Wnt/Wingless signaling promotes lipid mobilization through signal-induced transcriptional repression.

The Wnt/Wingless signaling pathway plays critical roles in metazoan development and energy metabolism, but its role in regulating lipid homeostasis remains not fully understood. Here, we report that the activation of canonical Wnt/Wg signaling promotes lipolysis while concurrently inhibiting lipogenesis and fatty acid ß-oxidation in both larval and adult adipocytes, as well as cultured S2R+ cells, in Drosophila. Using RNA-sequencing and CUT&RUN (Cleavage Under Targets & Release Using Nuclease) assays, we identified a set of Wnt target genes responsible for intracellular lipid homeostasis. Notably, active Wnt signaling directly represses the transcription of these genes, resulting in decreased de novo lipogenesis and fatty acid ß-oxidation, but increased lipolysis. These changes lead to elevated free fatty acids and reduced triglyceride (TG) accumulation in adipocytes with active Wnt signaling. Conversely, downregulation of Wnt signaling in the fat body promotes TG accumulation in both larval and adult adipocytes. The attenuation of Wnt signaling also increases the expression of specific lipid metabolism-related genes in larval adipocytes, wing discs, and adult intestines. Taken together, these findings suggest that Wnt signaling-induced transcriptional repression plays an important role in regulating lipid homeostasis by enhancing lipolysis while simultaneously suppressing lipogenesis and fatty acid ß-oxidation.

Metabolic control by the Bithorax Complex-Wnt signaling crosstalk in Drosophila.

Adipocytes distributed throughout the body play crucial roles in lipid metabolism and energy homeostasis. Regional differences among adipocytes influence normal function and disease susceptibility, but the mechanisms driving this regional heterogeneity remain poorly understood. Here, we report a genetic crosstalk between the Bithorax Complex ( BX-C ) genes and Wnt/Wingless signaling that orchestrates regional differences among adipocytes in Drosophila larvae. Abdominal adipocytes, characterized by the exclusive expression of abdominal A ( abd-A ) and Abdominal B ( Abd-B ), exhibit distinct features compared to thoracic adipocytes, with Wnt signaling further amplifying these disparities. Depletion of BX-C genes in adipocytes reduces fat accumulation, delays larval-pupal transition, and eventually leads to pupal lethality. Depleting Abd-A or Abd-B reduces Wnt target gene expression, thereby attenuating Wnt signaling-induced lipid mobilization. Conversely, Wnt signaling stimulated abd-A transcription, suggesting a feedforward loop that amplifies the interplay between Wnt signaling and BX-C in adipocytes. These findings elucidate how the crosstalk between cell-autonomous BX-C gene expression and Wnt signaling define unique metabolic behaviors in adipocytes in different anatomical regions of fat body, delineating larval adipose tissue domains.

Distinct effects of CDK8 module subunits on cellular growth and proliferation in Drosophila.

The Mediator complex, composed of about 30 conserved subunits, plays a pivotal role in facilitating RNA polymerase II-dependent transcription in eukaryotes. Within this complex, the CDK8 kinase module (CKM), comprising Med12, Med13, CDK8, and CycC (Cyclin C), serves as a dissociable subcomplex that modulates the activity of the small Mediator complex. Genetic studies in Drosophila have revealed distinct phenotypes of CDK8-CycC and Med12-Med13 mutations, yet the underlying mechanism has remained unknown. Here, using Drosophila as a model organism, we show that depleting CDK8-CycC enhances E2F1 target gene expression and promotes cell-cycle progression. Conversely, depletion of Med12-Med13 affects the expression of ribosomal protein genes and fibrillarin, indicating a more severe reduction in ribosome biogenesis and cellular growth compared to the loss of CDK8-CycC. Moreover, we found that the stability of CDK8 and CycC relies on Med12 and Med13, with a mutually interdependent relationship between Med12 and Med13. Furthermore, CycC stability depends on the other three CKM subunits. These findings reveal distinct roles for CKM subunits in vivo , with Med12-Med13 disruption exerting a more pronounced impact on ribosome biogenesis and cellular growth compared to the loss of CDK8-CycC. Significance: The CDK8 kinase module (CKM), comprising CDK8, CycC, Med12, and Med13, is essential in the Mediator complex for RNA polymerase II-dependent transcription in eukaryotes. While expected to function jointly, CKM subunit mutations result in distinct phenotypes in Drosophila . This study investigates the mechanisms driving these differing effects. Our analysis reveals the role of Med12-Med13 pair in regulating ribosomal biogenesis and cellular growth, contrasting with the involvement of CDK8-CycC in E2F1-dependent cell-cycle progression. Additionally, an asymmetric interdependence in the stability of CDK8-CycC and Med12-Med13 was observed. CKM mutations or overexpression are associated with cancers and cardiovascular diseases. Our findings underscore the distinct impacts of CKM mutations on cellular growth and proliferation, advancing our understanding of their diverse consequences in vivo .

Transcriptional coupling of telomeric retrotransposons with the cell cycle.

Instead of employing telomerases to safeguard chromosome ends, dipteran species maintain their telomeres by transposition of telomeric-specific retrotransposons (TRs): in Drosophila , these are HeT-A , TART , and TAHRE . Previous studies have shown how these TRs create tandem repeats at chromosome ends, but the exact mechanism controlling TR transcription has remained unclear. Here we report the identification of multiple subunits of the transcription cofactor Mediator complex and transcriptional factors Scalloped (Sd, the TEAD homolog in flies) and E2F1-Dp as novel regulators of TR transcription and telomere length in Drosophila . Depletion of multiple Mediator subunits, Dp, or Sd increased TR expression and telomere length, while over-expressing E2F1-Dp or knocking down the E2F1 regulator Rbf1 (Retinoblastoma-family protein 1) stimulated TR transcription, with Mediator and Sd affecting TR expression through E2F1-Dp. The CUT&RUN analysis revealed direct binding of CDK8, Dp, and Sd to telomeric repeats. These findings highlight the essential role of the Mediator complex in maintaining telomere homeostasis by regulating TR transcription through E2F1-Dp and Sd, revealing the intricate coupling of TR transcription with the host cell-cycle machinery, thereby ensuring chromosome end protection and genomic stability during cell division.

Cdk8 attenuates lipogenesis by inhibiting SREBP-dependent transcription in Drosophila.

Fine-tuning of lipogenic gene expression is important for the maintenance of long-term homeostasis of intracellular lipids. The SREBP family of transcription factors are master regulators that control the transcription of lipogenic and cholesterogenic genes, but the mechanisms modulating SREBP-dependent transcription are still not fully understood. We previously reported that CDK8, a subunit of the transcription co-factor Mediator complex, phosphorylates SREBP at a conserved threonine residue. Here, using Drosophila as a model system, we observed that the phosphodeficient SREBP proteins (SREBP-Thr390Ala) were more stable and more potent in stimulating the expression of lipogenic genes and promoting lipogenesis in vivo than wild-type SREBP. In addition, starvation blocked the effects of wild-type SREBP-induced lipogenic gene transcription, whereas phosphodeficient SREBP was resistant to this effect. Furthermore, our biochemical analyses identified six highly conserved amino acid residues in the N-terminus disordered region of SREBP that are required for its interactions with both Cdk8 and the MED15 subunit of the small Mediator complex. These results support that the concerted actions of Cdk8 and MED15 are essential for the tight regulation of SREBP-dependent transcription. This article has an associated First Person interview with the first author of the paper.

Metagenomic analysis and nitrogen removal performance evaluation of activated sludge from a sequencing batch reactor under different salinities.

The effect of salinity on the nitrogen removal performance and microbial community of activated sludge was investigated in a sequencing batch reactor. The NH4+-N removal efficiency was over 95% at 0-4% salinity, indicating that the nitrification performance of activated sludge was slightly affected by lower salinity. The obvious nitrite accumulation was observed with the increment of the salinity to 5%, followed by a notable decline in the nitrogen removal performance at 6% salinity. The salinity inhibited the microbial activity, and the specific rate of nitrification and denitrification was decreased by the increasing salinity obviously. Additionally, the lower activity of superoxide dismutase and peroxidase and higher reactive oxygen species content in activated sludge might account for the deteriorative nitrogen removal performance at 6% salinity. Metagenomics analysis revealed that the genes encoding the ABC-type quaternary amine transporter in the ABC transporter pathway were abundant in the activated sludge at 2% and 4% salinity, and the higher salinity of 6% led to the loss of the genes encoding the p-type Na+ transporter in the ABC transporter pathway. These results indicated that the salinity could weaken the ABC transporter pathway for the balance of osmotic pressure in activated sludge. The microbial activity and nitrogen removal performance of activated sludge were decreased due to the unbalanced osmotic pressure at higher salinity.

Effect of external carbon addition and enrofloxacin on the denitrification and microbial community of sequencing batch membrane reactor treating synthetic mariculture wastewater.

The effect of sequencing batch membrane bioreactor (SMBR) on external carbon addition and enrofloxacin was investigated to treat synthetic mariculture wastewater. Anoxic/anaerobic and low COD/TN can improve the ammonia oxidation of the system, and the NH4+-N removal efficiency above 99%. External carbon was added and an anoxic environment was set to provide a suitable environment for denitrifying bacteria. When the external carbon source was 50-207 mg/L, the TN removal efficiency (31.82%-37.73%) and the COD of the effluent (28.85-36.58 mg/L) had little change. The partition resistance model showed that cake deposition resistance (RC,irr) and irreversible resistance (RPB) were the main components. And with the increase in cleaning times, the fouling rate of membrane components accelerated. Enrofloxacin can promote the TN removal efficiency (45.66%-93.74%) and had a significant effect on TM7a, Cohaesibacter, Vibrio and Phaeobacter.

Impact of sulfamethoxazole and organic supplementation on mixotrophic denitrification process: Nitrate removal efficiency and the response of functional microbiota.

Recirculating aquaculture systems (RAS) effluent is characterized by low COD to total inorganic nitrogen ratio (C/N), excessive nitrate, and the presence of traces of antibiotics. Hence, it urgently needs to be treated before recycling or discharging. In this study, four denitrification bioreactors at increasing C/N ratios (0, 0.7, 2, and 5) were started up to treat mariculture wastewater under the sulfamethoxazole (SMX) stress, during which the bioreactors performance and the shift of mixotrophic microbial communities were explored. The result showed that during the SMX exposure, organic supplementation enhanced nitrate and thiosulfate removal, and eliminated nitrite accumulation. The denitrification rate was accelerated by increasing C/N from 0 to 2, while it declined at C/N of 5. The decline was ascribed to which SMX reduced the relative abundance of denitrifiers, but improved the capability of dissimilatory nitrogen reduction to ammonia (DNRA) and sulfide production. The direct evidence was the relative abundance of sulfidogenic populations, such as Desulfuromusa, Desulfurocapsa, and Desulfobacter increased under the SMX stress. Moreover, high SMX (1.5 mg L-1) caused the obvious accumulation of ammonia at C/N of 5 due to the high concentration of sulfide (3.54 ± 1.08 mM) and the enhanced DNRA process. This study concluded that the mixotrophic denitrification process with the C/N of 0.7 presented the best performance in nitrate and sulfur removal and indicated the maximum resistance to SMX.

Removal effect of enrofloxacin from mariculture sediments by bioelectrochemical system and analysis of microbial community structure.

Based on the application of sediment microbial fuel cell (SMFC) in the bioremediation of sediment, this study used the sediment microbial fuel cell technology as the leading reactor. Modification of anode carbon felts (CF) by synthesis of PANI/MnO2 composited to improve the electrical performance of the sediment microbial fuel cell. This study investigated the degradation effects, degradation pathways of the specific contaminant enrofloxacin and microbial community structure in sediment microbial fuel cell systems. The results showed that the sediment microbial fuel cell system with modified anode carbon felt (PANI-MnO2/CF) prepared by in-situ chemical polymerization had the best power production performance. The maximum output voltage was 602 mV and the maximum power density was 165.09 mW m-2. The low concentrations of enrofloxacin (12.81 ng g-1) were effectively degraded by the sediment microbial fuel cell system with a removal rate of 59.52%.

Nitrogen and sulfamethoxazole removal in a partially saturated vertical flow constructed wetland treating synthetic mariculture wastewater.

This study investigated the removal of nitrogen and sulfamethoxazole (SMX), and the microbial communities in a partially saturated vertical flow constructed wetland (PS-VFCW) fed with synthetic mariculture wastewater operated at different saturated zone depths (SZDs), i.e. 51, 70, and 60 cm. Removal efficiencies were 99.8%-100.0% for COD, 34.1%-100.0% for NH4+-N, 67.8%-97.3% for total inorganic nitrogen (TIN), and 29.8%-57.2% for SMX. Excellent nitrification performance was achieved at the SZDs of 51 and 60 cm. Denitrification performed well at 70 and 60 cm SZDs. The highest TIN removal efficiency (97.3%) was achieved as the SZD was 60 cm. SMX removal was significantly influenced by SZD and was promoted by higher SZD. The removal of organics, nitrogen, and SMX mainly occurred in the unsaturated zone. Ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, denitrifying bacteria, and SMX-degrading bacteria were detected in the unsaturated and saturated zones, and showed an increasing trend in abundance along the depth.

Insights into the response of anammox sludge to the combined stress of nickel and salinity.

Anaerobic ammonium oxidation (anammox) is a promising technology applied to treat industrial wastewater, while the commonly coexistent heavy metals and salinity usually become a challenging issue to be addressed. In this study, the responses of anammox sludge in terms of performance, activity, functional enzyme and extracellular polymeric substance (EPS) to the combined stress of Ni(II) and salinity (20 ‰) were investigated holistically. It turned out that low Ni(II) concentration (0.2 mg·L-1) together with salinity (20 ‰) showed an insignificant effect on the anammox performance, while a decreased nitrogen removal by 46.96 % was observed with the increased Ni(II) concentration to 1 mg·L-1. It should be pointed out that the anammox system exhibited good robustness evidenced by rapid recovery to achieve 89.13 % of nitrogen removal efficiency and 1.21 kg·m-3·d-1 of nitrogen removal rate after the elimination of stress factors within 40 days. Ni(II) concentration was revealed to play a more important role in the specific activity of anammox sludge. The functional enzymes related to nitrogen removal, e.g. nitrite reductase (NIR), hydrazine oxidase (HZO) and heme c were found to be inhibited by the combined stress of Ni(II) and salinity, with decreased activity by 49.54 %, 39.39 % and 45.88 %, respectively. However, the enzyme related to assimilation, e.g. alkaline phosphatase (AKP) and nitrate reductase (NAR) appeared to be enhanced. The EPS content was found to decrease by 55.19 % under the combined stress. Detailed analysis of 3D-EEM and FTIR spectra further revealed that the combined stress of Ni(II) and salinity could change both the quantity and composition of EPS in anammox sludge. These results are expected to offer insights into the combined effect of nickel and salinity on the anammox system, and benefit the application of anammox technology for industrial metal-rich saline wastewater treatment.

Electrochemical degradation of tetracycline hydrochloride in sulfate solutions on boron-doped diamond electrode: The accumulation and transformation of persulfate.

In this study, a novel electrifying mode (divided power-on and power-off stage) was applied in the system of BDD activate sulfate to degrade tetracycline hydrochloride (TCH). The BDD electrode could activate sulfate and H2O to generate sulfate radicals (SO4•-) and hydroxyl radicals (•OH) to remove TCH, and SO4•- could dimerize to form S2O82-. Then, the S2O82- was activated by heat and quinones to generate SO4•- for the continuous degradation of TCH during the power-off stage. In addition, the intermittent time has a significant effect on the degradation of TCH. Factors, affecting the accumulation of S2O82-, were analyzed using a full factorial design, and the accumulation of S2O82- could reach 16.2 mM in 120 min. The results of electron spin resonance and radical quenching test showed that SO4•-, •OH, direct electron transfer (DET), and non-radical in the system could effectively degrade TCH, and SO4•- was dominated. The intermediate products of TCH were analyzed by HPLC-QTOF-MS/MS, and the TCH mainly underwent hydroxylation, demethylation and ring opening reactions to form small molecules, and finally mineralized. The results of the feasibility analysis revealed that some intermediates have high toxicity, but the system could improve the toxicity. The results of energy consumption indicated that the intermittent electrifying mode could make full use of the persulfate generated during the power-on stage and reduce about 30% energy consumption. In conclusion, this work demonstrated that it was economically feasible to degrade TCH in wastewater by activating sulfate with BDD electrodes with an intermittent electrifying mode.

Comparison of primary and secondary sludge carbon sources derived from hydrolysis or acidogenesis for nitrate reduction and denitrification kinetics: Organics utilization and microbial community shift.

Seeking available and economical carbon sources for denitrification process is an intractable issue for wastewater treatment. However, no study compared different types of waste sludge as carbon source from denitrification mechanism, organics utilization and microbial community aspects. In this study, primary and secondary sludge were pretreated by thermophilic bacteria (TB), and its hydrolysis or acidogenic liquid were prepared as carbon sources for denitrification. At C/N of 8-3, the variations of NO3--N and NO2--N were profiled in typical cycles and denitrification kinetics was analyzed. Primary sludge achieved a competitive NOX-N removal efficiency with less dosage than secondary sludge. Fourier transform infrared (FTIR) spectroscopy was introduced to analyze organic composition from functional-group perspective and the utilization of organic matters in different sludge carbon sources was investigated. To further analyze the microbial community shift in different denitrification systems, high-throughput sequencing technology was applied. Results showed that denitrifier Thauera, belonging to Proteobacteria, was predominant, and primary sludge acidogenic liquid enriched Thauera most intensively with relative abundance of 47.3%.

Insight in degradation of tetracycline in mariculture wastewater by ultraviolet/persulfate advanced oxidation process.

The direct discharge of trace amounts of antibiotics in mariculture wastewater results in adverse effect on the ecological environment of receiving waters. Hence, the degradation of tetracycline (TC) in mariculture wastewater by the ultraviolet/peroxydisulfate (UV/PS) process was investigated in this study. The results revealed that 95.73% removal of TC with 5 mg/L dosage was achieved after 30 min UV/PS treatment. Chloride ion (Cl-) in mariculture wastewater slightly inhibited TC degradation by scavenging free radicals. Comparably, bromine ion (Br-) significantly enhanced the removal of TC and even doubled the degradation rate. Reactive bromine species (RBS) made a major contribution to the TC removal, followed by free chlorine and other reactive chlorine species (RCS). The TC degradation pathway revealed that functional group shedding and ring-opening reactions occurred successively. In addition, TC mineralization rate was low within 30 min, causing the inefficient reduction of acute toxicity of TC and its intermediates, which could be improved by optimizing the process parameters. These results indicated that UV/PS is a new alternative process for the harmless treatment of mariculture wastewater containing the antibiotics.

Sulfamethoxazole removal from mariculture wastewater in moving bed biofilm reactor and insight into the changes of antibiotic and resistance genes.

Antibiotics are widely dosed in mariculture sector, resulting in substantial antibiotics residues. Hence, mariculture wastewater is urgent to be treated before discharging. In this study, the anoxic/oxic moving bed biofilm reactor (A/O-MBBR) was used to treat the wastewater containing sulfamethoxazole (SMX) from mariculture, SMX removal mechanism and the variation of antibiotic-resistant genes (ARGs) were investigated. The results showed that 22%-33% of SMX was removed by the bioreactor, where a small amount of SMX was adsorbed and stored by the extracellular polymers and most of SMX (>80%) was biodegraded in the anoxic tank. Occurrence of nitrate in anoxic condition was conducive to SMX degradation. Pseudomonas, Desulfuromusa, and Methanolobus species, as well as microbial catalase contributed to the SMX biotransformation. Quantitative PCR analysis of ARGs (sul1, sul2 and int1) and mRNA (sul1, sul2) showed that SMX enriched SMX-related ARGs and enhanced the expression of corresponding genes. Most of ARGs finally were discharged with effluent. Hence, the effluent from biologically based processes treating mariculture wastewater still contained antibiotics residue and resistance genes, which should be further controlled by suitable techniques.

Enhanced aerobic granular sludge by static magnetic field to treat saline wastewater via simultaneous partial nitrification and denitrification (SPND) process.

Saline wastewater poses a threat to biological nitrogen removal. This study investigated whether and how static magnetic field (SMF) can improve the salt-tolerance of aerobic granular sludge (AGS) in two simultaneous partial nitrification and denitrification (SPND) reactors. Results confirmed that the SMF improved the mean size and settleability of granules, stimulated secretion of extracellular polymeric substances with high protein content, in turn enhancing the aerobic granulation. Although high salt stress inhibited functional microorganisms, the SMF maintained better SPND performance with average COD removal, TN removal and nitrite accumulation ratio finally recovering to 100%, 72.9% and 91.1% respectively. High throughput sequencing revealed that functional bacteria evolved from Paracoccus to halotolerant genera Xanthomarina, Thauera, Pseudofulvimonas and Azoarcus with stepwise increasing salinity. The enhanced salt-tolerance may be because the SMF promoted the activity of these halotolerant bacteria. Therefore, this study proposes an economic, effective and environmental biotechnology for saline wastewater treatment.

Comparison on anaerobic phosphorus release and recovery from waste activated sludge by different chemical pretreatment methods: Focus on struvite quality and benefit analysis.

Phosphorus recovery from waste activated sludge (WAS) is expected to alleviate the shortage of phosphate rock and reduce eutrophication. In this study, acid, alkali and sodium polyacrylate (PAAS) were compared to enhance phosphorus release and recovery from WAS. During anaerobic fermentation (AF) stage, the optimal pretreated conditions for ortho-phosphate release were the pH of 4 (AF 12 h), 13 (AF 12 h) and 22.4 g PAAS/L (AF 24 h) with the phosphorus release efficiencies of 40.9%, 62.6% and 31.7%, respectively. Acid, alkali and PAAS addition were beneficial for apatite phosphorus (AP), non-apatite inorganic phosphorus (NAIP) and organic phosphorus (OP) release from WAS, respectively. Strong acidic (pH = 4) and alkaline (pH = 12 and 13) conditions inhibited the release of soluble ammonia, while PAAS would not have a negative impact on the release of soluble ammonia. By means of precipitation crystallization, the ortho-phosphate could be almost recovered after acid/alkali pretreatment compared with PAAS (88.9%) at optimal Mg/P molar ratio of 1.5:1. The XRD, FT-IR and SEM-EDX analyses confirmed the main component in the product was struvite. The purity of the struvite in the product recovered from acid (named PreAC, 78.9%) and alkali (named PreAL, 89.6%) pretreated sludge were higher than that of the PAAS (named PrePA, 72.3%) by elemental analysis. The mercury and chromium content existed in PreAC were above the Control Standards of Pollutants in Sludge for Agricultural Use, whereas detected heavy metal elements level of the PreAL and PrePA were below the standard. By means of cost analysis, acid/alkali pretreatment could obtain economic benefits compared with PAAS. Thus, those discoveries would broaden the phosphorus recovery way to serve in practice.

Control of toxic sulfide in mariculture environment by iron-coated ceramsite and immobilized sulfur oxidizing bacteria.

Hydrogen sulfide (H2S) is considered one of the serious toxic pollutants in mariculture environment. Consequently, it is necessary to develop an effective strategy to prevent the production of sulfide. In this study, we modified the ceramsite with iron (ICC) and prepared a microbial agent, i.e., the immobilized sulfur-oxidizing-bacterium on the ICC (SICC), the microbial agent was following dosed in the simulated mariculture systems to control the sulfide pollutant. Results showed that the sulfide removal capacity of the new material ICC reached to 3.42 mg S g-1 in 24 h. Comparably, the microbial agent SICC presented a stable capability in oxidizing sulfide and the sulfide removal was above 65% in test media feeding with 600 mg L-1 sulfide even after five times of recycling. The microcosm experiments conducted in the simulated mariculture systems showed that the application of the ICC together with the SICC was able to quickly remove the existing sulfide and persistently inhibit the production of sulfide, the immobilized sulfur-oxidizing-bacterium survived stably in the new environment accounting for 1.22% of total microbial community. Therefore, dosing the ICC and SICC simultaneously might be a preferable strategy and presented a promising perspective in remediating the deteriorated mariculture environment.

Enhanced in-situ electro-generation of H2O2 using PTFE and NH4HCO3 modified C/PTFE electrode for treatment of landfill leachate.

In this study, the carbon black/polytetrafluoroethylene (C/PTFE) electrode was prepared under the best conditions, and then it was modified by PTFE and NH4HCO3 to make a PTFE-C/PTFE electrode. PTFE-C/PTFE electrode was used to enhance H2O2 in-situ electro-generation and the electro-peroxone process (EPP) treatment of leachate. Various analytical methods results were applied to prove that the PTFE-C/PTFE electrode greatly improved the performance of H2O2 generation and electrode stability. The effects of initial pH, current intensity, ozone flow and Cl- concentration on the removal of NH4+ and chemical oxygen demand (COD) from landfill leachate were studied in the EPP with PTFE-C/PTFE as cathode (MEPP) by one factor at a time (OFAT) method. The initial pH value 7.5, current intensity 300 mA, ozone flow 875 mg/h and Cl- concentration value 4198 mg/L were selected as the best operating parameters. A response surface methodology based on box-behnken design (BBD) was employed to optimize running conditions of the MEPP of leachate. After optimization, Mineralization efficiency of the NH4+ and COD was obtained to be 79.83% and 52.14%, and biochemical oxygen demand (BOD5)/COD ratio increased to 0.38 after 4 h. The removal curves of NH4+ and COD in the MEPP conforms to the zero-order and first-order reaction kinetics, respectively. Three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) analysis shows that MEPP has a good removal effect on organics in leachate. Energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis were carried out for the cathode sediment, which was mainly magnesium ion silicate precipitation and NaCl.

Effects of salinity on pollutant removal and bacterial community in a partially saturated vertical flow constructed wetland.

This study investigated the influence of salinity on pollutant removal and bacterial community within a partially saturated vertical flow constructed wetland (PS-VFCW). High removal rates of NH4+-N (88.29 ± 4.97-100 ± 0%), total inorganic nitrogen (TIN) (50.00 ± 7.21-62.81 ± 7.21%) and COD (91.08 ± 2.66-100 ± 0%) were achieved at 0.4-2.4% salinity levels. The removal of ammonia, TIN and organic matter occurred mainly in unsaturated zone. Salt-adaptable microbes became the dominant bacteria with salinity elevated. The proportion of ammonia-oxidizing bacteria (AOB) in the 0-5 cm depth layer (unsaturated zone) decreased obviously as the salinity increased to 2.4%. Nitrite-oxidizing bacteria (NOB) in the 0-5 cm depth layer showed a decreasing trend with elevated salinity. Denitrifying bacteria (DNB) in the 0-5 cm depth layer maintained high abundance (27.70-53.60%) at 0.4-2.4% salinity levels. At 2.4% salinity, AOB, NOB and DNB were observed in the unsaturated zones and saturated zones, and showed higher abundance in the unsaturated zone.