Enhancing Extracellular Electron Transfer of a 3D-Printed Shewanella Bioanode with Riboflavin-Modified Carbon Black Bioink.

3D printing of a living bioanode holds the potential for the rapid and efficient production of bioelectrochemistry systems. However, the ink (such as sodium alginate, SA) that formed the matrix of the 3D-printed bioanode may hinder extracellular electron transfer (EET) between the microorganism and conductive materials. Here, we proposed a biomimetic design of a 3D-printed Shewanella bioanode, wherein riboflavin (RF) was modified on carbon black (CB) to serve as a redox substance for microbial EET. By introducing the medicated EET pathways, the 3D-printed bioanode obtained a maximum power density of 252 ± 12 mW/m2, which was 1.7 and 60.5 times higher than those of SA-CB (92 ± 10 mW/m2) and a bare carbon cloth anode (3.8 ± 0.4 mW/m2). Adding RF reduced the charge-transfer resistance of a 3D-printed bioanode by 75% (189.5 ± 18.7 vs 47.3 ± 7.8 Ω), indicating a significant acceleration in the EET efficiency within the bioanode. This work provided a fundamental and instrumental concept for constructing a 3D-printed bioanode.

Longitudinal and vertical distribution of microplastics in various pipe scales in an operating drinking water distribution system.

Microplastics (MPs) are ingested by humans through the daily consumption of drinking water. Pipe scales are recognized as important sites of MPs occurrence in the drinking water distribution system (DWDS). Despite extensive research on drinking water, no study has been conducted to investigate the distribution of MPs in pipe scales within an operational DWDS. The underground placement of DWDSs brings challenges for sampling pipe scales. In this study, 5 tap water and 16 pipe scales samples were collected from a typical DWDS. The analysis of MPs abundance in these 21 samples filled the data gap in the distribution of MPs in both pipe scales and tap water along the DWDSs. MPs were detected in all water samples (1.74-20.88 MPs/L) and pipe scales samples (0.03-3.48 MPs/cm2). In tap water, MPs abundance increased abruptly in the stagnant-slow flow region and reached the maximum value (20.88 MPs/L), even surpassing the abundance in raw water (6.42 MPs/L). In the pipe scales, MPs abundance decreased from the upstream to downstream of DWDS and was associated with the heavy metal concentration. MPs smaller than 150 µm accounted for 91.6% of the tap water (21-971 µm) and pipe scales (20-2055 µm). The abundance of MPs showed a logarithmic increase as the size decreased. The proportion of MPs fibers in tap water was lower than that in pipe scales. A total of 35 MPs polymers were detected, with 34 polymers in pipe scales and 26 polymers in tap water. In terms of abundance, polyethylene terephthalate (50.0%) was the dominant polymer in pipe scales, while polyamide (70.3%) was the dominant polymer in tap water. Regarding detection rate, polyamide was detected in all 21 samples, followed by polyurethane in 19 samples. The distribution of MPs along the longitudinal direction of the DWDS was correlated with heavy metal. While the distribution of MPs in the vertical direction of large diameter pipe scales was dependent on their sizes, and densities. The greatest abundance, size and density of MPs were detected at the bottom 120-degree.

Simultaneous adsorption and biodegradation of polychlorinated biphenyls using resuscitated strain Streptococcus sp. SPC0 immobilized in polyvinyl alcohol­sodium alginate.

Enhanced bioremediation of polychlorinated biphenyls (PCBs) is a promising and effective strategy for eliminating the risks posed by PCBs. In the present study, the feasibility of utilizing an immobilization approach to enhance the PCBs degradation performance of a resuscitated strain Streptococcus sp. SPC0 was evaluated. The results indicated that a mixed matrix containing polyvinyl alcohol (PVA) and sodium alginate (SA) used as immobilized carriers provided a porous microstructure space for SPC0 colonization and proliferation. The enhanced removal of PCBs by immobilized SPC0 was attributed to simultaneous adsorption and biodegradation performances of PVA-SA-SPC0 beads. The relative equilibrium adsorption capacity of immobilized beads increased with elevated initial concentration, and the maximum theoretical value calculated was 1.64 mg/g. The adsorption process of PCBs by immobilized beads was well fitted to the quasi-second-order kinetic model, and most suitable for Langmuir isotherm model. Immobilized SPC0 enhanced PCB removal with 1.0-7.1 times higher than free cells. Especially, more effective removal of PCBs at higher concentrations could be achieved, in which 73.9 % of 20 mg/L PCBs was removed at 12 h by immobilized SPC0, whereas only 12.0 % by free cells. Moreover, the immobilized SPC0 with excellent stability and reusability retained almost 100 % of the original PCBs removal activity after reusing four times. These results revealed the application potential of immobilizing resuscitated strains for enhanced bioremediation of PCBs.

Effect of microplastics on microbial dechlorination of a polychlorinated biphenyl mixture (Aroclor 1260).

Microplastics (MPs) and polychlorinated biphenyls (PCBs) generally coexist in the environment, posing risks to public health and the environment. This study investigated the effect of different MPs on the microbial anaerobic reductive dechlorination of Aroclor 1260, a commercial PCB mixture. MP exposure inhibited microbial reductive dechlorination of PCBs, with inhibition rates of 39.43%, 23.97%, and 17.53% by polyethylene (PE), polypropylene (PP), and polystyrene (PS), respectively. The dechlorination rate decreased from 1.63 µM Cl- d-1 to 0.99-1.34 µM Cl- d-1 after MP amendment. Chlorine removal in the meta-position of PCBs was primarily inhibited by MPs, with no changes in the final PCB dechlorination metabolites. The microbial community compositions in MP biofilms were not significantly different (P > 0.05) from those in suspension culture, although possessing greater Dehalococcoides abundance (0.52-0.81% in MP biofilms; 0.03-0.12% in suspension culture). The co-occurrence network analysis revealed that the presence of MPs attenuated microbial synergistic interactions in the dechlorinating culture systems, which may contribute to the inhibitory effect on microbial PCB dechlorination. These findings are important for comprehensively understanding microbial dechlorination behavior and the environmental fate of PCBs in environments with co-existing PCBs and MPs and for guiding the application of in situ PCB bioremediation.

Beta-cyclodextrin enhanced phytoremediation of aged PCBs-contaminated soil from e-waste recycling area.

The objective in the first phase of this study was to screen four plant species (alfalfa, ryegrass, tall fescue and rice) for phytoremediation of aged polychlorinated biphenyl (PCB)-contaminated soil from an electronic and electric waste (e-waste) recycling site. Glucose, biphenyl and three surfactants (TritonX-100, randomly methylated-beta-cyclodextrins and beta-cyclodextrin) were used to enhance the phytoremediation process. During the second phase, the focus was rhizosphere characteristics and plant uptake to investigate the mechanism of PCB removal from soil. In the first phase, all the tested plant species showed a significantly greater PCB removal percentage compared to the unplanted controls, while different amendments showed no significant difference. The most effective plant (ryegrass) combined with beta-cyclodextrin was selected for further studies. During the rhizosphere characteristics and plant uptake study, the highest PCB removal percentage (38.1%) was observed in the ryegrass planted soil when beta-cyclodextrin was amended at 1.0% (w/w). The presence of plants significantly increased the biological activity (microbial counts and enzyme activity) of both beta-cyclodextrin amended and non-amended soils. Higher levels of PCB removal were closely related to greater microbial counts and soil enzyme activities by correlation analysis. After 120 days of plant growth, ryegrass accumulated 708.7-820.1 ng PCBs/g in the root and 71.7-110.8 ng PCBs/g in the shoot, resulting in about 0.08% PCBs removal from soil. It was concluded that high PCB degradation was due to the increased PCB bioavailability as well as biostimulation of microbial communities after plantation and beta-cyclodextrin addition. Furthermore, results suggested that PCB removal was mainly contributed by microbial degradation rather than plant uptake or abiotic dissipation.

Surfactant enhanced pyrene degradation in the rhizosphere of tall fescue (Festuca arundinacea).

The present study was conducted to evaluate the effect of two non ionic surfactants (Tween 80 and Triton X-100), a biosurfactant (Lecithin), and randomly methylated-ß-cyclodextrins (RAMEB) on the remediation of pyrene from soil planted with tall fescue (Festuca arundinacea). Soils with pyrene concentration of about 243 mg kg(-1) was grown with tall fescue and were individually amended with 0, 200, 600, 1000, and 1500 mg kg(-1) of Tween 80, Triton X-100, biosurfactant, and RAMEB. The results show that all surfactants significantly increased plant biomass compared to unamended soil. Dehydrogenase activity was also stimulated as a result of surfactant addition. Only 3.9 and 3.2 % of pyrene was decreased in the uncovered and covered abiotic sterile control, suggesting that microbial degradation was the main removal mechanism of pyrene from soil. In the planted treatment receiving no surfactant, the remediation of pyrene was 45 % which is significantly higher than that of corresponding unplanted control soil, suggesting that the cultivation of tall fescue alone could enhance the overall remediation of pyrene in soil. All surfactants had significantly higher rates of pyrene remediation compared to the unamended planted soil. Generally, RAMEB displayed the highest remediation rates, i.e., 64.4-79.1 % followed by the Triton X-100, i.e., 60.1-74.8 %. The positive impact of surfactants on pyrene remediation could possibly be because of their capacities to increase its bioavailability in soil. The evidence from this study suggests that the addition of surfactants could enhance phytoremediation of PAHs polluted soil.

[Environmental behavior and ecological effect of polydimethylsiloxane: a review].

Polydimethylsiloxane (PDMS) is widely used in industrial products, medical and health care products, and personal care products. In the treatment process of sewage, PDMS can be hardly biodegraded but enter the environment mainly through the discharge of excess sludge, and only a small amount of PDMS adsorbed on the suspended solids or sludge particle surface is discharged into water body and sediment with treated sewage. There is no enough evidence to verify that PDMS can vertically migrate in sediment. The degradation of PDMS in sediment is very slow, but PDMS can be degraded in different types of soils. PDMS has less risk to aquatic ecosystem, and no apparent acute toxicity to benthos. In soil environment, PDMS and its degradation products have no significant effects on the soil microorganisms, soil animals, and crops. Though a few studies indicated that PDMS and its degradation products have relatively low ecological toxicity in various environments, it is still very important to clarify the potential threat of PDMS to the environment because of the increasingly large number of PDMS being produced and used.

Levels and patterns of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in municipal waste incinerator bottom ash in Zhejiang province, China.

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were analyzed in bottom ash from municipal solid waste (MSW) incineration in six cities in Zhejiang province, where one-fourth of the MSW incinerators of China are located. Total PAH contents varied from 2222.53 to 6883.91 microg/kg. The patterns of PAHs were found to be very similar in all the samples, dominated by three-ring and four-ring PAHs. Total PCB concentrations in bottom ash ranged from 1.00 to 1.31 microg/kg, while the coplanar PCBs in the bottom ash were in the range of 0.08-0.52 microg/kg. Among PCB congeners, low chlorinated PCBs contributed to the majority of total PCBs. Generally, PAH concentrations in cities with fluidized bed incinerator were less than those in cities with grate furnace incinerator. PAH and PCB levels were affected by both plastic content in MSW incinerator feed and combustion efficiency. However, further study is required to investigate the effect of these two variables deeply, as well as other influencing factors.