Efficient biodechlorination at the Fe3O4-based silicone powder modified chlorobenzene-affinity anode.

The treatment of chlorinated volatile organic compounds faces challenges of secondary pollution and less-efficiency due to the substitution of chlorine. Microbial fuel cells (MFCs) provide a promising opportunity for its abatement. In this study, a novel Fe3O4 nanoparticles and silicone-based powder (SP) were integrated and immobilized on carbon felt (CF+Fe3O4@SP), which was further used as anode in the chlorobenzene (CB) powered MFC. Owing to the cooperation between SP and Fe3O4, the anode exhibited excellent performance for both biodechlorination and power generation. The results indicated that the CF+Fe3O4@SP anode loaded MFC achieved 98.5% removal of 200 mg/L CB within 28 h, and the maximum power density was 675.9 mW/m3, which was a 45.6% increase compared to that of the bare CF anode. Microbial community analysis indicated that the genera Comamonadaceae, Pandoraea, Obscuribacteraceae, and Truepera were dominated, especially, the Comamonadaceae and Obscuribacteraceae showed outstanding affinity for Fe3O4 and SP, respectively. Moreover, the proportion of live bacteria, secretion of extracellular polymer substances, and protein content in the extracellular polymer substances were significantly increased by modifying Fe3O4@SP onto the carbon-based anode. Thus, this study provides new insights into the development of MFCs for refractory and hydrophobic volatile organic compounds removal.

Assessment of flavor characteristics in snakehead (Ophiocephalus argus Cantor) surimi gels affected by atmospheric cold plasma treatment using GC-IMS.

The gel formation ability of freshwater surimi is weak, resulting in its poor flavor and quality. Atmospheric cold plasma (ACP), a widely developed non-thermal processing technology in the food industry, is considered to have potential applications in maintaining and improving the flavor characteristics of surimi gels. In this study, the effect of ACP on snakehead surimi gels flavor at different treatment times was investigated by sensory evaluation and gas chromatography-ion mobility spectrometry (GC-IMS) analysis. The results showed that ACP could better maintain and improve the original appearance and tissue state characteristics of surimi gels, scoring about 1-2 points higher than the ACP-untreated group. GC-IMS analysis demonstrated the obvious difference in the volatile organic compounds (VOCs) among the treatment groups. Specifically, the samples treated for 120 s with ACP exhibited the most unique aroma characteristics, which probably related to the highest thiobarbituric acid reactive substances values (73.28 µmol MDA/kg sample). Meanwhile, the reduced TCA-soluble peptides content indicated that ACP could inhibit protein degradation to maintaining the tissue state and flavor characteristics of the surimi gels. In conclusion, the advantages of ACP treatment, such as little damage to nutrients, and maximum retention of original sensory properties, provide new ideas for its application in the flavor characteristics of the snakehead surimi gels.

Investigation of reduction in risk from antibiotic resistance genes in laboratory wastewater by using O3 , ultrasound, and autoclaving.

Biological laboratory wastewater containing both antibiotic-resistant bacteria (ARB) and antibiotics is a potential source of antibiotic resistance genes (ARGs). Thus, we determined the efficacy of autoclaving, a common disinfection method, in eliminating 5 ARGs (sul1, sul2, tetW, tetM, amp) and the integrase-encoding gene intI1 from laboratory wastewater. Autoclaving (15 min, 121°C) inactivated all bacteria including ARB, whereas ARGs persisted in the wastewater with limited reduction even after 60 min of treatment. Ozonation (O3 ), ultrasound (US), O3 /US, and autoclaving followed by O3 were investigated for their ability to reduce ARGs in laboratory wastewater. With O3 and O3 /US, the reduction rate ranged from 5.44 to 7.13 log for all ARGs investigated. Wastewater treatment with US alone did not reduce ARGs under the present experimental conditions (150 W, 53 kHz). Among the four treatments, autoclaving followed by O3 treatment showed the highest reduction rates in the shortest time; however, further optimization and investigation are needed for the advanced treatment of bio-laboratory wastewater. Overall, this study provides novel insights into ARG sources and demonstrates that advanced oxidation methods can be useful to optimize laboratory wastewater treatment for ARG inactivation. PRACTITIONER POINTS: Bio-laboratory wastewater is potential reservoir of ARGs. Conventional autoclaving was not able to reduce ARGs to a low level. Autoclaving-O3 completely eliminate all the bacteria. Autoclaving-O3 reduced ARGs efficiently (6.12-7.86 logs removal in 60 min).

Interactions and microbial variations in a biotrickling filter treating low concentrations of hydrogen sulfide and ammonia.

A lab-scale biotrickling filter (BTF) packed with porcelain Rasching ring and ceramsite was applied for co-treating of low concentrations of hydrogen sulfide (H2S) and ammonia (NH3), as major pollutants typically found in e.g., intensive livestock production facilities. In this study, the outlet gas concentrations of H2S and NH3 were used for indicators if the treated gas reached odor-free condition. Overall, excellent removal efficiencies were obtained for both H2S and NH3 in the BTF during Stage I (H2S alone) and Stage II (H2S and NH3). Specifically, the H2S outlet concentration was below the detection limit (∼3.6 ppbv) and the NH3 outlet concentration was less than 0.4 ppmv when the inlet concentrations of H2S and NH3 were around 1.8 ppmv and 35.3 ppmv, respectively. In this case, the running empty bed residence time was 10.2 s. During Stage II, the outlet H2S concentration was decreased significantly when the inlet NH3 concentration was increased, likely due to the influence by pH. Meanwhile, the outlet nitrous oxide (N2O) concentration was kept low (<2% NH3) during the experiment, suggesting a proper operation of the BTF. After the inlet gas shifted from H2S alone at Stage I to H2S and NH3 at Stage II, the main sulfur-oxidizing bacteria (SOB) species in the BTF switched from Acidithiobacillus to Thiobacillus.

Microbial and isotopomer analysis of N2O generation pathways in ammonia removal biofilters.

Ammonia removal biofilters can be a potential source of nitrous oxide (N2O) production as a result of microbial nitrification and denitrification. In this study, these two N2O generation pathways was quantified using isotopic site preference values (SP, 33‰ for nitrification and 0‰ for denitrification) in a 204-d operation. Tests with two moisture conditions (45% and 55%) and three inlet NH3 concentrations (35, 18 and 0 ppmv) were performed. A 55+% NH3 removal efficiency was achieved in biofilters with 35 and 18 ppmv ammonia supply, but no significant difference (p > 0.05) was found between the moisture treatments. Results showed that biofilters were clearly net sources of N2O, and biofilters with higher moisture content generated significantly (p < 0.05) higher N2O concentration. The N2O generation did not stop even after the biofilters were terminated. The percentage of inlet NH3-N converted into N2O-N were 5.2%, 8.5% for biofilters with 45% moisture content, and 14.8%, 10.8% for those with 55% moisture content. Gene abundance of amoA and nosZ in packing materials (taken on days 64, 107, 140, 180 and 204) increased due to NH3 input reaching the highest on day 140 and then decreased in response to reduced NH3 supply on day 180 and 204. The changes of SP values suggested a shift between nitrification and denitrification with regard to N2O generation. Overall, the nitrification was the dominant pathway for N2O generation, but uncertainty exits as well. This study confirmed that NH3-loaded biofilters were net sources of N2O, and use of SP-N2O may be helpful in better understanding the processes responsible for such emissions.

Effects of carbon sources on 17 beta-estradiol degradation by Sphingomonas sp. and the analysis of the involved intracellular metabolomics.

17ß-estradiol (E2) ubiquitously exists in various water bodies with long-term endocrine-disrupting and carcinogenic impacts on wildlife even at the trace level of ng L-1. However, it remains unclear how easy-to-degrade carbon sources alter E2 biodegradation patterns. In this study, E2 biodegradation by Sphingomonas sp. MCCC 1A06484 was investigated with regard to alternative carbon sources. Results showed that the bacterium preferentially utilized glucose, sodium succinate and sodium acetate over E2. Interestingly, the presence of these preferred nutrients increased the E2 removal efficiency by 20.1%. Furthermore, a positive relation (p < 0.05) between the utilization of total organic carbon (TOC) and E2 was found. Using intracellular metabolomics by UHPLC-QTOF-MS, 11 up-regulated and 35 down-regulated metabolites (variable importance > 1, p < 0.05) were identified in the bacterium when cultivated with E2 under various carbon and nitrogen backgrounds. The E2 exposure contributed to metabolism changes of lipid, nucleotide, carbohydrate, amino acid and membrane transport, which were considered to play roles in the E2 metabolism. The up-regulated phosphatidylcholine might act as an indicator during the bacterial degradation of E2. Generally, this study contributes to an in-depth understanding of E2 biodegradation in complex environments with multiple carbon and nitrogen sources.

Thymol confers tolerance to salt stress by activating anti-oxidative defense and modulating Na+ homeostasis in rice root.

Modulation of plant salt tolerance has been drawing great attention. Thymol is a kind of natural chemical that has been developed as anti-microbial reagent and medicine. To date, we still have limited knowledge about thymol-modulated plant physiology. In this work, physiological, histochemical, and biochemical methods were adopted to study thymol-conferred salt resistance in the root of rice (Oryza sativa). Thymol significantly rescued root growth under salt stress. Thymol ameliorated cell membrane damage, oxidative stress, ROS accumulation, and cell death in roots under salt stress. Thymol-attenuated oxidative stress may be resulted from the activation of anti-oxidative capacity, including both enzymatic and non-enzymatic system. Thymol treatment significantly decreased Na+ content in root cells upon salt stress, which might be ascribed to the upregulation of OsSOS1 (salt overly sensitive 1) facilitating Na+ exclusion. In addition, thymol stimulated the expression of genes encoding tonoplast OsNHX (Na+/H+antiporter), which may help root cells to compartmentalize Na+ in vacuole. The results of these works evidenced that thymol was capable of inducing salt tolerance by reestablishing ROS homeostasis and modulating cellular Na+ flux in rice roots. These findings may be applicable to improve crop growth in salinity area.

Start-up evaluations and biocarriers transfer from a trickling filter to a moving bed bioreactor for synthetic mariculture wastewater treatment.

Mariculture wastewater treatment by nitrification requires a long start-up time due to high salinity stress. This study aimed to verify the faster start-up of a trickling filter (TF) compared to a moving bed bioreactor (MBBR) treating synthetic mariculture wastewater, and to investigate the feasibility of transferring mature biocarriers from the TF to a new MBBR (TF-MBBR). The nitrogen removal performance, biofilm physicochemical properties and microbial communities were investigated. The results obtained showed that, the TF started up 41 days faster than the MBBR, despite the richer microbial diversity in the latter. Lower biofilm roughness and protein content as well as higher adhesive force and polysaccharide content in the TF were obtained compared to the MBBR. Adhesive force was found to be negatively correlated with roughness (r = -0.630, p = 0.069). Transmittance assigned to amide II (1538 cm-1) and amid III (1243 cm-1) through Fourier transform infrared spectroscopy (FTIR) determination was only obtained in the TF, which was likely related to the faster start-up. Nitrosomonas and Nitrospira were detected as the predominant nitrifiers in both reactors. In addition, the new MBBR, incubated with the mature biocarriers transferred from the TF, had a satisfactory nitrification performance with no lag time. Interestingly, the transfer action increased the microbial diversity and made the biofilm physicochemical characteristics shift toward those of the MBBR. Taken together, the study confirmed that MBBR nitrification start-up can be accelerated via TF and biocarrier transfer.

High removal efficiency of antibiotic resistance genes in swine wastewater via nanofiltration and reverse osmosis processes.

Swine wastewater treatment plant has become one of the main sources of antibiotic resistance genes (ARGs). Membrane treatment processes are promising solutions for removal of the emerging contaminants. However, limited studies have investigated the effects of nanofiltration and reverse osmosis treatment in removing ARGs in swine wastewater. In this study, the presence and the fate of common ARGs including sul1, sul2, tetA, tetM and tetW, as well as intI1 and 16S rRNA gene, were investigated in a medium-sized (6500) pig farm wastewater treatment plant (WWTP) equipped with conventional biological treatment and advanced membrane processing system. All of the genes were detected with highly abundance in the raw sewage. The biological treatments of the swine wastewater treatment plant did not reduce the quantity of the ARGs. As expected, nanofiltration and reverse osmosis treatment reduced the absolute gene copy number of ARGs efficiently (4.98-9.52 logs removal compared to raw sewage). Compared to the reverse osmosis effluent, however, the absolute abundance of ARGs in the artificial wetland increased by 1.00-2.06 logs. Meanwhile, the relative abundance of sulfonamide resistant genes were basically unchanged, while tetracycline resistance genes (tetA, tetM and tetW) decreased by 0.88, 3.47, 2.51 log, respectively. The results demonstrated that advanced membrane treatments are capable of removing various kinds of ARGs efficiently, as well as some common nitrogen and phosphorus contaminants. This study suggested a mature alternative method for the removal of ARGs from livestock wastewater.

Microbial N Transformations and N2O Emission after Simulated Grassland Cultivation: Effects of the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP).

Grassland cultivation can mobilize large pools of N in the soil, with the potential for N leaching and N2O emissions. Spraying with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) before cultivation was simulated by use of soil columns in which the residue distribution corresponded to plowing or rotovation to study the effects of soil-residue contact on N transformations. DMPP was sprayed on aboveground parts of ryegrass and white clover plants before incorporation. During a 42-day incubation, soil mineral N dynamics, potential ammonia oxidation (PAO), denitrifying enzyme activity (DEA), nitrifier and denitrifier populations, and N2O emissions were investigated. The soil NO3- pool was enriched with 15N to trace sources of N2O. Ammonium was rapidly released from decomposing residues, and PAO was stimulated in soil near residues. DMPP effectively reduced NH4+ transformation irrespective of residue distribution. Ammonia-oxidizing archaea (AOA) and bacteria (AOB) were both present, but only the AOB amoA transcript abundance correlated with PAO. DMPP inhibited the transcription of AOB amoA genes. Denitrifier genes and transcripts (nirK, nirS, and clades I and II of nosZ) were recovered, and a correlation was found between nirS mRNA and DEA. DMPP showed no adverse effects on the abundance or activity of denitrifiers. The 15N enrichment of N2O showed that denitrification was responsible for 80 to 90% of emissions. With support from a control experiment without NO3- amendment, it was concluded that DMPP will generally reduce the potential for leaching of residue-derived N, whereas the effect of DMPP on N2O emissions will be significant only when soil NO3- availability is limiting. IMPORTANCE: Residue incorporation following grassland cultivation can lead to mobilization of large pools of N and potentially to significant N losses via leaching and N2O emissions. This study proposed a mitigation strategy of applying 3,4-dimethylpyrazole phosphate (DMPP) prior to grassland cultivation and investigated its efficacy in a laboratory incubation study. DMPP inhibited the growth and activity of ammonia-oxidizing bacteria but had no adverse effects on ammonia-oxidizing archaea and denitrifiers. DMPP can effectively reduce the potential for leaching of NO3- derived from residue decomposition, while the effect on reducing N2O emissions will be significant only when soil NO3- availability is limiting. Our findings provide insight into how DMPP affects soil nitrifier and denitrifier populations and have direct implications for improving N use efficiency and reducing environmental impacts during grassland cultivation.