In this study, wasted mask is chosen as a pyrolysis feedstock whose generation has incredibly increased these days due to COVID-19. We suggest a way to produce value-added chemicals (e.g., aromatic compounds) from the mask with high amounts through catalytic fast pyrolysis (CFP). To this end, the effects of zeolite catalyst properties on the upgradation efficiency of pyrolytic products produced from pyrolysis of wasted mask were investigated. The compositions and yields of pyrolytic gases and oils were characterized as functions of pyrolysis temperature and the type of zeolite catalyst (HBeta, HY, and HZSM-5), including the mesoporous catalyst of Al-MCM-41. The mask was pyrolyzed in a fixed bed reactor, and the pyrolysis gases evolved in the reactor was routed to a secondary reactor inside which the zeolite catalyst was loaded. It was chosen 550 °C as the CFP temperature to compare the catalyst performance for the production of benzene, toluene, ethylbenzene, and xylene (BTEX) because this temperature gave the highest oil yield (80.7 wt%) during the non-catalytic pyrolysis process. The large pore zeolite group of HBeta and HY led to 134% and 67% higher BTEX concentrations than HZSM-5, respectively, likely because they had larger pores, higher surface areas, and higher acid site density than the HZSM-5. This is the first report of the effect of zeolite characteristics on BTEX production via CFP.

The use of the phenicol antibiotic florfenicol in livestock can select for the optrA gene, which also confers resistance to the critically important oxazolidinone antibiotic linezolid. However, the occurrence and dissemination of florfenicol and linezolid cross-resistance genes in anaerobic treatment systems for livestock waste are unknown. Herein, the phenotypes and genotypes (optrA, fexA, fexB, and cfr) of florfenicol and linezolid cross-resistance were investigated in 339 enterococci strains isolated from lab- and full-scale mesophilic anaerobic digestion systems treating swine waste. It was found that optrA, fexA, and fexB were frequently detected in isolated enterococci in both systems by PCR screening, whereas cfr was not detected. The most abundant gene was optrA, which was detected in 73.5% (n = 50) and 38.9% (n = 23) of enterococci isolates in the full-scale influent and effluent, respectively. Most strains carried more than two resistance genes, and the average percentage of co-occurrence of optrA/fexA was 16.6%. Based on minimum inhibitory concentrations of the enterococci strain phenotypes, 85.7%, 77.5%, and 77.5% of strains in influent were resistant to chloramphenicol, florfenicol, and linezolid, respectively, while 56.3%, 65.2%, and 13% in the effluent isolates were found, respectively, which was consistent with the genotype results. The phenotypes and genotypes of florfenicol and linezolid resistance were relative stable in the enterococci isolated from the influent and effluent in lab-scale anaerobic digestion system. The findings signify the enterococci isolates harboring the optrA gene remained in effluents of both full- and lab-scale swine waste anaerobic digestion system; hence, effective management strategies should be implemented to prevent the discharge of antibiotic resistance from the livestock waste treatment systems.

Bioelectrochemical systems (BESs) have been widely investigated for recalcitrant waste treatment mainly because of their waste removal effectiveness. Electroactive microbes (EMs) have long been thought to contribute to the high effectiveness by interacting with electrodes via electron chains. However, this work demonstrated the dispensable role of EMs for enhanced recalcitrant contamination degradation in BESs. We revealed enhanced p-fluoronitrobenzene (p-FNB) degradation in a BES by observing a defluorination efficiency that was three times higher than that in biodegradation or electrochemical processes. Such an improvement was achieved by the collaborative roles of electrode biofilms and planktonic microbes, as their individual contributions to p-FNB degradation were found to be similarly stimulated by electricity. However, no bioelectrochemical activity was found in either the electrode biofilms or the planktonic microbes during stimulated p-FNB degradation; because no biocatalytically reductive or oxidative turnovers were observed on cyclic voltammetry curves. The non-involvement of EMs was further proven by the similar microbial community evolution for biofilms and planktonic microbes. In summary, we proposed a mechanism for indirect electrical stimulation of microbial metabolism by electrochemically generating the active mediator p-fluoroaniline (p-FA) and further degradation by a sequential combination of electrochemical p-FNB reduction and biological p-FA oxidation by non-EMs.

Anaerobic digestion is an attractive waste treatment technology, achieving both pollution control and energy recovery. Though the inhibition of polystyrene nanoplastics in anaerobic granular sludge is well studied, no direct evidence has been found on the interaction of methanogens and nanoplastics. In this study, to characterize the location of nanoplastics, Pd-doped polystyrene nanoplastics (Pd-PS) were used to explore the inhibition mechanism of anaerobic sludge through short-term exposure to Methanosarcina acetivorans C2A. The results showed that Pd-PS inhibited the methanogenesis of the anaerobic sludge, and the methane production decreased as the Pd-PS increased, with a 14.29% reduction at the Pd-PS concentration of 2.36 × 10¹⁰ particles/mL. Also, Pd-PS interacted with the protein in the extracellular polymeric substances (EPS). Furthermore, Pd-PS inhibited the methanogenesis of M. acetivorans C2A without exhibiting an evident reduction in the growth. The inhibition of Pd-PS on methane was due to the inhibition of methane production related genes, MtaA and mcrA. These results provide potential explication for the inhibition of nanoplastics on the methanogens, which will fulfill the knowledge on the stability of methanogens under the short-term exposure of nanoplastics.

Water bodies contain a large number of harmful environmental pollutants, including oil, heavy metal ions and dyes, which has become a major global problem. The current work focusses on the development and future prospect of sustainable application of biodegradable cellulose-biomass materials in water treatment, considering that they show an important prospect in wastewater treatment. This paper summarizes the advantages and disadvantages of cellulose-biomass materials in removing harmful substances and pollutants from water and the key problems the technology faces. Cellulose-biomass material has unique structure, is environment friendly, degradable, renewable and provides low energy cost benefits, among other advantages. In this paper, the research progress of wastewater treatment in recent years is reviewed from the following three aspects: oil-water separation, heavy metal ions in water, and dye adsorption. The future research direction is also discussed.

Many aspects of modern life of our civilization are associated with using electrical and electronic devices (EEE). Ever-increasing demand for high-performance EEE and accelerated technological development make the replacement of EEE become frequent. This leads to the generation of a tremendous amount of electronic waste (E-waste). Challenges of the management of E-waste have recently arisen out of a dearth of proper technologies to treat E-waste. Pyrolysis process can thermochemically treat waste materials that have a complicated nature and inhomogeneity. This article gives a systematic review as an effort to tackle the challenges in the context of achievements in pyrolysis process in E-waste management sector. Pyrolysis mechanism and types of pyrolysis processes and pyrolysis reactors are first discussed. Various pyrolysis technologies applied to the E-waste treatment are then summarized and compared to each other. Points to be considered for further research and pending challenges of E-waste pyrolysis are also discussed. The pyrolysis treatment of E-waste is not yet fully industrialized mostly because of high costs. However, there should be much room for further developing the E-waste pyrolysis; hence, its industrialization and commercialization is just a matter of time.

The process of anaerobic digestion in food waste treatment plants generates a large amount of volatile organic compounds (VOCs). Long-term exposure to this exhaust gas can pose a threat to the health of workers and people living nearby. In this study, VOCs emitted from different working units in a food waste anaerobic digestion plant were monitored for a year. Variations in VOCs emitted from each unit were analyzed and a health risk assessment was conducted for each working unit. The results show that the concentration of VOCs in different units varied greatly. The highest cumulative concentration of VOCs appeared in the hydrothermal hydrolysis unit (3.49 × 10⁴ μg/m³), followed by the sorting/crushing room (8.97 × 10³ μg/m³), anaerobic digestion unit (6.21 × 10² μg/m³), and biogas production unit (2.01 × 10² μg/m³). Oxygenated compounds and terpenes were the major components of the emitted VOCs, accounting for more than 98% of total VOC emissions. The carcinogenic risk in the plant exceeded the safety threshold (ILCR<1 × 10⁻⁶), while the non-carcinogenic risk was within the acceptable range (HI < 1). The carcinogenic risk from the hydrothermal hydrolysis unit was the highest, reaching 4.4 × 10⁻⁵, and was labeled as “probable risk.” The carcinogenic risk at the plant boundary was 1.2 × 10⁻⁵, indicating exhaust gases can cause a health threat to neighbors. Therefore, management VOCs in anaerobic digestion plants should receive more attention, and employees should minimize the time they spend in the hydrothermal hydrolysis unit.

To simultaneously achieve biological denitrification and bio-energy recovery from sludge, the effects of nitrite on the two-phase anaerobic digestion (AD) of waste activated sludge were explored. Herein, effects of nitrite on the acidogenic phase are optimized, and the corresponding influence mechanisms are investigated. The experimental results show that the optimal nitrite treatment conditions for improving the acidogenic phase are an initial pH of 8.0, a nitrite addition concentration of 500 mg NO₂⁻-N·L⁻¹, and a fermentation time of six days. By comparing the effects of nitrite and nitrate on the acidogenic phase, it was found that it was the nitrite, not the nitrate, that significantly enhanced the sludge organic solubilization, hydrolysis, and acidification, which are primarily attributed to the redox property of nitrite. Based on an analysis of different forms of soluble nitrogen concentrations, there was no obvious accumulation of nitrite or nitrate during the acidogenic phase. An analysis of the methane production and the volatile solid (VS) degradation during the two-phase AD revealed that the nitrite improved the methane production from the methanogenic phase and enhanced the VS degradation of sludge during the entire two-phase AD process. These findings could provide references for simultaneously treating nitrite-rich wastewater and improving anaerobic sludge digestion via two-phase system.

The challenge of sludge digester liquor treatment is its high ammonium nitrogen (NH₄⁺-N) concentration. Early reports found that complete ammonia oxidation (comammox) was not present and anaerobic ammonia oxidation (anammox) was difficult to achieve in most sludge digester liquor treatments. In this study, NH₄⁺-N removal by cooperation between partial-nitrification, comammox, and anammox processes was achieved in a sequencing batch reactor (SBR) for sludge digester liquor treatment. The results showed that 2100–2200 mg/L of NH₄⁺-N was removed in the SBR with 98.82% removal efficiency. In addition, 55.11% of NH₄⁺-N was converted to nitrite nitrogen (NO₂⁻-N) by partial-nitrification, 25.43% of NH₄⁺-N was converted to nitrate nitrogen (NO₃⁻-N) by comammox, and 18.28% of NH₄⁺-N was removed by anammox. During the operation, in the SBR, the relative abundance of the dominant ammonia-oxidizing bacteria (Chitinophagaceae) was 18.89%, that of the dominant anammox bacteria (Candidatus Kuenenia) was 0.10%, and that of the dominant comammox bacteria (Nitrospira) was 0.20%. Therefore, the high nitrogen removal efficiency in this system was considered the result of the combination of the three processes. These results showed that comammox and anammox could play very important roles in nitrogen transformation and energy-saving in nitrogen removal systems.

Antibiotics can effectively protect livestock from pathogen infection, but residual antibiotics in manure bring risks to ecosystems and public health. Here, we demonstrated that black soldier fly larvae (BSFL) could provide an environmentally friendly manure treatment based on their ability to effectively and rapidly degrade tetracycline (TC). Investigation of the biological mechanisms and degradation pathways of TC by BSFL indicated that nearly 97% of TC was degraded within 12 days in a non-sterile BSFL treatment system, which is up to 1.6-fold faster than that achieved by normal composting. Our results showed that rapid TC-degradation was largely carried out by the intestinal microbiota of the larvae, which doubled the TC-degradation rates compared to those achieved in sterile BSFL systems. This conclusion was further supported by highly-efficient TC-biodegradation both in vivo and in vitro by four larval intestinal isolates. Moreover, detailed microbiome analysis indicated that intestinal bacterial and fungal communities were modified along with significantly increased tet gene copy number in the gut, providing the means to tolerate and degrade TC. Through analysis of TC degradation in vitro, four possible biodegradation products, two hydrolysis products and three conceivable inactivation products were identified, which suggested TC degradation reactions including hydrolysis, oxygenation, deamination, demethylation, ring-cleavage, modification, etc. In conclusion, our studies suggested an estimation of the fate of TC antibiotics in manure treatment by BSFL colonized by gut microbes. These results may provide a strategy for accelerating the degradation of antibiotics by adjusting the intestinal microbiota of BSFL.