 2017 Society of Chemical Industry

Anoxic biodegradation of BTEX in a biotrickling filter

Emissions of BTEX (benzene, toluene, ethylbenzene and xylene) from the petrochemical industry are characterized by a low pollutants concentration and the absence of oxygen. Biodegradation of these pollutants using nitrate as the electron acceptor is of key interest to reuse the residual gas for inertization purposes. However, the biological mineralization of BTEX is often limited by their recalcitrant nature and the toxicity of the secondary metabolites produced. The potential of an anoxic biotrickling filter for the treatment of a model O2-free BTEX-laden emission at inlet individual concentrations of ~700mgm−3 was here evaluated. A UV oxidation step was also tested both in the recycling liquid and in the inlet gas emission prior to biofiltration. Removal efficiencies >90% were achieved for both toluene and ethylbenzene, corresponding to elimination capacities (ECs) of 1.4±0.2gm−3h−1 and 1.5±0.3gm−3h−1, respectively, while ~45% of xylene (EC=0.6±0.1g m−3h−1) was removed at a liquid recycling rate of 2mh−1. Benzene biodegradation was however limited by the accumulation of toxic metabolites in the liquid phase. The oxidation of these intermediates in the recycling liquid by UV photolysis boosted benzene abatement, achieving an average EC of 0.5±0.2gm−3h−1 and removals of ~40%. However, the implementation of UV oxidation as a pretreatment step in the inlet gas emission resulted in the deterioration of the BTEX biodegradation capacity of the biotrickling filter. Finally, a high bacterial diversity was observed throughout the entire experiment, the predominant phyla being Proteobacteria and Deinococcus-thermus.

Impact of Different Packing Materials on Hydrogen Sulfide Biooxidation in Biofilters Installed in the Industrial Environment

Three pilot scale anoxic biotrickling filters containing different packing materials were built and tested over an extended period in the municipal wastewater treatment plants (WWTP). Performance of biological beds containing polyethylene elements, ceramic Raschig rings, and keramzite particles was investigated at hydrogen sulfide concentrations in biogas ranging from 369 to 1733 mg/m3. The dependence of the number of colony forming units on hydrogen sulfide concentration and location in the bed was determined. Microbial enumeration was performed for all three columns using cultivation methods. The best results of desulfurization were observed for polyethylene elements. For this material the optimum empty bed retention time was 12 min and the minimum concentration of nitrate ions in a nutrient solution was 50 mg/L. The hydrogen sulfide reduction over 99% was achieved at loading rates (LR) of 1.79–5.08 g/m3/h. The increase in LR to 8.45 g/m3/h reduced the removal efficiency to 96%. The results of kinetic a...