Effects of sulfur-metabolizing bacterial community diversity on H2S emission behavior in landfills with different operation modes

A critical review of sulfide and methane control in urban sewer systems using nitrogen compounds

Sewer gases, primarily hydrogen sulfide and methane, are detrimental to the wastewater infrastructure and environment by causing odour, corrosion, and greenhouse gas emissions. This article critically reviewed the dosing strategies, working mechanisms and effectiveness of widely used nitrogen compounds including nitrate, nitrite, free nitrous acid (FNA), free ammonia (FA), and organic silicon quaternary ammonium salt (QSA) in mitigating sewer emissions. Nitrate and nitrite play pivotal roles in increasing redox potentials and introducing microbial sulfide and methane oxidation. FNA and FA, known for their potent inhibitory and biocidal properties, effectively reduce sulfate reduction and methane production by disrupting cell membranes, altering intracellular pH, and blocking metabolic pathways. A systematic summary of the control effectiveness and associated change of microbial community were conducted based on different dosing strategies involving continuous or intermittent dosing patterns with constant, diurnal, dynamic and shock concentration profiles. Beyond their effectiveness in controlling emissions, nitrogen compounds like nitrite and FNA are effective in mitigating sewer concrete corrosion but also raise concerns about potential nitrous oxide (N2O) emissions. The innovative use of urine to produce FNA and FA may lead to a closed-loop strategy to achieve sustainable sewer emission control. This comprehensive review covering the dosing strategies, mechanisms, and effectiveness of nitrogen compounds will support the further development and optimal implementation.

Bioremediation of non-point hydrogen sulfide emissions using bacterial cellulose/activated carbon membrane

BACKGROUND

Hydrogen sulfide (H2S) gas, characterized by its low odor threshold and toxicity, poses significant challenges in non-point source odor management. Traditional biotechnologies are effective in removing malodorous gases from point sources but they are limited for non-point source odor control.

RESULTS

In this study, the sqr and pdo genes from Cupriavidus pinatubonensis JMP134 were introduced into the bacterial cellulose-producing strain Kosakonia oryzendophytica FY-07. This genetic modification enhanced the strain's sulfur oxidation capacity, which increased over time, with an average transformation capacity of approximately 275 mg·L- 1·day- 1. By incorporating 1% activated carbon, an efficient, naturally degradable bio-composite membrane was developed, achieving a maximum H2S adsorption capacity of 7.3 g·m- 3·day- 1. FY-07 remained stable in soil and improved the microbial community for H2S treatment.

CONCLUSION

The resulting bio-composite membrane is environment-friendly and efficient, making it suitable for emergency odor control in landfills. This study offers recommendations for using membrane materials in managing non-point hydrogen sulfide emissions.

Effect of incubation temperature on identification of key odorants of sewage sludge using headspace GC analysis

Currently, headspace gas chromatography-mass spectrometry is a widely used method to identify the key odorants of sludge. However, the effect of incubation temperature on the generation and emission of key odorants from sludge was still uncertain. Thus, in this paper, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-coupled ion mobility spectrometry (HS-GC-IMS) were carried out to analyze the volatiles emitted from the sludge incubated at different temperatures (30 °C, 50 °C, 60 °C, and 80 °C). The results indicated that the total volatile concentration of the sludge increased with temperatures, which affected the identified proportion of sludge key odorants to a certain extent. Differently from the aqueous solutions, the variation of volatile emission from the sludge was inconsistent with temperature changes, suggesting a multifactorial influence of incubation temperature on the identification of sludge odorants. The microbial community structure and adenosine triphosphate (ATP) metabolic activity of the sludge samples were analyzed at the initial state, 30 °C, and 80 °C. Although no significant effect of incubation temperature on the microbial community structure of the sludge, the incubation at 80 °C led to a noticeable decrease in microbial ATP metabolic activity, accompanied by a significant change in the proportion of odor-related microorganisms with low relative abundances. Changes in the composition and activity of these communities jointly contributed to the differences in odor emission from sludge at different temperatures. In summary, the incubation temperature affects the production and emission of volatiles from sludge through physicochemical and biochemical mechanisms, by which the microbial metabolism playing a crucial role. Therefore, when analyzing the key odorants of sludge, these factors should be considered.

Exploring the link between sulphur-containing compounds and noxious odours at waste management facilities: implications for odour monitoring and mitigation strategies

With this study we challenge the widely held assumption that sulphur-containing compounds in ambient air are good indicators of the presence noxious odours near waste management facilities. We analysed an extensive set of olfactometric data and data on the concentrations of hydrogen sulphide and trace sulphur compounds (TSCs) near a waste management facility in Croatia in 2021. The results show that the presence of noxious odours significantly correlates only with the concentrations of hydrogen sulphide and methyl mercaptan in ambient air but not with other measured TSCs. Thus, in addition to the measurement of pollutants in ambient air, Integrated Pollution and Prevention Control (IPPC) permits should mandate olfactometric measurements to detect and mitigate noxious odours near waste management facilities.

Localized intensification of arsenic methylation within landfill leachate-saturated zone

Leachate-saturated zone (LSZ) of landfills is a complicated biogeochemical hotspot due to the continuous input of electron donors and acceptors from the top refuse layer with leachate migration. In this study, the methylation behavior of the arsenic (As) was investigated. The results indicate that As-methylation processes are influenced by temperature fields in LSZ. The dimethylarsinic acid biotransformation capability can be enhanced with an increase in temperature. Microbial diversity, quantification of functional gene (arsM), and co-occurrence network analysis further characterized the drivers of As methylation in LSZ. As-biogeochemical cycle pathways, as well as As-functional gene distribution among different temperature fields, were modeled on the basis of KEGG annotation. Binning analysis was further employed to assemble As-methylated metagenomes, enabling the identification of novel species for As methylation in landfills. Then, 87 high-quality draft metagenome-assembled genomes (MAGs) were reconstructed from LSZ refuse samples; nearly 15 % (13 of 87) belonged to putative As-methylates functional MAGs. Combined with the model of the As-biogeochemical cycle, nine putative functional species could complete methylation processes alone. The findings of this study highlighted the temperature influence on the As-methylation behavior in LSZ and could facilitate the management of As contamination in landfills.

Effect of air and water on the release of chlorine from semi-aerobic landfill

Landfill leachate has a high chloride (Cl^-) content. Because it is highly mobile, and cannot be sorbed or transformed bio-chemically, it is important to have detailed information about how it migrates in landfill sites. In this study, we set up four lab-scale simulated landfills, including an anaerobic landfill (AL), an anaerobic landfill with leachate recirculation (RAL), an anaerobic/semi-anaerobic landfill with leachate recirculation (RASL), and an anaerobic/semi-aerobic landfill (ASL), to explore how, when regulated, moisture and air affected the migration of chlorine. We found that water and air had a strong influence on the release of Cl^-. Leachate obviously promoted Cl^- dissolution in refuse when recirculated. When air was introduced into landfill, thereby changing it from anaerobic to semi-aerobic, the leachate Cl^- concentration increased sharply from around 4-9 g L^-1 (RASL) and 18 g L^-1 (ASL), respectively. In principle, Cl^- is released continuously when leachate is recirculated in landfills (RAL and RASL), but it can also be found a terminal when the leachate recirculation stops (AL and ASL). Cumulative amounts of 64, 66, 27, and 53 g of Cl^- were released from the AL, RAL, RASL, and ASL, respectively. Lower COD/Cl and NH4+-N/Cl ratios in ASL and RASL after day 175 indicated that lower Cl^- pollution risk than that in AL and RAL.

Microbial Community Structure of Arsenic-Bearing Groundwater Environment in the Riverbank Filtration Zone

Arsenic (As) contamination of groundwater is a global public health problem. Microorganisms have a great effect on the migration and transformation of arsenic. Studying the effect of microbial community structure and function on arsenic release in the groundwater environment of the riverbank filtration zone has important theoretical and practical significance. In this paper, in-situ monitoring technology and molecular biology technology were used to study the microbial community in the process of river water infiltration in the Shenyang Huangjia water source, China. The results showed that the structure, diversity and abundance of the microbial community in groundwater were closely related to the arsenic content. Proteobacteria was the dominant phylum in groundwater of the study area, and Acinetobacter, Pseudomonas, Sulfuritalea, Sphingomonas and Hydrogenophaga etc. were the main dominant bacterial genera. In addition to reducing and oxidizing arsenic, these functional microorganisms also actively participated in the biogeochemical cycle of elements such as iron, manganese, nitrogen and sulfur. There was a significant correlation between dominant bacteria and environmental factors. Fe/Mn had a significant positive correlation with As, which brought potential danger to the water supply in high iron and manganese areas.

Sulfate-reduction behavior in waste-leachate transition zones of landfill sites

The sulfate reduction behavior of the waste-leachate transition zone of landfill was investigated at different temperatures and moisture contents. Marked differences in the sulfate reduction behavior were observed in the waste-leachate transition zone. The highest H₂S concentration was observed when the solid-to-liquid ratio was 1:3 at both temperatures. Although more leachate led to higher H₂S concentrations, the solid-to-liquid ratio was likely of subordinate significance compared with temperature. The microbial community was more unstable at 50 °C and more extensive mutualistic interactions among bacteria were observed, resulting in SRB showing a more violent response to changes in the solid-to-liquid ratio. At 25 °C, it's the opposite. A temperature of 25 °C was suitable for most SRB (such as Desulfomicrobium and Desulfobulbus), while some specific SRB that did not contain the functional genes (such as Dethiobacter and Anaerolinea) played a pivotal role in the significant differences in sulfate reduction behavior observed at 50 °C. This study provides a theoretical basis for controlling the release of H₂S from landfill.

Corrosion mitigation by nitrite spray on corroded concrete in a real sewer system

Microbially influenced concrete corrosion (MICC) in sewers is caused by the activity of sulfide-oxidizing microorganisms (SOMs) on concrete surfaces, which greatly deteriorates the integrity of sewers. Surface treatment of corroded concrete by spraying chemicals is a low-cost and non-intrusive strategy. This study systematically evaluated the spray of nitrite solution in corrosion mitigation and re-establishment in a real sewer manhole. Two types of concrete were exposed at three heights within the sewer manhole for 21 months. Nitrite spray was applied at the 6th month for half of the coupons which had developed active corrosion. The corrosion development was monitored by measuring the surface pH, corrosion product composition, sulfide uptake rate, concrete corrosion loss, and the microbial community on the corrosion layer. Free nitrous acid (FNA, i.e. HNO₂), formed by spraying a nitrite solution on acidic corrosion surfaces, was shown to inhibit the activity of SOMs. The nitrite spray reduced the corrosion loss of concrete at all heights by 40-90% for six months. The sulfide uptake rate of sprayed coupons was also reduced by about 35%, leading to 1-2 units higher surface pH, comparing to the control coupons. The microbial community analysis revealed a reduced abundance of SOMs on nitrite sprayed coupons. The long-term monitoring also showed that the corrosion mitigation effect became negligible in 15 months after the spray. The results consistently demonstrated the effectiveness of nitrite spray on the MICC mitigation and identified the re-application frequencies for full scale applications.

Identification of Plant Growth Promoting Rhizobacteria That Improve the Performance of Greenhouse-Grown Petunias under Low Fertility Conditions

The production of greenhouse ornamentals relies on high fertilizer inputs to meet scheduling deadlines and quality standards, but overfertilization has negative environmental impacts. The goals of this study were to identify plant-growth-promoting rhizobacteria (PGPR) that can improve greenhouse ornamental crop performance with reduced fertilizer inputs, and to identify the best measurements of plant performance for assessing the beneficial impact of PGPR on ornamentals. A high-throughput greenhouse trial was used to identify 14 PGPR isolates that improved the flower/bud number and shoot dry weight of Petunia × hybrida ‘Picobella Blue’ grown under low fertility conditions in peat-based media. These 14 PGPR were then applied to petunias grown under low fertility conditions (25 mg L⁻¹ N). PGPR-treated plants were compared to negative (untreated at 25 mg L⁻¹ N) and positive (untreated at 50, 75, 100, and 150 mg L⁻¹ N) controls. Multiple parameters were measured in the categories of flowering, vegetative growth, and vegetative quality to determine the best measurements to assess improvements in ornamental plant performance. Caballeronia zhejiangensis C7B12-treated plants performed better in almost all parameters and were comparable to untreated plants fertilized with 50 mg L⁻¹ N. Genomic analysis identified genes that were potentially involved in plant growth promotion. Our study identified potential PGPR that can be used as biostimulants to produce high-quality greenhouse ornamentals with lower fertilizer inputs.

Arsenic transformation behavior mediated by arsenic functional genes in landfills

Landfill arsenic pollution is a complicated problem because of the sophisticated species and transformation of fractions involved. This study investigated arsenic transformation behavior from the viewpoint of arsenic functional genes based on analysis of 29 aged refuse samples collected from 11 sanitary landfills in 10 cities in Zhejiang Province, China. Arsenic species distribution varied significantly with landfill process. Landfill contains rich arsenic resistant microbes. arrA genes were the key factor responsible for arsenic transformation and migration in landfill. Although the abundance of aioA genes was the lowest among the four tested arsenic functional genes, it was the second important genes for arsenic distribution. Microbial metabolic activity was the main cause of arsenic transformation, and arsenate reduction by microbes was a key driver of arsenic mobilization in landfills. Moreover, arsenate was reduced to arsenite and further methylated to monomethylarsine (MMA) and dimethylarsine (DMA), decreasing the total arsenic content during the landfill process, but also inducing a new risk because of the arsenic effluent will be more easily as the state of arsenite, MMA, and DMA in the liquid phase. Overall, this study provides a picture of arsenic species transformation and insight into key roles involved in arsenic pollution during landfill processes.

Effect of substrate sulfur state on MM and DMS emissions in landfill

Methyl mercaptan (MM) and dimethyl sulfide (DMS) are typical landfill odorous gases that have received little attention compared with hydrogen sulfide (H₂S). In this study, landfill MM and DMS emissions were investigated regarding their origin from substrates with different sulfur states, namely, intrinsic organic sulfur and external inorganic sulfur (SO₄^2-). Substrates with high protein contents showed the highest potential for MM and DMS emissions, at 46.0 and 9.2 μL·g^-1 substrate, respectively. Meanwhile, a comparable contribution by SO₄^2- was achieved when the SO₄^2- content comprised over 40% of the substrate. The substrate contribution to DMS emission was up to 10 times the SO₄^2- contribution. Meanwhile, the SO₄^2- contribution to MM emission was over 1000 times that to DMS emissions. MM and DMS can accumulate in landfill sites and then be transformed into H₂S or sulfide (S^2-). This research offers a comprehensive understanding of MM and DMS emissions in landfill and provides a basis for classification management methods in landfill sites.

Sulfate reduction behavior in the leachate saturated zone of landfill sites

Municipal solid waste landfills are considered one of the most important parts of the sulfur cycle. However, few studies have focused on sulfate reduction in the leachate saturated zone, where the temperature may be variable. In this work, the sulfate reduction behavior was evaluated in a landfill leachate saturated zone under temperatures between 30 and 80 °C. The results show that microbial sulfate reduction is high in the saturated zone, especially when the temperature is at 50-60 °C. The microbial diversity and the abundance of functional genes results reveal that specific sulfate-reducing bacteria such as Dethiobacter, the bacteria that offer energy to them, and genes other than dsrA and dsrB may have a close relationship with the variation in the reduction of sulfate. This work may improve the knowledge of sulfate reduction in the landfill sites and therefore offer theoretical support to management strategies.

In-situ biodegradation of volatile organic compounds in landfill by sewage sludge modified waste-char

VOCs are the major harmful pollutants released from MSW landfills, which are toxicity to human health. In order to in-situ biodegradation of VOCs released from landfill, two novel laboratory-scale biocovers, including waste-char obtained from MSW pyrolysis (WC), and sewage sludge modified the WC (SWC), are used to degradate VOCs. The removal performances of VOCs as well as the bacterial community in the WC and SWC are investigated in a simulated landfill systems with the contrast experiment of a landfill cover soil (LCS) for 60 days. Meanwhile, the adsorption-biodegradation of VOCs model compounds over the LCS, WC, and SWC are also tested in fixed-bed adsorption reactor and in-situ FTIR. The VOCs removal efficiencies by the SWC are maintained above 85% for a long-term, much higher than that of the LCS and WC. The higher removal efficiencies and long-term stability for VOCs degradation in SWC are attributed to a strongly positive synergistic between adsorption and biodegradation that the gaseous VOCs released from MSW is effectively adsorbed by the SWC due to its higher VOCs adsorption capacity, and then the adsorbed-VOCs is converted into CO₂ and H₂O by the microorganisms that consuming the adsorbed-VOCs as energy and carbon sources. Subsequently, the decrease of the adsorbed-VOCs in SWC would also promote the transformation of the gaseous VOCs into the adsorbed VOCs and accelerate the growth of microorganisms by taking the adsorbed-VOCs as the energy and carbon source, resulted in a higher adsorption rate and degradation rate for VOCs.

Simultaneous mitigation of methane and odors in a biowindow using a pipe network

In this study, a biowindow with a piped gas collection network is proposed as an area-efficient landfill gas treatment system. A 9-m² biowindow was constructed for treating landfill gas collected from an area of 450 m² in a sanitary landfill, and its performance was evaluated for 224 days. The methane removal efficiency was 59-100% at 146.3-675.1 g-CH₄ m^-2 d^-1. Odorous compounds were also removed by the biowindow, with a complex odor intensity removal rate of 93-100%. In particular, the removal efficiency for hydrogen sulfide and methanethiol, major contributors to the complex odor intensity, was 97% and 91%, respectively. Metagenomic analysis showed that the dominant bacterial genera shifted from Acinetobacter and Pseudomonas to Methylobacter and Methylocaldum due to the high concentration of methane. A high bacterial diversity was maintained, which may have contributed to the robust performance of the biowindow against environmental fluctuations. At 1/50th of the size of conventional biocovers, the proposed biowindow can greatly reduce the required installation area and represents a competitive method for the simultaneous treatment of methane and odor in landfills.

Odor removal by and microbial community in the enhanced landfill cover materials containing biochar-added sludge compost under different operating parameters

Odor problem has become a growing concern for municipal solid waste (MSW) operators and communities located close to landfill sites. In this study, nine laboratory-scale landfill reactors were used to simulate in-situ odor control by a novel landfill cover material consisting of biochar-added sludge compost under various operating parameters. Characterization of odor removal and microbial community in the cover layer under various operating parameters was conducted using gas chromatograph-mass spectrometry and 454 high-throughput pyrosequencing, respectively. Results showed that H₂S (76.9-86.0%) and volatile organic sulfur compounds (VOSCs) (12.3-21.7%) were dominant according to their theoretical generated odor concentrations. The total odor REs calculated using the theoretical odor concentrations in the landfill reactors were different than using the measured odor values, which were ranked from high to low as: R6 > R5 > R7 > R4 > R8 > R9 > R3 > R2 > R1, showing the largest discrepancy of 25.3%. The optimum combination of operating parameters based on the theoretical odor concentration was different with that based on the measured odor concentrations. Moreover, although Firmicutes (12.21-91.48%), Proteobacteria (3.55-51.03%), and Actinobacteria (4.01-47.39%) were in general the three major bacterial phyla found in the landfill covers, the detailed bacterial communities in the cover materials of the simulated reactors varied with various operating parameters. Alicyclobacillus and Tuberibacillus showed positive correlations with the removal efficiencies (REs) of chlorinated compounds, H₂S, aromatic compounds, volatile organic sulfur compounds (VOSCs), and organic acids. The correlations of Rhodanobacter, Gemmatimonas, Flavisolibacter and Sphingomonas were strongly positive with ammonia RE and relatively positive with REs of organic acids, VOSCs, and aromatic compounds. These findings are instrumental in understanding the relationship between the structure of microbial communities and odor removal performances, and in developing techniques for in-situ odor control at landfills.

Genome analysis and -omics approaches provide new insights into the biodegradation potential of Rhodococcus

The past few years observed a breakthrough of genome sequences of bacteria of Rhodococcus genus with significant biodegradation abilities. Invaluable knowledge from genome data and their functional analysis can be applied to develop and design strategies for attenuating damages caused by hydrocarbon contamination. With the advent of high-throughput -omic technologies, it is currently possible to utilize the functional properties of diverse catabolic genes, analyze an entire system at the level of molecule (DNA, RNA, protein, and metabolite), simultaneously predict and construct catabolic degradation pathways. In this review, the genes involved in the biodegradation of hydrocarbons and several emerging plasticizer compounds in Rhodococcus strains are described in detail (aliphatic, aromatics, PAH, phthalate, polyethylene, and polyisoprene). The metabolic biodegradation networks predicted from omics-derived data along with the catabolic enzymes exploited in diverse biotechnological and bioremediation applications are characterized.

Performance evaluation of an on-site biocomplex textile as an alternative daily cover in a sanitary landfill, South Korea

The performance of a biocomplex textile prototype was evaluated as an alternative daily cover at an operational landfill site to mitigate odors and methane. The biocomplex textile prototype consisted of two layers of nonwoven fabric and biocarrier immobilized microorganisms and showed excellent removal of odors and methane compared to landfill cover soil. The complex odor intensity (odor dilution ratio (ODR)) on the surface of landfill cover soil was 1,000-10,000 ODR (average of 4,204 ODR), whereas it was 5-250 ODR (average of 55 ODR) on the surface of biocomplex textile. Hydrogen sulfide, which contributes a significant odor intensity, had an average concentration on the biocomplex textile of 8.64 parts-per-billion (ppb), compared to 1733.21 ppb on the landfill cover soil. The biocomplex textile also showed effective methane removal with methane concentrations of 0-1.2% (average of 0.3%) on the biocomplex textile compared to 0-20% (average of 5.3%) on the landfill cover soil. Bacterial community diversity in the biocomplex textile increased with time until an operating period of 66 days, after which diversity indices were maintained at a constant level. The dominant species were the methanotrophs Methylocaldum and Methylobacter, and the non-methanotrophs Acinetobacter, Serpens, Ohtaekwangia, and Actinophytocola. These results demonstrate that on-site biocomplex textile is a suitable alternative daily cover to mitigate odors and methane in landfills.

A novel aerobic sulfate reduction process in landfill mineralized refuse

It is thought that mineralized refuse could be excavated from almost-full landfill sites to provide space for the increasing burden of municipal solid waste. When excavating, however, the H₂S emissions from the mineralized waste need to be considered carefully. In an attempt to understand how H₂S emissions might change during this excavation process, we carried out a series of tests, including exposing anaerobic mineralized refuse to oxygen, isolating and determining possible functional bacteria, and characterizing the electron donors and/or acceptors. The results showed that H₂S would be released when landfill mineralized refuse was exposed to oxygen (O₂), and could reach concentrations of 6 mg m^-3, which was 3 times the concentrations of H₂S released from anaerobic mineralized refuse. Sulfur-metabolized microorganisms accounted for only 0.5% of the microbial functional bacteria (MFB) derived from the mineralized refuse when exposed to O₂ for 60 days, and SRB were not present. The MFB maintained H₂S production by aerobic sulfate reduction using SO₄^2- and S₂O₃^2- as electron acceptors, and sulfate-reducing rates of 16% and 55%, respectively, were achieved. Lactate and S₂O₃^2- were the preferred electron donor and acceptor, respectively. By enhancing the carbon source and electron transfer, MFB may undergo strong aerobic sulfate reduction even at low abundances of sulfur-metabolized microorganisms.

Odor mitigation and bacterial community dynamics in on-site biocovers at a sanitary landfill in South Korea

Unpleasant odors emitted from landfills have been caused environmental and societal problems. For odor abatement, two pilot-scale biocovers were installed at a sanitary landfill site in South Korea. Biocovers PBC1 and PBC2 comprised a soil mixture with different ratios of earthworm casts as an inoculum source and were operated for 240 days. Their odor removal efficiencies were evaluated, and their bacterial community structures were characterized using pyrosequencing. In addition, the correlation between odor removability and bacterial community dynamics was assessed using network analysis. The removal efficiency of complex odor intensity in the two biocovers ranged from 81.1% to 97.8%. Removal efficiencies of sulfur-containing odors (hydrogen sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide), which contributed most to complex odor intensity, were greater than 91% in both biocovers. Despite the fluctuations in ambient temperature (-8.2 to 31.3 °C) and inlet complex odor intensity (10,000-42,748 of odor dilution ratio), biocovers PBC1 and PBC2 displayed stable deodorizing performance. A high ratio of earthworm casts as an inoculum source led to high odor removability during the first 25 days of operation, but different mixing ratios of earthworm casts did not significantly affect overall odor removability. A bacterial community analysis showed that Methylobacter, Arthrobacter, Acinetobacter, Rhodanobacter, and Pedobacter were the dominant genera in both biocovers. Network analysis results indicated that Steroidobacter, Cystobacter, Methylosarcina, Solirubrobacter, and Pseudoxanthomonas increased in relative abundance with time and were major contributors to odor removal, although these bacteria had a relatively low abundance compared to the overall bacterial community. These data contribute to a more comprehensive understanding of the relationship between bacterial community dynamics and deodorizing performance in biocovers.

Biodesulfurization of sulfide wastewater for elemental sulfur recovery by isolated Halothiobacillus neapolitanus in an internal airlift loop reactor

The biodesulfurization of sulfide wastewater for elemental sulfur recovery by isolated Halothiobacillus neapolitanus in an internal airlift loop reactor (IALR) was investigated. The flocculant producer Pseudomonas sp. strain N1-2 was used to deposit the produced elemental sulfur during biodesulfurization. The functional group analysis indicated that biofloculation was closely associated with NH and CO. The biodesulfurization system performed well under moderate water quality fluctuations (1.29-3.88 kg·m^-3·d^-1 COD; 1.54-3.08 kg·m^-3·d^-1·S^2-) as it maintained stable S^2- removal and sulfur flocculation rates. Meanwhile, the qRT-PCR analysis indicated that the transcriptional level of cbbL decreased in the presence of organic carbon, while the expressions of sqr, sat, and cytochrome C3 increased under higher sulfide stress. Moreover, the relative proportions of Halothiobacillus was strengthened via microbial intervention of the LJN1-3 strain. The S^2- removal efficiency and elemental sulfur production was further improved by 32.5% and 28.2%, respectively, in an IALR.