H2S Removal Research Articles

Synthesis of Hydroxyapatite/Zinc Oxide Nanoparticles from Fish Scales for the Removal of Hydrogen Sulfide

The presence of hydrogen sulfide (H2S) is an issue for industrial processing, such as gasoline, natural gas, and biogas. In this study, hydroxyapatite (HA) nanoparticles with high purity were successfully extracted from red tilapia fish scales and used as supporting materials for zinc oxide (ZnO) to remove H2S. Various amounts of ZnO decorated on HA nanoparticles were prepared from a zinc nitrate hexahydrate precursor. Powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) of the ZnO/HA samples demonstrated the successful synthesis of ZnO/HA with high purity. The scanning electron microscope (SEM) image analysis confirmed the uniform deposition of ZnO on HA nanoparticles which were smaller than 245 nm. The ZnO/HA samples with different ZnO loadings (i.e., 5, 10, and 15 wt%) were used to remove H2S at room temperature. The specific surface area of HA and ZnO/HA determined by the Brunauer-Emmett-Teller (BET) method was 37.022 (m2/g) and 111.609 (m2/g), respectively. The experimental results demonstrated the highest breakthrough sulfur capacity of 26.3 mg S/g with the sorbent ZnO (15 wt%)/HA nanoparticles. This H2S adsorption capacity was the highest capacity ever achieved for ZnO/HA.Therefore, there are great possibilities for effective removal of H2S at the ambient conditions using the ZnO (15 wt%)/HA nanoparticles, where HA nanoparticles could be sustainably extracted from the abundant organic source of red tilapia fish scales.

Technology Focus: Natural Gas Processing and Handling (April 2022)

Natural gas has two faces. On one side, it is an important part of the energy-transformation toolkit. On the other side, it is a potent greenhouse gas. Technology can bring the two sides together. The three papers selected for this Tech Focus feature describe technologies that can make natural gas safer to move and store. The first paper, OTC 30655, describes an effort to eliminate flaring during offloading from a floating liquefied natural gas facility (FLNG) and an LNG carrier. Managing the balance of fuel gas and boiled-off gas between the FLNG and the carrier is vital to maintaining equilibrium and eliminating flaring. The paper looks at carriers with spherical tanks and presents a process study to identify potential causes of flaring during offtake and corrections that could eliminate it without capital modifications. The second paper, OTC 30871, considers the benefits of barges over ship-type LNG carriers. Ship-type LNG carriers are designed to operate offshore over fields, which does not necessarily provide optimal opportunity for monetization. The paper argues that near-shore barges holding liquefaction facilities linked to the rest of the system elsewhere could be a more-viable gas-monetization concept. The third paper, SPE 204787, describes a characterization and monitoring approach for underground gas storage. The approach involves close integration of subsurface understanding with the optimization of surface facilities. It also addresses sustainable operations through an asset-integrity-management plan. To learn more about the advancement of technology in the natural gas space, check out the suggested additional reading and visit the OnePetro online library. Recommended additional reading at OnePetro: www.onepetro.org. IPTC 19783 - Hybrid System—An Emerging Solution to Sour Gas Treatment by Siddharth Parekh, Schlumberger SPE 202984 - Sour Gas Has a Sweeter Future—Bulk H2S Removal Using Polymeric Cellulose Triacetate-Based Membranes by Pinkesh Sanghani, Schlumberger, et al. SPE 208134 - Inventory Verification in Underground Gas Storage Rebuilt From Depleted Gas Reservoir: A Case Study From China by Lina Song, PetroChina, et al. SPE 207956 - Unconventional Waste and Flare Gas Recovery System in New Circular Economy by Mohamed Ahmed Soliman, Saudi Aramco, et al.

Lab-scale biogas production from co-digestion of super-intensive shrimp sludge and potential biomass feedstocks

This study evaluated biogas production potentials from local biomass feedstocks comprising of rice straw (RS), steamed lemongrass (SL), bagasse (BA) and desiccated coconut (DC) on super-intensive shrimp sludge (SS) anaerobic digestion. A series of batch anaerobic digestion experiments was conducted at an organic loading rate of 50 g-VS L-1 and a C/N ratio of 25 under mesophilic conditions. The results indicate that co-digested biomass substrates are more suitable than single sludge except for DC supplementation, which exhibited a severe pH inhibition for methanogenesis activities. A reactor supplemented with BA achieved the highest overall biogas production (126.78 L kg-VSadded-1), which increased biogas yields 53.70% compared to a mono-sludge reactor. Furthermore, reactors with RS and SL increased biogas yields by 26.40% and 29.21%, respectively. Irrespective of initial materials, the H2S concentration in biogas compositions was measured at very high levels (23,710 - 65,040 ppm) after 10-15 days of digestion, while a decreasing trend was recorded for the remaining digestion period (16 - 60 days), yet still maintained relatively high levels (5,873 - 9,155 ppm). The study suggests that future works should focus on pH neutralization within the reactor with DC substrates and H2S removal in biogas composition.

Rate-based model for predicting and evaluating H2S absorption in the haloalkaliphilic biological desulfurization process

The highly efficient performance of H2S absorption is the crucial indicator for haloalkaliphilic biological desulfurization (HBDS) because it immediately concerns the H2S removal efficiency and pH change of alkaline solutions. Therefore, we investigated the effect of operating parameters on the H2S absorption's performance under haloalkaline conditions. The gas–liquid ratio and packing height significantly improve H2S removal efficiency, from 80% to 90% and 66% to 99%, respectively. The absorption temperature had a trivial impact on the H2S removal efficiency, and the maximum value appeared at 45 °C. Additionally, all operating parameters caused pH changes that varied in the acceptable range (0.1 to 0.5) during the absorption process. A rate-based model was successfully developed to predict the haloalkaliphilic H2S absorption process accurately. Moreover, this model could be implemented to effectively evaluate the HBDS system's stability and provide reliable theoretical guidance for the industrial HBDS process to ensure good process stability.

Whey as a sustainable binder for the production of extruded activated carbon

Whey, the main by-product of the dairy industry, is proposed as a sustainable binder for the production of extruded activated carbon. Coconut shell char was mixed with controlled quantities of either rehydrated whey powders or partially dehydrated liquid whey. After extrusion, extrudates were dried, and carbonised or activated under N2 or CO2 atmosphere, respectively. A comprehensive study of the effect of different parameters including binder proportion, coconut shell char particle size and carbonisation temperature was carried out. The composition of whey prompted Maillard reactions boosted with temperature that conferred a resin-like behaviour to the binder. Quality parameters of the resulting extrudates were their ball-mill hardness, real and bulk densities. All whey-bound pellets retained their original shape after the high temperature treatment. The hardness of those whey extrudates was particularly remarkable considering the biomass origin of this binder. The carbonisation temperature had little effect in the hardness or densities of the carbon pellets. The best pellet formulation comprised the use of coconut shell char powders with particle sizes < 212 µm, in mixtures having a 7/3 char/dry whey mass ratio. The properties of the pellets obtained after the activation of such pellets were comparable to those of commercial activated carbon extrudates. The use of partially dehydrated liquid whey rather than re-hydrated dry whey rendered very similar results. The alkalinity of the binder made the resulting activated carbons adequate for H2S removal at room temperature. An economic estimation of the process placed whey in a practical position within the binder market.

Biogas purification by adsorption of hydrogen sulphide on NaX and Ag-exchanged NaX zeolites

Biogas is a cheap renewable and eco-friendly alternative energy to fossil fuels. However, biogas is made up of a mixture of gases including hydrogen sulphide (H2S), a corrosive and toxic gas. The current study was carried out to purify biogas by adsorbing H2S on NaX and Ag-exchanged NaX zeolites. Pure crystalline NaX zeolites were synthesized by microwave heating technique. NaX zeolites were then modified following Ag-exchange with various aqueous solutions of AgNO3 (11.5%, 34.1%, 71.6%, 76.7%, and 78.8%) at 40 °C for 2–12 h. Compositional and structural analyses of NaX and Ag-exchanged NaX zeolites were done using powder X-ray diffraction (XRD), elemental analysis, nitrogen adsorption porosimetry, and atomic absorption spectrometry. Anaerobic digestion (AD) was carried out by feeding the digesters with a mixture of 600 mL of dairy manure and 4.0 g L−1 NaX and Ag-exchanged NaX zeolites. An almost complete exchange of Na+ cations by Ag+ cations was observed. The Ag-exchanged zeolites exhibited type I isotherm features with no modification to the shape. A well-dispersed Ag+ ion in the zeolite framework was observed. More H2S was efficiently removed in Ag-exchanged NaX zeolites digesters when compared to that of NaX zeolite. Methane yield was significantly increased from 167.31 (control) to 215.33 (78.8% Ag/NaX) mL g−1 after 48 days. Ag-exchanged NaX zeolites in the current study is a promising adsorbent for H2S removal in biogas.

Oxidative removal of gaseous hydrogen sulfide by a dual ions-dual oxidants coupling activation system

A gaseous hydrogen sulfide (H2S) oxidative removal technology by a dual ions-dual oxidants coupling activation system (i.e., Cu2+/Fe2+/persulfate(PS)/H2O2 coactivation system) was put forward. The fundamental issues, mainly including H2S removal performance, process parameters optimization, products, free radicals, synergy mechanism and desulfurization mechanism were studied systematically in a bubble column reactor. The study indicates that compared with Fenton system and non-coupling activation systems, the new dual ions-dual oxidants coupling coactivation system shows much higher free radical yield and H2S removal efficiency owing to significant synergistic activation effect. Higher concentrations of Cu2+ or Fe2+ greatly increase the H2S removal efficiency. With the increase of PS concentration, H2O2 concentration or reagent pH value, the H2S removal efficiency is first enhanced, and afterwards slightly declined. The H2S removal efficiency is declined via increasing operating temperature, gas flow rate and contents of H2S, SO2, NO and CO, and is almost not affected by content of Hg0. Sulfate, CuS and elemental sulfur are determined to be the products of H2S removal, and no by-products are produced after the reaction. Oxidation via ·OH and SO4-· plays a crucial role in H2S removal, which is proved to be the primary pathways of H2S removal. Finally, the recovery strategy of the products is discussed preliminarily.

Steel Manufacturing EAF Dust as a Potential Adsorbent for Hydrogen Sulfide Removal.

Electric arc furnace dust (EAFD) is a high-volume steel manufacturing byproduct with currently limited value-added applications. EAFD contains metal oxides that can react with H2S to form stable sulfides. Hence, the valorization potential of EAFD as an adsorbent material for syngas H2S removal was investigated. EAFD from European steel plants was characterized and tested in dynamic H2S breakthrough tests and benchmarked against a commercial ZnO-based adsorbent. For this, the EAFD was first processed into adsorbents by simple milling and granulation steps. The EAFD samples exhibited sulfur capture capacities at 400 °C and an SV of 17,000 h–1 that correlated with the sample milling times and Zn concentrations. It was verified that only zinc participated in sulfur capture. Yet, both ZnO and the zinc in ZnFe2O4 were found to be active in sulfidation. At higher temperatures (500 and 600 °C), EAFD sample performance drastically improved and even exceeded the reference zinc oxide performance. The high-zinc (48% by mass) EAFD-B sample exhibited the highest tested performance at 500 °C, with a sulfur capture capacity of 234 mg g–1. The results indicate that sufficiently high-zinc-content EAFD could serve as a viable sulfur capture material.

Copper supported on activated carbon from hydrochar of pomelo peel for efficient H2S removal at room temperature: Role of copper valance, humidity and oxygen

In this work, the activated carbon prepared from KOH activation of pomelo peel hydrochar was selected as support to synthesize various valance copper adsorbents (maintaining a 20 wt% total content of copper) for H2S adsorption at room temperature, with a focus on the desulfurization performance under moist or oxygen conditions. The results showed that Cu0/activated carbon has a highest H2S breakthrough capacity of 358.3 mg/g under co-presence of steam and oxygen, followed by Cu+ and Cu2+ loaded activated carbon. The H2S removal process consists of catalytic oxidation and reactive adsorption, resulting in the formation of large amount of elemental sulfur and part of sulfate and sulfide. The presence of steam or oxygen mainly enhances the catalytic oxidation of H2S to form elemental sulfur, and the breakthrough sulfur capacity decreases in the order of moist oxygen, moist nitrogen, dry oxygen and dry nitrogen conditions. The evolution of desulfurization product at different reaction times indicate that the sulfate and sulfide are mainly generated at prometaphase stage of desulfurization, while the elemental sulfur could be formed in the whole stage. These findings provide a new route to prepare in-expensive and high efficient copper-based H2S adsorbent from high moisture organic waste.

Simultaneous Removal of Hg0 and H2S over a Regenerable Fe2O3/AC Catalyst

Simultaneous removal of Hg0 and H2S over a regenerable activated coke supported Fe2O3 catalyst (Fe2O3/AC) was studied in simulated coal-derived syngas. It was found that the Fe2O3/AC catalyst exhibited high capability for Hg0 and H2S removal, which was attributed to the catalytic oxidation activity of Fe2O3. Its capability for Hg0 and H2S removal increased with an increase of Fe2O3 loading amount, and the highest was at 150 °C for Hg0 removal. CO and H2 showed no obvious effect on Hg0 removal by Fe2O3/AC, while H2S had a promotion effect, which was due to S and FeSx produced by the H2S reaction on Fe2O3/AC. The results of SEM-EDX and the temperature programmed desorption experiment (TPD) revealed that Fe2O3 played a critical role in Hg0 oxidation, and HgS was generated upon the reaction of Hg0 with H2S on Fe2O3/AC. The used Fe2O3/AC catalyst after Hg0 and H2S removal could be effectively regenerated and still had high capability for Hg0 and H2S removal.

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.

Efficient removal of H2S with zinc oxide/nitrogen-doped ordered mesoporous carbons at room temperature

Nitrogen-doped ordered mesoporous carbon (NMC) was prepared via an organic–inorganic co-assembly method to support ZnO for the efficient removal of H 2 S at room temperature. NMCs with large BET specific surface areas, copious ordered mesopores, and controllable nitrogen doping worked cooperatively with uniformly dispersed ZnO, to improve desulfurization capability at room temperature. Among these, NMC-2 possessed a BET surface area as high as 1172 m 2 /g, a large pore volume of 1.09 cm 3 /g, and a conducive nitrogen content. The appropriate residual ordered mesopores after ZnO loading provided a fast–H 2 S–diffusion channel in NMC-2-20%, an accessible interfacial area (925 m 2 /g), and a sufficient space for product storage (0.9 cm 3 /g). The introduction of nitrogen as Lewis basic sites not only promoted the dissociation of H 2 S but also accelerated the lattice diffusion rate during the desulfurization process. The synergy of the above advantages resulted in an excellent desulfurization performance of 151.2 mg/g. This study presents the effective application of NMC as a support for ZnO for a fine desulfurization at room temperature. • NMC was prepared via the organic-inorganic co-assembly method. • The ordered mesopores improve H 2 S diffusion and provide sufficient space for product. • N doping could promote the H 2 S dissociation and accelerate lattice diffusion rate. • NMC-2-20% has well desulfurization performance.

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.

Production and purification of biogas from cassava peel using cow dung as inoculum

The study examined biogas production from cassava peel and cow dung due to the large quantity of cassava peel disposed at dumpsites in local cassava processing sites. A 200L biodigester was used for the experiment. It contained 25 kg of cassava peel, 25 kg of cow dung and 100 kg of water in the ratio of 1:1:4, respectively. A cumulative volume of 937.3L of biogas was generated after the 30 days digestion period. The biogas generated was pass through a combined absorption and adsorption pre-treatment process to reduce the concentration of impurities in the biogas. The procedure had a 91.5% CO2removal efficiency and 88% H2S removal efficiency. The biogas, after purification can be used for cooking. Also, the digestate from the anaerobic digestion process is rich in NPK, which can be used as fertilizer.

Efficiency, Economic, Energy, and Safety (3ES) Analyses on Different Configurations of MDEA Absorption Process for Coke Oven Gas Desulfurization

The purification of Coke Oven Gas received great attention due to its high potential of utilization for power generation and hydrogen production. This study simulated different configuration of MDEA process flowsheet and implemented the comprehensive evaluation. The comprehensive evaluation included H2S removal efficiency, energy consumption, techno-economic analysis, and safety assessment. The modified MDEA processes applied additional flash drums to enhance H2S removal efficiency and reduce heat duty of distillation column reboiler. MDEA with two intermediate flash drums showed the highest efficiency (96.5%), lowest reboiler duty (6.27 MW), and the lowest operation cost ($ 50/ Nm3-y). Conventional MDEA process exhibited the lowest capital cost ($ 1.531 million) and H2S leakage amount (30.3 kg) for an accident. MDEA with two flash drums process can be recommended when high purity coke oven gas was required. Conventional MDEA was recommended to consider safety and short-term operation with the lowest capital cost. MDEA with one flash drum can be recommended for stable desulfurization operation.

Low Temperature H2S Removal by Adsorbent Prepared using Water Treatment Sludge

Water treatment sludge (WTS), hydrothermally synthesized powder (HSP) using the WTS, and CuO added HSP (CuHSP) after heat treatment at 500℃ were prepared and its hydrogen sulfide (H₂S) removal properties were investigated. The physicochemical properties of adsorbents were studied by N₂ adsorption-desorption, scanning electron microscope, x-ray diffraction, and thermogravimetric-differential thermal analysis. The specific surface area for the WTS was 42.7㎡/g and was increased by 78.1㎡/g after the hydrothermal reaction and was maximized by 168.7㎡/g after the heat treatment at 500℃ for 1 h. The breakthrough time of the WTS, HSP, and CuHSP for H₂S removal at 25℃ was measured for 10 min, 20 min, and 170 min, respectively, thus demonstrating an effective application of WTS as the catalytic carrier for low temperature H₂S removal.

Removal of Gaseous Hydrogen Sulfide by a FeOCl/H2O2 Wet Oxidation System

The removal of gaseous hydrogen sulfide using FeOCl/H2O2 was studied. The effects of the FeOCl dosage, the H2O2 concentration, the reaction temperature, and the gas flow rate on the removal of H2S were investigated. The reaction products were analyzed, and the characterization of FeOCl was carried out by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy. Furthermore, radical quenching experiments were carried out using butylated hydroxytoluene, isopropanol, and benzoquinone. It was found that the H2S removal rate for a H2S gas concentration of 160 ppm reached 85.6% when bubbling through 100 mL of an aqueous solution containing FeOCl (1 g/L) and H2O2 (0.33 mol/L) at 293 K with a flow rate of 135 mL/min. Although the dissolution of chlorine in FeOCl was found to result in reduced catalytic performance, the activity was restored after soaking the catalyst in concentrated hydrochloric acid (37%) and subsequent calcination. The mechanism of H2S removal was also discussed, and it was found that this process was controlled by H2S diffusion. FeOCl was found to activate H2O2 and produce radicals, such as •OH and •O2–, resulting in the formation of a water film rich in radicals on the FeOCl surface. Following the diffusion of H2S into the water film, it underwent oxidation by radicals to produce SO42–. Overall, the catalyst and the product can be effectively separated.

The efficiency and mechanism of humidity in alleviating CO2 inhibition on H2S adsorption to straw biochars

Adsorption tests were conducted to clarify the impact of carbon dioxide (CO2) on hydrogen sulfide (H2S) removal to straw biochars and the role of humidity in affecting the CO2 impact. When straw biochars were dry, CO2 proved significantly detrimental to their H2S adsorption, regardless of the CO2 contents. In contrast, when adjusting the humidity of the biochars to 20%, the presence of CO2 promoted the conversion of H2S into sulfites, though still inhibited the generation of elemental sulfur, through which the original negative CO2 impact was nearly compensated. The presence of low to medium contents of CO2 even slightly improved the adsorption capacity and extended the breakthrough time. This phenomenon was ascribed to a favorable carbon surface environment for H2S dissociation and oxidation, created from the reactions of the major minerals (Ca and Mg) with CO2 and water. To sum up, the CO2 inhibition on the H2S adsorption to biochars was ascribed to the competition of CO2 for the active sites; however, humidity induced a series of CO2-participated chemical reactions between H2S and the minerals, sufficiently alleviating the CO2 inhibition. The results also highlight the necessity to recognize the most critical biochar properties or an efficient balance of crucial biochar properties in achieving an optimal H2S removal when CO2 is present in the syngas.

Insights on Cryogenic Distillation Technology for Simultaneous CO2 and H2S Removal for Sour Gas Fields.

Natural gas demand has dramatically increased due to the emerging growth of the world economy and industry. Presently, CO2 and H2S content in gas fields accounts for up to 90% and 15%, respectively. Apart from fulfilling the market demand, CO2 and H2S removal from natural gas is critical due to their corrosive natures, the low heating value of natural gas and the greenhouse gas effect. To date, several gas fields have remained unexplored due to limited technologies to monetize the highly sour natural gas. A variety of conventional technologies have been implemented to purify natural gas such as absorption, adsorption and membrane and cryogenic separation. The application of these technologies in natural gas upgrading are also presented. Among these commercial technologies, cryogenic technology has advanced rapidly in gas separation and proven ideally suitable for bulk CO2 removal due to its independence from absorbents or adsorbents, which require a larger footprint, weight and energy. Present work comprehensively reviews the mechanisms and potential of the advanced nonconventional cryogenic separation technologies for processing of natural gas streams with high CO2 and H2S content. Moreover, the prospects of emerging cryogenic technologies for future commercialization exploitation are highlighted.

Optimization of activated sludge recycling and oxidized ammonium recycling as odour control strategies in wastewater treatment plants

New odour prevention strategies in wastewater treatment facilities need to be investigated to find effective and low-cost technologies for the control of malodorous emissions. In this study, the potential of activated sludge (AS) and oxidized nitrogen (N-NOx) recycling as an environmentally-friendly and cost-effective strategy for the prevention and minimization of odour nuisance during wastewater treatment was evaluated and optimized using H2S, acetic acid and α-pinene as model odorants in 2.1 L gas tight bottles. This approach uses by-products from wastewater treatment to mitigate odour annoyance. Preliminary abiotic tests showed headspace concentration losses of 25% for H2S and α-pinene, and 7% for acetic acid due to odorant adsorption in 4 h. The experiments carried out at different concentrations of AS (0, 10, 25, 50, 100 mg VSS/L) and oxidized nitrogen (1.5, 5, 7.5 and 10 mg N-NOx/L) revealed an effective H2S removal at 7.5–10 mg N-NOx/L and 50–100 mg VSS/L. Interestingly, NO3− was more effective than NO2− as electron acceptor during the biodegradation of H2S regardless of the AS concentration and N-NOx concentrations. In the presence of dissolved H2S and AS concentrations of 50–100 mg VSS/L, acetic acid was partially metabolized by microorganisms at the end of experiment (from 27 to 23 ppmv in 4.5 h), while α-pinene concentrations experienced a similar gradual decrease than in the abiotic tests. Finally, the assays carried out at concentrations ≥5 mg NO3−/L and 25 mg VSS/L showed a reduction of NO3− to NO2− correlated with the biological oxidation of H2S, which suggested the need to control NO3− supply under sulphur limiting conditions to prevent toxicity problems during wastewater treatment.