Exhaust Air Treatment Research Articles

Heating Performance and Ammonia Removal of a Single-Stage Bioscrubber Pilot Plant with Integrated Heat Exchanger under Field Conditions

In this study, biological exhaust air treatment was combined with a recuperative heat exchanger in one process stage. The aim of this plant development and testing is not only to reduce ammonia from the exhaust air of pig houses but also to recover thermal energy at the same time. This is intended to offset the high operating costs of exhaust air treatment with savings of heating costs in cold seasons and to use the plant more efficiently. This system was tested for the first time under practical conditions in a pig fattening house in southern Germany. Three different assembly situations of the heat exchanger were examined for 13 days each and then compared with each other. The heating performance of the plant is primarily dependent on the outside air temperature and secondarily on the scrubbing water temperature. Depending on the assembly situation of the heat exchanger, an average heating performance of between 6.0 and 10.0 kW was observed; the amount of recovered thermal energy was between 1860 and 3132 kWh. The coefficient of performance (COP) ranked between 7.1 and 11.5. Furthermore, ammonia removal up to 64% was demonstrated. A long-term investigation of the system under practical conditions is recommended to validate the data collected in this study.

Oxidation of Aqueous Toluene by Gas-Phase Pulsed Corona Discharge in Air-Water Mixtures Followed by Photocatalytic Exhaust Air Cleaning

The treatment of wastewaters containing hazardous volatile organic compounds (VOCs) requires the simultaneous treatment of both water and air. Refractory toluene, extensively studied for its removal, provides a basis for the comparison of its abatement methods. The oxidation of aqueous toluene by gas-phase pulsed corona discharge (PCD) in combination with the subsequent photocatalytic treatment of exhaust air was studied. The PCD treatment showed unequalled energy efficiencies in aqueous and gaseous toluene oxidation, reaching, respectively, up to 10.5 and 29.6 g·kW−1·h−1. The PCD exhaust air contained toluene residues and ozone in concentrations not exceeding 0.1 and 0.6 mg·L−1, respectively. As a result of the subsequent photocatalytic treatment, both airborne residues were eliminated within a contact time with TiO2 as short as 12 s. The results contribute to the possible application of the studied approach in closed-loop energy-saving ventilation systems.

Heating performance of a laboratory pilot-plant combining heat exchanger and air scrubber for animal houses

Exhaust air treatment systems (EATS) are used in animal husbandry to reduce emissions. However, EATS are associated with high acquisition and operating costs. Therefore, a plant technology is being developed that integrates a recuperative heat exchanger into a biological air scrubber. The overall aim is to reduce total costs of livestock buildings with EATS by saving heating costs and to improve animal environment. In this study, a special pilot-plant on a small-scale, using clean exhaust air, was constructed to evaluate the heating performance on laboratory scale. Three assembly situations of the heat exchanger into trickle-bed reactor were part of a trial with two different defined air flow rates. In all three assembly situations, preheating of cold outside air was observed. The heating performance of the assembly situation with the sprayed heat exchanger arranged below showed an average of 4.4 kW at 1800 m3 h−1 (outside air temperature range 0.0–7.9 °C). This is up to 18% higher than the other two experimental setups. The heating performance of the pilot-plant is particularly influenced by the outside air temperature. Further research on the pilot-plant is required to test the system under field conditions.

Analysis of basic airflow configurations for separate sensible and latent cooling systems with indoor air recirculation

Separate sensible and latent cooling (SSLC) is a technology with efficiency and comfort advantages over conventional cooling systems used for space conditioning of buildings. Using multiple cooling processes at different temperatures allows SSLC to save energy by raising the evaporation temperature of the sensible cooling process. In this paper, all possible airflow configurations of SSLC systems are enumerated under the following constraints: exactly two heat exchangers are used, and air is recirculated to the conditioned space (no exhaust or outdoor air treatment). Seven designs are identified, with varying free operating variables, and each is modeled. Analysis reveals that several configurations are equivalent, and there is only one unique basic airflow SSLC configuration: the one with the sensible and latent heat exchangers placed in series. The efficiency of the SSLC system is compared against that of the conventional system. Under standard conditions, an SSLC system can improve the coefficient of performance by 14.8%. In addition to the numerical simulation, the optimal operating condition of the basic air configuration of the SSLC system is derived analytically. The basic SSLC system is shown to offer the highest performance improvement when the outdoor temperature is relatively cool and the space sensible heat ratio is high.

COVID Operation Theatre- Advisory and Position Statement of Indian Society of Anaesthesiologists (ISA National).

COVID Operation Theatre- Advisory and Position Statement of Indian Society of Anaesthesiologists (ISA National).

Suitability of Different Filling Materials for a Biofilter at a Broiler Fattening Facility in Terms of Ammonia and Odour Reduction

A two-stage exhaust air treatment system installed at a broiler fattening facility with 40,000 animals was investigated. The facility’s exhaust air was treated first by use of a chemo-scrubber (stage 1) and afterwards by a vertical biofilter (stage 2). The biofilter was equipped with root wood and honeycombed paper pad layers (half/half) to enable a direct comparison of both filter materials’ suitability. Odour samples were taken on site and afterwards analysed at an olfactometry laboratory. Ammonia concentration values were collected continuously using a photoacoustic multi-gas monitor. High mitigation performance was achieved with both filter materials, with the honeycombed paper pad layer being less susceptible to fungal growth than the root wood filter. Cellulose seems to be a proper alternative for use in biofilters, but further research is needed to estimate the long-term stability of this material.

Study of Exhaust Air Treatment From a Ship Building Factory Painting Facility Using Pulse Plasma Technology

Ship building companies are exposed to increasingly strict regulations on exhaust air from painting facilities, which current exhaust air treatment methods cannot adequately meet. We propose the use of a plasma system using a pulsed-power supply, which we constructed and tested at the painting facility of a ship building factory. Through gas chromatography and facility efficiency analysis, we found flexibility in design of the plasma system. We demonstrate the efficiency and safety of our plasma system, and emphasize the importance of posttreatment facilities for the secondary pollutant treatment.

Bioscrubber treatment of exhaust air from intensive pig production: Case study in northern Germany at mild climate condition.

Treatment by field-scale bioscrubber of exhaust air, including ammonia (NH3) and the greenhouse gases methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2), from 13 intensive pig production houses located in northern Germany were investigated in 2013 and 2015. NH3 removal efficiencies varied between 35 and 100% with an overall average value of 79% under the NH3 inlet fluctuations from 34 to 755 g d-1 m-3 in both 2013 and 2015. Results of the electron microscopic analyses demonstrated that the bacteria Nitrosomonas sp. and methanotrophs type I were the dominant NH3 and CH4 oxidizers, respectively. However, overall average removal efficiencies of CH4 was approximately zero, which means CH4 is hard to remove in bioscrubbers under normal operation. The pH of recirculation water in the bioscrubber varied from 6.1 to 8.1, and the bioscrubbers with low pH values (<7.0) had high NH3 removal efficiencies (>79%). Electrical conductivity was commonly used to diagnose the bioscrubbers' performance; in the present study, electrical conductivity presented a significant linear relationship with dissolved inorganic nitrogen, which indicates the performance stability of the 13 selected bioscrubbers.

Performance evaluation and optimization of field-scale bioscrubbers for intensive pig house exhaust air treatment in northern Germany

The treatment of exhaust air from three intensive pig houses in northern Germany by field-scale bioscrubbers (BS.1, BS.2, and BS.3) were evaluated monthly in 2015. The simultaneous removal of NH3 and CH4 was investigated by connecting a second bioscrubber (BS.2-2) to one of the three bioscrubbers (BS.2) to create a two-series connected bioscrubber (BS.2+BS.2-2). Additionally, whether isolated methanotrophic bacterial inoculation in BS.2-2 intensified CH4 removal was examined. Average NH3 removal efficiencies of 86%, 80%, and 77% were observed for BS.1, BS.2, and BS.3, respectively, under fluctuate NH3 inlet concentrations (variation of 22%-54%) throughout the study year. However, average CH4 removal efficiencies were lower than 10% in the three bioscrubbers. The pH of the recirculation water, which ranged from 5.7 to 8.1, was demonstrated to be an important factor for NH3 removal and negatively correlated with NH3 removal and NH4+-N concentration in the recirculation water. The dominant NH3-oxidizing and methanotrophic bacteria in the bioscrubbers, analysed by transmission electron microscopy, were Nitrosomonas sp. and Type I methanotrophs, respectively. NH3 removal efficiency reached 100% in the two-series connected bioscrubber, however, CH4 removal was still low (average of 2%). After inoculating isolated methanotrophic bacteria into BS.2-2, the average CH4 removal was enhanced to 35%, offering a great option for bioscrubbers application to intensify CH4 removal. Therefore, a two-series connected bioscrubber inoculated with methanotrophic bacteria would be an option for simultaneous removal of NH3 and CH4 from the exhaust air of animal houses.

Detection of Legionella-contaminated aerosols in the vicinity of a bio-trickling filter of a breeding sow facility – A pilot study

The urbanization of agricultural areas results in a reduction of distances between residential buildings and livestock farms. In the public debate, livestock farming is increasingly criticized due to environmental disturbance and odor nuisance originating from such facilities. One method to reduce odor and ammonia is by exhaust air treatment, for example, by biological exhaust air purification processes with bio-trickling filters filled with tap water. Higher temperatures in the summer time and the generation of biofilms are ideal growth conditions for Legionella. However, there are no studies on the presence of Legionella in the water of bio-trickling filters and the release of Legionella-containing aerosols. Therefore, the aim of this study was to investigate Legionella in wash water and emitted bioaerosols of a bio-trickling filter system of a breeding sow facility. For this purpose, measurements were carried out using a cyclone sampler. In addition, samples of wash water were taken. Legionella were not found by culture methods. However, using molecular biological methods, Legionella spp. could be detected in wash water as well as in bioaerosol samples. With antibody-based methods, Legionella pneumophila were identified. Further studies are needed to investigate the environmental health relevance of Legionella-containing aerosols emitted by such exhaust air purification systems.

Biofiltration of Ammonia and GHGs from Swine Gestation Barn Pit Exhaust

<abstract> <b><sc>Abstract.</sc></b> Livestock barn emissions can affect public health, the environment, and quality of life. While these emissions can be mitigated using several methods, exhaust air treatment may be required in some situations. Biofiltration is one of the most cost-effective exhaust air treatment methods. In a biofilter, polluted air passes through a moist medium (e.g., compost) where the water-soluble gases are dissolved and then degraded by microorganisms into harmless or less harmful compounds. In this study, a downflow biofilter using a compost and wood chip medium was evaluated over summer, fall, and winter (August 2010 to January 2011) for its ability to mitigate emissions of ammonia (NH₃) and three greenhouse gases (GHGs): methane (CH₄), nitrous dioxide (N₂O), and carbon dioxide (CO₂). Biofilter medium properties were analyzed at the beginning and twice during the study. Changes in medium properties and CO₂ data indicated greater heterotrophic microbial activity during summer through fall and greater autotrophic activity during fall through winter. Regardless of empty bed residence time (EBRT) (5.3 to 26 s), NH₃ removal efficiency (RE) was about 90% with inlet concentrations of ≤1.1 mg m^-3. With higher NH₃ loading rates, the RE may differ from this study. In fall, CH₄ RE was 49% (EBRT = 26 s) but only 13% in summer (EBRT = 13 s). Nitrous oxide RE varied in a narrow range of 14% to 18% over the study. In summer, CO₂ removal was negligible but was 15% in fall and 34% in winter. While a compost based medium may be more effective for CH₄ and N₂O mitigation, a wood chip based medium would be more economical. Care should be taken when using a photoacoustic sensor for high-frequency and low-concentration NH₃ measurements.

Biofiltration of Ammonia and GHGs from Swine Gestation Barn Pit Exhaust

<abstract> <b><sc>Abstract.</sc></b> Livestock barn emissions can affect public health, the environment, and quality of life. While these emissions can be mitigated using several methods, exhaust air treatment may be required in some situations. Biofiltration is one of the most cost-effective exhaust air treatment methods. In a biofilter, polluted air passes through a moist medium (e.g., compost) where the water-soluble gases are dissolved and then degraded by microorganisms into harmless or less harmful compounds. In this study, a downflow biofilter using a compost and wood chip medium was evaluated over summer, fall, and winter (August 2010 to January 2011) for its ability to mitigate emissions of ammonia (NH₃) and three greenhouse gases (GHGs): methane (CH₄), nitrous dioxide (N₂O), and carbon dioxide (CO₂). Biofilter medium properties were analyzed at the beginning and twice during the study. Changes in medium properties and CO₂ data indicated greater heterotrophic microbial activity during summer through fall and greater autotrophic activity during fall through winter. Regardless of empty bed residence time (EBRT) (5.3 to 26 s), NH₃ removal efficiency (RE) was about 90% with inlet concentrations of ≤1.1 mg m^-3. With higher NH₃ loading rates, the RE may differ from this study. In fall, CH₄ RE was 49% (EBRT = 26 s) but only 13% in summer (EBRT = 13 s). Nitrous oxide RE varied in a narrow range of 14% to 18% over the study. In summer, CO₂ removal was negligible but was 15% in fall and 34% in winter. While a compost based medium may be more effective for CH₄ and N₂O mitigation, a wood chip based medium would be more economical. Care should be taken when using a photoacoustic sensor for high-frequency and low-concentration NH₃ measurements.

Biological exhaust air treatment systems as a potential microbial risk for farm animals assessed with a computer simulation

Livestock operations are under increasing pressure to fulfil minimum environmental requirements and avoid polluting the atmosphere. In regions with high farm animal densities, new farm buildings receive building permission only when biological exhaust air treatment systems (BEATS) are in place, such as biofilters. However, it is currently unknown whether BEATS can harbour pathogens such as zoonotic agents, which are potentially emitted via the purified gas. Because BEATS are located very close to the livestock building, it is assumed that BEATS-related microorganisms are aerially transported to farm animals via the inlet system of the ventilation system. To support this hypothesis, a computer simulation was applied to calculate the wind field around a facility consisting of a virtual livestock house and an adjacent biofilter. Under the chosen wind conditions (speed and direction), it can be shown that turbulences and eddies may occur in the near surrounding of a livestock building with an adjacent biofilter. Consequently, this might cause the entry of the released biofilter's purified gas into the barn, including possible microorganisms within this purified gas. If field investigations verify the results of the simulations, counter-measures must be taken to ensure biosecurity on farms with BEATS.

A Novel Concept for the Removal of Solvent Vapors from Exhaust Air

The emission of large amounts of solvent vapors with exhaust air from industrial production into the environment is a serious problem. In Germany, industry-sector-specific threshold values are applied and technical measures for pollution reduction are required. Different techniques for exhaust air cleaning are in use but still posing problems concerning costs and reliability. For these reasons, the development of processes for exhaust air treatment is the subject of the current research. A new concept for exhaust air cleaning is introduced that combines absorption of a solvent vapor by an organic fluid and a subsequent adsorption by a molecular sieve placed in the absorber. It was managed to close the loops of solvent recovery and sorbents regeneration. In laboratory-scale experiments it was possible to reduce an initial ethylacetate pollution of 800 mg/m3 or 349 mg C/m3 below the limit value of 75 mg C/m3 over 60 h duration. Thermogravimetric measurements assisted to define optimum conditions for solvent recovery at 180°C from the molecular sieve. One unexpected positive finding was the considerable increase in the solvent release in the presence of the absorption fluid while adsorption isotherms revealed first insight into this process.

Effect of atmospheric surface plasma on the adsorption of ethanol at activated carbon filter element

Atmospheric non-thermal plasma has been recognized as a successful tool for the treatment of exhaust and waste air for abatement of pollutants, air cleaning, and odor removal. To improve the efficiency of plasma cleaning processes a combination of plasma with adsorption filters and or catalysts is used. The fundamental interaction mechanisms of the surface, plasma, and gas remain the subject of further investigations of the details. A quantitative FTIR-spectroscopic study of the effect of surface barrier discharge on the adsorption and desorption of ethanol at activated carbon is presented. First of all the adsorption and desorption were characterized for different input concentrations and different carrier gas flows without operating the plasma. After that the interaction of the plasma and the gas mixture was analyzed. Finally the activated carbon filter was reinstalled behind the plasma stage and the loading and unloading of the activated carbon filter element were investigated while burning the plasma. It is shown that the plasma stage initiates an additional decomposition of ethanol at the surface of the activated carbon because of the interaction of long-lived O3 with physical adsorbed C2H5OH. The total amount of filtered C2H5OH does not change but the portion of decomposed C2H5OH that is not rinsed out increases. The plasma caused effect at the surface reaches 68% of the effect of plasma in the gas phase.

Biotrickling filter for the treatment of exhaust air from a pig rearing building: Ammonia removal performance and its fluctuations

The removal of ammonia (NH3) by a full scale packed-bed biotrickling filter (packing volume: 3.8 m3; water buffer tank: 20 m3) under fluctuating loading conditions was studied. The unit was operated at an animal house for treatment of exhaust air at an average air contact time of 1.2 s. Continuous long-term ammonia measurements showed average inlet and outlet air concentrations of 14 ppm and 2.4 ppm, respectively, and a removal efficiency of 82%. The average temperature of the water was 16 °C, the pH 6.6, the ammonium concentration 1.9 g N l−1, and the nitrate concentration 1.8 g N l−1; no nitrite was detected. The average ammonia loading and removal rate were 29 and 24 g NH3 m−3 h−1, respectively. A daily and seasonal pattern could be observed in the ammonia removal performance. With increasing outside temperature ammonia loading rate, ammonia removal rate, and ammonia outlet concentration increased, resulting in a net decrease of the ammonia removal efficiency. This phenomenon might be explained by the existence of equilibrium between the ammonia concentration in the outlet air and the concentration of dissolved ammonia in the water, which is influenced by fluctuating air and water temperature. A nitrogen balance indicated that 86% of the removed ammonia-N was discharged or accumulated in the water as ammonium and nitrate, and 5% was emitted as nitrous oxide (N2O). The fluctuating removal patterns that were found suggest that current regulatory performance monitoring practices need to be improved.

Nitrification processes in scrubbing liquid of an exhaust air treatment system of a large-scale pig housing facility

The use of multi-staged exhaust air treatment systems is an effective method of substantially reducing the emission of ammonia, dust particles and odorous substances. Wet filter walls are able to absorb large amounts of ammonia when scrubbing fluid containing sulphuric acid is used. In addition, due to their large surface areas and the permanent supply of oxygen and nutrients, wet filter walls provide a basis for the development of biofilms containing nitrogen-converting bacteria. Cyclic nitrification processes could be observed in a two-stage exhaust air treatment system, which had been converted to function as a regulated process control system (elutriation at κ = 20 mS cm(-1); pH 6.5-6.8). With this system, the sulphuric acid requirement was periodically reduced every 6-8 weeks to less than 1 kg H(2)SO(4) per fattening place and year. There was an increased formation of nitrous oxide gas during nitrification after the wet filter stage. Electron-microscopic images of the biofilm growing on the wet filter wall showed aggregates of possible ammonium-oxidising and nitrite-oxidising bacteria.

Entwicklung der Abluftreinigung in der Tierhaltung in Deutschland

The number of exhaust air treatment installations built in Germany accumulated from 1997 to 2010 to 1014, as producer inquiries showed. In this connection 762 installations were allotted to pig housing, 170 to poultry housing and 82 to other applications. In pig housing predominantly approved exhaust air treatment installations were used. The market share, related to the number of installations, for bio filters, trickle bed filters and multistage operations amounted to 26.4, 24.0 and 43.2 % in 2010. In poultry housing approved exhaust air treatment installations were scarcely used so far. In this respect conclusions are neither possible concerning the process technique nor their effectivity. Growing environmental regulations and growing opposition by local communities for larger pig and poultry husbandries will result in marginal development perspectives in future without using approved exhaust air treatment installations.

Mehrstufige Abluftreinigung für die Geflügelhaltung

In spite of considerable fluctuating operation conditions a multi-stage test facility for the treatment of poultry exhaust air secured a good and reliable particulate matter reduction. It was equipped with an initial dry dedusting unit, an acidic and a subsequent water scrubber unit. At fi lter loads between 1 800 and 3 600 m³/(m² • h) a mean particle reduction effi ciency (n = 149) of at least 57 % was verifi ed for a particle diameter between 2.0 and 2.5 µm and more than 98 % for a particle diameter between 6.5 and 7.5 µm. Also 72 % of the nitrogen was separated in a useable form from the raw gas as a nitrogen balance over six month of operation showed. The considerable fluctuating ammonia emissions from the tested animal house offered a noticeable correlation with the dung removalinterval.

Selective Adsorbents Enhancing Exhaust Air Treatment for the Food‐Processing Industry

AbstractEs werden Methoden und Kriterien zur Auswahl und Charakterisierung spezifisch wirkender Adsorbentien vorgestellt. Die Untersuchungen sollen ein neues multivariates Clusterverfahren für Adsorptive verifizieren, das gegenüber den sonst üblichen Screeningverfahren den zeitlichen und materiellen Aufwand zur Auswahl optimierter Adsorbentien minimiert. Die Bedeutung der Adsorption von Wasserdampf und die Einflussmöglichkeiten durch Modifikationen der Adsorbentien werden vorgestellt. Abschließend werden die wirtschaftlichen und technischen Vorteile adsorptiver Trennverfahren zur Abluftbehandlung in lebensmittelverarbeitenden Betrieben diskutiert.