The performance of a two-layer biotrickling filter filled with new mixed packing materials for the removal of H2S from air

Biodegradation of carbon disulfide and hydrogen sulfide using a moving bed biofilm reactor coupled with sulfur recycling: Performance, mechanism, and potential application

In this work, a moving bed biofilm reactor (MBBR) was equipped for simultaneous biodegradation of CS2 and H2S. MBBR was started up and operated with different inlet concentrations and retention time; results indicated that approximately 81.9% CS2 and 93.9% H2S could be degraded, and the maximum elimination capacities of 209.3 g/(m3·h) and 138.5 g/(m3·h) were achieved for CS2 and H2S, respectively. The biodegradation mechanisms, including mass transfer, kinetics, and electron transfer, were then investigated. The mass transfer fraction and the maximum degradation rate per unit filter volume were calculated for evaluating the characteristics of mass transfer in MBBR. The variations of extracellular polymeric substances secretion, electron transport system activity and ATP enzyme activity showed that MBBR had an excellent performance for waste gas purification. Subsequently, the recovery of sulfur was explored via morphology, crystal structure, and generation kinetics, indicating that a modified Gompertz model could precisely describe the kinetics of sulfur recovery, and the product selectivity of 51.7% was achieved for sulfur. The microbial community analysis suggested that the dominant genera for biodegradation and sulfur recovery were Acidithiobacillus and Mycobacterium. Finally, MBBR system was validated for treatment of actual waste gas; results indicated that maximum elimination capacities of 134.1 g/(m3·h) and 117.1 g/(m3·h) were obtained for CS2 and H2S, respectively, suggesting that MBBR had the potential for application.

Odor and volatile organic compounds biotreatment using compact trickle bed bioreactors (CTBB) in a wastewater treatment plant

The main aim of this study was to optimize and maximize the impacts of odor and volatile organic compounds (VOCs) biodegradation in a wastewater treatment plant utilizing a pilot-scale compact trickle bed bioreactor (CTBB). A CTBB was built and tested for its long-term performance during which gases were supplied from the tank containing semi-liquid fats, oils, and fat waste. The concentrations of pollutants ranged from 0 to 140.75 mg/m³ H₂S, 0 to 2500 mg/m³ VOCs, and 0 to 21.5 mg/m³ NH₃. The CTBB was tested at different gas flow rates and at two pH values for the liquid phase: pH = 7.0 and 5.0. In the liquid phase, the pollutant removal efficiency was higher at pH = 7.0 than at pH = 5.0. Overall, the removal efficiency was between 81.5 % and 99.5 % for the VOCs and 87.5 % and 98.9 % for H₂S, while NH₃ removals were >99 %.

Absorption processes in reducing the odor nuisance of wastewater

Deep social awareness, especially in highly developed countries, imposes pressure on entrepreneurs and service providers, forcing them to undertake effective actions to minimize the effects of their activities also in terms of the emission of malodorous substances. The article presents information on the absorption processes harnessed in the deodorization of gases from wastewater management and the characteristics of these gases. Avoiding emissions is not always possible, hence there is a need to conduct an inventory of such gases and use deodorization methods. The specificity of gases from wastewater management and their prevalence urge the search for cheap and easy-to-use deodorization methods. It is obvious that the selection of deodorization technology is driven by many factors and should be preceded by a thorough analysis of the possibilities and limitations of various solutions. The aim of this article is, therefore, to present the characteristics of gases from wastewater management and to discuss various technologies based on absorption processes as a technology for deodorizing such gases in order to help potential investors choose an emission-reducing method suitable for particular conditions.•Malodorous substances in wastewater management.•Deodorization using water and chemical absorption.•Deodorization using biological purification.

Enhancement of H2S sensing performance of rGO decorated CuO thin films: experimental and DFT studies

We demonstrate a highly selective and sensitive Cupric oxide (CuO) thin film-based low concentration Hydrogen sulfide (H₂S) sensor. The sensitivity was improved around three times by decorating with reduced graphene oxide (rGO) nanosheets. CuO thin films were deposited by Chemical Vapor Deposition followed by inter-digital electrode fabrication by a thermal evaporations system. The crystal structure of CuO was confirmed by x-ray diffraction. The sensing response of pristine CuO was found around 54% at 100 °C to 100 ppm of H₂S. In contrast, the sensing response was enhanced to 167% by decorating with rGO of 1.5 mg ml^-1concentration solution. The sensing was improved due to the formation of heterojunctions between the rGO and CuO. The developed sensor was examined under various gas environments and found to be highly selective towards H₂S gas. The improvement in sensing response has been attributed to increased hole concentration in CuO in the presence of rGO due to the Fermi level alignment and increased absorption of H₂S molecules at the rGO/CuO heterojunction. Further, electronic structure calculations show the physisorption behavior of H₂S molecules on the different adsorption sites. Detailed insight into the gas sensing mechanism is discussed based on experimental results and electronic structure calculations.

Removal of Hydrogen Sulfide from Swine-Waste Biogas on a Pilot Scale Using Immobilized Paracoccus versutus CM1

Hydrogen sulfide (H2S) is a toxic and corrosive component that commonly occurs in biogas. In this study, H2S removal from swine-waste biogas using sulfur-oxidizing Paracoccus versutus CM1 immobilized in porous glass (PG) and polyurethane foam (PUF) biofilters was investigated. Bacterial compositions in the biofilters were also determined using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The biofilters were first tested on a laboratory scale under three space velocities (SV): 20, 30, and 40 h−1. Within 24 h, at an SV of 20 h−1, PG and PUF biofilters immobilized with P. versutus CM1 removed 99.5% and 99.7% of H2S, respectively, corresponding to the elimination capacities (EC) of 83.5 and 86.2 gm−3 h−1. On a pilot scale, with the horizontal PG-P. versutus CM1 biofilter operated at an SV of 30 h−1, a removal efficiency of 99.7% and a maximum EC of 113.7 gm−3 h−1 were achieved. No reduction in methane content in the outlet biogas was observed under these conditions. The PCR-DGGE analysis revealed that Paracoccus, Acidithiobacillus, and Thiomonas were the predominant bacterial genera in the biofilters, which might play important roles in H2S removal. This PG−P. versutus CM1 biofiltration system is highly efficient for H2S removal from swine-waste biogas.

Evaluation of continuous and intermittent trickling strategies for the removal of hydrogen sulfide in a biotrickling filter

Biotrickling filter (BTF) is a widely applied bioreactor for odour abatement in sewer networks. The trickling strategy is vital for maintaining a sound operation of BTF. This study employed a lab-scale BTF packed with granular activated carbon at a short empty bed residence time of 6 s and pH 1-2 to evaluate different trickling strategies, i.e., continuous trickling (different velocities) and intermittent trickling (different trickling intervals), in terms of the removal of hydrogen sulfide (H₂S), bed pressure drop, H₂S oxidation products and microbial community. The H₂S removal performance decreased with the trickling velocity (∼3.6 m/h) in BTF. In addition, three intermittent trickling strategies, i.e., 10-min trickling per 24 h, 8 h, and 2 h, were investigated. The H₂S elimination capacity deteriorated after about 2 weeks under both 10-min trickling per 24 h and 8 h. For both intermittent (10-min trickling per 2 h) and continuous trickling, the BTF exhibited nearly 100 % H₂S removal for inlet H₂S concentrations<100 ppmv, but intermittent BTF showed better removal performance than continuous trickling when inlet H₂S increased to 120-190 ppmv. Furthermore, the bed pressure drops were 333 and 3888 Pa/m for non-trickling and trickling periods, respectively, which makes intermittent BTF save 83 % energy consumption of the blower compared with continuous tirckling. However, intermittent BTF exhibited transient H₂S breakthrough (<1 ppmv) during trickling periods. Moreover, elemental sulfur and sulfate were major products of H₂S oxidation and Acidithiobacillus was the dominant genus in both intermittent and continuous trickling BTF. A mathematical model was calibrated for the intermittent BTF and a sensitivity analysis was performed on the model. It shows mass transfer parameters determine the H₂S removal. Overall, intermittent trickling strategy is promising for improving odour abatement performance and reducing the operating cost of the BTF.

Interaction of tetrahydrofuran and methyl tert-butyl ether in waste gas treatment by a biotrickling filter bioaugmented with Piscinibacter caeni MQ-18 and Pseudomonas oleovorans DT4

Bioaugmented biotrickling filter (BTF) seeded with Piscinibacter caeni MQ-18, Pseudomonas oleovorans DT4, and activated sludge was established to investigate the treatment performance and biodegradation kinetics of the gaseous mixtures of tetrahydrofuran (THF) and methyl tert-butyl ether (MTBE). Experimental results showed an enhanced startup performance with a startup period of 9 d in bioaugmented BTF (25 d in control BTF seeded with activated sludge). The interaction parameter I_2,1 of control (7.462) and bioaugmented BTF (3.267) obtained by the elimination capacity-sum kinetics with interaction parameter (EC-SKIP) model indicated that THF has a stronger inhibition of MTBE biodegradation in the control BTF than in the bioaugmented BTF. Similarly, the self-inhibition EC-SKIP model quantified the positive effects of MTBE on THF biodegradation, as well as the negative effects of THF on MTBE biodegradation and the self-inhibition of MTBE and THF. Metabolic intermediate analysis, real-time quantitative polymerase chain reaction, biofilm-biomass determination, and high-throughput sequencing revealed the possible mechanism of the enhanced treatment performance and biodegradation interactions of MTBE and THF.

Full-Scale Odor Abatement Technologies in Wastewater Treatment Plants (WWTPs): A Review

The release of air pollutants from the operation of wastewater treatment plants (WWTPs) is often a cause of odor annoyance for the people living in the surrounding area. Odors have been indeed recently classified as atmospheric pollutants and are the main cause of complaints to local authorities. In this context, the implementation of effective treatment solutions is of key importance for urban water cycle management. This work presents a critical review of the state of the art of odor treatment technologies (OTTs) applied in full-scale WWTPs to address this issue. An overview of these technologies is given by discussing their strengths and weaknesses. A sensitivity analysis is presented, by considering land requirements, operational parameters and efficiencies, based on data of full-scale applications. The investment and operating costs have been reviewed with reference to the different OTTs. Biofilters and biotrickling filters represent the two most applied technologies for odor abatement at full-scale plants, due to lower costs and high removal efficiencies. An analysis of the odors emitted by the different wastewater treatment units is reported, with the aim of identifying the principal odor sources. Innovative and sustainable technologies are also presented and discussed, evaluating their potential for full-scale applicability.

Screening and study of the degradation characteristics of efficient toluene degrading bacteria combinations

In this paper, three effective toluene-degrading bacteria were obtained through acclimation and screening by using landfill leachate as the initial liquid strain. The three obtained bacteria were denoted as J1, J2 and J3, and identified as Pseudomonas, Bacillus and Staphylococcus, respectively. We then identified the optimal combination of these toluene-degrading bacteria in the laboratory. The combination of J1 + J3 (1:1) exhibited the highest toluene removal efficiency (RE). A vertical bio-trickling filter (BTF) packed with ceramsite was started by inoculation with the effective combination. The performance of the BTF in treating toluene under various operating conditions was investigated. After 17 days of operation, the toluene RE reached about 90% and the maximum elimination capacity reached 42.0 g m^-3 h^-1. The scanning electron microscope (SEM) showed that after the successful start-up of the BTF, the biofilm on the packing surface primarily consisted of Bacillus and Staphylococcus. During the stable state, the RE of the BTF was maintained above 80%, the shortest empty bed residence time was 34 s and toluene concentrations ranged between 300 and 800 mg m^-3. The results indicate that the BTF started using the effective combination of bacteria described here is robust. This paper also provides a preliminary analysis of the mechanism of microbial degradation of pollutants in the BTF.

Assessment of hydrogen sulfide emission in a wastewater pumping station

Wastewater collection systems can be a source of odors that lead to complaints from plant workers, the public, and nearby property owners. The primary source of odors released from such systems is the presence of hydrogen sulfide (H₂S) gas at high concentrations. This study was conducted in the main pumping station in Kuwait with a capacity of 570,000 m³/day to assess H₂S gas emission, determine factors affecting H₂S generation, and evaluate the effectiveness of the odor control system comprising stripping using sodium hydroxide and carbon adsorption. Yearly data on wastewater flow rate, temperature, pH, BOD₅, and H₂S were obtained from plant records over the years 2013-2015, as well as monthly data measurements were conducted during May to December 2016, and weekly data were collected during a plant monitoring program in March and April 2017. Statistical analysis showed seasonal, daily, and hourly variations in H₂S concentrations, with higher values reported in summer, cyclic hourly patterns obtained daily, and peak H₂S level of 10 ppm recorded at 7 pm and 40 °C. The ANOVA test indicated that the wastewater temperature, flow rate, and BOD₅ were statistically significant factors affecting the formation of hydrogen sulfide gas because of the strong correlation and a p value less than the significance level of 0.05. It was evident that the wastewater temperature is the most influential factor. A model was developed to predict H₂S emission. The odor control system used in the station proved to be highly effective and able to remove up to 99.9% of H₂S released from wastewater.

Comparative evaluation on the utilization of applied electrical potential in a conductive granule packed biotrickling filter for continuous abatement of xylene: Performance, limitation, and microbial community

This study investigates the use of electrically conductive granules as packing material in biotrickling filter (BTF) systems as to provide insights on the specific microbial abundance and functions during the treatment of xylene-containing waste gas. In addition, the effect of applied potential on attached biofilm on conductive granules during xylene degradation was briefly investigated. During stable operation period, the conductive granules packed BTF achieved reactor performance of no less than 80% with a maximum EC of 137.7 g/m³ h. Under applied potential of 1V, the BTF system showed deterioration of xylene removal by ranging from 21 to 76%, which also affected the distribution and relative abundance of the major microorganisms such as Xanthobacter, Acidovorax, Rhodococcus, Hydrogenophaga, Arthrobacter, Brevundimonas, Pseudoxanthomonas, Devosia, Shinella, Sphingobium, Dokdonella, Pseudomonas and Bosea. The acclimation of applied potential led to the enrichment of autotrophic bacteria and strains, which are correlated to improved nitrogen cycling. In general, applying electrical potential is feasible to shape the microbiological structure of biofilms to selectively adjust their biochemical functions.

Preparation and Evaluation of a Composite Filler Micro-Embedded with Pseudomonas putida for the Biodegradation of Toluene : Preparation of composite filler with high toluene removal efficiency

The main objective of this study was to evaluate the performance of a self-developed filler micro-embedded with Pseudomonas putida (P. putida) for toluene removal in a biofilter under various loading rates. The results show that the biofilter could reach 85% removal efficiency (RE) on the eighth day and remain above 90% RE when the empty bed residence time (EBRT) was 18 s and the inlet loading was not higher than 41.4 g m−3 h−1. Moreover, the biofilter could tolerate substantial transient shock loadings. After two shut-down experiments, the removal efficiency could be restored to above 80% after a recovery period of three days and six days, respectively. Sequence analysis of the 16S rRNA gene of fillers in four operating periods revealed that the highly efficient bacterial colonies in fillers mainly included Firmicutes, Actinobacteria and Proteobacteria and that the abundance of Bacteroidetes increased significantly during the re-start period.

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.

Application of a compact trickle-bed bioreactor for the removal of odor and volatile organic compounds emitted from a wastewater treatment plant

A compact trickle-bed bioreactor (CTBB) was tested for the removal of volatile organic compounds (VOCs) and hydrogen sulphide (H₂S) present in the exhaust air of a wastewater treatment plant. At gas-flow rates varying between 2.0 and 30.0 m³/h and for specific pollutant loads up to 20 g/(m³·h), removal efficiencies for H₂S and VOC were >95%. The CTBB was designed for a maximum H₂S concentration of ∼200 ppm and removal efficiencies >97% were noticed. VOC concentrations were in the range of 25-240 ppm_v and the removal efficiency was in the range of 85-99%. Possible consequences of an excessive pollutant overload and the time required for regenerating the microbial activity and reviving stable process conditions in the CTBB were also investigated. An increase in the H₂S concentration from 400 to 600 ppm_v for a few hours caused bioreactor poisoning; however, when original H₂S concentrations were restored, stable CTBB operation was ascertained within 3 h.

Technologies for deodorization of malodorous gases

There is an increasing number of citizens' complaints about odor nuisance due to production or service activity. High social awareness imposes pressure on entrepreneurs and service providers forcing them to undertake effective steps aimed at minimization of the effects of their activity, also with respect to emission of malodorous substances. The article presents information about various technologies used for gas deodorization. Known solutions can be included into two groups: technologies offering prevention of emissions, and methodological solutions that enable removal of malodorous substances from the stream of emitted gases. It is obvious that the selection of deodorization technologies is conditioned by many factors, and it should be preceded by an in-depth analysis of possibilities and limitations offered by various solutions. The aim of the article is presentation of the available gas deodorization technologies as to facilitate the potential investors with selection of the method of malodorous gases emission limitation, suitable for particular conditions.

Comparative Evaluation of Selected Biological Methods for the Removal of Hydrophilic and Hydrophobic Odorous VOCs from Air

Due to increasingly stringent legal regulations as well as increasing social awareness, the removal of odorous volatile organic compounds (VOCs) from air is gaining importance. This paper presents the strategy to compare selected biological methods intended for the removal of different air pollutants, especially of odorous character. Biofiltration, biotrickling filtration and bioscrubbing technologies are evaluated in terms of their suitability for the effective removal of either hydrophilic or hydrophobic VOCs as well as typical inorganic odorous compounds. A pairwise comparison model was used to assess the performance of selected biological processes of air treatment. Process efficiency, economic, technical and environmental aspects of the treatment methods are taken into consideration. The results of the calculations reveal that biotrickling filtration is the most efficient method for the removal of hydrophilic VOCs while biofilters enable the most efficient removal of hydrophobic VOCs. Additionally, a simple approach for preliminary method selection based on a decision tree is proposed. The presented evaluation strategies may be especially helpful when considering the treatment strategy for air polluted with various types of odorous compounds.

Performance and microbial community evolution of toluene degradation using a fungi-based bio-trickling filter

Fungi have their unique advantages in capturing and degrading hydrophobic VOCs. To study the performance of fungi-based bio-trickling filters (BTFs) with respect to the degradation of toluene, and the succession process of the fungal colony under different operating conditions, a three-layer BTF packed by dominant Fusarium oxysporum immobilized with ceramic particles were set up. The fungal BTF started quickly within 7 days and restarted less than 7 days after starvation; its average RE was higher than 92.5% when the toluene inlet loading rate (ILR) ranging from 7.0 to 100.9 g m^-3 h^-1 at steady state. Moreover, the maximum elimination capacity (EC) of 98.1 g m^-3 h^-1 was obtained at a toluene ILR of 100.3 g m^-3 h^-1. The microorganism analysis of time and space revealed that the dominant fungi Fusarium were replaced by Paramicrosporidium saccamoebae after a certain evolutionary period. The intermediate layer had more microbes and a more complex community than the other two layers, and was more suitable for the survival of the varieties of microbes.

Recent progress and perspectives in biotrickling filters for VOCs and odorous gases treatment

Pollution caused by volatile organic compounds (VOCs) and odorous pollutants in the air can produce severe environmental problems. In recent years, the emission control of VOCs and odorous pollutants has become a crucial issue owing to the adverse effect on humans and the environment. For treating these compounds, biotrickling filter (BTF) technology acts as an environment friendly and cost-effective alternative to conventional air pollution control technologies. Besides, low concentration of VOCs and odorous pollutants can also be effectively removed using BTF systems. However, the VOCs and odorants removal performance by BTF may be limited by the hydrophobicity, toxicity, and low bioavailability of these pollutants. To solve these problems, this review summarizes the design, mechanism, and common analytical methods of recent BTF advances. In addition, the operating conditions, mass transfer, packing materials and microorganisms (which are the critical parameters in a BTF system) were evaluated and discussed in view of improving the removal performance of BTFs. Further research on these specific topics, together with the combination of BTF technology with other technologies, should improve the removal performance of BTFs.

A solid composite microbial inoculant for the simultaneous removal of volatile organic sulfide compounds: Preparation, characterization, and its bioaugmentation of a biotrickling filter

Volatile organic sulfide compounds (VOSCs) are usually resistant to biodegradation, thereby limiting the performance of traditional biotechnology dealing with waste gas containing such pollutants especially in mixture. In this study, a solid composite microbial inoculant (SCMI) was prepared to remove dimethyl sulfide (DMS) and propanethiol (PT). Given that the DMS degradation activity of Alcaligenes sp. SY1 is inducible and the PT-degradation activity of Pseudomonas putida S-1 is constitutive, different strategies are designed for cell cultivation to obtain high VOSC removal rates of SCMI. Compared with the microbial suspension, the prepared SCMI exhibited better storage stability at 4 and 25°C. Inoculation of the SCMI in biotrickling filters (BTFs) could effectively shorten the start-up period and enhance the removal performance. Microbial analysis by Illumina MiSeq indicated that Alcaligenes sp. SY1 and P. putida S-1 might be dominant and persistent among the microbial communities of the BTF during the operation.

Characteristics of odors emitted from municipal wastewater treatment plant and methods for their identification and deodorization techniques

Odors emitted from municipal wastewater treatment plants belong to a group of pollutants, which is the main cause of people complaining about atmospheric air quality. The limitation of emissions of unpleasant odors generated by wastewater treatment plants by using appropriate deodorization methods is omitted on numerous occasions. This can have a negative influence on public trust and the quality of atmospheric air. The article presents basic information on the characteristics of odors from wastewater treatment lines and wastewater processing and management lines in a model biological wastewater treatment plant conducting the biogas recovery process and also information is provided on deodorization methods, such as odor masking, biofiltration, thermal disposal and diffusion through activated sludge dedicated to neutralization of odors in biological treatment plants. The main focus is on the field olfactometry technique, which is one of the tools used in environmental protection. Its application facilitates performance of tests concerning the assessment of olfactory properties of odorants in polluted air.