Biotreatment of ammonia from air by an immobilized Arthrobacter oxydans CH8 biofilter

Simultaneous biodegradation of BTX by isolated degrading bacterial strains in a newly designed modulated bio-scrubber assisted to airlift parallel bioreactors

A new approach in this present study, isolated bacteria from refinery sludge were used in a laboratory-scale bio-scrubber, connecting with two parallel airlift bioreactors to eliminate harmful and toxic fumes of BTX. One of the main features of this bio-scrubber is using porous mineral pumice fillers (Lava Rock) inside poly-urethane foam (PUF) module tower, connecting with agitator bio-phasic continuously stirred tank bio-reactor (CSTbR) to increase retention time and contact surface. The bio-scrubber and airlift plug flow bio-reactor (PFbR) were used in parallel with cooling flow to be more efficient in preservation of the corresponding heater and endothermic from removal reactions. Performance of bio-scrubber in removing BTX vapors with 10 % silicone oil and grade 350 poise as organic phase in the inlet concentration range of 180 ± 0.3 to 1950.5 ± 0.1 mg /m³ (ppmv) for up to 6 months in two air flow rate's 2.5 and 3.5 (lit/min) that each treatment lasted about 2 months. The rate of biodegradation in this study was carried out by mixing 3 isolated bacteria, obtaining from refinery sludge, named DBIS-03, DTIS-12, and DXIS-09, which they had highest biodegradability than all the isolated strains. The results of BTX biodegradation at each EBRT (Empty Bed Retention Time) showed that the removal efficiency of BTX with isolated bacterial samples was able to grow and multiply on porous fillers and regenerate the growth medium of autotrophic bacterial strain with O₂ gas and micronutrients from contaminated air flow with minimum concentration. Benzene, toluene and xylene inputs maximum concentration over a period of 20 days loading, respectively: B :99.2 % (at 2.5 lit/min and 183.2 ± 0.2 mg /m³ (ppmv)), T: 98 % (at 2.5 lit/min and 327.1 ± 0.1 mg /m³ ( ppmv)) and X: 85.9 % (at 2.5 lit/min and 296.8 ± 0.8 mg /m³ (ppmv)) compared to 3.5 lit/min and so show the best performance in removing BTX from polluted air in period of 30 days.

A review of biotechnologies for the abatement of ammonia emissions

Ammonia emissions are found in a wide range of facilities such as wastewater treatment plants, composting plants, pig houses, as well as the fertilizer, food and metallurgy industries. Effective management of these emissions is important for minimizing the detrimental effects they can have on health and the environment. Physical-chemical (thermal oxidation, absorption, catalytic oxidation, etc.) treatments are the most common techniques for the abatement of ammonia emissions. However, the requirement for more eco-friendly techniques has increased interest in biological alternatives. Accordingly, several bio-based process configurations (biofilters, biotrickling filters and bioscrubbers) have been reported for ammonia abatement in a wide spectrum of conditions. Due to ammonia is a highly soluble compound, bioscrubber seems to be the best option for ammonia abatement. However, this technology is still not widely studied. The proper managements of the ammonia bio-oxidation sub-products is a key parameter for the correct operation of the process. The aim of this review is to critically examine the biotechnologies currently used for the treatment of ammonia gas emissions highlighting the pros and cons of each technology. The key parameters for each configuration used in both full-scale and lab-scale bioreactors are analyzed and summarized according to previous publications.

Gel-encapsulated microorganisms used as a strategy to rapidly recover biofilters after starvation interruption

Biosystems used for volatile organic compound (VOC) control have slow re-acclimation after extended starvation. In this study, a gel-encapsuled microorganism biofilter (GEBF) for the treatment of VOCs was used for rapid recovery after starvation interruption. Another conventional perlite biofilter (BF) was used as a control. Results showed that GEBF and BF needed 3 and 6 days for fully recovery after short-term (6 days) starvation. For long-term (20 days) starvation, GEBF fully recovered the removal performance after 9 days, whereas BF recovered only 70% within the same period. Flow cytometry analysis indicated that GEBF presented better viability state of microbial population than that in BF under starvation. The average metabolic activity of microorganisms in GEBF remained a relatively high during and after starvation (0.0049 h^-1). However, the average metabolic activity of microorganisms in BF decreased from 0.0042 h^-1 before starvation to 0.0033 h^-1 under starvation. Changes in the microbial community structure in GEBF and BF were investigated and compared by high-throughput sequencing and principal component analysis. Notably, the microbial community structure in the two biofilters showed different behavior. All these results demonstrated that the gel encapsulation of microorganisms is a promising strategy to resist starvation in biofiltration technologies.

Biological removal of nitrogen oxides by microalgae, a promising strategy from nitrogen oxides to protein production

Nitrogen oxides (NO_x) are the components of fossil flue gases that give rise to serious environmental and health hazards. Among the available techniques for NO_x removal, microalgae-based biological removal of NO_x (BioDeNO_x) is a promising and competent technology with eco-friendly path of low energy and low-cost solution for the pollution. In this review article, current biological technologies including bacteria-based and microalgae-related BioDeNO_x are discussed. Comparing to direct BioDeNO_x approach, indirect BioDeNO_x by microalgae is more promising since it is more stable, reliable and efficient. By transforming inorganic nitrogen nutrients to organic nitrogen, microalgae can potentially play an important role in converting NO_x into high-value added products. The microalgae-based BioDeNO_x process displays an attractive prospect for flue gas treatment to reduce environmental NO_x pollution and potentially supply protein products, establishing an efficient circular-economy strategy.

Airlift bioreactor system for simultaneous removal of hydrogen sulfide and ammonia from synthetic and actual waste gases

The effectiveness of an airlift reactor system in simultaneously removing hydrogen sulfide (H₂S) and ammonia (NH₃) from synthetic and actual waste gases was investigated. The effects of various parameters, including the ratio of inoculum dilution, the gas concentration, the gas retention time, catalyst addition, the bubble size, and light intensity, on H₂S and NH₃ removal were investigated. The results revealed that optimal gas removal could be achieved by employing an activated inoculum, using a small bubble stone, applying reinforced fluorescent light, adding Fe₂O₃ catalysts, and applying a gas retention time of 20 s. The shock loading did not substantially affect the removal efficiency of the airlift bioreactor. Moreover, more than 98.5% of H₂S and 99.6% of NH₃ were removed in treating actual waste gases. Fifteen bands or species were observed in a profile from denaturing gradient gel electrophoresis during waste gas treatment. Phylogenetic analysis revealed the phylum Proteobacteria to be predominant. Six bacterial strains were consistently present during the entire operating period; however, only Rhodobacter capsulatus, Rhodopseudomonas palustris, and Arthrobacter oxydans were relatively abundant in the system. The photosynthetic bacteria R. capsulatus and R. palustris were responsible for H₂S oxidation, especially when the reinforced fluorescent light was used. The heterotrophic nitrifier A. oxydans was responsible for NH₃ oxidation. To our knowledge, this is the first report on simultaneous H₂S and NH₃ removal using an airlift bioreactor system. It clearly demonstrates the effectiveness of the system in treating actual waste gases containing H₂S and NH₃.

Comparison between absorption and biological activity on the efficiency of the biotrickling filtration of gaseous streams containing ammonia

Polluted air streams can be purified using biological treatments such as biotrickling filtration, which is one of the most widely accepted techniques successfully tuned to treat a wide variety of exhausted gaseous streams coming from a series of industrial sectors such as food processing, flavor manufacturers, rendering, and composting. Since the degradation of a pollutant occurs at standard pressure and temperature, biotrickling filtration, whether compared with other more energy-demanding chemical-physical processes of abatement (such as scrubbing, catalytic oxidation, regenerative adsorption, incineration, advanced oxidation processes, etc.), represents a very high energy-efficient technology. Moreover, as an additional advantage, biodegradation offers the possibility of a complete mineralization of the polluting agents. In this work, biotrickling filtration has been considered in order to explore its efficiency with respect to the abatement of ammonia (which is a highly water-soluble compound). Moreover, a complete mathematical model has been developed in order to describe the dynamics of both absorption and biological activities which are the two dominant phenomena occurring into these systems. The results obtained in this work have shown that the absorption phenomenon is very important in order to define the global removal efficiency of ammonia from the gaseous stream (particularly, 44% of the ammonia is abated by water absorption). Moreover, it has been demonstrated (through the comparison between experimental results and theoretical simulations) that the action of bacteria, which enhance the rate of ammonia transfer to the liquid phase, can be modeled through a simple Michaelis-Menten relationship.

Removal of cyclohexane gaseous emissions using a biotrickling filter system

The removal of cyclohexane from gaseous emissions was studied using a biotrickling filter packed with polyurethane foam. Acivodorax sp. CHX100 was chosen as inoculum due to its ability to use cyclohexane as carbon source. Performance was evaluated by means of different resident times from 18 s to 37 s and concentration levels of 60, 90, 120, 160, 320, 480 and 720 mg C m^-3, respectively. Removal efficiencies of 80%-99% and elimination capacities in the range of 5.4 g C m^-3 h^-1-38 g C m^-3 h^-1 were achieved for concentrations among 60 mg C m^-3-480 mg C m^-3. The removal efficiency decreased to 40% at concentrations of cyclohexane of 720 mg C m^-3. The dynamics of the microbial population showed the strain CHX100 as predominant during the different operational process of biotrickling filter. The results of this study propose a novel approach for cleaning waste air containing cyclohexane by means of a biotrickling filter.

Potential of electric discharge plasma methods in abatement of volatile organic compounds originating from the food industry

Increased volatile organic compounds emissions and commensurate tightening of applicable legislation mean that the development and application of effective, cost-efficient abatement methods are areas of growing concern. This paper reviews the last two decades' publications on organic vapour emissions from food processing, their sources, impacts and treatment methods. An overview of the latest developments in conventional air treatment methods is presented, followed by the main focus of the paper, non-thermal plasma technology. The results of the review suggest that non-thermal plasma technology, in its pulsed corona discharge configuration, is an emerging treatment method with potential for low-cost, effective abatement of a wide spectrum of organic air pollutants. It is found that the combination of plasma treatment with catalysis is a development trend that demonstrates considerable potential. The as yet relatively small number of plasma treatment applications is considered to be due to the novelty of pulsed electric discharge techniques and a lack of reliable pulse generators and reactors. Other issues acting as barriers to widespread adoption of the technique include the possible formation of stable oxidation by-products, residual ozone and nitrogen oxides, and sensitivity towards air humidity.

Removal of gaseous toluene using immobilized Candida tropicalis in a fluidized bed bioreactor

A pure yeast strain Candida tropicalis was immobilized on the matrix of powdered activated carbon, sodium alginate, and polyethylene glycol (PSP beads). The immobilized beads were used as fluidized material in a bioreactor to remove toluene from gaseous stream. Applied toluene loadings were 15.4 and 29.8 g/m³ h in Step 1 and Step 2, respectively, and toluene removal was found above 95% during the entire operation. A continuous pH decline was observed and pH of the suspension was just above 6 in Step 2 but no adverse effects on treatment efficiency were observed. The CO₂ yield values were found to be 0.57 and 0.62 g- in Step 1 and Step 2, respectively. These values indicate that a major portion of toluene-carbon was channeled to yeast respiration even at higher toluene loading. In conclusion, immobilized C. tropicalis can be used as a fluidized material for enhanced degradation of gaseous toluene.

Removal of high concentrations of NH(3) by a combined photoreactor and biotrickling filter system

Average emission levels as high as 800 ppm(v) NH(3) have often been found during the anaerobic fermentation process. At these levels, NH(3) is regarded as an environmental toxic compound. High concentrations of NH(3) gas are difficult to treat in a single treatment process, suggesting that, in terms of economic cost and treatment performance, a coupled system may be a feasible technological alternative. In the coupled TiO(2) photocatalytic-biological treatment system evaluated here, the optimal gas retention time for NH(3) removal--in terms of removal efficiency and capital cost--was 26 s. High gas temperatures, high NH(3) concentrations, and low oxygen contents were unfavorable conditions for NH(3) removal by the photoreactor. The coupled system successfully removed concentrated NH(3) gas (R % > 97 %) under disrupted and shutdown conditions. The photoreactor component of the system successfully fulfilled its role as a pretreatment process and enhanced the performance of the biotrickling filter at a high inlet NH(3) load (2,277 g-N m(-3) day(-1)). Potential ammonia-oxidizing bacteria, including Bacillus cereus, Pseudomonas aeruginosa, and Stenotrophomonas sp., were isolated under the high inlet NH(3) load condition. These microbial strains have a potential as biological agents in the removal of high concentrations of NH(3) in waste gas or wastewater.

Removal of ammonia by immobilized Nitrosomonas europaea in a biotrickling filter packed with polyurethane foam

A biotrickling filter with Nitrosomonas europaea immobilized on polyurethane foam is proposed for treating ammonia contaminated air. The effect of the surface velocity of the recirculation medium, nitrite concentration, pH, empty bed residence time (EBRT) and ammonia inlet load on the NH(3) removal process was investigated. The total amount of biomass immobilized on the carrier was 3.29+/-0.52 x 10(10) cells g(-1) dry carrier. The maximum elimination capacity of the biotrickling filter was 270 g Nm(-3)h(-1) at pH 7.5, an EBRT of 11s, and nitrite concentrations below 100mM. These results show that system studied can be considered as a viable alternative for the treatment of gaseous emissions containing high concentrations of ammonia.

Removal of ammonia from contaminated air in a biotrickling filter - denitrifying bioreactor combination system

The removal of gaseous ammonia in a system consisting of a biotrickling filter, a denitrification reactor and a polishing bioreactor for the trickling liquid was investigated. The system allowed sustained treatment of ammonia while preventing biological inhibition by accumulating nitrate and nitrite and avoiding generation of contaminated water. All bioreactors were packed with cattle bone composite ceramics, a porous support with a large interfacial area. Excellent removal of ammonia gas was obtained. The critical loading ranged from 60 to 120 gm(-3)h(-1) depending on the conditions, and loadings below 56 gm(-3)h(-1) resulted in essentially complete removal of ammonia. In addition, concentrations of ammonia, nitrite, nitrate and COD in the recycle liquid of the inlet and outlet of each reactor were measured to determine the fate of nitrogen in the reactor, close nitrogen balances and calculate nitrogen to COD ratios. Ammonia absorption and nitrification occurred in the biotrickling filter; nitrate and nitrite were biologically removed in the denitrification reactor and excess dissolved COD and ammonia were treated in the polishing bioreactor. Overall, ammonia gas was very successfully removed in the bioreactor system and steady state operation with respect to nitrogen species was achieved.

Evaluation of gas removal and bacterial community diversity in a biofilter developed to treat composting exhaust gases

The performance of a new, but simply constructed, biofilter system, developed to purify composting exhaust air, was evaluated. The biofilter was packed with mature compost mixed with activated carbon and sludge sourced from a wastewater treatment plant. An alternating air flow system and a bioaerosol reduction device were designed to prevent pressure drop and reduce bioaerosol release. Experimental results demonstrated that satisfactory removal efficiencies of nitrogen-containing compounds, sulfur-containing compounds, fatty acids, total hydrocarbon and odor were achieved at an empty bed retention time (EBRT) of 30s. No significant acidification or alkalinity in the biofilter was observed, and the system was characterized by a small pressure drop and a low level of bioaerosol emission. Denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH) techniques were used to uncover the changes in the bacterial community of the biofilter during the deodorization processes. A minimum of 16 bands were observed in the DGGE profile. Phylogenetic analysis revealed the phylum of Proteobacteria to be predominant, followed by Actinobacteria, Bacteroidetes, and Firmicutes, in descending order. However, the occurrence and predominance of specific bacterial species varied with the environmental conditions of the biofilter. Our results demonstrate - from both an engineering and biological point of view - the feasibility of the biofilter system described herein in purifying the gases derived from composting food waste.

Microbial degradation of livestock-generated ammonia using biofilters at typical ambient temperatures

The purpose of this research was to neutralize livestock-generated ammonia by using biofilters packed with inexpensive inorganic and organic packing material combined with multicultural microbial load at typical ambient temperatures. Peat and inorganic supporting materials were used as biofiltration matrix packed in a perfusion column through which gas was transfused. Results show the ammonia removal significantly fell in between 99 and 100% when ammonia concentration of 200 ppmv was used at different gas flow rates ranged from 0.030 to 0.060 m3 h(-1) at a fluctuating room temperature of 27.5 +/- 4.5 C (Mean +/- SD). Under these conditions, the emission concentration of ammonia that is liberated after biofiltration is less than 1 ppmv (0.707 mg m(-3)) over the period of our study, suggesting the usage of low-cost biofiltration systems for long-term function is effective at wider ranges of temperature fluctuations. The maximum (100%) ammonia removal efficiency was obtained in this biofilter was having an elimination capacity of 2.217 g m(-3) h(-1). This biofilter had high nitrification efficiencies and hence controlled ammonia levels with the reduced backpressure. The response of this biofilter to shut down and start up operation showed that the biofilm has a superior stability.

Hydrogen sulfide effects on ammonia removal by a biofilter seeded with earthworm casts

Ammonia (NH3) removal efficencies were evaluated when hydrogen sulfide (H2S) and NH3 in binary mixture gases were supplied to a ceramic biofilter seeded with earthworm (Lumbricus terrestris) casts. The effect of inlet H2S concentration and space velocity (SV) on the removal of NH3 was investigated after the acclimation of the biofilter with NH3 gas. When NH3 was singly supplied to the biofilter, NH3 removal was maintained at almost 100% until inlet NH3 concentration was increased up to 600 microL L(-1) and SV up to 330 h(-1), at which the elimination capacity of NH3 was 148 g N m(-3) h(-1). When H2S was supplied simultaneously, however, the accumulation of toxic sulfide ions showed dual effects on NH3 removal efficiencies. First, no effects were observed at inlet H2S loading below 60 g S m(-3) h(-1); however, inhibition by H2S at higher loading was observed above 60 g S m(-3) h(-1). The point at which loading achieved a maximum of more than 99% NH3 removal efficiency was 139 g N m(-3) h(-1), when inlet H2S concentration was held under 100 microL L(-1), but it dropped to 76 and 30 g N m(-3) h(-1) when the inlet H2S concentration increased to 220 and 460 microL L(-1), respectively. The critical points of inlet H2S loading that guaranteed over 99% NH3 removal were determined as 100, 100, 60, and 40 g S m(-3) h(-1) at inlet NH3 concentrations of 100, 200, 400, and 600 microL L(-1), respectively. Inlet NH3 loading had synergic effects of increasing the inhibition of inlet H2S loading on the NH3 removability of the biofilter.

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.

Biofiltration--the treatment of fluids by microorganisms immobilized into the filter bedding material: a review

Biofiltration is distinguished from other biological waste treatments by the fact that there is a separation between the microorganisms and the treated waste. In biofiltration systems the microorganisms are immobilized to the bedding material, while the treated fluid flows through it. In recent decades, a vast amount of literature has been written on single experiments involving the treatment of fluids by immobilized microorganisms. Several artificial immobilization methods have been examined and impressive results have been achieved in the treatment of fluids with one of the artificial immobilization methods the entrapment of microorganisms within polymer beads. This method, even though it needs to be improved, seems to have a future potential in commercial biofiltration systems. The methods of artificial immobilization of microorganisms within biofiltration systems have several advantages, but also suffer from several disadvantages in comparison to the treatment of fluids by naturally attached microorganisms. Understanding the mechanisms and forces responsible for the attachment of microbes to the bedding material, in attempt to improve this attachment, is of the utmost importance. Further improvement of the artificial entrapment of microorganisms within polymers will allow the exploitation of the advantages of this method in the treatment of fluids. The aim of this review essay is to introduce the main principles of two immobilization processes - the self-attachment of microorganisms to the bedding material and the artificial entrapment of microorganisms within polymer beads. Both treatments of liquids and gases with each immobilization process are discussed. The advantages and disadvantages of each immobilization process are pointed out and different aspects of the fluid treatment with the two immobilization processes are compared.

Removal of a high load of ammonia gas by a marine bacterium, Vibrio alginolyticus

A newly isolated marine bacterium, Vibrio alginolyticus was used to remove a high load of ammonia gas. By a stepwise increase in ammonia supply over the concentration range of 120-2000 ppm (v/v), complete removal of ammonia was observed from the start of the experiment in a suspended culture of the bacterium in basal medium containing 3% NaCl. When cells were inoculated onto an inorganic packing material in a biofilter, and a high load of ammonia was introduced continuously under nonsterile conditions, the average percentage of gas removed exceeded 85% for a 61-d operation. The maximum removal capacity and the complete removal capacity were 22.8 g-N/kg-dry packing material/d and 18.6 g-N/kg-dry packing material/d, respectively, which were about four times larger than those obtained in nitrifying sludge inoculated onto the same packing material. During this operation, the nonsterile air supply had no adverse effect on the removability of ammonia by V. alginolyticus.

New microcapsules based on oligoelectrolyte complexation

A new one-step microencapsulation procedure has been developed. For the alginate/oligochitosan system the molar mass of the chitosan is a key parameter in the formation of stable, elastic capsules with high modulus. Furthermore, the selection of an optimum molar mass provides an additional degree of freedom, permitting the simultaneous regulation of mechanical properties and permeability without the need for multicomponent organic-inorganic chemistries as have been previously employed. The effects of molar mass of chitosan, its concentration, the alginate molar mass and its metal salt on the preparation, physical properties, and release characteristics of the capsules have been studied.