Degradation of ethyl mercaptan and its major intermediate diethyl disulfide by Pseudomonas sp. strain WL2

Co-Treatment with Single and Ternary Mixture Gas of Dimethyl Sulfide, Propanethiol, and Toluene by a Macrokinetic Analysis in a Biotrickling Filter Seeded with Alcaligenes sp. SY1 and Pseudomonas Putida S1

The biotrickling filter (BTF) treatment is an effective way of dealing with air pollution caused by volatile organic compounds (VOCs). However, this approach is typically used for single VOCs treatment but not for the mixtures of VOC and volatile organic sulfur compounds (VOSCs), even if they are often encountered in industrial applications. Therefore, we investigated the performance of BTF for single and ternary mixture gas of dimethyl sulfide (DMS), propanethiol, and toluene, respectively. Results showed that the co-treatment enhanced the removal efficiency of toluene, but not of dimethyl sulfide or propanethiol. Maximum removal rates (rmax) of DMS, propanethiol and toluene were calculated to be 256.41 g·m−3·h−1, 204.08 g·m−3·h−1 and 90.91 g·m−3·h−1, respectively. For a gas mixture of these three constituents, rmax was measured to be 114.94 g·m−3·h−1, 104.17 g·m−3·h−1 and 99.01 g·m−3·h−1, separately. Illumina MiSeq sequencing analysis further indicated that Proteobacteria and Bacteroidetes were the major bacterial groups in BTF packing materials. A shift of bacterial community structure was observed during the biodegradation process.

Application of activated sludge for odor control in wastewater treatment plants: Approaches, advances and outlooks

Odors from wastewater treatment plants (WWTPs) have attracted extensive attention and stringent environmental standards are more widely adopted to reduce odor emissions. Biological odor treatment methods have broader applications than the physical and chemical counterparts as they are environment-friendly, cost-effective and generate low secondary wastes. The aqueous activated sludge (AS) processes are among the most promising approaches for the prevention or end-of-pipe removal of odor emissions and have the potential to simultaneously treat odor and wastewater. However, AS deodorization biotechnologies in WWTPs still need to be further systematically summarized and categorized while in-depth discussions on the characteristics and underlying mechanisms of AS deodorization process are still lacking. Recently, considerable studies have been reported to elucidate the microbial metabolisms in odor control and wastewater treatment. This paper reviews the fundamentals, characteristics, advances and field experiences of three AS biotechnologies for odor treatment in WWTPs, i.e., AS recycling, microaeration in AS digester and AS diffusion. The underlying deodorization mechanisms of typical odors have been revealed through the summary of recent advances on multi-element conversions, metabolic interactions of bacteria, microscopic characterization and identification of functional microorganisms. Future research aspects to advance the emerging deodorization AS process, such as deodorization mechanisms, simultaneous odor and water treatment, synergistic treatment with other air emissions, are discussed.

Enhancement of using combined packing materials on the removal of mixed sulfur compounds in a biotrickling filter and analysis of microbial communities

Background

Packing materials is a critical design consideration when employing biological reactor to treat malodorous gases. The acidification of packing bed usually results in a significant drop in the removal efficiency. In the present study, a biotrickling filter (BTF2) packed with plastic balls in the upper layer and with lava rocks in the bottom layer, was proposed to mitigate the acidification.

Results

Results showed that using combined packing materials efficiently enhanced the removal performance of BTF2 when compared with BTF1, which was packed with sole lava rocks. Removal efficiencies of more than 92.5% on four sulfur compounds were achieved in BTF2. Average pH value in its bottom packing bed was about 4.86, significantly higher than that in BTF1 (2.85). Sulfate and elemental sulfur were observed to accumulate more in BTF1 than in BTF2. Analysis of principal coordinate analysis proved that structure of microbial communities in BTF2 changed less after the shutdown but more when the initial pH value was set at 5.5. Network analysis of significant co-occurrence patterns based on the correlations between microbial taxa revealed that BTF2 harbored more diverse microorganisms involving in the bio-oxidation of sulfur compounds and had more complex interactions between microbial species.

Conclusions

Results confirmed that using combined packing materials effectively improved conditions for the growth of microorganisms. The robustness of reactor against acidification, adverse temperature and gas supply shutdown was greatly enhanced. These provided a theoretical basis for using mixed packing materials to improve removal performance.

Evaluation on the removal performance of dichloromethane and toluene from waste gases using an airlift packing reactor

Biological removal of dichloromethane (DCM) from pharmaceutical industry is limited by its recalcitrance. In this study, an airlift packing reactor (ALPR), which combined the suspended and fixed-film microbial growth system, was set up to remove DCM and co-existed toluene. The removal performance of the ALPR for DCM was greater than traditional airlift reactor (ALR). The maximum elimination capacity (EC_max) of the ALPR for DCM reached 108 g m^-3 h^-1 with removal efficiency (RE) of 41%, increased by 145% if compared to the ALR. The EC_max for toluene was 172 g m^-3 h^-1 with RE of 70%, decreased by 25% if compared to the ALR, which was mainly due to the higher liquid-phase biomass in the ALR. The results of high-throughput sequencing showed that the microbial composition on the packings of the ALPR had a large difference from its liquid-phase or the liquid-phase of the ALR. Gemmobacter, Rhizomicrobium, Chitinophaga, Vampirovibrio, and Fodinicurvata were genera with great abundance fixed on the packings and Rhizomicrobium, Chitinophaga, Vampirovibrio, and Fodinicurvata are first to be reported in VOCs biological removal. This study indicated that the ALPR can augment the microbial community and effectively improve the removal of recalcitrant VOCs.

Ethanethiol gas removal in an anoxic bio-scrubber

The performance of ethanethiol removal in an anoxic lab-scale bio-scrubber was investigated under different operating parameters and conditions for 300 days. The removal efficiency (RE) of ethanethiol was examined as a function of inlet concentration, empty bed residence time (EBRT) and spray density of irrigation. The results showed the best operation conditions and operation characteristics of the bio-scrubber for this study were at an inlet concentration of 150 mg/m³, a spray density of 0.23 m³/m² h and an EBRT of 90 s. An average RE of 91% and elimination capacity (EC) of 24.74 g/m³ h was found for all inlet ethanethiol concentrations. Variations in spray density higher than 0.23 m³/m² h had no effect on ethanethiol RE at different ethanethiol concentrations. The average experimental yield values were closer to the Y_ET/NO3^- theoretical value of 0.74 when the main product was elemental sulphur (S^o). This indicates that S^o and other forms of sulphur were formed rather than sulphate (SO₄^2-) as the end product. Furthermore, growth kinetics for bio-degradation were evaluated in batch culture experiments using the Monod model, and bio-kinetic parameters of μ_max, K_s, Y_xs and q_max were obtained as 0.14 1/h, 1.17 mg/L, 0.52 g_x/g_s and 0.26 g_s/g_x h, respectively.

Polypyrrole-Grafted Coconut Shell Biological Carbon as a Potential Adsorbent for Methyl Tert-Butyl Ether Removal: Characterization and Adsorption Capability

Methyl tert-butyl ether (MTBE) has been used as a common gasoline additive worldwide since the late twentieth century, and it has become the most frequently detected groundwater pollutant in many countries. This study aimed to synthesize a novel microbial carrier to improve its adsorptive capacity for MTBE and biofilm formation, compared to the traditional granular activated carbon (GAC). A polypyrrole (PPy)-modified GAC composite (PPy/GAC) was synthesized, and characterized by Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) surface area analysis. The adsorption behaviors of MTBE were well described by the pseudo-second-order and Langmuir isotherm models. Furthermore, three biofilm reactors were established with PPy/GAC, PPy, and GAC as the carriers, respectively, and the degradation of MTBE under continuous flow was investigated. Compared to the biofilm reactors with PPy or GAC (which both broke after a period of operation), the PPy/GAC biofilm column produced stable effluents under variable treatment conditions with a long-term effluent MTBE concentration <20 μg/L. Pseudomonas aeruginosa and Acinetobacter pittii may be the predominant bacteria responsible for MTBE degradation in these biofilm reactors.

Biodegradation of Methyl tert-Butyl Ether by Co-Metabolism with a Pseudomonas sp. Strain

Co-metabolic bioremediation is supposed to be an impressive and promising approach in the elimination technology of methyl tert-butyl ether (MTBE), which was found to be a common pollutant worldwide in the ground or underground water in recent years. In this paper, bacterial strain DZ13 (which can co-metabolically degrade MTBE) was isolated and named as Pseudomonas sp. DZ13 based on the result of 16S rRNA gene sequencing analysis. Strain DZ13 could grow on n-alkanes (C₅-C₈), accompanied with the co-metabolic degradation of MTBE. Diverse n-alkanes with different carbon number showed a significant influence on the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA). When Pseudomonas sp. DZ13 co-metabolically degraded MTBE with n-pentane as the growth substrate, a higher MTBE-degrading rate (V_max = 38.1 nmol/min/mg_protein, K_s = 6.8 mmol/L) and lower TBA-accumulation was observed. In the continuous degradation experiment, the removal efficiency of MTBE by Pseudomonas sp. Strain DZ13 did not show an obvious decrease after five times of continuous addition.

Cometabolic degradation of ethyl mercaptan by phenol-utilizing Ralstonia eutropha in suspended growth and gas-recycling trickle-bed reactor

The degradability of ethyl mercaptan (EM), by phenol-utilizing cells of Ralstonia eutropha, in both suspended and immobilized culture systems, was investigated in the present study. Free-cells experiments conducted at EM concentrations ranging from 1.25 to 14.42 mg/l, showed almost complete removal of EM at concentrations below 10.08 mg/l, which is much higher than the maximum biodegradable EM concentration obtained in experiments that did not utilize phenol as the primary substrate, i.e. 2.5 mg/l. The first-order kinetic rate constant (kSKS) for EM biodegradation by the phenol-utilizing cells (1.7 l/g biomass/h) was about 10 times higher than by cells without phenol utilization. Immobilized-cells experiments performed in a gas recycling trickle-bed reactor packed with kissiris particles at EM concentrations ranging from 1.6 to 36.9 mg/l, showed complete removal at all tested concentrations in a much shorter time, compared with free cells. The first-order kinetic rate constant (rmaxKs) for EM utilization was 0.04 l/h for the immobilized system compared to 0.06 for the suspended-growth culture, due to external mass transfer diffusion. Diffusion limitation was decreased by increasing the recycling-liquid flow rate from 25 to 65 ml/min. The removed EM was almost completely mineralized according to TOC and sulfate measurements. Shut down and starvation experiments revealed that the reactor could effectively handle the starving conditions and was reliable for full-scale application.