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

Development of microbial enrichments for simultaneous removal of sulfur and nitrogenous metabolites in saline water aquaculture

AIM

The aim of the study was to develop microbial enrichments from the nitrifying microbial consortia and the environment for simultaneous removal of ammonia, nitrate, and sulfide in aquaculture systems at varied salinities.

METHODS AND RESULTS

Sulfur and nitrogen metabolites are the major factors affecting the farmed aquatic animal species and deteriorate the receiving environments causing ecological damage. The present study reports the development of microbial enrichments from the nitrifying microbial consortia and the environment. The enrichments used thiosulfate or thiocyanate as an energy source and simultaneously removed sulfur, ammonia, and nitrite in spiked medium (125 mg/l ammonia; 145 mg/l nitrite). Further, the microbes in the enrichments could grow up to 30 g/l salinity. Metagenomic studies revealed limited microbial diversity suggesting the enrichment of highly specialized taxa, and co-occurrence network analysis showed the formation of three micro-niches with multiple interactions at different taxonomic levels.

CONCLUSIONS

The ability of the enrichments to grow in both organic and inorganic medium and simultaneous removal of sulfide, ammonia, and nitrite under varied salinities suggests their potential application in sulfur, nitrogen, and organic matter-rich aquaculture pond environments and other industrial effluents.

Exceptional High and Reversible Ammonia Uptake by Two Dimension Few-layer BiI3 Nanosheets

The emission of NH₃ into atmosphere is seriously harmful for human health and public safety, thus the capture and recovery of NH₃ from ammonia emissions is highly desirable. In recent years, many kinds of solid adsorbents have been exploited to absorb NH₃. However, these materials do not show the advantages of high uptake capacity and good recyclability at the same time. Here, nontoxic and low cost few-layer BiI₃ nanosheets have been prepared from bulk BiI₃ powder by a simple and efficient liquid phase exfoliation strategy using green solvents and then applied for the NH₃ capture for the first time. The results show that the adsorption capacity of NH₃ of BiI₃ nanosheets reaches up to 22.6 mmol/g at 1.0 bar and 25 °C, which approaches the record value for NH₃ adsorption. Importantly, the NH₃ uptake in BiI₃ nanosheets is completely reversible and no clear loss in uptake capacity is observed after 10 cycles of adsorption-desorption. Furthermore, the BiI₃ nanosheets exhibit remarkable selectivity for the separation of NH₃/CO₂ at 70 °C with theoretical selectivity coefficient of 700, which is promising for the selective separation of NH₃ and CO₂ in hot tail gas of some industrial processes. Mechanism studies indicate that such superior NH₃ capacity, excellent reversibility and remarkable selectivity are primarily attributed to the Bi³⁺-NH₃ coordination interactions.

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.

Simultaneous biofiltration of H2S and NH3 using compost mixtures from lignocellulosic waste and chicken manure as packing material

Biofiltration offers an efficient and economical alternative for the elimination of offensive odors caused by hydrogen sulfide, ammonia, and volatile organic compounds. Considering that packing materials affect the performance and represent the main installation cost, the purpose of this work was to evaluate the biofiltration of H₂S and NH₃ comparing three composted mixtures made from chicken manure and lignocellulosic residues (pruning waste, sugarcane bagasse, and rice husk) used as packing material. A range of gas concentrations similar to those of a municipal WWTP was used in the biofiltration of a contaminated stream performed on a laboratory scale. The results indicate that at low concentrations of H₂S (6-36 ppm) and NH₃ (0-1 ppm), the three biofilters showed 100% removal efficiency. Now, at the maximum levels of gas concentrations of H₂S (250 ppm) and NH₃ (19 ppm) while the removal efficiency of H₂S remained higher than 90% in all cases, the removal efficiency of NH₃ remained higher than 90% only in the sugarcane bagasse biofilter. Compost mixtures with sugarcane bagasse and rice husk are highly reliable as packing material for biofiltration at high concentration of H₂S. Specifically, the sugarcane bagasse mixture had the highest removal efficiency (99% H₂S and 95% NH₃) and the highest elimination capacity (15 g H₂S/m³h and 0.6 g NH₃/m³h), making it a better option for the elimination of both gases. These results represent a contribution to the construction of a low-price elimination system of offensive odors in WTTPs and other industries.

Removal of Odors (Mainly H2S and NH3) Using Biological Treatment Methods

This study reviews the available and most commonly used methods of gas deodorization. Comparing various methods of odor removal, undoubtedly biological methods of pollution degradation have an advantage over others—chemical and physical. This advantage is manifestedmainly in ecological and economic terms. The possibility of using biological methods to remove H2S and NH3, as the most common emitted by the municipal sector companies, was analyzed in terms of their removal efficiency. The method of bio-purification of air in biotrickling filters is more advantageous than the others, due to the high effectiveness of VOCs and odors degradation, lack of secondary pollutants, and economic aspects—it is a method competitive to the commonly used air purification method in biofilters.

Evaluation of Immobilization of Selected Peat-Isolated Yeast Strains of the Species Candida albicans and Candida subhashii on the Surface of Artificial Support Materials Used for Biotrickling Filtration

The paper describes the process of n-butanol abatement by unicellular fungi, able to deplete n-butanol content in gas, by using n-butanol as source of carbon. Isolated and identified fungi species Candida albicans and Candida subhashii were subjected to a viability process via assimilation of carbon from hydrophilic and hydrophobic compounds. The isolates, which exhibited the ability to assimilate carbon, were immobilized on four different types of artificial support materials used for biotrickling filtration. Application of optical microscopy, flow cytometry and the tests employing propidium iodide and annexin V revealed viability of the fungi isolated on support materials’ surfaces at the average level of 95%. The proposed method of immobilization and its evaluation appeared to be effective, cheap and fast. Based on performed comparative analyses, it was shown that polyurethane foam and Bialecki rings (25 × 25) could be attractive support materials in biotrickling filtration.

Technical and economic investigation of chemical scrubber and bio-filtration in removal of H2S and NH3 from wastewater treatment plant

A detailed techno-economic comparison of a chemical scrubber (CS) and a bio-filter (BF) was conducted over a 45-day time period at a municipal wastewater treatment plant (WWTP), Yazd city. The assessment of emissions quantity indicated that odor emissions from the Yazd WWPT mainly consist of hydrogen sulfide (H₂S) and ammonia (NH₃). It was also found that odor gaseous loading changes corresponding to water consumption pattern in society (R² = 0.922) for H₂S and (R² = 0.978) for NH₃. The highest level of 25 and 3 ppm for H₂S and NH₃, respectively were detected at specific times during the day. The BF system was continuously supplied with Yazd WWPT's off-gas treatment while the CS was only examined at the times during the day when the gas emissions are at the highest level. The removal efficiency of NH₃ and H₂S were found to be affected by their respective loading rate. Additionally, among the various oxidants examined in the CS, the NaOCl solution showed the best results in terms of removal efficiency and compatibility. The experiment revealed almost complete removal of NH₃ while the H₂S removal efficiency remained above 95% for both systems regardless of the operating conditions. This study clearly demonstrates the effectiveness of both systems in treating actual waste gases containing H₂S and NH₃. By comparing the gas loading rate of both systems and considering limitations of the BF system, the CS seems to be more efficient applicable odor control technology from a technical viewpoint. From the economic viewpoint, comparisons revealed that chemical usage and operating expenses were costly parts of the CS and the BF, respectively. The economic indexes of 1.58 €.m^-3. h^-1 and 2.57 €.m^-3. h^-1 were obtained for the BF and CS, respectively, reflecting cost-effectiveness of the BF system.

Trickling filter technology for biotreatment of nitrogenous compounds emitted in exhaust gases from fishmeal plants

Odour emissions are a major environmental issue associated with fishmeal production. Laboratory-scale biotrickling filters (BTFs) were inoculated with microbial consortia derived from sewage sludge, with the goal to study the biotreatment of low-loads of methylamines and ammonia that are main components of odorous exhaust gases produced by fishmeal processing plants. A BTF packed with ceramic rings was subjected to a real fishmeal plant emission containing trimethylamine (TMA), dimethylamine (DMA) and monomethylamine (MMA). The highest elimination capacities (ECs) obtained were 372 mg TMA m^-3 h^-1, 5.518 mg DMA m^-3 h^-1 and 1.038 mg MMA m^-3 h^-1, with maximal removal efficiencies of 92% (TMA), 83% (DMA) and 95% (MMA) after 30 days operation. In a different experiment, a polyurethane foam packing was employed to treat ammonia (NH₃) at low inlet loads, reaching an EC of 47.19 mg N m^-3 h^-1 with 99.8% efficiency (inlet load of 47.27 mg N m^-3 h^-1). Likewise, the microbial community of the polyurethane-associated biofilm was diverse and stable during operation. These results suggested that elimination of volatile amino-compounds using BTFs inoculated with a methylotrophic microbial consortium holds potential for odour removal. In addition, sequencing analysis of 16S rDNA gene fragments allowed the identification of heterotrophic ammonia-oxidizing bacteria that are promising candidates to effectively maintain ammonia elimination in a biotreatment operation of nitrogenous compounds present in exhaust gases from fishmeal facilities.

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.

Identify biosorption effects of Thiobacillus towards perfluorooctanoic acid (PFOA): Pilot study from field to laboratory

The concentration of Perfluoroalkyl acids (PFAAs) and the bacterial community composition along the Xiaoqing River were explored with HPLC-MS/MS and Illumina high-throughput sequencing in present study. The results showed that perfluorooctanoic acid (PFOA) was the predominant PFAAs in all sediment samples, and high level of PFOA could lead to an evident increase in the abundance of Thiobacillus. Thiobacillus was identified with the survival ability in high concentrations of PFOA accordingly. Therefore, Thiobacillus thioparus and Thiobacillus denitrificans were selected as receptors to design indoor biosorption experiment. The growth curves under different PFOA concentrations and residual rates of PFOA in the processes of cultivation were analyzed. The results showed that upwards concentrations of PFOA below 5000 ng/L led to an obvious increase in the growth rate of T. thioparus. Whereas PFOA promoted the growth of T. denitrificans in a relatively limited range of concentration, and the effect was not obvious. The addition of different concentrations of PFOA had no apparent effects on pH values in the media of both T. thioparus and T. denitrificans. The concentrations of PFOA in liquid media reduced after the process of bacteria culturing. The removal rates of T. thioparus and T. denitrificans to PFOA were 21.1-26.8% and 13.5-18.4%, respectively. The current findings indicated that T. thioparus could play a significant role as potential biosorbent with the ability to eliminate PFOA effectively in aquatic environment, which would provide novel information for PFOA ecological decontamination and remediation.

Simultaneous removal of ammonia and hydrogen sulfide gases using biofilter media from the biodehydration stage and curing stage of composting

Biofiltration of NH₃ and H₂S with different packing media, biodehydration stage compost (BSC), and curing stage compost (CSC) was studied. Meanwhile, fluorescence excitation-emission matrix (EEM) spectroscopy was used to characterize the conversion mechanisms of organic matter during these biofiltration processes. Both biofilters were effective for the simultaneous removal of NH₃ and H₂S when inlet concentrations of NH₃ and H₂S were 0-50 and 50-250 mg/m³, respectively. An abrupt increase in the inlet gas concentrations of NH₃ and H₂S to 100-150 and 200-250 mg/m³, respectively, caused the decrease in the removal efficiencies (REs) of NH₃ and H₂S in the BSC biofilter, followed by a slow upturn. By contrast, relatively steady REs of both NH₃ and H₂S were observed in the CSC biofilter. After 60 days of operation, the average REs of NH₃ and H₂S were more than 95 % in the CSC biofilter. During the operation of CSC, nitrate and nitrite peaked around the 30th day, whereas sulfate showed a steady increase. The excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) indicated that the simultaneous inlet of NH₃ and H₂S facilitated the degradation of protein-like substances, whereas humic-like substances played an important role in the packing filters for the treatment of the two odorous pollutants.

An overview of principles of odor production, emission, and control methods in wastewater collection and treatment systems

Odorous gases are the most important reason that people register complaints with organizations responsible for wastewater collection and treatment systems (WCTS). Although several studies have been conducted for prevention and control of odorous gases, no comprehensive research exists about recent achievements in this area. The aim of the present study is to collect and categorize the new achievements in preventing and controlling odorous gases in WCTS. Two strategies for controlling odor emissions from WCTS are (1) prevention of odor production and (2) removal of odorous compounds from emissions of WCTS. Between the two, priority goes to preventing odorous compounds' production. Several methods have been developed to prevent odor production, such as increasing oxidation reduction potential; inhibiting the activity of sulfide reducing bacteria; chemical removal of hydrogen sulfide; applying formaldehyde and paraformaldehyde to prevent hydrogen sulfide production; and using fuel cells in hydrogen sulfide inhibition and gradual release of oxygen in gas phase by using MgO2 or CaO2. In addition to preventing odorous compounds in WCTS, many other methods have been introduced to remove odorous compounds from emissions of WCTS, such as biofilters; bioscrubbers; biotrickling filters; suspended growth reactors; and membrane bioreactors and scrubbers. Through this review, responsible organizations can find new, effective, and economical strategies to prevent and control odorous gases in WCTS.

Removal of odorous compounds from poultry manure by microorganisms on perlite--bentonite carrier

Laboratory-scale experiments were conducted using poultry manure (PM) from a laying hen farm. Six strains of bacteria and one strain of yeast, selected on the base of the previous study, were investigated to evaluate their activity in the removal of odorous compounds from poultry manure: pure cultures of Bacillus subtilis subsp. spizizenii LOCK 0272, Bacillus megaterium LOCK 0963, Pseudomonas sp. LOCK 0961, Psychrobacter faecalis LOCK 0965, Leuconostoc mesenteroides LOCK 0964, Streptomyces violaceoruber LOCK 0967, and Candida inconspicua LOCK 0272 were suspended in water solution and applied for PM deodorization. The most active strains in the removal of volatile odorous compounds (ammonia, hydrogen sulfide, dimethylamine, trimethylamine, isobutyric acid) belonged to B. subtilis subsp. spizizenii, L. mesenteroides, C. inconspicua, and P. faecalis. In the next series of experiments, a mixed culture of all tested strains was immobilized on a mineral carrier being a mixture of perlite and bentonite (20:80 by weight). That mixed culture applied for PM deodorization was particularly active against ammonia and hydrogen sulfide, which were removed from the exhaust gas by 20.8% and 17.5%, respectively. The experiments also showed that during deodorization the microorganisms could reduce the concentrations of proteins and amino acids in PM. In particular, the mixed culture was active against cysteine and methionine, which were removed from PM by around 45% within 24 h of deodorization.

A new cytoplasmic monoheme cytochrome c from Acidithiobacillus ferrooxidans involved in sulfur oxidation

Acidithiobacillus ferrooxidans can obtain energy from the oxidation of various reduced inorganic sulfur compounds (RISCs, e.g., sulfur) and ferrous iron in bioleaching so has multiple branched respiratory pathways with a diverse range of electron transporters, especially cytochrome c proteins. A cytochrome c family gene, afe1130, which has never been reported before, was found by screening the whole genome of A. ferrooxidans. Here we report the differential gene transcription, bioinformatics analysis, and molecular modeling of the protein encoded by the afe1130 gene (AFE1130). The differential transcription of the target afe1130 gene versus the reference rrs gene in the A. ferrooxidans, respectively, on the culture conditions of sulfur and ferrous energy sources was performed through quantitative reverse transcription polymerase chain reaction (qRT-PCR) with a SYBR green-based assay according to the standard curves method. The qRT-PCR results showed that the afe1130 gene in sulfur culture condition was obviously more transcribed than that in ferrous culture condition. Bioinformatics analysis indicated that the AFE1130 was affiliated to the subclass ID of class I of cytochrome c and located in cytoplasm. Molecular modeling results exhibited that the AFE1130 protein consisted of 5 alpha-helices harboring one heme c group covalently bonded by Cys13 and Cys16 and ligated by His17 and Met62 and owned a big raised hydrophobic surface responsible for attaching to inner cytomembrane. So the AFE1130 in A. ferrooxidans plays a role in the RISCs oxidation in bioleaching in cytoplasm bound to inner membrane.

Biodegradation of toluene using Candida tropicalis immobilized on polymer matrices in fluidized bed bioreactors

A yeast strain, Candida tropicalis, was whole-cell-immobilized on polymer matrices of polyethylene glycol (PEG) and polyethylene glycol/activated carbon/alginate (PACA). The polymer matrices were used as fluidized materials in bubble-column bioreactors for the biodegradation of toluene. Simultaneously, another bubble-column bioreactor using granular activated carbon (GAC) and a conventional compost biofilter were operated for comparison. In the compost biofilter, the toluene removal efficiency gradually deteriorated due to the limitation of microbial activity. The toluene removal in the GAC bioreactor was relatively high because of an increase of toluene mass transfer. However, low toluene removal efficiencies were observed in the PEG bioreactor, presumably because the synthetic polymer alone was not suitable for yeast cell immobilization. In the PACA bioreactor, toluene removal was found to be greater than 95% overall. The CO(2) yield coefficient calculated at the highest toluene loading condition for the PACA bioreactor was found to be higher than those observed in the other bioreactors. Furthermore, almost complete elimination capacities were observed in the PACA bioreactor at short-term toluene loading up to 180 g/m(3)/h. In conclusion, the immobilization of C. tropicalis in the PACA matrix resulted in enhanced toluene biodegradation because of the increases of both mass transfer and microbial activity.

HdrC2 from Acidithiobacillus ferrooxidans owns two iron-sulfur binding motifs but binds only one variable cluster between [4Fe-4S] and [3Fe-4S]

The heterodisulfide reductase complex HdrABC from Acidithiobacillus ferrooxidans was suggested to own novel features that act in reverse to convert the sulfane sulfur of GS( n )H species (n > 1) into sulfite in sulfur oxidation. The HdrC subunit is potentially encoded by two different highly upregulated genes sharing only 29 % identity in A. ferrooxidans grown in sulfur-containing medium, which were named as HdrC1 and HdrC2, respectively and had been confirmed to contain iron-sulfur cluster by expression and characterization, especially the HdrC1 which had been showed to bind only one [4Fe-4S] cluster by mutations. However, the mutations of the HdrC2 remain to be done and the detailed binding information of it is still unclear. Here, we report the expression, mutations, and molecular modeling of the HdrC2 from A. ferrooxidans. This HdrC2 had two identical motifs (Cx(2)Cx(2)Cx(3)C) containing total of eight cysteine residues potentially for iron-sulfur cluster binding. This purified HdrC2 was exhibited to contain one variable cluster converted between [4Fe-4S] and [3Fe-4S] according to different conditions by the UV-scanning and EPR spectra. The site-directed mutagenesis results of these eight residues further confirmed that the HdrC2 in reduction with Fe(2+) condition loaded only one [4Fe-4S](+) with spin S = 1/2 ligated by the residues of Cys73, Cys109, Cys112, and Cys115; the HdrC2 in natural aeration condition lost the Fe atom ligated by the residue of Cys73 and loaded only one [3Fe-4S](0) with spin S = 0; the HdrC2 in oxidation condition loaded only one [3Fe-4S](+) with spin S = 1/2. Molecular modeling results were also in line with the experiment results.

Kinetic evaluation of removal of odorous contaminants in a three-stage biological air filter

Biofiltration is a cost-effective technology for removing air contaminants from animal facilities. Kinetic analysis can be helpful in understanding and designing the process but has not been performed on full-scale filters treating complex mixtures. In this study, kinetics was investigated in a full-scale biological filter treating air pollutants from a pig facility. Due to the high air flow rates used in the filter, both a plug flow model and a model based on complete mixing were tested with respect to kinetic order and Michaelis-Menten kinetics. Application of these models only gave poor to moderate agreement with air filter removal data. Two alternative kinetic models (Stover-Kincannon model and Grau second-order model) adopted from wastewater biofiltration process analysis were introduced to analyze contaminant removal in the biological air filter. Data analysis demonstrated the applicability of these two models with a high degree of precision on contaminant removal in the biological air filter. Whereas the Stover-Kincannon model demonstrated that pollutant removal rates were related to the mass loading rates, the Grau second-order kinetic model indicated that the removal efficiencies were dependent on air loading rates. Therefore, the kinetic data can be used for comparing biofilter performances and for design purposes.

Expression, purification and molecular modeling of another HdrC from Acidithiobacillus ferrooxidans which binds only one [4Fe-4S] cluster

The heterodisulfide reductase complex HdrABC from Acidithiobacillus ferrooxidans was predicted to have novel features that work in reverse to catalyse the sulfane sulfur of GSnH species (n > 1) into sulfite in sulfur oxidation. There are two different highly upregulated genes potentially encoding the HdrC subunit in A. ferrooxidans grown in sulfur-containing medium. An HdrC containing iron-sulfur cluster from A. ferrooxidans corresponding to one of the genes had been expressed and biophysically characterized. Comparatively, here we report the cloning, expression, and characterization of another HdrC from A. ferrooxidans. This HdrC was expressed in inclusion bodies in all conditions tested. This purified HdrC displayed brown color and contained the [4Fe-4S] cluster confirmed by the UV-scanning and EPR spectra. This HdrC owned two identical motifs (Cx(2)Cx(2)Cx(3)C) including total of eight cysteine residues for [4Fe-4S] cluster binding. To our surprise, the site-directed mutagenesis results of these eight residues revealed that respective removal of the sulfhydryl group of Cys73, Cys76, Cys79, and Cys37 resulted in the cluster loss, but those of Cys27, Cys30, Cys33, and Cys83 had no influence, which demonstrated that this HdrC bound only one cluster, and it might be responsible for causing the HdrABC in A. ferrooxidans working in reverse. Molecular modeling results also supported the above results and showed that this cluster was ligated by Cys73, Cys76, and Cys79 in one motif and Cys37, however, in another motif.

Microbial monitoring and performance evaluation for H2S biological air emissions control at a wastewater lift station in South Texas, USA

A pilot-scale biological sequential treatment system consisting of a biotrickling filter and two biofilters was installed at Waste Water Lift Station # 64 in Brownsville, Texas, USA to evaluate the performance of the system being loaded with variable concentrations of wastewater hydrogen sulfide (H(2)S) emissions. In this study, the effectiveness of sulfur oxidizing bacteria along with the distribution of various sulfur species and their correlation with the performance of the biofilters was evaluated. The biofilters were packed with engineered media consisting of plastic cylinders with compacted organic material which was supplied by Met-Pro Environmental Air Solutions (formerly Bio·Reaction Industries). The overall performance of the pilot-scale biological sequential treatment system with an Empty Bed Residence Time (EBRT) of 60s and the overall performance of the biofilter unit with an EBRT of 35s developed a removal efficiency of > 99% at H(2)S levels up to 500 ppm. A decrease in performance over time was observed in the first and second sections of the first biofilter unit with the third section of the biofilter unit ultimately becoming the most robust unit removing most of the pollutant. The second biofilter unit was not needed and subsequently removed from the system. The number of CFUs in sulfur oxidizing T.thioparus selective media grew significantly in all four sections of the biofilter over the two months of pilot operation of the biological unit. The sulfur oxidizer growth rates appeared to be highest at low total sulfur content and at slightly acidic pH levels. This study has implications for improving the understanding of the distribution of sulfur oxidizing bacteria throughout the length of the biofilter columns, which can be used to further optimize performance and estimate breakthrough at these very high H(2)S input loadings.

Impact of substrates acclimation strategy on simultaneous biodegradation of hydrogen sulfide and ammonia

Three columns were differentiated with feeding mixture of H(2)S and NH(3) (MFC), feeding NH(3) followed by H(2)S (NFC), and feeding H(2)S followed by NH(3) (SFC). Removal performance, biodegradation capacity and microbial community structures in the three columns were compared. The results show that NFC has a shorter acclimation period for the removal of NH(3) gas and nitrification than MFC. Under the high loading of H(2)S and NH(3) at 164 and 82 gm(-3) h(-1), respectively, NFC exhibited high removal efficiency of NH(3) (>95%) while the removal efficiencies were obtained at 63 and 75% in MFC and SFC, respectively. The removal of NH(3) gas in NFC was significantly attributed to nitrification (over 50%), while adsorption and chemical reaction contributed to the removal of NH(3) in MFC and SFC. The different biodegradation capacities of NH(3) could be due to the dissimilarity in the microbial population presented in each column.

Removal of hydrogen sulfide by immobilized Thiobacillus thioparus in a biotrickling filter packed with polyurethane foam

In the work described here, a biotrickling filter with Thiobacillus thioparus (ATCC 23645) immobilized on polyurethane foam is proposed for the removal of hydrogen sulfide contained in air. The effect of surface velocity of the recirculation medium (5.9-1.2 m/h), sulfate concentration inhibition (3.0-10.7 g/L), pH (6.0-8.2), empty bed residence time (EBRT) (150-11 s) for constant loads of 11.5 and 2.9 g S/m(3)/h, and pressure drop of the system were investigated. The total amount of biomass immobilized on the carrier was 8.2+/-1.3x10(10) cells/g. The optimal values of the operating variables were: pH between 7.0 and 7.5, surface velocity of 5.9 m/h and sulfate concentration below 5 g/L. The critical EC value was 14.9 g S/m(3)/h (removal efficiency of 99.8%) and the EC(max) was 55.0 g S/m(3)/h (removal efficiency of 79.8%) for an EBRT of 150 s. For loads of 2.89+/-0.05 and 11.5+/-0.1 g S/m(3)/h, the removal efficiency was higher than 99% for an EBRT over 90 s.

Biofiltration of trimethylamine, dimethylamine, and methylamine by immobilized Paracoccus sp. CP2 and Arthrobacter sp. CP1

A biofilter using granular activated carbon with immobilized Paracoccus sp. CP2 was applied to the elimination of 10-250 ppm of trimethylamine (TMA), dimethylamine (DMA), and methylamine (MA). The results indicated that the system effectively treated MA (>93%), DMA (>90%), and TMA (>85%) under high loading conditions, and the maximum degradation rates were 1.4, 1.2, and 0.9g-Nkg(-1) GAC d(-1). Among the three different amines treated, TMA was the most difficult to degrade and resulted in ammonia accumulation. Further study on TMA removal showed that the optimal pH was near neutral (6.0-8.0). The supply of high glucose (>0.1%) inhibited TMA removal, maybe due to substrate competition. However, complete TMA degradation was achieved under the co-immobilization of Paracoccus sp. CP2 and Arthrobacter sp. CP1 ( approximately 96%). Metabolite analysis results demonstrated that the metabolite NH(4)(+) concentrations decreased by a relatively small 27% while the metabolite NO(2)(-) apparently increased by heterotrophic nitrification of Arthrobacter sp. CP1 in the co-immobilization biofilter.

Effects of pollutant concentration ratio on the simultaneous removal of NH3, H2S and toluene gases using rock wool-compost biofilter

The biological treatment of a tri-component mixed waste gas system in BRC1 and BRC2 biofilters packed with rock wool-compost media was studied. The model gases were NH(3), H(2)S and toluene. The gases were fed initially at about 50-55 ppm each. H(2)S was found to have the shortest start-up while toluene had the longest. Under two different NH(3):H(2)S:toluene concentration ratios of 250:120:55 and 120:220:55 (in ppm) for BRC1 and BRC2, the removal efficiencies of NH(3), H(2)S and toluene were found to be affected by their respective loading rate. On the other hand, toluene removal was observed to be inhibited at H(2)S concentration of 220 ppm as well. Almost complete removal of NH(3) and H(2)S was achieved when loading rate was applied up to 16.14 g-NH(3)/(m(3) bed h) and 36.09 g-H(2)S/(m(3) bed h), respectively. The maximum elimination capacity for NH(3) was determined to be 23.67 g-NH(3)/(m(3) bed h) at 78.6% removal efficiency and for H(2)S, 38.50 g-H(2)S/(m(3) bed h) at 68.1% removal efficiency. The maximum toluene elimination capacity was 30.75 g-toluene/(m(3) bed h) at 87.9% removal efficiency when the concentration of NH(3):H(2)S:toluene was 250:120:55 in BRC1, and was 16.60 g-toluene/(m(3) bed h) at 45.5% removal efficiency when the concentration of NH(3):H(2)S:toluene was 120:220:55 in BRC2. The pressure drops along both columns were low and the ratio of bed compactions over biofilter height was observed to be less than 0.02.

Biological oxidation of hydrogen sulfide under steady and transient state conditions in an immobilized cell biofilter

The removal of hydrogen sulfide (H(2)S) was investigated in a lab scale biofilter packed with biomedia, encapsulated by sodium alginate and polyvinyl alcohol (PVA). The main H(2)S oxidation products were SO(4)(2-), SO(3)(2-), S(2-) and S(0). The immobilized cell biofilter required no separate acclimatization period and showed high removal efficiencies (RE) within the first few days of experiments. The removal efficiencies in the biofilter were consistently greater than 99% even when H(2)S loading was 6 g m(-3)h(-1). The maximum elimination capacity achieved in this study is 8 g H(2)Sm(-3)h(-1) at a loading rate of 13 g H(2)Sm(-3) h(-1). The response of the immobilized cells to fluctuations in inlet concentration and flow rate was determined by subjecting the biofilter to inlet loads of up to 10 g H(2)Sm(-3)h(-1). The biofilter responded effectively to these shock loading conditions and convalesced rapidly within 4-8h. Pressure drop values were consistently less throughout the operational period. The results from this study suggest that an immobilized cell biofilter is effective in treating H(2)S under steady and transient operating conditions.

Performance of an immobilized cell biofilter for ammonia removal from contaminated air stream

The performance of a lab scale biofilter packed with biomedia, encapsulated by sodium alginate and polyvinyl alcohol was used for treating ammonia (NH(3)) gas at different loading rates. The metabolic end products during NH(3) oxidation were NH(4)(+), NO(3)(-) and NO(2)(-). It is noteworthy to mention that the immobilized cell biofilter required no separate acclimatization period and showed high removal efficiencies during the start of continuous experiments. The removal efficiency was nearly 100% when ammonia loading was 4.5gm(-3)h(-1) and the maximum elimination capacity achieved in this study was 5.5gNH(3)m(-3)h(-1) at a loading rate of 7.5gm(-3)h(-1). Shock loading studies were carried out to ascertain the response of the immobilized cells to fluctuations in inlet concentration and flow rate. The inlet loading rates were varied between 0.05 and 6gNH(3)m(-3)h(-1) during this phase of operation. The biofilter responded effectively to these shock loading conditions and recovered rapidly within 4-8h. Pressure drop values were consistently less and insignificant. The results from this study indicated that this immobilized cell biofilter could be considered as a potential option to treat NH(3) under steady and transient state operation.

Isolates identification and characteristics of microorganisms in biotrickling filter and biofilter system treating H2S and NH3

A combination system of biotrickling filter (BTF) and biofilter (BF), adopting surfactant-modified clinoptilolite and surfactant-modified wood chip as the media respectively, was applied to treat H2S and NH3 simultaneously. The identification and sole carbon sources utilization patterns of isolates in the combination system were studied by Biolog system. The isolates were identified as Bacillus sphaericus, Geobacillus themoglucosidasius (55 degrees C) and Micrococcus luteus (ATCC 9341) in BTF, and Aspergillus sydowii (Bainier & Sartory) Thorm & Church in BF. Among 95 substrate classes supplied by Biolog system, the carboxylic acids and methyl esters had the highest utilization extent for the four species, followed by the amino acids and peptides. The descending sequence of carbon sources utilization capability of isolates was A. sydowii (52.6%), M. luteus (39.5%), B. sphaericus (21.6%), and G. thermoglucosidasius (17.7%).

Assessment of permeable covers for odour reduction in piggery effluent ponds. 2. Field-scale trials

The efficacy of supported covers was investigated under field conditions using a series of prototypes deployed on an anaerobic pond treating typical piggery waste. Research focused on identifying effective cover support materials and deployment methods, quantifying odour reduction, and estimating the life expectancy of various permeable cover materials. Over a 10-month period, median odour emission rates were five to eight times lower from supported straw cover surfaces and a non-woven, spun fibre polypropylene weed control material than from the adjacent uncovered pond surface. While the straw covers visually appeared to degrade very rapidly, they continued to reduce odour emissions effectively. The polypropylene cover appeared to offer advantages from the perspectives of cost, reduced maintenance and ease of manufacture.

Simultaneous removal of H2S and NH3 in biofilter inoculated with Acidithiobacillus thiooxidans TAS

H2S and NH3 gases are toxic, corrosive and malodorous air pollutants. Although there are numerous well-established physicochemical techniques presently available for the treatment of these gases, the growing demand for a more economical and improved process has prompted investigations into biological alternatives. In biological treatment methods, H2S is oxidized to SO4(2-) by sulfur-oxidizing bacteria, and then NH3 is removed by chemical neutralization with SO4(2-) to (NH4)2SO4. Since the accumulated (NH4)2SO4 can inhibit microbial activity, it is important to utilize an effective sulfur-oxidizing bacterium that has tolerance to high concentrations of (NH4)2SO4 for the simultaneous removal of H2S and NH3. In this study, a sulfur-oxidizing bacterium with tolerance to high concentrations of (NH4)2SO4 was isolated from activated sludge and identified as Acidithiobacillus thiooxidans TAS. A. thiooxidans TAS could display its sulfur-oxidizing activity in a medium supplemented with 60 g.l(-1) (NH4)2SO4, even though its growth and sulfur-oxidizing activity were completely inhibited in 80 g.l(-1) (NH4)2SO4. When H2S alone was supplied to a ceramic biofilter inoculated with A. thiooxidans TAS, an almost 100% H2S removal efficiency was maintained until the inlet H2S concentration was increased up to 900 microl.l(-1) and the space velocity up to 500 h(-1), at which the amount of H2S eliminated was 810 g-S.m(-3).h(-1). However, when NH3 (50-500 microl.l(-1)) was simultaneously supplied to the biofilter with H2S, the maximum amount of H2S eliminated decreased to 650 g-S.m(-3).h(-1). The inhibition of H2S removal by low NH3 concentrations (50-200 microl.l(-1)) was similar to that by high NH3 concentrations (300-500 microl.l(-1)). The critical inlet H2S load that resulted in over 99% removal was determined as 400 g-S.m(-3).h(-1) in the presence of NH3.

Operational characteristics of effective removal of H2S and NH3 waste gases by activated carbon biofilter

Simultaneous removal of hydrogen sulfide (H2S) and ammonia (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.

Dynamic behavior of compost biofilters during periods of starvation and fluctuating hydrogen sulfide loadings

To understand transient-state performance of biofilters and the phenomena occurring during changes and interruptions in their operating conditions, dynamic behavior of biofilters exposed to shock loadings of contaminant (H2S) and periods of starvation has been investigated. The initial startup and the response of the biofilters to step changes in the H2S concentration and air-loading rate were also presented and discussed. Biofilters responded very effectively to H2S concentration spikes at H2S mass loading rates of 19.8-48.0 g/m3h by rapidly recovering their original removal rates within 1.2-20.2 min. The recovery time after each spike showed a positive correlation to the total amount of H2S loadings during the spike. Biofilters showed capabilities of withstanding 11-28 days of starvations and recovered their full performances after the starvations without any evident lag period.

Kinetic evaluation of H2S and NH3 biofiltration for two media used for wastewater lift station emissions

In this study, biofiltration using a natural wood chip medium and a commercial biofiltration medium was evaluated for the removal of moderate concentrations of hydrogen sulfide (H2S) (up to 100 parts per million by volume [ppmv]) in the presence of significant concentrations of ammonia (NH3). These levels were chosen as representative of wastewater lift station emissions in the Brownsville, TX, area. NH3-removing portions of the biofilms may compete with H2S-removing portions and inhibit H2S removal. H2S process removal efficiencies for the commercial and natural media ranged from 90 to 96% depending on inlet loading and media type and bed height. Kinetic analysis of the H2S removal process followed apparent first-order reaction behavior. The average first-order reaction rates were 0.03 sec(-1) for the commercial medium and 0.09 sec(-1) for the natural medium. Pressure drops across the columns ranged from 0.41 in. H2O/ft for the commercial medium to 1.41 in. H2O/ft for the natural medium. NH3 gas levels of up to 80 ppmv did not affect the H2S removal process efficiency, and calculated kinetic rate constants for H2S removal remained almost the same. The NH3 gas also was removed simultaneously with the H2S up to 98% removal efficiency by the commercial medium.

Effects of periods of nonuse and fluctuating ammonia concentration on biofilter performance

A systematic study on the transient behavior of odor treatment using biofilters is described. The biofilters were exposed to variations in contaminant loading and periods of nonuse. Two bench-scale biofilters with different filter media were used. Mixtures of compost/perlite (5:1) and dry sludge/granular active carbon (5:1) were used as filter media. Ammonia (NH3), one of the main malodorous gases, was used as the target compound. The response of each biofilter to variations in contaminant mass loading, periodic nonuse, water content, and inlet concentration pulse was studied. The nonuse period comprised of two stages: the "idle phase" when no air was passing through the biofilters, and the "no-contaminant-loading phase" when only humidified air was passing through the biofilters. Concentration spike was applied to study the effects of shock loading on the biofilter performance. Biofilters responded effectively to NH3 concentration variations and shock loading by rapidly recovering to the original removal rates within 6-12h. The results indicated re-acclimation times ranged from several hours to longer than a day. Longer idle phase produced longer re-acclimation periods than periods of no contaminant loading. When the media was dried during the biofiltration process, elimination capacity dropped accordingly for both biofilters. After 24 h of drying, the biofilter experiment could be restarted and run for a few days for recovering.

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.

Retrofitting existing chemical scrubbers to biotrickling filters for H2S emission control

Biological treatment is a promising alternative to conventional air-pollution control methods, but thus far biotreatment processes for odor control have always required much larger reactor volumes than chemical scrubbers. We converted an existing full-scale chemical scrubber to a biological trickling filter and showed that effective treatment of hydrogen sulfide (H2S) in the converted scrubber was possible even at gas contact times as low as 1.6 s. That is 8-20 times shorter than previous biotrickling filtration reports and comparable to usual contact times in chemical scrubbers. Significant removal of reduced sulfur compounds, ammonia, and volatile organic compounds present in traces in the air was also observed. Continuous operation for >8 months showed stable performance and robust behavior for H2S treatment, with pollutant-removal performance comparable to that achieved by using a chemical scrubber. Our study demonstrates that biotrickling filters can replace chemical scrubbers and be a safer, more economical technique for odor control.

Biological treatment process of air loaded with an ammonia and hydrogen sulfide mixture

The physico-chemical characteristics of granulated sludge lead us to develop its use as a packing material in air biofiltration. Then, the aim of this study is to investigate the potential of unit systems packed with this support in terms of ammonia and hydrogen sulfide emissions treatment. Two laboratory scale pilot biofilters were used. A volumetric load of 680 g H2S m(-3) empty bed day(-1) and 85 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to a unit called BGSn (column packed with granulated sludge and mainly supplied with hydrogen sulfide); a volumetric load of 170 g H2S m(-3) empty bed day(-1) and 340 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to the other called BGNs (column packed with granulated sludge and mainly supplied with ammonia). Ammonia and hydrogen sulfide elimination occur in the biofilters simultaneously. The hydrogen sulphide and ammonia removal efficiencies reached are very high: 100% and 80% for BGSn; 100% and 80% for BGNs respectively. Hydrogen sulfide is oxidized into sulphate and sulfur. The ammonia oxidation products are nitrite and nitrate. The nitrogen error mass balance is high for BGSn (60%) and BGNs (36%). This result could be explained by the denitrification process which would have occurred in anaerobic zones. High percentages of ammonia or hydrogen sulfide are oxidized on the first half of the column. The oxidation of high amounts of hydrogen sulfide would involve some environmental stress on nitrifying bacterial growth and activity.

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.