Bioaerosol emissions of pilot-scale low-pH and neutral-pH biofilters treating odors from landfill leachate: Characteristics and impact factors

Do full-scale gas-phase biofilters reduce or increase bioaerosol emissions?

Biofilters are widely utilized for treating odorous gases. Understanding the biosafety of biofilters in real-world applications necessitates a comprehensive investigation into their bioaerosol emission characteristics. In this study, bioaerosols captured from the inlet and outlet, along with packing material microbiome were investigated over a 12-month period from three full-scale biofilters. Their characteristics, size distribution, and sources were investigated and analyzed. Notably, over 96 % of the bioaerosols originated from the inlet air rather than from the packing materials. Full-scale biofilters not only reduced bacterial emissions by 5-17 % but also lowered the potential pathogenicity. Although biofilters effectively diminished bioaerosol emissions, there are still potential pathogenicity primarily originated from the inlet air. This study emphasizes the significance of considering upstream processes when evaluating the risks associated with bioaerosols in real-world applications.

Bioaerosols and VOC emissions from landfill leachate treatment processes: Regional differences and health risks

The landfill leachate treatment process (LLTP) is a crucial anthropogenic source of bioaerosols and volatile organic compounds (VOCs) with potential environmental impacts and on-site health risks to plant workers. However, factors influencing microbial aerosol and VOC emissions remain poorly understood. We sampled and analyzed bioaerosols and VOCs in two process sections (oxidation ditch [OD] and reverse osmosis membrane [RO]) of LLTPs in northern (NLF) and southern (SLF) China. Bioaerosol concentrations were highest in OD, and particle size predominantly ranged from 0.654.7 µm. Microbial community analysis revealed distinct differences between geographical locations and process sections, with 332 genera identified. Genera such as Paenibacillus, Bacillus, and Pseudomonas were prevalent at all sampling sites. Oxygen-containing compounds (e.g., acetophenone and propionic acid) were the dominant VOCs, particularly in SLF-OD. Network analysis showed complex interactions, with Sphingomonas and ketones playing central roles in microbial and VOC communities, respectively. Partial least squares (PLS) modeling indicated a significant correlation between bioaerosols and VOCs. Specific microorganisms, such as TK10, Adhaeribacter, and Lachnospiraceae, were major contributors to emissions of hazardous VOCs (e.g., toluene and styrene). The ozone-generation potential and olfactory effect of the OD were significantly higher than those of RO; and those of SLF were higher than those of NLF. Health risk assessments indicated potential chronic toxicity and cancer risks associated with VOC exposure to specific compounds, such as trichloroethylene. Bioaerosol exposure occurred primarily through inhalation, particularly in male workers. This study establishes a theoretical foundation for the prevention and control of air-phase pollutant risks associated with LLTPs.

Removal of terpenes in the presence of easily degradable compounds during biofiltration of gas emissions from composting of municipal solid waste

Composting of the organic fraction of municipal solid waste (OFMSW) is accompanied by the emission of large volumes of harmful, hazardous and foul-smelling volatile organic compounds (VOCs). To improve the efficiency of terpenes removal, which constitute a significant part of VOCs, pure cultures of microorganisms dominating in its microbiota were isolated from the microbial community of the biofilter, which has been cleaning such emissions for a long time. Seven pure cultures were isolated and then tested for being able to grow on a mineral medium in the presence of terpene vapor as the only source of carbon and energy. Three of the most actively growing cultures were selected, characterized and identified by the 16S rRNA gene as Rhodococcus erythropolis CA1, Rhodococcus pyridinivorans CA3 and Gordonia sp. CA6. Three identical laboratory biofilters (BF) were inoculated with a mix of these cultures to test the possibility of more complete removal of terpenes. Biofilters were adapting to clearing the model mix of terpineols and geraniol vapors for 45 days. During 45 days the purification efficiency of the model mix reached an average of 91.5% with a contact time (CT) of 3.7 ± 0.2 s and the terpene vapors concentration of 14 ± 2 mg m-3. Then the biofilters number BF2.1 and BF3.1 were connected to real emission from composting OFMSW. The biofilter BF2.1 purified the emission directly, whereas BF3.1 purified similar discharge after the intermediate biofilter of the 1st stage of purification (BF0.0). The BF1.0 was left connected to purification of the model mix as a control. The effectiveness of biofiltration of hard-to-remove terpenes was evaluated by gas chromatography of samples taken at the inlet and outlet of biofilters. The average efficiency of removing terpenes from real emissions by BF2.1 was 93.1 % (CT = 5.5 s). The total efficiency of removing terpenes by (BF0.0 + BF3.1) complex was 93.2 % (total CT = 7.4 s). A study of the microbiota of inoculated biofilters after 60 and 90 days of purification the real emission by cultivation from dilutions, identification by the 16S rRNA gene and fingerprinting showed that in BF2.1 and BF3.1 Rhodococcus erythropolis CA1 and Rhodococcus pyridinivorans CA3 were preserved among living cells at a level of 6.5-12.4 %, and genetically fully corresponded to the original cultures. These results could have a positive impact on improving the results of deodorization of emissions from OFMSW composting by biofiltration, simplifying the design of the biofiltration facility (one stage instead of two) and reducing the total time for effective biofiltration. This, in turn, would contribute to the wider introduction of highly efficient emission purification methods at OFMSW composting facilities in order to create more comfortable and ecologically clean environmental conditions around them.

Bioaerosols released from multistage biofilter for gaseous benzene removal: Escape behavior and pathogenicity

Biological deodorization systems are widely used to control odors and volatile organic compounds. However, the secondary contamination of bioaerosol emissions is a noteworthy issue in the operation of biofilters for off-gas purification. In this study, a multistage biofilter for benzene treatment was utilized to investigate the bioaerosol emissions under different flow rates and spray intervals. At the outlet of the biofilter, 99-7173 CFU/m3 of bioaerosols were detected, among which pathogens accounted for 8.93-98.73 %. Proteobacteria and Firmicutes dominated bioaerosols at the phylum level. The Mantel test based on the Bray-Curtis distance revealed strong influences of flow rate introduced to the biofilter and biomass colonized on the packing materials (PMs) on bioaerosol emissions. The non-metric multidimensional scaling results suggested a correlation between the bioaerosol community and bacteria on the PMs. Bacillus and Stenotrophomonas were the two main genera stripped from the biofilm on PMs to form the bioaerosols. SourceTracker analysis confirmed that microorganisms from the PMs near outlet contributed an average of 22.3 % to bioaerosols. Pathogenic bacteria carried by bioaerosols included Bacillus, Serratia, Stenotrophomonas, Achromobacter, Enterococcus, and Pseudomonas. Bioaerosols were predicted to cause human diseases, with antimicrobial drug resistance and bacterial infectious disease being the two main pathogenic pathways. Stenotrophomonas sp. LMG 19833, Pseudomonas sp., and Stenotrophomonas sp. were the keystone species in the bioaerosol co-occurrence network. Overall, results of present study promote the insight of bioaerosols, particularly pathogen emissions, and provide a basis for controlling bioaerosol contamination from biofilters.

A novel integrated industrial-scale biological reactor for odor control in a sewage sludge composting facility: Performance, pollutant transformation, and bioaerosol emission mechanism

In order to remove multiple pollutants in the sewage sludge (SS) composting facility, a novel integrated industrial-scale biological reactor based on biological trickling filtration and fungal biological filtration (BTF-FBF) was developed. This study examined bioaerosol emission, odour removal, pollutant transformation mechanism, and project investment. At an inlet flow rate of 7200 m³/h, the average removal efficiencies of hydrogen sulfide (H₂S), ammonia (NH₃), and volatile organic compounds (VOCs) during the steady stage were 97.2 %, 98.9 %, and 92.2 %. The BTF-FBF separates microbial phases (bacteria and fungi) of different modules. BTF removed most hydrophilic compounds, while FBF removed hydrophobic ones. Moreover, the reactor could effectively remove pathogens or opportunistic pathogens bioaerosols, such as Escherichia coli (61.9%), Salmonella sp. (85%), and Aspergillus fumigatus (82.1%). The pollutant transformation mechanism of BTF-FBF was proposed. BTF-FBF annualized costs were 324,783 CNY/year at 15 years. In conclusion, BTF-FBF provides new insights into composting facility bioaerosol, odour, and pathogen emission control.

A review on biofiltration techniques: Recent advancements in the removal of volatile organic compounds and heavy metals in the treatment of polluted water

Good quality of water determines the healthy life of living beings on this earth. The cleanliness of water was interrupted by the pollutants emerging out of several human activities. Industrialization, urbanization, heavy population, and improper disposal of wastes are found to be the major reasons for the contamination of water. Globally, the inclusion of volatile organic compounds (VOCs) and heavy metals released by manufacturing industries, pharmaceuticals, and petrochemical processes have created environmental issues. The toxic nature of these pollutants has led researchers, scientists, and industries to exhibit concern towards the complete eradication of them. In this scenario, the development of wastewater treatment methodologies at low cost and in an eco-friendly way had gained importance at the international level. Recently, bio-based technologies were considered for environmental remedies. Biofiltration based works have shown a significant result for the removal of volatile organic compounds and heavy metals in the treatment of wastewater. This was done with several biological sources such as bacteria, fungi, algae, plants, yeasts, etc. The biofiltration technique is cost-effective, simple, biocompatible, sustainable, and eco-friendly compared to conventional techniques. This review article provides deep insight into biofiltration technologies engaged in the removal of volatile organic compounds and heavy metals in the wastewater treatment process.

Evaluation of the Impact of Different Natural Zeolite Treatments on the Capacity of Eliminating/Reducing Odors and Toxic Compounds

Unlike odorants that mask odors, natural zeolite acts as a molecular sieve that captures and eliminates odors. Different treatment methods can be applied to influence the properties of the natural zeolites. To enhance the odor adsorption capacities of the natural zeolite two types of treatment methods were applied: chemical (acid, basic) and thermal. The initial natural zeolites and the activated one were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM-EDX). Two experiments were performed to establish the odor adsorption capacity of the activated natural zeolites. The best zeolite for the adsorption of humidity, ammonia and hydrogen sulfide was the 1-3 mm zeolite activated through thermal treatment. For the adsorption of PAHs, the best zeolite was the one activated through basic treatment, with an adsorption capacity of 89.6 ng/g.