Hydrogen Sulfide Emissions Research Articles

Applied Research Note: Evaluation of a Bacillus-based direct-fed microbial as a strategy to reduce hydrogen sulfide emissions from poultry excreta using a practical monitoring method

Effective implementation of noxious odor mitigation strategies requires a thorough understanding of production causes, a clear definition of harmful odor limits, and practical and effective methods to measure emissions into the environment. With the increasing demand for poultry products and consequently, intensification of production systems, there is a need for versatile odor remediation approaches. Hydrogen sulfide ( H 2 S ) is a pungent noxious gas associated with poultry farms. The presence and intensity of H 2 S from animal excreta is the result of the dynamic balance of its formation and reduction, under primarily anaerobic microbial fermentation conditions. Unlike other odors such as ammonia, H 2 S production and emission is a less researched subject. In the present study, a practical monitoring method was devised to evaluate the efficacy of a Bacillus -based microbial product as a strategy to remediate H 2 S emissions from poultry excreta. The evaluated excreta were preconditioned with distilled water and then incubated for 24 h under controlled temperature before odor measurement. Plastic containers were used as incubation units, and H 2 S diffusion tubes were used as the monitoring tool. Hydrogen sulfide emitted from the excreta of broilers fed the microbial product was reduced on average by 42.9% compared to a nonmicrobial fed group. Under the current trial conditions, H 2 S emitted from growing broiler chicken excreta was easily detectable and variation was low. Moreover, the method allowed dynamic and quick H 2 S monitoring that will further offer tools to the commercial poultry industry for evaluating the effectiveness of feeding strategies in odor remediation.

Predicting H2S emission from gravity sewer using an adaptive neuro-fuzzy inference system

Abstract A predictive model to estimate hydrogen sulfide (H2S) emission from sewers would offer engineers and asset managers the ability to evaluate the possible odor/corrosion problems during the design and operation of sewers to avoid in-sewer complications. This study aimed to model and forecast H2S emission from a gravity sewer, as a function of temperature and hydraulic conditions, without requiring prior knowledge of H2S emission mechanism. Two different adaptive neuro-fuzzy inference system (ANFIS) models using grid partitioning (GP) and subtractive clustering (SC) approaches were developed, validated, and tested. The ANFIS-GP model was constructed with two Gaussian membership functions for each input. For the development of the ANFIS-SC model, the MATLAB default values for clustering parameters were selected. Results clearly indicated that both the best ANFIS-GP and ANFIS-SC models produced smaller error compared with the multiple regression models and demonstrated a superior predictive performance on forecasting H2S emission with an excellent R2 value of >0.99. However, the ANFIS-GP model possessed fewer rules and parameters than the ANFIS-SC model. These findings validate the ANFIS-GP model as a potent tool for predicting H2S emission from gravity sewers.

Adsorption of Hydrogen Sulfide (H2S) from Municipal Solid Waste by Using Biochars

The emission of hydrogen sulfide (H2S) from municipal solid waste is one of the environmental issues that raised the public’s attention and awareness. Exposure to H2S that brings a foul smell of rotten eggs will cause headaches, irritation, dizziness, fatigue, and even death if the concentration of H2S is too high. The study’s goals are to investigate the properties of biochars made from rice hulls, banana peels, and sawdust; to compare the biochars’ physical and chemical properties; and establish the H2S removal efficiency of the three biochars. Biochars derived from rice hull (RHB-500), banana peel (BPB-550), and sawdust (SDB-500) by pyrolysis were used as the adsorbents. The biochar yield, pH, ash content, surface functional group, and morphology of the biochars produced were investigated. In this study, H2S was synthesized by mixing food waste and soil in the experimental column. The H2S produced was reduced by the adsorption method. The removal efficiencies of H2S for each biochar were determined by allowing the synthetic H2S to flow through the two columns that were packed with sand (act as control) and biochars, respectively. All biochars were alkaline, and BPB-550 had the highest pH, followed by SDB-500 and finally RHB-500. The order for removal efficiency of H2S (>94%) is BPB-550 > SDB-500 > RHB-500. Overall, the biochars derived from biomass had a strong ability to act as the adsorbents for H2S removal.

Effect of Rotten Butter Shock Load on Anaerobic Digestion of Chicken Manure

Anaerobic digestion is a popular method for improving fertilizing properties, but there is no report on the effect of shock load with butter on anaerobic digestion of chicken manure. Therefore, this study aimed to investigate the anaerobic digestion of chicken manure with butter addition. The volatile suspended solid (VSS) was set at 20g VSS/L with different butter additions from 0 to 60 g VSS/L and different oxygen flow rate (OFR) from 0 to 2.5 mL/h. The results showed that ammonia ranged from 0.072 g/L to 0.082 g/L, while the volatile acids ranged from 425 mg/L to 325 mg/L. The volatile organic acid was significantly influenced by a change in OFR compared to ammonia, while a correlation between hydrogen and hydrogen sulfide was observed. The results showed that the highest hydrogen and methane production was obtained at butter addition of 30 g VSS/L with OFR 1.4 mL/h with volumes of 78 mL and 25 L respectively. In addition, hydrogen sulfide emissions induced rapid growth with increase in butter concentration.

CFD modeling of different mass transfer coefficients on hydrogen sulfide emission in a flux chamber.

Hydrogen sulfide (H2S) is commonly used as an indicator for odorous gas emission monitoring in wastewater treatment plants. The H2S emission estimations can be performed using algebraic mathematical models or carrying out measurements at the source, with the dynamic flux chamber, for example. This work brings together these two methodologies in a computational fluid dynamics analysis. Fifteen liquid-phase mass transfer coefficient ([Formula: see text]) models were initially evaluated in establishing, at the liquid-gas interface in a flux chamber, an H2S emission flux based on the friction velocity field from three different inlet flows (2, 5, and 10 L min-1). Ten [Formula: see text] models were fully simulated, and the numerical results were compared with available experimental data. The higher the inlet flow, the higher the friction velocity at the interface, and the higher the H2S emission. The H2S emission was also strongly dependent on the constant coefficients of the existing [Formula: see text] models. Small variability on those coefficients generates considerable changes in emissions at the interface. Few and different models performed well in describing the available concentration data at the outlet sampling probe for different inlet flows, which shows there is still no single model capable of representing all simulated friction velocity ranges (0.005 to 0.017ms-1).

Improved effect of manure acidification technology for gas emission mitigation by substituting sulfuric acid with acetic acid

Animal manure is a significant source of ammonia, methane, hydrogen sulfide, and odor emissions. Manure acidification to pH 5.5 using sulfuric acid (H2SO4) is an approved method for reducing ammonia and methane emissions from barns and retaining bioavailable nitrogen in the slurry for subsequent field fertilization. However, the use of H2SO4 may increase the emission of malodorous sulfur compounds and reduces subsequent biogas production. In this study, we investigated if substituting a part of the H2SO4 treatment with acetic acid (CH3COOH) improves manure emissions. In two experiments, cattle manure was incubated for 11 days each and acidified daily with either i) H2SO4 (4M) or CH3COOH (4M), or ii) mixes of both acids (4M H2SO4 + 8M CH3COOH, in volume ratios of 75:25, 50:50, and 25:75) until pH 5.5. The emission of ammonia, methane, hydrogen sulfide, and volatile organic compounds (VOCs) was monitored continuously. At the end of both experiments, cumulative ammonia emission was reduced by 75% by H2SO4 and by 83% by CH3COOH, indicating that CH3COOH was more efficient. Acetic acid almost completely eliminated CH4 emission, while H2SO4 reduced CH4 emission by 89%. Furthermore, CH3COOH acidification resulted in lower odorant emissions compared to H2SO4. Based on the second experiment, we recommend using a high percentage of CH3COOH during the first days of acidification, followed by a mix containing at least 50% CH3COOH, to achieve a high mitigation efficiency with a lower emission of sulfur compounds compared to H2SO4 alone.

Comparison of H2S Gas Sensors: A Sensor Management Procedure for Sewer Monitoring

Hydrogen sulphide (H2S) emissions are one of the major problems associated with sewer networks. This gas, with its characteristic smell of rotten eggs is highly toxic and leads to the corrosion of sewer infrastructures. To protect cities and ensure the safety of sewer workers, sewers are commonly monitored using H2S gas sensors. In this work, three commercial H2S gas sensors for air quality monitoring were compared at two different sites in Berlin, Germany. Two of the sensors provide online access to data, while the other one is a data logger. Moreover, based on statistical measures (RMSE, MAE, MB, and a graphical analysis), we evaluated whether a rotation/exchange between data logger (reference) and online sensors is possible without significant differences in the gas measurements. Experimental evaluation revealed that measurement differences are dependent on the H2S concentration range. The deviation between sensors increases as the H2S concentration rises. Therefore, the interchange between reference and online sensors depends on the application site and the H2S levels. At lower ranges (0–10 ppm) there were no observed problems. Finally, to support practitioners on-site, a management procedure in the form of a decision-making tool is proposed for assessing whether gas sensors should be exchanged/rotated.

Sodium butyrate reduce ammonia and hydrogen sulfide emissions by regulating bacterial community balance in swine cecal content in vitro

Reducing the production of odor during swine breeding has attracted attention. Ammonia (NH3) and hydrogen sulfide (H2S) contributed to the odor emissions from swine breeding because NH3 emissions are high and hydrogen sulfide (H2S) has a low odor threshold. Sodium butyrate reduces the odor emissions caused by NH3 and H2S, but the corresponding mechanism is unclear. After mixing the feces of six fattening pigs, the mixture was used to process in vitro fermentation experiment. The purpose was researching the effect of sodium butyrate reduced NH3 and H2S emissions in swine cecal contents. The control group was denoted CK, and the treatment groups with different sodium butyrate concentrations (0.015%, 0.030% and 0.150%) were denoted L, M and H. The NH3, H2S, total gas production and physicochemical indexes were measured, and the bacterial communities in the fermented product were analyzed by 16 S rDNA sequencing. The results showed that group M reduced NH3, H2S and total gas production by 17.96%, 12.26% and 30.30%, respectively. Sodium butyrate promoted SO42- accumulation and lowered the pH. Importantly, sodium butyrate decreased the relative abundance of bacteria positively correlated with NH3 and H2S production, but increased the negatively correlated ones. Proteobacteria made a greater contribution to reducing emissions than did other bacterial phyla. Our results showed that adding 0.030% sodium butyrate can significantly reduce NH3 and H2S production, which occurred via alterations in the physicochemical indicators to adjust the abundance of the bacteria related to odor production, including Proteobacteria.

Hydrogen sulfide occurrence states in China's coal seams

The occurrence states of hydrogen sulfide in coal seams are crucial in preventing and controlling hydrogen sulfide emission in coal mines and the safe development of coal bed methane. In this study, the research status of the occurrence states of free-state, adsorbed-state, and water-soluble hydrogen sulfide in coal seams was systematically analyzed. H2S anomaly areas in China's coal seams are mainly located in the Carboniferous-Permian and Jurassic series of northern, eastern, central, and northwest regions of China. Bacterial sulfate reduction accounts for most of the hydrogen sulfide anomalies of low-rank coal, while thermochemical decomposition thermal desorption spectroscopy and thermochemical sulfate reduction may also result in hydrogen sulfide anomaly in medium- and high-rank coal. In contrast, magmatism-induced hydrogen sulfide anomalies are rarely found. Absorbed-state hydrogen sulfide anomalies are prevailing, while water-soluble and free-state hydrogen sulfide anomalies are relatively scarce. Coal seam's porosity mainly controls the hydrogen sulfide adsorption, pressure, coalification degree, pore volume, and specific area, while water-soluble hydrogen sulfide is influenced by pressure, sulfate-reducing bacteria, burn, porosity, fractures, water temperature, and hydrodynamic conditions. The fractures in coal seams, their burial depth, coal quality, coal rank, roof, and floor lithology are the main factors controlling the free-state hydrogen sulfide preservation. The absorbed-state hydrogen sulfide in coal seams is mainly mitigated by varying the ventilation mode, increasing the ventilation capacity, spraying alkali fog into the air, and injecting alkali liquid into coal seams for governance.

Bacterial dynamics for gaseous emission and humification in bio-augmented composting of kitchen waste

Using high-throughput sequencing and Functional Annotation of Prokaryotic Taxa (FAPROTAX), this study aimed to elucidate the effect of bacterial dynamics on gaseous emission and humification of kitchen and garden wastes during composting augmented with microbial inoculants. Microbial inoculant addition at up to 0.9% resulted in a diverse bacterial community with more functional bacteria to amend gaseous emission and enhance humification. Microbial inoculation facilitated the enrichment of aerobic bacteria (e.g. the genus Bacillus and Thermobifida) to enhance cellulolysis and ligninolysis to advance organic humification. By contrast, several bacteria, such as the genus Weissella and Pusillimonas were inhibited by microbial inoculation to weaken fermentation and nitrate respiration. As such, bio-augmented composting with 0.9% microbial inoculant reduced the emission of methane by 11–20% and nitrogen oxide by 17–54%. On the other hand, ammonia and hydrogen sulphide emissions increased by 26–62% and 5–23%, respectively, in bio-augmented composting due to the considerable proliferation of the genus Bacillus and Desulfitibacter to enhance ammonification and sulphur-related respiration. Results from this study highlight the need to further develop efficient and multifunctional microbial inoculants that promote humification and deodorization for bio-augmented composting of kitchen waste as well as other carbon and nutrient rich organic wastes.

Variation in hydrogen sulfide emissions from a U.S. Midwest anaerobic dairy lagoon.

Hydrogen sulfide (H2 S) emissions from midwestern United States dairy anaerobic waste lagoons are episodic and seasonal. Emissions were modeled using an inverse diffusion model in conjunction with measured concentrations and turbulence. The potential for lagoon mixing was estimated by the Brunt frequency using a theoretical Fourier series temperature profile model constructed from measured air and lagoon temperatures. Annual H2 S emissions from the dairy parlor and holding area liquid waste, based on 318 d of measurement, were 212g m-2 or 807g head of cattle-1 . Hydrogen sulfide emissions were highest in the spring and the fall. Eleven days with emissions >7g d-1 head-1 accounted for 25% of the annual emissions. Shear mixing appeared to dominate the mixing in the lagoon when the lagoon was estimated to be nearly isothermal. Wind shear correlated with significantly greater daily mean emissions. The H2 S emissions from this lagoon appeared to result from a series of processes; biogenic production of H2 S in the sludge, H2 S-enriched bubbles rise through the lagoon by buoyancy and wind shear induced mixing, and bubbles bursting at the surface either due to desiccation of the bubbles or surface disturbances induced by wind and precipitation.

Bioaugmentation mitigates ammonia and hydrogen sulfide emissions during the mixture compost of dewatered sewage sludge and reed straw.

This study investigated the effectiveness of bio-augmenting aerobic cell culture to mitigate ammonia and hydrogen sulfide emission in sewage sludge composting amended with reed straw (with the weight ratio of 1:0.3-0.4). During the 20-day aerated lab-scale composting, adding 200-mL culture (56.80 NTU) reduced ammonia and hydrogen sulfide emissions by 38.00% and 54.32%, and conserved total nitrogen and sulfate by 39.42% and 70.75%, respectively. Organic matters degradation was quick started 1 day ahead. Comparing to the control, nitrate content increased 38.75% at the end of the compost. Bioaugmentation evened the distributions of bacterial communities in the thermophilic phase. The shift was mainly due to 22.97% of relative abundance of Proteobacteria depressed and 157.16% of Bacteroidetes increased, which were beneficial for nitrogen conservation and glycan breakdown, respectively. In summary, the results demonstrated that bioaugmentation addition could be an effective strategy for enhanced sludge composting.

Ferric Oxide-Containing Waterworks Sludge Reduces Emissions of Hydrogen Sulfide in Biogas Plants and the Needs for Virgin Chemicals

Ferric oxide-containing waterworks sludge can be used to reduce the formation of hydrogen sulfide during anaerobic digestion. The ferric compound is reduced biochemically in the digester and forms insoluble pyrite in digester sludge. Virgin ferric chloride is often used to solve the hydrogen sulfide problem. Since 2013, Sydvatten AB has supplied a growing number of digestion plants in Sweden with ferric-containing dewatered waterworks sludge derived from the drinking water treatment plant Ringsjöverket to limit the formation of hydrogen sulfide. At the waterworks, ferric chloride is added to enhance the coagulation of organic matter from the source water. The sludge formed in this process is dewatered and landfilled, but also recycled in biogas production in order to decrease the hydrogen sulfide concentration. In this study, the use of sludge for hydrogen sulfide removal in digesters was technically and economically evaluated via case studies from 13 full-scale digesters in Sweden. Compared with the use of fresh ferric chloride, the operational costs are reduced by up to 50% by using sludge. The quality of the sludge is high and its content in metals is low or very low, especially when compared with the requirements of different certification standards for biosolid reuse applied in Sweden. The addition of waterworks sludge containing iron to a digester for the removal of dissolved hydrogen sulfide is a technically and economically good alternative when producing biogas. It is also one step closer to a circular economy, as replacing the use of virgin chemicals with the by-product waterworks sludge saves energy and materials and reduces the carbon footprint of the waterworks.

Volatile sulfur compound emissions and health risk assessment from an A2/O wastewater treatment plant

Anoxic/anaerobic/oxic (A2/O) wastewater treatment has emerged as a major process for treatment of domestic wastewater. One of the issues with wastewater treatment plants (WWTPs) is that volatile sulfur compounds (VSCs) are discharged from them and pose numerous health risks. This study characterized VSC emissions at the water-air interface and concentrations of ambient air exposure from different treatment units in an A2/O WWTP. AERMOD modeling was used to simulate the atmospheric behaviors of discharged VSCs. Results demonstrated that VSC emission fluxes and exposure concentrations had followed a descending order of pretreatment>biological treatment>advanced treatment. Emissions were affected by sulfate concentrations and chemical oxygen demand in the wastewater, and control strategies based on these values were proposed. The AERMOD results indicated that the majority of the total hydrogen sulfide (87%) and methyl mercaptan (65%) emissions came from the primary sedimentation tank, while the majority of dimethyl sulfide (81%), carbon disulfide (84%), and dimethyl disulfide (93%) were emitted from the oxic area. MT and DMS were the main odorous components of the VSCs in ambient air based on the indicator of odor activity values. Noncancer health risks, determined by having a hazard quotient >1, of the measured VSCs were beyond acceptable limits. Overall, efforts should be made to minimize noncancer health risks as individuals are exposed to VSCs not only in treatment units but also in areas surrounding WWTPs.

Mitigation of Acute Hydrogen Sulfide and Ammonia Emissions from Swine Manure during Three-Hour Agitation Using Pelletized Biochar

The risk of inhalation exposure to elevated concentrations of hydrogen sulfide (H2S) and ammonia (NH3) during the agitation of stored swine manure is high. Once or twice a year, farmers agitate manure before pump-out and application to fields. Agitation of the swine manure causes the short-term releases of highly toxic levels of H2S and NH3. In our previous pilot-scale studies, the biochar powder showed significant mitigation of H2S and NH3 emissions when it was surficially applied to manure immediately before agitation. However, fine biochar powder application poses hazards by itself and may not be practical to apply on a farm scale, especially when livestock and workers are present. We hypothesized that applying pelletized biochar to manure surfaces is just as effective as applying powder to protect farmers and animals from excessive exposure to H2S and NH3. This work reports on the lab-scale proof-of-the-concept trials with biochar pellets on the lab scale. The objective was to compare the biochar pellets and biochar powder on their effectiveness of mitigation on H2S and NH3 gases during 3-h-long swine manure agitation. Three scenarios were compared in (n = 3) trials: (i) control, (ii) 12.5 mm thick surficial application to manure surface of biochar powder, and (iii) an equivalent (by mass) dose of pelletized biochar applied to the manure surface. The biochar powder was bound with 35% (wt) water into ~5 × 10 mm (dia × length) pellets. The biochar powder was significantly (p < 0.05) more effective than the biochar pellets. Still, pellets reduced total H2S and NH3 emissions by ~72% and ~68%, respectively (p = 0.001), compared with ~99% by powder (p = 0.001). The maximum H2S and NH3 concentrations were reduced from 48.1 ± 4.8 ppm and 1810 ± 850 ppm to 20.8 ± 2.95 ppm and 775 ± 182 ppm by pellets, and to 22.1 ± 16.9 ppm and 40.3 ± 57 ppm by powder, respectively. These reductions are equivalent to reducing the maximum concentrations of H2S and NH3 during the 3-h manure agitation by 57% and 57% (pellets) and 54% and 98% (powder), respectively. Treated manure properties hinted at improved nitrogen retention, yet they were not significant due to high variability. We recommend scaling up and trials on the farm-scale level using biochar pellets to assess the feasibility of application to large manure surfaces and techno-economic evaluation.

Assessment of H2S and BTEX concentrations in ambient air using passive sampling method and the health risks.

Wastewater treatment plants (WWTPs) may be a source of nuisance in neighbouring places due to hydrogen sulphide (H2S) and BTEX (benzene, toluene, ethylbenzene, and xylenes) emissions. In this study, samples were collected from WWTP workplace ambient air and outdoor ambient air around one of the largest WWTPs in Istanbul with a capacity of 250,000 m3/day to evaluate the effects of H2S and BTEX emissions. Samples were collected in three seasons for 15-day durations: winter (November 2015), spring (May 2015), and summer (August 2016). Average concentrations of H2S and BTEX were determined as 1.1 and 56.2µg/m3, respectively. Average concentrations BTEX components were 4.9, 20.7, 6.4, and 24.2µg/m3, respectively. Health risk assessment for plant workers and local residents was performed for H2S and BTEX inhalation exposure using the method by USEPA. Results show that H2S and BTEX emissions do not have harmful effects on human health.

Nutrients and carbon fate in two lowland contrasting soils amended with compost

The present study investigated the transient effects of compost application combined with minimum tillage followed by traditional fertilization in two contrasting agricultural soils of the Po River plain, where both nutrients leaching and carbon cycle were monitored for three years (2016–2019) via several campaigns of soil and groundwater sampling and gas emissions. The results of this work highlight that the effects of compost on nutrients leaching is transient and is soon lessened over time if new incorporations do not take place. Nutrients leaching was minimal on shallow groundwater quality with the following decreasing order: nitrate > ammonium > nitrite > phosphate. Moreover, the nutrients distribution profiles (nitrate, nitrite, ammonium and phosphate) also depended on the groundwater fluxes and on boundary conditions (geogenic sources and previous fertilizations). The soil organic carbon results highlight that its increase (approximately 1 ± 0.4% in both soils) was temporary and was not anymore discernible after three years since compost incorporation. The carbon dioxide emissions behave like the soil organic carbon, with an initial increase (approximately 66 ± 17 mM/m2/d in both soils) due to mineralization and a subsequent decrease, while no methane and hydrogen sulphide emission were detected. Moreover, carbon dioxide fluxes were also driven by the soil with nearly doubled fluxes in the site with a higher soil organic carbon baseline.

Reducing air pollution from broiler farms

Broiler farms are the main supplier of national meat needs in Indonesia. Production of broilers in Indonesia continues to increase every year as a consequence of the Indonesian population increase. The main issue in animal production is environmental pollution including in broiler production. This study aimed to identify the source of air pollution related to broiler farms and how to overcome air pollution from broiler farms. The result of the study showed that there were several primary air pollutions from broiler farms, i.e., the pollution from emissions of ammonia, hydrogen sulfide, greenhouse gasses, odor, and dust. Generally, air pollution from the broiler farm resulted mainly from broiler manure. It has been concluded that manure management is the main way in the reduction of air pollution from broiler farms. Management of feeding is the other way to reduce air pollution from broiler farms, it is because the air pollution from broiler manure resulted from excess nutrients from feed which released through manure. Applicating feed additives and waste additive is the other way which recommendation to reduce air pollution from broiler farms, besides other kinds of approaches.

Titanium Trisulfide Nanoribbons Affect the Downy Birch and Poplar × Aspen Hybrid in Plant Tissue Culture via the Emission of Hydrogen Sulfide

Plant tissue culture is an important tool for accelerated vegetative reproduction of woody plants. To increase the efficiency of this method, it is necessary to search for new growth stimulators and protectors of microshoots. Two-dimensional (2D) nanomaterials are highly promising for applications in medicine and biotechnologies. We have studied the effects of TiS3 nanoribbons with the following mean dimensions: thickness less than 100 nm, length 1–10 μm and width 0.4–1 μm upon poplar × aspen hybrid and downy birch microclones in plant tissue culture. We have found the effectiveness of this particular nanomaterial as a sterilizing and stimulating agent in the initial growth stage and as a rhizogenesis-activating agent in the rooting stage. We analyzed a wide range of TiS3 concentrations in the nutrient media and identified 1.5 and 3 μg/L as optimal. However, concentration-dependent toxic effects manifesting themselves through microclones viability suppression have been discovered in the groups exposed to 6 and 15 μg/L TiS3. We have established that plant reaction to TiS3 treatment is specific for different plant species, i.e., downy birch is generally more tolerant than poplar × aspen hybrid. Here, we propose that the protective and stimulating effects of titanium trisulfide as well as its toxicity in high concentrations can be explained by the release of hydrogen sulfide as a result of aqueous hydrolysis of nanoribbons and its effect on plants. Additional studies are required in order to assess all biological effects produced by TiS3 nanoribbons at further stages of ontogenetic development and to identify the mechanisms of their action.

Assessment of hydrogen sulfide emission in a wastewater pumping station.

Wastewater collection systems can be a source of odors that lead to complaints from plant workers, the public, and nearby property owners. The primary source of odors released from such systems is the presence of hydrogen sulfide (H2S) gas at high concentrations. This study was conducted in the main pumping station in Kuwait with a capacity of 570,000 m3/day to assess H2S gas emission, determine factors affecting H2S generation, and evaluate the effectiveness of the odor control system comprising stripping using sodium hydroxide and carbon adsorption. Yearly data on wastewater flow rate, temperature, pH, BOD5, and H2S were obtained from plant records over the years 2013-2015, as well as monthly data measurements were conducted during May to December 2016, and weekly data were collected during a plant monitoring program in March and April 2017. Statistical analysis showed seasonal, daily, and hourly variations in H2S concentrations, with higher values reported in summer, cyclic hourly patterns obtained daily, and peak H2S level of 10ppm recorded at 7pm and 40°C. The ANOVA test indicated that the wastewater temperature, flow rate, and BOD5 were statistically significant factors affecting the formation of hydrogen sulfide gas because of the strong correlation and a p value less than the significance level of 0.05. It was evident that the wastewater temperature is the most influential factor. A model was developed to predict H2S emission. The odor control system used in the station proved to be highly effective and able to remove up to 99.9% of H2S released from wastewater.