Average H2S Concentration Research Articles

H2S mitigation for biogas upgrading in a full-scale anaerobic digestion process by using artificial neural network modeling

Biogas production by anaerobic digestion (AD) has emerged as a prominent bio-renewable energy source in recent years. However, the process also produces undesirable by-products, including H2S, thereby negatively impacting the biogas quality. This study focused on mitigating H2S in a full-scale AD located at a wastewater treatment plant (WWTP) by controlling the internal operational parameters by using an artificial neural network (ANN) model. Data from 54 days of AD operation were used to train and validate a structured ANN with a 5-3-1 topology. To minimize the H2S content, optimum values for dry solid (DS), volatile solid (VS), pH, temperature, and primary sludge fraction (PS) were determined to be 6.2 %, 63 %, 7.7, 35.6 °C, and 67.6 %, respectively, using the particle swarm optimization (PSO) algorithm. This optimization indicated a 49 % reduction in the average H2S concentration, from 6117 ppm to 3107 ppm. The analysis of relative importance (RI) showed that the pH (RI = −29.5) and PS (RI = −28.7) were the most critical factors affecting biogas quality. Additionally, several solutions derived from the optimization results were practically implemented in the Qom WWTP to achieve optimal conditions, and the outcomes were discussed.

Measurement of Ammonia and Hydrogen Sulfide Emission from Three Typical Dairy Barns and Estimation of Total Ammonia Emission for the Chinese Dairy Industry.

There is an urgent need for accurate measurement for emissions of ammonia (NH3) and hydrogen sulfide (H2S) in dairy barns in order to obtain reliable emission inventories and to develop and evaluate abatement strategies. This experiment was performed on three dairy farms in central China during 14 consecutive days in the winter 2020. Concentrations of NH3 and H2S were measured every two hours. The samples were taken inside and outside of barns from 7 sites at two heights (at floor and 1.5 over the floor). The results show that the average NH3 concentration was 2.47 mg/m3 with a maximum of 4.62 mg/m3, while the average H2S concentration was 0.179 mg/m3 with a maximum of 0.246 mg/m3. Lactating cows produced significantly more NH3 (3.73 mg/m3 versus 2.34 mg/m3) and H2S (0.24 mg/m3 versus 0.14 mg/m3) than non-lactating cows. NH3 and H2S concentrations were higher at 0 m than at 1.5 m, especially during the day. In addition, the average daily emission rates per animal unit (AU = 500 kg weight) were 23.5 g and 0.21 g for NH3 and H2S, respectively. The emission rate for NH3 was then used to extrapolate the NH3 emission from the Chinese dairy production. Our estimation for 2016 was 0.45 Tg, and it could reach 1.35 Tg by 2050. These numbers reflected our first attempt to calculate emission inventories for the Chinese dairy industry. Our results also suggest that more concrete measures must be taken to reduce the uncertainties of NH3 emissions from dairy cow production in China.

H2S Emission and Microbial Community of Chicken Manure and Vegetable Waste in Anaerobic Digestion: A Comparative Study

In order to solve the problem of H2S corrosion in biogas utilization, it is necessary to understand the characteristics and mechanisms of H2S production in chicken manure anaerobic digestion (CMAD) and vegetable waste anaerobic digestion (VWAD). In this study, lab-scale batch tests of CMAD and VWAD were conducted for 67 days at 35 °C. The results showed that sulfide was found to be the major form of sulfur in CMAD (accounting for 90%) and VWAD (70%). The average concentration of H2S was 198 ± 79 ppm in CMAD and 738 ± 210 ppm in VWAD. Moreover, 81% of total H2S was produced at 20 days of methane production in CMAD, but 80% of total H2S was produced in the first day in VWAD because of the rapid production of biogas and fermentation acidification. The sulfide ion equilibrium model could universally and feasibly predict the H2S production in CMAD and VWAD. The abundance of Firmicutes, Bacteroidetes, Proteobacteria and Euryarchaeota accounted for about 95% of the total microbes in both CMAD and VWAD; the influence of the fermentation stage on the microbial community was greater than that of the difference between CM and VW; the abundance of SRB was 0.01~0.07%, while that concerning organosulfur compounds fermentation was 22.8~30.5%. This study indicated that the H2S concentration of CMAD biogas was more than five times that of VWAD because CM is alkalescent but VW is acidic.

ANALYSIS OF LIVER FUNCTION DISORDERS IN CRUMB RUBBER FACTORY WORKERS IN PALEMBANG CITY, SOUTH SUMATRA

Workers are required to receive Occupational Safety and Health protection. Work accidents can be influenced by physical, chemical, biological, ergonomic and psychological factors. Natural rubber factory is one of the industries that have risks to these factors. This study used a cross-sectional design. Data analysis used the CHAID (Chi-Square Automatic Interaction) method. P value < 0.05 was considered statistically significant. The results of the study showed that the average concentration of H2S in the air and in solids was above the quality standard and the average concentration of H2S in water was still below the quality standard. The average concentration of NH3 in water and in solids is above the quality standard and the average concentration of NH3 in the air is still below the quality standard. The results of the CHAID method analysis showed that glucose levels were associated with impaired liver function (p = 0.000; chi square = 48.766) and the risk of H2S exposure in the air with impaired liver function (p = 0.007; chi square = 7.944). In addition, 3 segments of liver function disorders were also found, namely Segment 1: Workers with abnormal BBS levels, high air exposure H2S; segment 2: Workers with abnormal glucose levels, low air exposure H2S; segment 3: Workers with normal glucose levels. Based on this segment, it was also found that the percentage of risk of experiencing liver function disorders were workers in segment 2 (36.3%) and segment 1 (17.4%).

ANALYSIS OF FLOWRATE, SULFATE, AND TOTAL SULFUR PATTERN IN WASTEWATER INLET TANKS FOR HS MANAGEMENT

Hydrogen sulfide (H2S) is a major source of concrete corrosion in a wastewater treatment plant (WWTP) that causes significant financial losses. Variations in the flow rate and composition of incoming wastewater has significant impact on H2S generation. During anaerobic conditions, sulfur present in excreta and sulfate from rainfall become the source of electron acceptors for the conversion of sulfate to sulfide in wastewater. Sulfide, in turn, is converted to H2S and later to sulfuric acid which leads to concrete corrosion. Flowrate directly relates to the amount of wastewater entering the plant. Hence understanding flow rate pattern will help to analyze H2S generation. Flow rate and H2S concentrations were recorded every two-hours for four days in a wastewater treatment plant. Wastewater samples of 50ml were collected at each sampling event coinciding the recording intervals. Samples were analyzed for sulphate and sulfide concentrations using HACH© kits. Total sulfur was calculated from the collected data. The correlations were analyzed using Minitab©. It was found out that average flow rate was negatively related to average H2S concentration. H2S concentration is higher during night when the flow rate is lower, which is a result of greater resident time. Flowrate changes in a cyclic manner throughout the day. During night, sulfate and total sulfur concentrations are higher, H2S concentration is maximum during this time. It is contrariwise during the day. Sulfate and total sulfide follow a pattern that is similar to that of flowrate. Analyzing these parameters is a critical step in successfully modelling H2S generation.

ANALYSIS OF FLOWRATE, SULFATE, AND TOTAL SULFUR PATTERN IN WASTEWATER INLET TANKS FOR HS MANAGEMENT

Hydrogen sulfide (H2S) is a major source of concrete corrosion in a wastewater treatment plant (WWTP) that causes significant financial losses. Variations in the flow rate and composition of incoming wastewater has significant impact on H2S generation. During anaerobic conditions, sulfur present in excreta and sulfate from rainfall become the source of electron acceptors for the conversion of sulfate to sulfide in wastewater. Sulfide, in turn, is converted to H2S and later to sulfuric acid which leads to concrete corrosion. Flowrate directly relates to the amount of wastewater entering the plant. Hence understanding flow rate pattern will help to analyze H2S generation. Flow rate and H2S concentrations were recorded every two-hours for four days in a wastewater treatment plant. Wastewater samples of 50ml were collected at each sampling event coinciding the recording intervals. Samples were analyzed for sulphate and sulfide concentrations using HACH© kits. Total sulfur was calculated from the collected data. The correlations were analyzed using Minitab©. It was found out that average flow rate was negatively related to average H2S concentration. H2S concentration is higher during night when the flow rate is lower, which is a result of greater resident time. Flowrate changes in a cyclic manner throughout the day. During night, sulfate and total sulfur concentrations are higher, H2S concentration is maximum during this time. It is contrariwise during the day. Sulfate and total sulfide follow a pattern that is similar to that of flowrate. Analyzing these parameters is a critical step in successfully modelling H2S generation.

Fluxes of H2S and SO2 above a subtropical forest under natural and disturbed conditions induced by temporal land-use change

Hydrogen sulfide (H2S) is one of predominant biogenic sulfur gases, influencing aerosol formation and climate change. There is considerable uncertainty of the global budget of H2S due to limited field data, especially in subtropical forests. In addition, an interaction between soil-emitted H2S and ambient sulfur dioxide (SO2) might exist within forest ecosystems. In this study, the aerodynamic gradient method was applied to consecutively measure H2S and SO2 fluxes above a subtropical forest canopy in Southwest China under natural and disturbed conditions induced by temporal land-use changes. The average H2S concentration and flux under natural conditions were 0.79 ± 0.07 ppbv and 0.04 ± 0.01 g S m−2 yr−1, respectively. The emission was larger than that in most croplands and freshwater wetlands. Vegetation emissions might account for about 26% of the total forest H2S emissions at this site. The deposition of SO2 was likely balanced by H2S oxidization under the forest canopy, with the mean concentration and net flux as 1.23 ± 0.11 ppbv and −0.03 ± 0.10 g S m−2 yr−1, respectively. Under disturbed conditions with soils excavation and scattering on the forest floor, simultaneously high emissions of H2S and SO2 were observed above the canopy, reaching 5.78 ± 0.16 and 1.60 ± 0.87 g S m−2 yr−1, respectively. This suggested that land-use change in subtropical forests might lead to release of legacy S in subsoils to the atmosphere in the form of H2S and SO2. Regarding the widely documented large S accumulation and expanding deforestation across subtropical forests, potentially high emissions of H2S and SO2 from subtropical forests should be carefully considered in regional air quality control and forest management.

Sanitation Network Sulfide Modeling as a Tool for Asset Management. The Case of the City of Murcia (Spain)

Hydrogen sulfide (H2S) generated in sewer networks induces corrosion which today constitutes the main cause of deterioration of concrete pipes. Information regarding the H2S concentration inside sewer networks, as well as its control and reduction, has become one of the most important concerns in sanitation systems management nowadays. Modeling sulfide dynamics is the key to understanding corrosion processes. A dynamic model (called EMU-SANETSUL) was developed to calculate the H2S concentration in both the water and the gas phases of the main sewers of the city of Murcia (Spain). The model was calibrated with data from field measurements taken from both the gas phase and wastewater. Samples were taken in the network from 2016 to 2019. The model achieved an accuracy index and error index in the ranges of 57% and 15%, respectively. Empirical equations of reaction are used, and calibration parameters are detailed. The code uses an explicit discretization technique, named the Discrete Volume Element Method (DVEM). A map with the annual average concentration of H2S at the gas phase inside each pipe of the simulated network is presented. Values are compared with the mechanical deterioration inventory from closed-circuit television (CCTV) inspections performed by the Municipal Sanitation Company of the city of Murcia (EMUASA). Mechanical deterioration of pipes has diverse causes, including corrosion of pipes by H2S. Sections with high H2S concentrations that match with mechanical wear can be considered susceptible to being prioritized when rehabilitation works are being planned. Therefore, H2S concentration modeling provides valuable information for asset management of the sewer network.

Characteristics and mechanisms of H2S production in anaerobic digestion of food waste

The biogas produced in food waste anaerobic digestion (FWAD) contains H2S which can lead to corrosion, bad smell and poisoning accident. To control H2S pollution, the characteristics and mechanisms of H2S production in FWAD should be known. In this study, a lab-scale FWAD batch test was applied for 20 days under 35 °C. The production potential and average concentration of H2S were 765 ± 163 g/t (TS) and 1065 ± 267 ppm, respectively. 76% of total H2S was produced within 6 h on the first day of fermentation, acidification and gas production were key reasons for high H2S production at this time. Compared to H2S peak production time, that of methane was long (4 days) and after that of H2S. Sulfides were found to be the dominant form of sulfur (accounting for 20–70% of total sulfur) in the mixed fermentation liquor in fermentation batch. These sulfides were from protein, which could be decomposed slowly to sulfide by protein-using bacteria and methanogen at the time of methane production peak, and sulfate, which could be converted to sulfide by Sulfate reducing bacteria (SRB) during the first two days of fermentation. Protein would be the main contributor to sulfide/H2S for the continuous feeding FWAD system in long term operation, due to its presence as the main form of sulfur in food waste.

Comparison of Hydrogen Sulfide Concentrations and Odor Annoyance Frequency Predictions Downwind from Livestock Facilities

Estimating and measuring the occurrence of a sensation, odor, around livestock facilities is challenging. This research compares the estimated frequency of odor nuisance with measured hydrogen sulfide (H2S) concentrations at various distances around a swine and a dairy operation, and discusses the results based on time of day, weather conditions, distance, and topography. The estimated odor annoyance-free and odor annoyance frequencies were based on a publically available calculator of odor impact derived from average odor emission rates, historical, and regional weather patterns, and dispersion modeling. Continuous monitoring of H2S was by single point monitors (SPM) at locations around the operations. Time-weighted average H2S concentrations were less than 10 ppb for odor annoyance-free frequencies, and less than 10 to at least 73 ppb for odor-annoyance frequencies. Verifying a proxy odor indicator can help update odor annoyance models and respond to site-specific concerns for existing facilities.

The experimental study of biogas production when digesting chicken manure with a biochar additive

AbstractThe research aims to evaluate the output of biogas and the concentration of CH4 and gaseous impurities such as CO2 and H2S in the process of digesting chicken manure without additives (experiment A) and with 10% of biochar additive (by mass of the dry load) (experiment B) under anaerobic and mesophilic conditions. It has been found that the average output of biogas from a particular amount of chicken manure (experiments A and B) obtained in the 45‐day experimental research is similar in both cases and reaches 12.88 l d–1 and 12.36 l d–1, respectively. However, the biochar additive increases CH4 concentration in biogas and reduces the concentration of gaseous impurities (CO2 and H2S) in biogas. The maximum concentration of CH4 in biogas obtained from a load of manure with biochar additive is higher than that in biogas obtained by using a load without a biochar additive, and reaches 72.0% and 68.5%, respectively. The average CO2 concentration, reaching 33.09% and 47.5%, respectively, in biogas obtained from the load with 10% of biochar additive is lower than that in biogas obtained from the manure load without an additive. The average concentration of H2S in the biogas obtained in experiment B is lower than that in experiment A and reaches 95.9 mg m–3 and 195.5 mg m–3, respectively. The biochar additive adsorbs gaseous impurities (CO2 and H2S) from biogas without adsorbing CH4. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Periodic deprivation of gaseous hydrogen sulfide affects the activity of the concrete corrosion layer in sewers

Sulfide induced concrete corrosion significantly reduces the service life of the sewer systems. Gaseous hydrogen sulfide (H2S) levels are a key factor affecting the corrosion rate and these fluctuate due to the diurnal flow pattern of sewers. Currently, there is little known about how such fluctuations, in particular the periodic deprivation of H2S, may affect the corrosion activity. This study investigated the impact of the deprivation of H2S on the sulfide uptake rate (SUR) of concrete coupons incubated in laboratory corrosion chambers. After systematic evaluation of the gaseous H2S concentration profiles of two sewer systems, two types of profiles, i.e. short- (1 h) and long- (12 h) term deprivation of H2S, were applied to the concrete coupons. In comparison to the baseline SUR, exposing the concrete coupon to 0 ppm of H2S for 1 h consistently caused a temporary increase of the SUR (i.e. 3.2%–12.5%) following re-supply of H2S at baseline levels. With the continuous re-supply of H2S, there was gradual and steady decrease of SUR to the level close to the baseline SUR. However, for the case after deprivation of H2S for 12 h, the SUR was 5.1% lower than baseline SUR and gradually increased to a level similar to the baseline SUR during the 20–30 min of continuous re-supply of H2S. In addition, the simultaneous deprivation of H2S and O2 for 1 h had negligible impact on the SUR. Further analysis suggests that the historically accumulated intermediates of sulfide oxidation could act as electron donors for sulfide oxidizing bacteria (SOB). The replenishment of the intermediates upon the re-supply of H2S could play a key role in the increase of SUR after short-term deprivation of H2S. However, the activity of SOB could be diminished after long-term deprivation of H2S, although the sulfur intermediates still could be available. Estimating the sulfide uptake by concrete using the SUR of the average H2S concentration could lead to overestimation of the sulfide uptake. There could be more significant overestimation for the case with longer deprivation of H2S.

A Study on the Distribution Characteristics of Sulfur Compounds in Ambient air using Continuous Monitoring Method in Incheon Area

This paper focuses on the applicability of a continuous monitoring method on trace sulfur compounds in the ambient air by TD and GC/PFPD. The target compounds for monitoring include H2S(hydrogen sulfide), Methyl mercaptan, Dimethyl Sulfide, and Dimethyl disulfide. The result of QA/QC on monitoring instruments satisfies all the standards of Odor Measurement and Analysis Method, showing that the reproductivity of the compounds by concentration is within 10%, linearity is above 0.98 of a correlation efficient, method detection limit is 0.16 ppb by MM standard, and recovery rate is over 70%. Monitoring was conducted for two years from March 2006 to February 2008. As a result of the monitoring, the average concentration of H2S was 0.08 ppb, with the maximum concentration at 16.15 ppb. The result indicates that it is reasonable to do continuous monitoring as there appears a spontaneous event of high concentration by the condition of the site during monitoring odor-causing substances. Therefore, it is suggested that the continuous monitoring method used in this paper is appropriate to identify the characteristics of sudden occurrence and concentration variations of sulfur compounds.

Chemical characterization of emissions from a municipal solid waste treatment plant

Gaseous emissions are an important problem in municipal solid waste (MSW) treatment plants. The sources points of emissions considered in the present work are: fresh compost, mature compost, landfill leaks and leachate ponds. Hydrogen sulphide, ammonia and volatile organic compounds (VOCs) were analysed in the emissions from these sources. Hydrogen sulphide and ammonia were important contributors to the total emission volume. Landfill leaks are significant source points of emissions of H2S; the average concentration of H2S in biogas from the landfill leaks is around 1700ppmv. The fresh composting site was also an important contributor of H2S to the total emission volume; its concentration varied between 3.2 and 1.7ppmv and a decrease with time was observed. The mature composting site showed a reduction of H2S concentration (<0.1ppmv). Leachate pond showed a low concentration of H2S (in order of ppbv). Regarding NH3, composting sites and landfill leaks are notable source points of emissions (composting sites varied around 30–600ppmv; biogas from landfill leaks varied from 160 to 640ppmv).Regarding VOCs, the main compounds were: limonene, p-cymene, pinene, cyclohexane, reaching concentrations around 0.2–4.3ppmv.H2S/NH3, limonene/p-cymene, limonene/cyclohexane ratios can be useful for analysing and identifying the emission sources.

The effect of biogas sparging on cow manure characteristics and its subsequent anaerobic biodegradation

A study of the influence of biogas sparging on the characteristics of raw liquid cow manure and its subsequent anaerobic digestion process was carried out. Preliminary experiments have demonstrated that a biogas sparging rate of 2 L h−1 for 120 min causes a reduction in the initial pH of the substrate to values close to 7.0, which are appropriate for its posterior anaerobic biodegradation. Two laboratory-scale anaerobic digesters were operated for 40 days, one (D1) which digests cow manure after biogas sparging and the other (D2) which treats untreated manure as the control. After the sparging process the biogas slightly increased its average methane content from 61% to 62%, decreasing the average CO2 concentration from 35.4% to 32.4%. However, after sparging and during the first 35 days of the experimental period, the average H2S concentration in the biogas increased from 231 to 637 ppm, which resulted in a decrease in the H2S concentration in the liquid manure, favoring its subsequent anaerobic digestion. Higher average COD, total solid (TS) and volatile solid (VS) removals were always achieved in digester D1 when compared to D2. For instance, mean VS removal efficiencies of 45.1% and 36.5% were reached in digesters D1 and D2, respectively. An increase of 9.3% and 9.1% in the biogas and methane production rates respectively were also obtained when the influent was previously treated with biogas sparging (D1). Finally, an increase in the methane yield coefficient from 0.13 to 0.20 L CH4 g COD−1 was also achieved after the sparging pre-treatment.

The Study on the Inhibiting Effect of Denitrifying Bacteria on Sulfate-Reducing Process

The average concentration of H2S in Changqing oil Field is higher than 100mg/m3,which is much higher than the demand of “Operational Site Harm Factor Occupation Contact Limiting Value” (GBZ2-2002). Taking this factor into consideration, the experiment aimed at reducing H2S concentration in crude oil gatering and transferring systems by using the denitrifying bacteria. The experiment has two parts: First sulphat reduction process and then denitrification inhibit process. Therefore, two UASB reactors are used in a series to achieve these two processes. The first UASB reactor are mainly used to create SRB bacteria and H2S gas .After the first UASB reactor successfully starting, sodium nitrite are added in the second UASB to achieve denitrification inhibit process. The experiment showed that after the first UASB reactor start, the S2- can achieve 120mg/L and SO42- concentration is about 200 mg/L. So the Sulfate conversion rate can achieve 75%. Then, when the second UASB reactor started successfully, the S2- concentration sharply droped into 20 mg/L and SO42- concentration increased to 400mg/L, the sulphat reduction can achieve 83%. Also, advanced research showed that both SO42-concentration ratio and ORP value can contribute to restraining the SRB bacteria.Finally，through DGGE technology,many kinds of bacteria take into this process, for example pseudomonas aeruginosa. The results of this experiment has a great value to refrain the concentration of H2S in oil fields.

Environmental Exposure to Hydrogen Sulfide in Central Slovakia (Ružomberok Area) in Context of Health Risk Assessment

The activities of the kraft pulp-mill in Ruzomberok have great impact on ambient air quality in the town and the neighboring villages. The malodorous sulfur compounds adversely contribute to the overall emission profile. The reduced sulfur proportion forms the inorganic and organic compounds containing sulfur atoms in their lowest oxidation condition (S2-). The total sulfur proportion reduced includes hydrogen sulfide, mercaptans, dimethyl sulfide, dimethyl disulfide and other sulfur compounds. Hydrogen sulfide (H2S)--as mentioned above--is of prime importance. The kraft pulp-mill has measured of hydrogen sulfide contained in ambient air since 2002. The environmental samples were collected in 7 localities in all their selection based on the geographic, climatic and demographic factors. Four exposure localities in the Ruzomberok neighborhood, have been defined by the specified criteria. Exposure assessment was made for each exposure locality by determination of the average daily inhalation dose. The average concentration of H2S reached 5.8 microg x m(-3) in the most polluted locality (Cernová, 2003). To complete the health risk assessment, the standard risk characterization procedure was made by the Hazard Quotient (HQ) calculation for hydrogen sulfide exposure. The highest level of HQ, almost 7, was identified in the event of a worst case exposure scenario (using the 95% concentrations), as for exposure group C. Statistically significant decrease of reported H2S levels was noted during the entire measurement period (-0.25/year, p < 0.001).

Swine Production Impact on Residential Ambient Air Quality

ABSTRACT Numerous residents in agricultural areas are concerned about the impact that the swine industry may have on the ambient air quality. They assume there is a risk because there is limited information on the airborne contaminant that may originate from these facilities. The objective of the project was to assess the impact of swine production on ambient air quality related to public health in farming communities. Of the six chosen communities, three were considered not to be in a swine production area, whereas the three others were considered to be within a swine production area. Data were collected during three periods in spring and summer 2006. Ammonia and hydrogen sulfide concentrations were monitored on a continuous basis whereas odor concentrations and intensities were monitored twice a week. Odor concentrations were measured by dynamic olfactometry and odor intensities were determined by trained odor assessors. Public health was evaluated by survey questionnaires sent to a sample of residents in each of the six communities. Average NH3 concentrations ranged from 6.9 to 12.6 ppb for nonexposed communities and from 8.9 to 18.3 ppb for exposed communities. Average H2S concentrations ranged from 1.1 to 1.5 ppb for nonexposed communities and from 1.1 to 1.6 ppb for exposed communities. For a community in a swine production area, ambient NH3 and H2S concentrations were found to be higher than those communities not in a swine production area; however, that difference was not significant and they were within air quality standards for public health and safety. Odor concentrations showed no significant difference between the nonexposed and exposed communities and between evening and morning periods. Odor intensities were found to be significantly higher in the communities within swine production areas. More research will be required to fully understand the correlation between specific physical symptoms from residents and the presence of odors from swine production.

Technical and economical study of a full-scale biotrickling filter for H2S removal from biogas

The present study evaluates the technical and economical feasibility of the H2S elimination from an energy-rich gas using a full-scale biotrickling filter installed in a municipal waste water treatment plant. The study analyzes the continuous operation of a 4.5 months period, treating 80 m3 h-1 of biogas with an average H2S concentration of 3000 ppmv. The bioreactor was operated at a gas contact time of 180 seconds and maximum elimination capacities of 170 g H2S m-3 h-1 were obtained without any occurrence of neither biological nor mass transfer limitation. Elemental sulfur and sulfate were the main detected byproducts of the H2S treatment. The main drawback observed during the studied period was related to the air flow supply. This caused a removal efficiency decrease and an excess of sulfur production. A comparative cost-benefit analysis of the more applied chemical oxidation processes with the biological treatment was performed. Savings chemicals indicated that the payback time of the substitution treatment was about 4.5 years. Cost savings ranged between 11000€ per year, or 2.6€ per kg H2S treated. The results of this study have shown how to solve the main operational problems detected in the proposed system and the cost-benefit analysis suggests a significant benefit by replacing the current chemical treatment by the biological alternative not only from an environmental point of view, but also from an economical perspective.

Source and Receptor Ammonia and Hydrogen Sulfide Concentrations in Communities with and without Swine Emission Sources: Follow-Up Study

Research was conducted from May 2004 through September 2005 to investigate the concentration of hydrogen sulfide (H2S) at the perimeter of nine swine operations across the state of Iowa and the ammonia (NH3) and H2S concentrations near and inside residences located in the community of swine operations and in one area of the state not associated with animal agriculture. The nine sources monitored ranged from sites that housed approximately 1,800 to 4,000 finishing pigs. The results indicated that at the perimeter of all nine sources monitored, the overall average H2S concentration ranged from 1.92.7 ppb to 26.332.3 ppb (meanS.D.). Downwind samples, or samples collected during calm periods, resulted in average H2S concentrations that ranged from 7.46.9 ppb to 45.831.8 ppb. In both cases, the maximum H2S concentration was recorded at a finishing site where an earthen basin and a concrete formed below-grade basin existed in close proximity to the livestock housing. Measurements of H2S and NH3 were also conducted at five residences, four of which were located near the swine operation sites for perimeter H2S levels, with one located in an urban setting far removed from animal agriculture. The overall daily average NH3 concentration measured inside the homes ranged from 28.612.8 ppb to 94.728.1 ppb. The overall daily average NH3 concentration measured in the ambient air outside the homes ranged from 11.75.3 ppb to 55.120.6 ppb. The NH3 concentration inside the homes were significantly higher than in the ambient air outside of the homes (p<0.01). H2S concentration inside the homes ranged from 0.70.2 ppb to 2.51.5 ppb. Hydrogen sulfide concentration in the ambient air outside the home ranged from 0.40.2 ppb to2.42.4 ppb. For the residence monitored in an urban setting far removed from animal agriculture, the overall average H2S concentration outside the home was 0.40.2 ppb with the inside home averaging 0.70.2 ppb. The highest average inside home concentration for NH3 and H2S was 94.728.1 ppb and 2.51.5 ppb, respectively, both from a residence where the occupants smoked. The next highest inside home NH3 concentration was 85.715.3 ppb. For this residence the occupants did not smoke but felines were kept inside. The results from the residence ambient air monitoring indicate that the concentration and duration for either NH3 or H2S fell well below the Minimum Risk Levels (MRL) as defined by the Agency for Toxic Substances and Disease Registry (ATSDR, 2008).