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.     

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.     

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%。     

Biological Removal of Gaseous Ammonia in Biofilters: Space Travel and Earth-Based Applications

ABSTRACT

Gaseous NH₃ removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH₃ concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH₃ for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH₃ removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH₃ could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO₃ ^- early in the operation, but later both NO₂ ^- and NO₃ ^- accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20- and 50-ppm biofilters, respectively. A partial contributing factor to this drop in mass balance accountability was the production of NO and N₂O, which were detected in the biofilter exhaust.     

Methane biofiltration in the presence of ethanol vapor under steady and transient state conditions: an experimental study

Methane (CH₄) removal in the presence of ethanol vapors was performed by a stone-based bed and a hybrid packing biofilter in parallel. In the absence of ethanol, a methane removal efficiency of 55 ± 1% was obtained for both biofilters under similar CH₄ inlet load (IL) of 13 ± 0.5 g_CH4 m^?3 h^?1 and an empty bed residence time (EBRT) of 6 min. The results proved the key role of the bottom section in both biofilters for simultaneous removal of CH₄ and ethanol. Ethanol vapor was completely eliminated in the bottom sections for an ethanol IL variation between 1 and 11 g_ethanol m^?3 h^?1. Ethanol absorption and accumulation in the biofilm phase as well as ethanol conversion to CO₂ contributed to ethanol removal efficiency of 100%. In the presence of ethanol vapor, CO₂ productions in the bottom section increased almost fourfold in both biofilters. The ethanol concentration in the leachate of the biofilter exceeding 2200 g_ethanol m^?3 _leachate in both biofilters demonstrated the excess accumulation of ethanol in the biofilm phase. The biofilters responded quickly to an ethanol shock load followed by a starvation with 20% decrease of their performance. The return to normal operations in both biofilters after the transient conditions took less than 5 days. Unlike the hybrid packing biofilter, excess pressure drop (up to 1.9 cmH₂O m^?1) was an important concern for the stone bed biofilter. The biomass accumulation in the bottom section of the stone bed biofilter contributed to 80% of the total pressure drop. However, the 14-day starvation reduced the pressure drop to 0.25 cmH₂O m^?1.     

Design and Performance Characterization Strategy Using Modeling for Biofiltration Control of Odorous Hydrogen Sulfide

Abstract

Biofilter, dynamic modeling software characterizing contaminant removal via biofiltration, was used in the preliminary design of a biofilter to treat odorous hydrogen sulfide (H₂S). Steady-state model simulations were run to generate performance plots for various influent concentrations, loadings, residence times, media sizes, and temperatures. Although elimination capacity and removal efficiency frequently are used to characterize biofilter performance, effluent concentration can be used to characterize performance when treating to a target effluent concentration. Model simulations illustrate that, at a given temperature, a biofilter cannot reduce H₂S emissions below a minimum value, no matter how large the biofilter or how long the residence time. However, a higher biofilter temperature results in lower effluent H₂S concentrations. Because dynamic model simulations show that shock loading can significantly increase the effluent concentration above values predicted by the steady-state model simulations, it is recommended that, to consistently meet treatment objectives, dynamic feed conditions should be considered. This study illustrates that modeling can serve as a valuable tool in the design and performance optimization of biofilters.     

多层生物滤塔净化硫化氢废气研究

以木屑为填料,采用多层生物滤塔净化H2S气体,研究其适宜的工艺条件及生物降解宏观动力学.结果表明,填料分层可提高H2S去除率,当进气容积负荷＜153.2 g H2S/(m3·d)时,H2S的去除率保持在90%以上;进气浓度低于70 mg/m3,下层200mm填料对H2S总去除率的贡献在50%以上;填料含水率为50%～6...     

Sulfur Toxicity and Media Capacity for H2S Removal in Biofilters Packed with a Natural or a Commercial Granular Medium

Abstract

Two types of media, a natural medium (wood chips) and a commercially engineered medium, were evaluated for sulfur inhibition and capacity for removal of hydrogen sulfide (H₂S). Sulfate was added artificially (40, 65, and 100 mg of S/g of medium) to test its effect on removal efficiency and the media. A humidified gas stream of 50 ppm by volume H₂S was passed through the media-packed columns, and effluent readings for H₂S at the outlet were measured continuously. The overall H₂S baseline removal efficiencies of the column packed with natural medium remained >95% over a 2-day period even with the accumulated sulfur species. Added sulfate at a concentration high enough to saturate the biofilter moisture phase did not appear to affect the H₂S removal process efficiency. The results of additional experiments with a commercial granular medium also demonstrated that the accumulation of amounts of sulfate sufficient enough to saturate the moisture phase of the medium did not have a significant effect on H₂S removal.

When the pH of the biofilter medium was lowered to 4, H₂S removal efficiency did drop to 36%. This work suggests that sulfate mass transfer through the moisture phase to the biofilm phase does not appear to inhibit H₂S removal rates in biofilters. Thus, performance degradation for odor-removing biofilters or H₂S breakthrough in field applications is probably caused by other consequences of high H₂S loading, such as sulfur precipitation.     

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.     

Gaseous Ammonia Uptake in Compost Biofilters as Related to Compost Water Content

Abstract

Sewage sludge and yard waste compost were used as biofilter materials and tested with respect to their capacity for removing ammonia from air at different water contents. Ammonia removal was measured in biofilters containing compost wetted to different moisture contents ranging from air dry to field capacity (maximum water holding capacity). Filters were operated for 15 days and subsequently analyzed for NH₃/NH₄ ⁺, NO₂ ^-, and NO₃ ^-. The measured nitrogen species concentration profiles inside the filters were used to calculate ammonia removal rates. The results showed that ammonia removal is strongly dependent on the water content in the filter material. At gravimetric water contents below 0.25 g H₂O g solids^-1 for the yard waste compost and 0.5 g H₂O g solids^-1 ammonia removal rates were very low but increased rapidly above these values. The sewage sludge compost filters yielded more than twice the ammonia removal rate observed for yard waste compost likely because of a high initial concentration of nitrifying bacteria originating from the wastewater treatment process and a high air-water interphase surface area that facilitates effective ammonia dissolution and transport to the biofilm.     

Carbon Disulfide and Hydrogen Sulfide Removal with a Peat Biofilter

ABSTRACT

Simultaneous removal of H₂S and CS₂ was studied with a peat biofilter inoculated with a Thiobacillus strain that oxidizes both compounds in an acidic environment. Both sulfurous gases at concentrations below 600 mg S/m³ were efficiently removed, and the removal efficiencies were similar, 99%, with an empty bed retention time (EBRT) of more than 60 sec. Concentrations greater than 1300-5000 mg S/m³ caused overloading of the filter material, resulting in high H₂SO₄ production, accumulation of elemental sulfur, and reduced removal efficiency. The highest sulfur removal rate achieved was 4500 g-S/day/m³ filter material. These results indicate that peat is suitable as a biofilter material for the removal of a mixture of H₂S and CS₂ when concentrations of gases to be purified are low (less than 600 mg/m³), but it is still odorous and toxic to the environment and humans.     

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.     

Biotreatment of H2S- and NH3-containing waste gases by co-immobilized cells biofilter

Gas mixture of H2S and NH3 in this study has been the focus in the research area concerning gases generated from the animal husbandry and the anaerobic wastewater lagoons used for their treatment. A specific microflora (mixture of Thiobacillus thioparus CH11 for H2S and Nitrosomonas europaea for NH3) was immobilized with Ca-alginate and packed inside a glass column to decompose H2S and NH3. The biofilter packed with co-immobilized cells was continuously supplied with H2S and NH3 gas mixtures of various ratios, and the removal efficiency, removal kinetics, and pressure drop in the biofilter was monitored. The results showed that the efficiency remained above 95% regardless of the ratios of H2S and NH3 used. The NH3 concentration has little effect on H2S removal efficiency, however, both high NH3 and H2S concentrations significantly suppress the NH3 removal. Through product analysis, we found that controlling the inlet ratio of the H2S/NH3 could prevent the biofilter from acidification, and, therefore, enhance the operational stability. Conclusions from bioaerosol analysis and pressure drop in the biofilter suggest that the immobilized cell technique creates less environmental impact and improves pure culture operational stability. The criteria for the biofilter operation to meet the current H2S and NH3 emission standards were also established. To reach Taiwan's current ambient air standards of H2S and NH3 (0.1 and 1 ppm, respectively), the maximum inlet concentrations should not exceed 58 ppm for H2S and 164 ppm for NH3, and the residence time be kept at 72 s.     

亚铁离子生物氧化-还原法连续脱除硫化氢

为了降低工业废气中的硫化氢去除工艺成本和运行费用,对三价铁盐吸收与氧化亚铁硫杆菌对Fe²⁺的生物氧化联合作用脱除H₂S进行了研究。通过生物氧化塔中的固定化氧化亚铁硫杆菌细胞再生的Fe³⁺溶液,在H₂S还原吸收塔中脱除H₂S。通过单因素实验分别优化了生物氧化塔和H₂S吸收塔的运行参数,在生物氧化塔曝气量为150 L/h,停留时间为11 h,吸收液中Fe³⁺浓度为0.121~0.143 mol/L,吸收液流量为0.3 L/h,进气量为100 L/h条件下,进气中H₂S浓度分别为2.28和9.11 mg/L,系统连续运行至200 min时趋于相对稳定,当系统连续运行稳定时,H₂S的脱除率可分别达到95%和91%,脱除效果显著。     

O3/H2O2处理嘧啶废水的研究

采用O3/H2O2法对嘧啶废水进行处理,考察了不同反应条件对嘧啶和COD去除率的影响,并对O3/H2O2降解嘧啶的反应机制和动力学进行了初步探讨.实验结果表明,在pH值为11,反应时间为70 min,O3流量为4g/h,H2O2投加量为50 mmol/L的条件下,废水的嘧啶和COD的去除率分别达到86.46%和74.9...     

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.     

原位水解生成的羟基氧化铁凝聚吸附除磷效能与机制简

将不同摩尔比Fe³⁺与OH^-（[Fe³⁺]：[OH^-]=1：0、1：1、1：2和1：3）反应获得原位水解生成的羟基氧化铁（in situ FeO_xH_y）,研究了具有不同水解程度的羟基氧化铁对凝聚吸附除磷效能与机制。研究显示,In situ FeO_xH_y对磷的去除率随铁投量增大而升高,且均在中性pH范围内具有最佳除磷效果;在相同铁投量条件下,磷去除率随着[OH^-]：[Fe³⁺]的升高而降低;当体系碱度较低时（pH<6）,引入OH^-可促进Fe³⁺水解而提高除磷效果。4种羟基氧化铁均可在15 s内可快速吸附磷,且吸附过程符合准二级动力学模型;Freundlich模型均可很好地描述磷在4种羟基氧化铁表面的吸附行为。磷酸盐吸附后,In situ FeO_xH_y表面Zeta电位明显降低,且[Fe³⁺]：[OH^-]为1：0的羟基氧化铁降低最为显著。结合MINITEQ计算软件磷酸盐、铁盐形态分析结果显示,对于碱度较低的体系,通过投加一定量OH^-可促进Fe³⁺水解,进而使得其更易与水中H₂PO₄^-与HPO₄^2-结合,生成具有多核羟基的磷酸铁络合物,进而提高除磷效果。     

掺Al-TiO2改性膨润土去除微污染水中COD和NH4-N

采用掺Al-TiO2作为改性剂制备改性膨润土,考察了微波辐射功率、辐射时间、TiO2改性剂用量、铝盐掺杂量、pH值对微污染水中COD和NH4-N去除效果的影响。实验表明,微波辐射功率为460 W,辐射时间为8 min,TiO2改性剂用量为1.3 mmol/g,铝盐掺杂量为0.2 mmol/g为最佳制备条件。pH值为6.0,改性膨润土投加量为40 mg/L,沉淀时间为30min时,对微污染水中初始浓度15 mg/L的COD和5 mg/L的NH4-N去除率分别达到92%和59%以上。     

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.