Abatement of ammonia and hydrogen sulfide emissions from a swine lagoon using a polymer biocover

The purpose of this research was to determine the efficiency of a polymer biocover for the abatement of H2S and NH3 emissions from an east-central Missouri swine lagoon with a total surface area of 7800 m2. The flux rate of NH3, H2S, and CH4 was monitored continuously from two adjacent, circular (d = 66 m) control and treatment plots using a nonintrusive, micrometeorological method during three independent sampling periods that ranged between 52 and 149 hr. Abatement rates were observed to undergo a temporal acclimation event in which NH3 abatement efficiency improved from 17 to 54% (p = < 0.0001 to 0.0005) and H2S abatement efficiency improved from 23 to 58% (p < 0.0001) over a 3-month period. The increase in abatement efficiency for NH3 and H2S over the sampling period was correlated with the development of a stable anaerobic floc layer on the bottom surface of the biocover that reduced mass transfer of NH3 and H2S across the surface. Analysis of methanogenesis activity showed that the biocover enhanced the rate of anaerobic digestion by 25% when compared with the control. The biocover-enhanced anaerobic digestion process was shown to represent an effective mechanism to counteract the accumulation of methanogenic substrates in the biocovered lagoon.     

Enhanced deodorization and sludge reduction in situ by a humus soil cooperated anaerobic/anoxic/oxic (A2O) wastewater treatment system

Simultaneous sludge reduction and malodor abatement in humus soil cooperated an anaerobic/anoxic/oxic (A2O) wastewater treatment were investigated in this study. The HSR-A2O was composed of a humus soil reactor (HSR) and a conventional A2O (designated as C-A2O).The results showed that adding HSR did not deteriorate the chemical oxygen demand (COD) removal, while total phosphorus (TP) removal efficiency in HSR-A2O was improved by 18 % in comparison with that in the C-A2O. Both processes had good performance on total nitrogen (TN) removal, and there was no significant difference between them (76.8 and 77.1 %, respectively). However, NH₄ ⁺–N and NO₃ ^?–N were reduced to 0.3 and 6.7 mg/L in HSR-A2O compared to 1.5 and 4.5 mg/L. Moreover, adding HSR induced the sludge reduction, and the sludge production rate was lower than that in the C-A2O. The observed sludge yield was estimated to be 0.32 kg MLSS/day in HSR-A2O, which represent a 33.5 % reduction compared to a C-A2O process. Activated sludge underwent humification and produced more humic acid in HSR-A2O, which is beneficial to sludge reduction. Odor abatement was achieved in HSR-A2O, ammonium (NH₃), and sulfuretted hydrogen (H₂S) emission decreased from 1.34 and 1.33 to 0.06 mg/m³, 0.025 mg/m³ in anaerobic area, with the corresponding reduction efficiency of 95.5 and 98.1 %. Microbial community analysis revealed that the relevant microorganism enrichment explained the reduction effect of humus soil on NH₃ and H₂S emission. The whole study demonstrated that humus soil enhanced odor abatement and sludge reduction in situ.     

Biological elimination of H2S and NH3 from wastegases by biofilter packed with immobilized heterotrophic bacteria

Biotreatment of various ratios of H₂S and NH₃ gas mixtures was studied using the biofilters, packed with co-immobilized cells (Arthrobacter oxydans CH8 for NH₃ and Pseudomonas putida CH11 for H₂S). Extensive tests to determine removal characteristics, removal efficiency, removal kinetics, and pressure drops of the biofilters were performed. To estimate the largest allowable inlet concentration, a prediction model was also employed. Greater than 95% and 90% removal efficiencies were observed for NH₃ and H₂S, respectively, irrespective of the ratios of H₂S and NH₃ gas mixtures. The results showed that H₂S removal of the biofilter was significantly affected by high inlet concentrations of H₂S and NH₃. As high H₂S concentration was an inhibitory substrate for the growth of heterotrophic sulfur-oxidizing bacteria, the activity of H₂S oxidation was thus inhibited. In the case of high NH₃ concentration, the poor H₂S removal efficiency might be attributed to the acidification of the biofilter. The phenomenon was caused by acidic metabolite accumulation of NH₃. Through kinetic analysis, the presence of NH₃ did not hinder the NH₃ removal, but a high H₂S concentration would result in low removal efficiency. Conversely, H₂S of adequate concentrations would favor the removal of incoming NH₃. The results also indicated that maximum inlet concentrations (model-estimated) agreed well with the experimental values for space velocities of 50–150 h⁻¹. Hence, the results would be used as the guideline for the design and operation of biofilters.     

Effects of biofilter media depth and moisture content on removal of gases from a swine barn

Media depth (MD) and moisture content (MC) are two important factors that greatly influence biofilter performance. The purpose of this study was to investigate the combined effect of MC and MD on removing ammonia (NH₃), hydrogen sulfide (H₂S), and nitrous oxide (N₂O) from swine barns. Biofiltration performance of different MDs and MCs in combination based on a mixed medium of wood chips and compost was monitored. A 3 × 3 factorial design was adopted, which included three levels of the two factors (MC: 45%, 55%, and 67% [wet basis]; MD: 0.17, 0.33, and 0.50 m). Results indicated that high MC and MD could improve NH₃ removal efficiency, but increase outlet N₂O concentration. When MC was 67%, the average NH₃ removal efficiency of three MDs (0.17, 0.33, and, 0.50 m) ranged from 77.4% to 78.7%; the range of average H₂S removal efficiency dropped from 68.1–90.0% (1–34 days of the test period) to 36.8–63.7% (35–58 days of the test period); and the average outlet N₂O concentration increased by 25.5–60.1%. When MC was 55%, the average removal efficiency of NH₃, H₂S, and N₂O for treatment with 0.33 m MD was 72.8 ± 5.9%, 70.9 ± 13.3%, and –18.9 ± 8.1%, respectively; and the average removal efficiency of NH₃, H₂S, and N₂O for treatment with 0.50 m MD was 77.7 ± 4.2%, 65.8 ± 13.7%, and –24.5 ±12.1%, respectively. When MC was 45%, the highest average NH₃ reduction efficiency among three MDs was 60.7% for 0.5 m MD, and the average N₂O removal efficiency for three MDs ranged from –18.8% to –12.7%. In addition, the pressure drop of 0.33 m MD was significantly lower than that of 0.50 m MD (p < 0.05). To obtain high mitigation of NH₃ and H₂S and avoid elevated emission of N₂O and large pressure drop, 0.33 m MD at 55% MC is recommended.

Implications: The performances of biofilters with three different media depths (0.17, 0.33, and 0.50 m) and three different media moisture contents (45%, 55%, and 67% [wet basis]) were compared to remove gases from a swine barn. Using wood chips and compost mixture as the biofilters media, the combination of 0.33 m media depth and 55% media moisture content is recommended to obtain good reduction of NH₃ and H₂S, and to simultaneously prevent elevated emission of N₂O and large pressure drop across the media.     

Long-Term Operation of a Biofilter for Simultaneous Removal of H2S and NH3

Abstract

Simultaneous removal of NH₃ and H₂S was investigated using two types of biofilters—one packed with wood chips and the other with granular activated carbon (GAC). Experimental tests and measurements included analyses of removal efficiency (RE), metabolic products, and results of long-term operation (around 240 days). The REs for NH₃ and H₂S were 92 and 99.9%, respectively, before deactivation. After deactivation, the RE for NH₃ and H₂S were decreased to 30–50% and 75%, respectively. The activity of nitrifying bacteria was inhibited by high concentrations of H₂S (over 200 ppm) but recovered gradually after H₂S addition was ceased. However, the Thiobacillus thioparus as sulfur oxidizing bacteria did not show inhibition at the NH₃ concentration under 150-ppm conditions. The deactivation of the biofilter was caused by metabolic products [elemental sulfur and (NH₄)₂SO₄] ac-cumulating on the packing materials during the extended operation. The removal capacities for NH₃ and H₂S were 6.0–8.0 and 45–75 mg N, S/L/hr, respectively.     

Hydrogen Sulfide Gas Treatment by a Chemical‐Biological Process: Chemical Absorption and Biological Oxidation Steps

In order to remove high concentrations of hydrogen sulfide (H₂S) gas from anaerobic wastewater treatments in livestock farming, a novel process was evaluated for H₂S gas abatement involving the combination of chemical absorption and biological oxidation processes. In this study, the extensive experiments evaluating the removal efficiency, capacity, and removal characteristics of H₂S gas by the chemical absorption reactor were conducted in a continuous operation. In addition, the effects of initial Fe^2 + concentrations, pH, and glucose concentrations on Fe^2 + oxidation by Thiobacillus ferrooxidans CP9 were also examined. The results showed that the chemical process exhibited high removal efficiencies with H₂S concentrations up to 300 ppm, and nearly no acclimation time was required. The limitation of mass‐transfer was verified as the rate‐determining step in the chemical reaction through model validation. The Fe^2 + production rate was clearly affected by the inlet gas concentration as well as flow rate and a prediction equation of ferrous production was established. The optimal operating conditions for the biological oxidation process were below pH 2.3 and 35°C in which more than 90% Fe^3 + formation ratio was achieved. Interestingly, the optimal glucose concentration in the medium was 0.1%, which favored Fe^2 + oxidation and the growth of T. ferrooxidans CP9.     

The Recovery of Ammonia and Hydrogen Sulflde from Ground-Level Area Sources Using Dynamic Isolation Flux Chambers: Bench-Scale Studies

Abstract

Controlled bench-scale laboratory experiments were conducted to evaluate the recovery of ammonia (NH₃) and hydrogen sulflde (H₂S) from dynamic isolation flux chambers. H₂S (80–4000 ppb) and NH₃ (5000–40,000 ppb) samples were diffused through the flux chamber to simulate ground level area source emissions while measuring the inlet and outlet flux chamber concentrations simultaneously. Results showed that the recovery of H₂S during a 30-min sampling time was almost complete for concentrations >2000 ppb. At the lowest concentration of 80 ppb, 92.55% of the H₂S could be recovered during the given sampling period. NH₃ emissions exhibited similar behavior between concentrations of 5000–40,000 ppb. Within the 30-min sampling period, 92.62% of the 5000-ppb NH₃ sample could be recovered. Complete recovery was achieved for concentrations >40,000 ppb. Predictive equations were developed for gas adsorption. From these equations, the maximum difference between chamber inlet and outlet concentrations of NH₃ or H₂S was predicted to be 7.5% at the lowest concentration used for either gas. In the calculation of emission factors for NH₃ and H₂S, no adsorption correction factor is recommended for concentrations >37,500 ppb and 2100 ppb for NH₃ and H₂S, respectively. The reported differences in outlet and inlet concentration above these ranges are outside the full-scale sensitivity of the gas sensing equipment. The use of 46–90 m of Teflon tubing with the flux chambers has apparently no effect on gas adsorption, because recovery was completed almost instantaneously at the beginning of the tests.     

Measurement and analysis of atmospheric ammonia emissions from anaerobic lagoons

Ammonia-nitrogen flux (NH₃-N=(14/17)NH₃) was determined from six anaerobic swine waste storage and treatment lagoons (primary, secondary, and tertiary) using the dynamic chamber system. Measurements occurred during the fall of 1998 through the early spring of 1999, and each lagoon was examined for approximately one week. Analysis of flux variation was made with respect to lagoon surface water temperature (∼15 cm below the surface), lagoon water pH, total aqueous phase NH_x(=NH₃+NH₄⁺) concentration, and total Kjeldahl nitrogen (TKN). Average lagoon temperatures (across all six lagoons) ranged from approximately 10.3 to 23.3^°C. The pH ranged in value from 6.8 to 8.1. Aqueous NH_x concentration ranged from 37 to 909 mg N l⁻¹, and TKN varied from 87 to 950 mg N l⁻¹. Fluxes were the largest at the primary lagoon in Kenansville, NC (March 1999) with an average value of 120.3 μg N m⁻² min⁻¹, and smallest at the tertiary lagoon in Rocky Mount, NC (November 1998) at 40.7 μg N m⁻² min⁻¹. Emission rates were found to be correlated with both surface lagoon water temperature and aqueous NH_x concentration. The NH₃-N flux may be modeled as ln(NH₃-N flux)=1.0788+0.0406T_L+0.0015([NH_x]) (R²=0.74), where NH₃-N flux is the ammonia flux from the lagoon surface in μg N m⁻² min⁻¹, T_L is the lagoon surface water temperature in ^°C, and [NH_x] is the total ammonia-nitrogen concentration in mg N l⁻¹.     

A Passive Flux Denuder for Evaluating Emissions of Ammonia at a Dairy Farm

Abstract

Passive samplers have been shown to be an inexpensive alternative to direct sampling. Diffusion denuders have been developed to measure the concentration of species such as ammonia (NH₃), which is in equilibrium with particulate ammonium nitrate. Conventional denuder sampling that inherently requires air pumps and, therefore, electrical power. To estimate emissions of NH₃ from a fugitive source would require an array of active samplers and meteorological measurements to estimate the flux. A recently developed fabric denuder was configured in an open tube to passively sample NH₃ flux. Passive and active samplers were collocated at a dairy farm at the California State University, Fresno, Agricultural Research Facility. During this comparison study, NH₃ flux measurements were made at the dairy farm lagoon before and after the lagoon underwent acidification. Comparisons were made of the flux measurements obtained directly from the passive flux denuder and those calculated from an active filter pack sampler and wind velocity. The results show significant correlation between the two methods, although a correction factor needed to be applied to directly compare the two techniques. This passive sampling approach significantly reduces the cost and complexity of sampling and has the potential to economically develop a larger inventory base for ambient NH₃ emissions.     

酸性洗涤塔-生物滤塔-生物曝气池组合工艺处理恶臭气体NH3和H2S

采用酸性洗涤塔、生物滤塔和生物曝气池的组合工艺处理NH3、H2S恶臭混合气体,研究表明,该组合工艺对NH3和H2S有很好的去除效果,在进气流量为35 L/min,喷淋量45 L/h时,NH3进气浓度50.15~525.4 mg/m3,H2S进气浓度10.23~110.36 mg/m3时,NH3单一进气去除率稳定在99%以上,H2S单一进气去除率90%以上。混合进气后,NH3去除率几乎为100%,H2S的去除率提高至98%以上。在一定的浓度范围内,NH3和H2S之间的相互作用对两者的去除效果没有明显的影响,而且起到了相互促进降解的作用。同时,进气流量和填料层高度都会影响NH3、H2S的去除率。系统对进气容积负荷变化的缓冲能力强,在偶尔超负荷条件下运行并不能使系统崩溃,并且微生物对高负荷逐渐表现出适应性。大部分溶于水的氨由生物曝气池去除,去除率达到96.9%。     

Diurnal Odor,Ammonia, Hydrogen Sulfide,and Carbon Dioxide Emission Profiles of Confined Swine Grower/Finisher Rooms

Abstract

The objective of this study was to obtain diurnal variation profiles of odor and gas (ammonia [NH₃], hydrogen sulfide [H₂S], carbon dioxide [CO₂]) concentrations and emission rate (OGCER) from confined swine grower/finisher rooms under three typical weather conditions (warm, mild, and cold weather) in a year. Two grower/finisher rooms, one with a fully slatted floor and the other with partially slatted floors, were measured for 2 consecutive days under each weather condition. The results revealed that the diurnal OGCER in the room with a fully slatted floor was 9.2–39.4% higher than that with a partially slatted floor; however, no significant differences in the diurnal OGCER were found between these two rooms, except for the NH₃ concentrations in August, the NH₃ and H₂S concentrations and emissions in October, and odor concentrations and emissions in February (p > 0.05). The OGCER variations presented different diurnal patterns as affected by time of day, season, type of floor, ventilation rate, animal growth cycles, in-house manure storage, and weather conditions. Significant diurnal fluctuations in the OGCER (except for the odor concentrations and H₂S emissions) were observed in August (p < 0.05); all of the gas emissions in October and the CO₂ concentrations and emissions in February also showed significant diurnal variations (p < 0.05). These significant diurnal variations indicated that the OGCER during different periods of a day should be monitored when quantifying OGCER concentrations and emissions; for example, source emission data used in air dispersion modeling to decrease the great incertitude of setback determination using randomly measured data.     

Deodorization of pig manure using lignin peroxidase with different electron acceptors

Odor pollution is a big environmental problem caused by large-scale livestock production in China, and developing a practical way to reduce these odors is pressing. In this study, a combination of 0.2–1.0 U/mL lignin peroxidase (LiP) and one of three peroxides (H₂O₂, CaO₂, 2Na₃CO₃·3H₂O₂) was examined for its efficiency in reducing the release of eight chemicals (propionic acid, isobutyric acid, isocaproic acid, isovaleric acid, phenol, p-cresol, indole, and skatole), NH₃, H₂S, and odor intensity from pig manure. The results showed an approximately 90% reduction in p-cresol, 40–60% reduction in odor intensity, 16.5–40% reduction in indolic compounds, and 25–40% reduction in volatile fatty acids. Being the electron acceptors of LiP, 2Na₃CO₃·3H₂O₂ and CaO₂ performed better than H₂O₂ in reducing the concentration of eight chemicals, NH_3, H₂S, and odor intensity from pig manure. The effect of deodorization can last for up to 72 hr.

Implications: In China, one of the major environmental problems caused by confined feeding is odor pollution, which brings a major threat to the sustainability, profitability, and growth of the livestock industry. To couple the LiP with the electron acceptors, a low–cost, simple, and feasible method for odor removal was established in this study. Based on the study results, a practical treatment method was provided for odor pollution and supply the farm operators a more flexible time to dispose treated manure.     

1988 APCA Government Agencies Directory

The biowaste fractions in municipal solid waste (MSW) are the main odor sources in landfill and cause widespread complaints from residents. The ammonia (NH₃) and hydrogen sulfide (H₂S) generation processes were simulated and compared between four typical biowaste fractions individually and combined in the mixed MSW. Food waste was found to be the main contributor to odor emission in mixed MSW, with H₂S generation potential of 48.4 μg kg^?1 and NH₃ generation potential of 4742 μg kg^?1. Fruit waste was another source for NH₃ generation, with 3933 μg kg^?1 NH₃ generation potential. Meanwhile, nitrogen (N) was released in a faster way than sulfur (S) in waste, since 31% and 46% of total NH₃ and H₂S were generated in the first 90 days after disposal, with 1811 and 72 μg kg^?1, and more emphasis should be placed in this initial period.

Implications:?Monitoring of odor generation from biowastes in MSW on a laboratory scale showed that food waste is the main source for NH₃ and H₂S generation, whereas waste fruit is another main contributor for NH₃ released. Generally, N was released in a faster way than S from mixed-waste landfilling.     

Heavy-metal ion complexation by particulate matter in the leachate of solid waste: a multi-method approach

The metal ion binding characteristics of particulate matter obtained from column experiments on the anaerobic digestion of solid waste were studied using a titrimetric approach. The experimental set-up allowed us to study the dynamics of particle bound ligand concentrations during digestion processes typically found in landfills.We developed a continuous titration method by simultaneously using a Cd-sensitive and pH electrode and combining metal and acid/base titrations. This technique allows for a more precise determination of pK_a-log K_M pairs for each ligand than metal titrations alone. The results were compared with titration methods using differential pulse anodic stripping voltammetry (DPASV) and atomic absorption spectroscopy (AAS) with longer equilibration times in order to further characterize ligand properties such as reaction kinetics, the electrochemical lability of the respective complex during DPASV, the distinction between metal adsorption to particulate matter and metal complexation by soluble ligands adhered to particles, reversibility of the binding process by competition studies, and resistance against purging with nitrogen gas.The properties of seven major metal binding ligands were identified and assignments to the most likely functional groups were made. The most important ligand properties are for ligand A: pK_a ≈ 9.2, log K_cd ≈ 7.0 fast reaction kinetics (mercapto groups); ligand B: pK_a = 4.8, log K_Cd ≈ 6.0, slow reaction kinetics (chelates with 3 or 4 carboxylic groups); ligand C: pK_a ≈ 6.0, log K_Cd ≈ 13.0, irreversible metal binding at basic pH-values (uptake inside bacterial cells); ligand D: pK_a = 7.7, log K_Cd = 4.0, runs parallel to N content of particulate matter with digestion time (primary amines neighboring oxo groups); ligand E: pK_a ≈ 12.0, log K_Cd = 9.0, runs parallel to P content of particulate matter (phosphate); ligand F:pK_a > 9.0, log K_{Cdf = pKa + 0.4}, runs parallel to N content of particulate matter (primary amines neighboring SH groups); and ligand G: pK_a ≤ 4.8, log K_Pb ≈ 4.3, strong Pb²⁺ ligand, even at low pH-values.Metal ions were found to be irreversibly bound by ligand C at low heavy-metal concentratins, whereas at higher concentrations the binding is reversible and can be predicted using the mass of the digestion process (methanogenic phase). All other ligands have their concentration maximum in the transition phase between acetogenic and methanogenic phase.     

A Study of Ammonia Source at a Portland Cement Production Plant

A source and process sampling study was conducted at a dry process Portland Cement production plant. The study was performed to determine the nature of the formation of a highly visable plume related to the kiln emissions. One aspect of the study focused on the source or point of NH₃ within the production process. An extensive number of process solids from raw feeds to baghouse solids were collected and analyzed for NH₄ ⁺. Samples were analyzed for NH₄ ⁺ both by washing the solids with 0.1 N H₂SO₄ and by collecting NH₃ in impingers as it was evolved from heated solids. The results showed that NH₄ ⁺ was present in many process samples and that the collection efficiency of NH₄ ⁺ in the baghouse was related to baghouse temperature. The data also showed that NH₃ was derived from the shale used in the raw feed at this cement production plant.     

Diurnal and seasonal variations of odor and gas emissions from a naturally ventilated free-stall dairy barn on the Canadian prairies

This study characterized the seasonal concentration (C) and emission (E) patterns of odor, ammonia (NH₃), and hydrogen sulfide (H₂S) over the course of a whole year and their diurnal patterns in cold, warm, and mild seasons for a naturally ventilated free-stall dairy barn. It was found that seasonal odor and NH₃ and H₂S emissions varied greatly: from 17.2 to 84.4 odor units (OU) sec^?1 AU^?1 (AU: animal unit, 500 kg of animal body mass), from 0.27 to 0.92 mg sec^?1 AU^?1, and from 3 to 105 μg sec^?1 AU^?1, respectively. The overall concentrations of odor and NH₃ were higher in the winter, whereas the emissions were higher in the mild and warm seasons. Diurnal variation was most significant for odor emission (OE) in the mild season when the ratio of maximum (279.2 OU sec^?1 AU^?1) to minimum value (60.5 OU sec^?1 AU^?1) was up to 4.6. The indoor air quality was also evaluated by considering not only the health effect of individual gases, but also the additive effect of NH₃ and H₂S. Results showed that the indoor air quality was poorest in cold seasons when NH₃ C could exceed the threshold limit set out in occupational health regulation, and in fact could worsen due to the additive effect of the two gases. Further, it was suggested NH₃ was a good indicator for predicting odor concentration (OC) or OE. The impact of climatic parameters on odor and gases were also examined, and it was found ventilation rate (VR) negatively affected OC and NH₃ C, but positively impacted OE and NH₃ E. Using 70% of the total data, a multilinear model for OE was developed as a function of VR and indoor relative humidity and was validated to be acceptable using the rest of the data.

Implications: Diurnal and seasonal variations of odor, NH₃, and H₂S concentrations and emissions were monitored for a naturally ventilated dairy barn in a cold region. The emission factors were calculated and indoor air quality was evaluated. The overall odor and NH₃ concentrations were higher in winter, whereas emissions were higher in the mild and warm seasons. Diurnal variation was most significant for odor emission in the mild season, when the ratio of maximum to minimum value was up to 4.6. The results can be used to estimate odor and gas emissions from other dairy barns in Canada and other cold regions.     

新型微生物菌剂对垃圾渗滤液的除臭效果

利用从食材中筛选纯化的特定微生物制成新型复合菌剂,以不同浓度梯度处理垃圾渗滤液,测定其在自然条件下的嗅阈值,监测NH3和H2S即时挥发浓度的变化,评价菌剂的综合除臭效果,设计三因素三水平实验并采用响应面优化法对反应适宜的实验参数进行了优化。研究结果表明,新型复合菌剂的投加会使垃圾渗滤液嗅阈值明显下降;响应面优化模型分析表明,反应时间2.5 d时和0.5%的菌剂投加对抑制NH3的挥发效果最好,而反应时间2.5 d和0.2%的投入量对抑制H2S的挥发效果最好,氧气的供应情况对两者的挥发抑制效果影响不显著。     

Operational Characteristics of Effective Removal of H2S and NH3 Waste Gases by Activated Carbon Biofilter

Abstract

Simultaneous removal of hydrogen sulfide (H₂S) and am- gases. monia (NH₃) gases from gaseous streams was studied in a biofilter packed with granule activated carbon. Extensive studies, including the effects of carbon (C) source on the growth of inoculated microorganisms and gas removal efficiency, product analysis, bioaerosol emission, pressure drop, and cost evaluation, were conducted. The results indicated that molasses was a potential C source for inoculated cell growth that resulted in removal efficiencies of 99.5% for H₂S and 99.2% for NH₃. Microbial community observation by scanning electron microscopy indicated that granule activated carbon was an excellent support for microorganism attachment for long-term waste gas treatment. No disintegration or breakdown of biofilm was found when the system was operated for 140 days. The low bioaerosol concentration emitted from the biofilter showed that the system effectively avoided the environmental risk of bioaerosol emission. Also, the system is suitable to apply in the field because of its low pressure drop and treatment cost. Because NH₃ gas was mainly converted to organic nitrogen, and H₂S gas was converted to elemental sulfur, no acidification or alkalinity phenomena were found because of the metabolite products. Thus, the results of this study demonstrate that the biofilter is a feasible bioreactor in the removal of waste gases.     

金属铁铝对混凝强化初沉污泥中温厌氧消化的影响简

选取FeCl₃和AlCl₃·6H₂O作为混凝剂对城市污水进行一级强化混凝处理，降低二级生物处理的进水负荷，减少污水生物处理系统的能量消耗。主要研究混凝过程投加的金属盐对一级强化混凝产生的初沉污泥中温厌氧消化的影响。和剩余污泥相比，初沉污泥更适合厌氧消化处理，污泥降解性能和产气性能更高。当采用城市污水一级强化混凝处理时，污泥中的金属和金属盐水解引起的pH降低，使混凝强化初沉污泥的厌氧消化受到一定抑制。随着污泥中铝含量的降低和铁含量的增加，厌氧消化的COD降解率和挥发性固体（VS）降解率逐渐升高，生物气产量逐渐增大，产气速率加快。当混凝强化初沉污泥只含有铁时（铁含量为10.16 mg/L），混凝强化初沉污泥厌氧消化效果最好，产气稳定，而且产气速率高，生物气产量为237 mL，生物气甲烷含量为55.5%，降解单位VS产气量为0.80 L/g，均高于其他含铝的混凝强化初沉污泥。污泥中的铁对初沉污泥厌氧消化的抑制作用远远小于铝的作用，说明铁盐适合用于城市污水的一级强化混凝处理。     

Monitoring H2S air pollution caused by the industrial exploitation of geothermal energy: The pitfall of using lichens as bioindicators

This study showed that NH₃ emitted from geothermal power plants affects the surrounding epiphytic lichen vegetation and diversity, confounding the interpretation of lichen diversity counts in terms of air pollution by H₂S. The presence of nitrophytic lichen species around geothermal installations, determined by NH₃, caused relatively high diversity values that were not related with the levels of air pollution by H₂S. It is recommended that in the presence of NH₃ emission, nitrophytic species are excluded from the calculation of lichen diversity values.