Effects of ozone treatment on performance and microbial community composition in biofiltration systems treating ethyl acetate vapours

Contribution of sulfur-containing precursors to release of hydrogen sulfide in sludge composting

Hydrogen sulfide (H2S) production during composting can impact the environment and human health. Especially during the thermophilic phase, H2S is discharged in large quantities. However, in sludge composting, the contributions of different sulfur-containing precursors to H2S fluxes, key functional microorganisms, and key environmental parameters for reducing H2S flux remain unclear. Analysis of cysteine (Cys), methionine (Met), and sulfate (SO42-) concentrations, multiple stepwise regression analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis of metagenomes showed that Cys was the main contributor to the production of H2S and that Met was among the main sources during the first three days of composting, while the SO42- contribution to H2S was negligible. Fifteen functional genera involved in the conversion of precursors to H2S were identified by co-occurrence network analysis. Only Bacillus showed high temperature resistance (>50 °C) and the ability to reduce H2S. Redundancy analysis showed that total carbon (64.0 %) and pH (23.3 %) had significant effects on functional bacteria. H2S had a quadratic relationship with sulfur-containing precursors. All microbial network sulfur-containing precursors metabolism modules showed a highly significant relationship with Cys.

Improving the performance of biotrickling filter microbial fuel cells in treating exhaust gas by adjusting the oxygen content of the anode tank

A biotrickling filter (BTF) was combined with a microbial fuel cell (MFC) to remove ethyl acetate from exhaust gas while generating electricity in the process. The results indicated that the use of carbide porous ceramic rings (CPCR) as auxiliary anodes produced more biomass and exhibited a high average removal efficiency (98%), making it a superior microorganism growth carrier compared with carbon coke. When CPCR was used as the cathode in the BTF-MFC, the maximum power density (PD) was 5.64-14.8% of that achieved when carbon cloth was used as the cathode, revealing that CPCR is not a suitable cathode. The maximum elimination capacity (EC) and output voltage of the two-stage BTF-MFC (tBTF-MFC) were only 69.4% and 68.4% of those of the single-stage BTF-MFC (sBTF-MFC), presumably because of voltage reversal. Although the output voltage and EC in the tBTF-MFC were less than those in the sBTF-MFC, the follow-up field application involves stacking multiple small MFCs to remove high-concentration pollutants and generate a high power output. Additionally, continuously adding sodium sulfite decreased the average dissolved oxygen; generated an averaged closed-circuit voltage of 477 mV; and produced a maximum PD of 71.7 mW/m³. These findings demonstrated that the aforementioned method can effectively improve the problem of oxygen and MFC anodes competing for electrons, thus delivering a method that enhances MFC performance through controlling the amount of oxygen in practical applications.

Emissions, measurement, and control of odor in livestock farms: A review

Odor emissions from intensive livestock farms have attracted increased attention due to their adverse impacts on the environment and human health. Nevertheless, a systematic summary regarding the characteristics, sampling detection, and control technology for odor emissions from livestock farms is currently lacking. This paper compares the development of odor standards in different countries and summarizes the odor emission characteristics of livestock farms. Ammonia, the most common odor substance, can reach as high as 4100 ppm in the compost area. Sampling methods for point and area source odor emissions are introduced in this paper, and odor analysis methods are compared. Olfactometers, odorometers, and the triangle odor bag method are usually used to measure odor concentration. Odor control technologies are divided into three categories: physical (activated carbon adsorption, masking, and dilution diffusion), chemical (plant extract spraying, wet scrubbing, combustion, non-thermal plasma, and photocatalytic oxidation), and biological (biofiltration, biotrickling, and bioscrubbing). Each technology is elucidated, and the performance in the removal of different pollutants is summarized. The application scopes, costs, operational stability, and secondary pollution of the technologies are compared. The generation of secondary pollution and long-term operation stability are issues that should be considered in future technological development. Lastly, a case analysis for engineering application is conducted.

Enhancing performance evaluation and microbial community analysis of the biofilter for toluene removal by adding polyethylene glycol-600 into the nutrient solution

Polyethylene glycol-600 (PEG-600), as a carrier for slow release of organic substances, can improve the biocompatibility of packing fillers and the construction of biofilms. The gradient experiments were established to evaluate the feasibility of adding different content of PEG-600 to the biofilter for enhancing toluene removal. In particular, the evolution trend of microbial community embedded in packing fillers was measured by 16S rRNA-based gene sequencing. Results showed that the toluene removal efficiency of biofilter with 7.5% adding content of the PEG-600 was greatly improved, and the maximum elimination capacity of 152 g/(m³·h) was obtained. The introduction of PEG-600 enhanced the tolerance ability to withstand the transient impact loading and intensified the production of extracellular polymeric substances and bonding strength of biofilms. It should be noted that the abundance of Pseudomonas and Steroidobacter at genus level increased significantly. The microbial community evolved into a co-degradation system of toluene and PEG-600.

Mesoporous TiO2 Monoliths Impregnated with CdS and CuO Nanoparticles for Airborne Bacteria Inactivation Under Visible Light

In this work, macroscopic TiO₂ monoliths are proposed to serve simultaneously as support and co-catalyst in a continuous flow photoreactor. The impregnation via one-pot of mesoporous TiO₂ with CdS (m-TiO₂/CdS) and CuO (m-TiO₂/CuO) nanoparticles enabled the formation of photocatalytic heterojunctions retaining high specific surface area (~ 100 m²/g). The impregnated monoliths of 2-3 mm in size were employed as photocatalysts to inactivate airborne bacteria under blue light, reducing the emission of living airborne bacteria up to 0.1% and 37.7% when using m-TiO₂/CdS and m-TiO₂/CuO, respectively. Bacteria were characterized and quantified by flow cytometry and cell lysis was confirmed by SEM, detecting collapsed bacteria. Along 96 h of continuous photocatalysis at a flow rate of 2.2 L/min, the cell concentration presented maxima and minima due to the adsorption-desorption stages of bioaerosols over the catalysts, in concordance with thermal gravimetric analysis. The reactivation of catalysts was achieved by calcination at 400 °C, however, after a third re-cycle, the photocatalytic activity for all monoliths was practically negligible because the physicochemical surface changes hinder the adequate bioaerosol adsorption. These porous systems could emerge as promising gas-phase catalysts since the mass transport is facilitated by porosity and the release of catalyst nanoparticles is avoided by the active support, providing a safe and viable model for bioaerosols inactivation to improve indoor air quality with the use of interior lighting.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10562-021-03659-9.

The sequential dewatering and drying treatment enhanced the potential favorable effect of microbial communities in drinking water treatment residue for environmental recycling

The beneficial recycling of drinking water treatment residue (DWTR) for environmental remediation has received increasingly interests; whereas, the reported potential effect of microbial communities in different DWTR was ambiguous, which was unfavorable for the beneficial recycling. This study hypothesized that the varied treatment to DWTR in different waterworks induced the ambiguous effect; accordingly, responses of microbial communities in DWTR to the sequential dewatering and drying treatment were determined based on samples from three waterworks, in combination with 180-d incubation tests. The results showed that the microbial communities varied remarkably in different DWTR before being dewatered (DWTS). However, after dewatering, the increased microbial diversities were observed, and the microbial communities exhibited higher similarities among the dewatered DWTR from different waterworks; furthermore, the dewatered DWTR with subsequent drying treatment enriched more bacteria genus with potential environmental functions after incubation tests. The variations of microbial communities were closely related to DWTR properties, such as pH, organic matter, metals, P, and water extractable nutrients. Further analysis indicated that with maintaining high adsorption capability of DWTR, the dewatering treatment tended to retain specific microbial communities that may be induced by the applied similar techniques in different waterworks; the accumulated nutriments due to drying treatment and the stable DWTR pH enhanced the potential functional bacteria enrichment. Overall, the dewatering and drying treatment led to microbial communities with generality in different DWTR and increased the potential favorable microbial effect, promoting DWTR recycling in environmental remediation.

Hazardous wastes treatment technologies

A review of the literature published in 2019 on topics related to hazardous waste management in water, soils, sediments, and air. The review covered treatment technologies applying physical, chemical, and biological principles for the remediation of contaminated water, soils, sediments, and air. PRACTICAL POINTS: This report provides a review of technologies for the management of waters, wastewaters, air, sediments, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) in three scientific areas of physical, chemical, and biological methods. Physical methods for the management of hazardous wastes including general adsorption, sand filtration, coagulation/flocculation, electrodialysis, electrokinetics, electro-sorption ( capacitive deionization, CDI), membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non-thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed. Chemical methods including ozone-based, hydrogen peroxide-based, potassium permanganate processes, and Fenton and Fenton-like process were reviewed. Biological methods such as aerobic, anoxic, anaerobic, bioreactors, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed. Case histories were reviewed in four areas including contaminated sediments, contaminated soils, mixed industrial solid wastes and radioactive wastes.

Dynamic performance of a fungal biofilter packed with perlite for the abatement of hexane polluted gas streams using SIFT-MS and packing characterization with advanced X-ray spectroscopy

The use of Fusarium solani fungi in an expanded perlite packed biofilter was investigated for the treatment of a hexane polluted waste gas stream using selected ion flow tube mass spectrometry (SIFT-MS). The latter analytical technique proved to be of utmost importance to evaluate the performance of the biofilter at high time resolution (seconds) under various transient conditions, analogous to industrial situations. The biofilter was operational for 277 days with inlet loads varying between 1 and 14 g m^-3 h^-1 and applying an empty bed residence time of 116 s. The results showed a positive behaviour of the biofilter against different types of disruptions such as: (i) changes in the relative humidity of the inlet gas, (ii) stopping the carbon supply for 1, 5 and 10 days, (iii) varying the inlet hexane concentration (step increases and intermittent pulses) and (iv) limiting the availability of nutrients. X-ray imaging (both conventional 2D μCT and X-ray fluorescence, XRF) was applied for the first time on biofilter media in order to get insight in the internal structure of expanded perlite and to visualise the biomass growth. The latter in combination with online porosity measurements using SIFT-MS provides fundamental information regarding the biofiltration process.