Highly efficient degradation of hydrogen sulfide, styrene, and m-xylene in a bio-trickling filter

Elucidating styrene tolerance mechanisms in Gluconobacter oxydans through adaptive laboratory evolution

Biodegradation of styrene utilizing Gluconobacter oxydans (G. oxydans) is affected by the inhibitory and toxic effects of styrene concentrations. In this study, evolution experiments were conducted at low concentrations to mimic typical wastewater conditions to develop G. oxydans mutants with enhanced styrene tolerance. Physiological and biochemical analyses reveal that styrene hinders normal cell growth and damages cell membrane function and motility. Nevertheless, phenotypic heterogeneity and enhanced biofilm formation emerged as primary factors contributing to high styrene tolerance. Mutations in the flagella protein FlgE primarily affects cell motility, chemotaxis, and biofilm formation. TFs MarR and HipB positively regulate the tolerance phenotypes, with MarR playing a more pivotal role than HipB in regulating styrene tolerance, supporting tolerance up to 22 g·L-1 of styrene. This study clarifies potential mechanisms underlying styrene tolerance and, offering valuable insights for the application of G. oxydans in treating styrene-laden wastewater.

Fugitive gases reduction and carbon sequestration potential of ecological floating beds

Ecological floating beds (EFBs) are widely utilized as a green, cost-effective, and efficient technology for biologicalwater treatment in ponds, rivers, and secondary treatment of wastewater plant effluents. However, their potential for greenhouse gas (GHG) absorption and transformation is often overlooked. This paper begins by summarizing the accounting and emission status of GHGs from wastewater treatment plants (WWTPs), reviewing plant-microbial interactions in the phyllosphere and rhizosphere, and exploring plant-microbial-mediated transformations of carbon and nitrogen cycles. Special attention is given to variations in carbon and nitrogen cycling intensities within the plant phyllosphere and rhizosphere under warm and humid conditions with elevated GHG concentrations. We propose an exploratory approach using Ecological Floating Beds-Greenhouse (EFBs-GH) to absorb and transform fugitive gases from biochemical tanks, while enhancing sewage treatment efficiency. The study investigates the advantages and potential of EFBs for carbon sequestration and efficiency improvement in WWTPs, aiming to provide technical solutions and theoretical foundations for reducing fugitive gas emissions, including GHGs and odorous gases, etc., from concentrated sources such as WWTPs.

Activation of persulfate with magnetic Fe3O4-municipal solid waste incineration bottom ash-derived zeolite core-shell materials for tetracycline hydrochloride degradation

A novel and environmentally friendly magnetic iron zeolite (MIZ) core-shell were successfully fabricated using municipal solid waste incineration bottom ash-derived zeolite (MWZ) coated with Fe3O4 and innovatively investigated as a heterogeneous persulfate (PS) catalyst. The morphology and structure composition of as-prepared catalysts were characterised, and it was proved that the core-shell structure of MIZ was successfully synthesised by coating Fe3O4 uniformly on the MWZ surface. The tetracycline hydrochloride (TCH) degradation experiment indicate that the optimum equimolar amount of iron precursors was 3 mmol (MIZ-3). Compared with other systems, MIZ-3 possessed a superior catalytic performance, and the degradation efficiency of TCH (50 mg·L-1) in the MIZ-3/PS system reached 87.3%. The effects of reaction parameters on the catalytic activity of MIZ-3, including pH, initial concentration of TCH, temperature, the dosage of catalyst, and Na2S2O8, were assessed. The catalyst had high stability according to three recycling experiments and the leaching test of iron ions. Furthermore, the working mechanism of the MIZ-3/PS system to TCH was discussed. The electron spin resonance (ESR) results demonstrated that the reactive radicals generated in the MIZ-3/PS system were sulphate radical (S O 4 - ∙ ) and hydroxyl radical (•OH). This work provided a novel strategy for TCH degradation under PS with a broad perspective on the fabrication of non-toxic and low-cost catalysts in practical wastewater treatment.

Cellulosimicrobium sp. Strain L1: A Study on the Optimization of the Conditions and Performance of a Combined Biological Trickling Filter for Hydrogen Sulfide Degradation

Sulfide is a toxic and hazardous substance in the agricultural environment, which can cause damage to humans and livestock when exposed to large amounts of air. In this study, we performed one-factor optimization of the culture conditions and culture fractions of the Cellulosimicrobium sp. strain L1 and combined it with a biological trickling filter cell for the degradation of hydrogen sulfide for 24 consecutive days. The degradation effect of strain L1 and the biological trickling filter (BTF) on hydrogen sulfide was investigated, and the changes in intermediate products in the degradation process were briefly analyzed. The results showed that strain L1 had the highest conversion efficiency when incubated with 3 g/L sucrose as the carbon source and 1 g/L NH4Cl as the nitrogen source at a temperature of 35 °C, an initial pH of 5, and a NaCl concentration of 1%. The concentration of thiosulfate increased and then decreased during the degradation process, and the concentration of sulfate increased continuously. When strain L1 was applied to the biological trickling filter, it could degrade 359.53 mg/m3 of H2S. This study provides a deeper understanding of sulfide degradation in biological trickling filters and helps promote the development of desulfurization technology and the treatment of malodorous gasses produced by the accumulation of large quantities of livestock manure.

Analysis of latrine fecal odor release pattern and the deodorization with composited microbial agent

As an important source of malodor, the odor gases emitted from public toilet significantly interfered the air quality of living surroundings, resulting in environmental problem which received little attention before. Thus, this paper explored the odor release pattern of latrine feces and deodorization effect with composited microbial agent in Chengdu, China. The odor release rules were investigated in sealed installations with a working volume of 9 L for 20 days. The odor units (OU), ammonia (NH3), hydrogen sulfide (H2S) and total volatile organic compounds (TVOC) were selected to assess the release of malodorous gases under different temperature and humidity, while the highest malodor release was observed under 45℃, with OU and TVOC concentration was 643.91 ± 2.49 and 7767.33 ± 33.50 mg/m3, respectively. Microbes with deodorization ability were screened and mixed into an agent, which composited of Bacillus amyloliquefaciens, Lactobacillus plantarum, Enterococcus faecalis and Pichia fermentans. The addition of microbial deodorant could significantly suppress the release of malodor gas during a 20-day trial, and the removal efficiency of NH3, H2S, TVOC and OU was 81.50 %, 38.31 %, 64.38 %, and 76.86 %, respectively. The analysis of microbial community structure showed that temperature was the main environmental factor driving the microbial variations in latrine feces, while Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes were the main bacteria phyla involved in the formation and emission of malodorous gases. However, after adding the deodorant, the abundance of Bacteroidetes, Proteobacteria and Actinobacteria were decreased, while the abundance of Firmicutes was increased. Furthermore, P. fermentans successfully colonized in fecal substrates and became the dominant fungus after deodorization. These results expanded the understanding of the odor release from latrine feces, and the composited microbial deodorant provided a valuable basis to the management of odor pollution.

Effect of toluene on m-xylene removal in a biotrickling filter: Performance, biofilm characteristics, and microbial analysis

Hydrophobic volatile organic compounds (VOCs) pose a challenge to the removal efficiency in biotrickling filters (BTFs). The addition of relatively hydrophilic substances presents a promising approach for enhancing the elimination of hydrophobic VOCs. In this study, toluene was introduced into the BTF system alongside m-xylene, and their mixing ratios were changed to explore the interactions and mechanisms under different conditions. The result showed that the most pronounced synergistic interaction occurred when the mixing concentration ratio of m-xylene and toluene was 2:1. The removal efficiency (RE) of m-xylene increased from 88% to 97%, and the elimination capacity (EC) of m-xylene changed from 64 to 72 g m-3 h-1. Under this condition, there was a notable increase in biomass, extracellular polymeric substance (EPS) content, and relative hydrophobicity. Microbial diversity was enhanced observably with Berkeleyces and Mycobacterium potentially playing a positive role in co-degradation. Meanwhile, microbial metabolic function prediction indicated a significant enhancement in metabolic functions. Therefore, the introduction of relatively hydrophilic VOCs represents an effective strategy for enhancing the removal of hydrophobic VOCs in the BTFs.

Experimental and theoretical calculations insight into acetone adsorption by porous carbon at different pressures: Effects of pore structure and oxygen groups

The influence of different pore size and oxygen groups for porous carbons on acetone adsorption at different pressure was studied by using experimental data and theoretical calculation, and the results were applied to prepare carbon-based adsorbents with superior adsorption capacity. First, we successfully prepared five types of porous carbons with different gradient pore structure but similar oxygen contents (4.9 ± 0.25 at.%). We found that the acetone uptake at different pressure depends on the different pore sizes. Besides, we demonstrate how to accurately decompose the acetone adsorption isotherm into multiple sub-isotherms based on different pore sizes. Based on the isotherm decomposition method, the acetone adsorption at 18 kPa is mainly in the form of pore-filling adsorption in the pore size range of 0.6-2.0 nm. When the pore size is greater than 2 nm, the acetone uptake mainly depends on the surface area. Second, porous carbons with different oxygen content, similar surface area and pore structure were prepared to study the influence of oxygen groups on acetone adsorption. The results show that the acetone adsorption capacity is determined by the pore structure at relatively high pressure, and the oxygen groups only slightly increase the adsorption capacity. However, the oxygen groups can provide more active sites, thereby enhancing acetone adsorption at low pressure.

Biofilm-based technology for industrial wastewater treatment: current technology, applications and future perspectives

The microbial community in biofilm is safeguarded from the action of toxic chemicals, antimicrobial compounds, and harsh/stressful environmental circumstances. Therefore, biofilm-based technology has nowadays become a successful alternative for treating industrial wastewater as compared to suspended growth-based technologies. In biofilm reactors, microbial cells are attached to static or free-moving materials to form a biofilm which facilitates the process of liquid and solid separation in biofilm-mediated operations. This paper aims to review the state-of-the-art of recent research on bacterial biofilm in industrial wastewater treatment including biofilm fundamentals, possible applications and problems, and factors to regulate biofilm formation. We discussed in detail the treatment efficiencies of fluidized bed biofilm reactor (FBBR), trickling filter reactor (TFR), rotating biological contactor (RBC), membrane biofilm reactor (MBfR), and moving bed biofilm reactor (MBBR) for different types of industrial wastewater treatment. Besides, biofilms have many applications in food and agriculture, biofuel and bioenergy production, power generation, and plastic degradation. Furthermore, key factors for regulating biofilm formation were also emphasized. In conclusion, industrial applications make evident that biofilm-based treatment technology is impactful for pollutant removal. Future research to address and improve the limitations of biofilm-based technology in wastewater treatment is also discussed.

Removal of Volatile Organic Compounds (VOCs) from Air: Focus on Biotrickling Filtration and Process Modeling

Biotrickling filtration is a well-established technology for the treatment of air polluted with odorous and volatile organic compounds (VOCs). Besides dozens of successful industrial applications of this technology, there are still gaps in a full understanding and description of the mechanisms of biotrickling filtration. This review focuses on recent research results on biotrickling filtration of air polluted with single and multiple VOCs, as well as process modeling. The modeling offers optimization of a process design and performance, as well as allows deeper understanding of process mechanisms. An overview of the developments of models describing biotrickling filtration and conventional biofiltration, as primarily developed and in many aspects through similar processes, is presented in this paper.

The Comparison of Biotreatment and Chemical Treatment for Odor Control during Kitchen Waste Aerobic Composting

Odor ΨΩγemission has become mathvariant="normal" mathvariant="sans-serif-bold-italic" an important issue in kitchen waste management. Ammonia and hydrogen sulfide are the two most important odor sources as they contribute malodor and can cause health problems. As biotreatment and chemical treatment are two majorly applied technologies for odor control, in this study, they were used to remove ammonia and hydrogen sulfide and the performance of each process was compared. It was found that chemical absorption could efficiently eliminate both ammonia and hydrogenmathvariant="script" sulfide, and the removal efficiencies of ammonia and hydrogen sulfide highly depended on the pH of the adsorbent, contacting time, and gas and solution ratio (G/S). The ammonia-removal efficiency reached 100% within less than 2 s at G/S 600 and pH 0.1. The complete removal of hydrogen sulfide was achieved within 2 s at G/S 4000 and pH 13. Biotrickling filter showed better ability for hydrogen sulfide removal and the removal efficiency was 91.9%; however, the ammonia removal was only 73.5%. It suggests that chemical adsorption is more efficient compared to biotreatment for removing ammonia and hydrogen sulfide. In the combination of the two processes, biotrickling filter followed by chemical adsorption, the final concentrations of ammonia and hydrogen sulfide could meet the Level 1 standard of Emission Standards for Odor Pollution (China). The study provides a potential approach for odor control during kitchen waste aerobic composting.