Enhanced treatment of low C/N ratio rural sewage by a modified multi-stage tidal flow constructed wetland at low temperature: Quantitative contributions of key functional genera.

Rural sewage treatment was traditionally faced contradiction between low-treatment rates and the need for low-cost development. To address this challenge, we explored the coupling of effluent circulation and step-feeding strategies in a multi-stage tidal flow constructed wetland (TFCW) to achieve stable nitrogen (N) removal performance under conditions of low carbon-to-nitrogen (C/N) ratios and low temperatures. The modified multi-stage TFCW demonstrated the ability to significantly reduce the concentrations of effluent NH4+-N and NO3--N by 33.9 % and 54.8 % respectively, resulting in values of 7.47 mg/L and 3.93 mg/L. Additionally, it achieved an average TN removal efficiency of 69.2 %. The improved N removal performance of rural sewage by the modified multi-stage TFCW at low temperatures was primarily attributed to autotrophic nitrification, heterotrophic nitrification, and autotrophic denitrification. Among the identified functional genera, Nitrosomonas and Nitrosospira played key roles as autotrophic nitrification bacteria (ANB), contributing to 28.2 % of NH4+-N removal. The key heterotrophic nitrification bacteria (HNB) Acidovorax and Rudaea were mainly responsible for 71.3 % of NH4+-N removal via the two-step ammonia assimilation through the organic nitrogen pathway. Furthermore, Rhodanobacter and Acinetobacter emerged as key autotrophic denitrification bacteria (ADNB), accounting for 79.9 % of NO3--N conversion and removal. In summary, this study provides valuable theoretical insights and supports ongoing efforts in biological regulation to address the challenges associated with rural sewage treatment.

Experimental Study on Laminar Burning Characteristics of Premixed 2,5-Dimethylfuran/Air Mixtures at Elevated Pressures and Temperatures.

Experimental studies of laminar burning velocity and flame instabilities of 2,5-dimethylfuran (DMF) were conducted at different equivalence ratios (from 0.9 to 1.3), initial pressures (from 0.1 to 0.8 MPa), and initial temperatures (from 393 to 493 K) by the method of the schlieren and high-speed photography system in the constant-volume combustion bomb. The results showed that the laminar burning velocity of the DMF/air flame decreased with increasing initial pressure and increased with increasing initial temperature. The maximum laminar burning velocity occurred at φ = 1.1, regardless of the initial pressure and temperature conditions. The power law fitting of baric coefficients, thermal coefficients, and laminar burning velocity was obtained, and the laminar burning velocity of DMF/air flame can be predicted well in the study range. The diffusive-thermal instability of the DMF/air flame was more pronounced during rich combustion. Increasing the initial pressure increased both the diffusive-thermal instability and the hydrodynamic instability of the flame, while increasing the initial temperature increased the diffusive-thermal instability of the flame, which was mainly responsible for flame propagation. In addition, the Markstein length, density ratio, flame thickness, critical radius, acceleration index, and classification excess of the DMF/air flame were investigated. The results of this paper provide a theoretical support for the application of DMF in engineering.

Quantitative ecology associations between heterotrophic nitrification-aerobic denitrification, nitrogen-metabolism genes, and key bacteria in a tidal flow constructed wetland.

This study explored the quantitative mechanisms of heterotrophic nitrification-aerobic denitrification (HN-AD) in a pilot-scale two-stage tidal flow constructed wetland (TFCW). The TFCW packed shale ceramsite (SC) and activated alumina (AA) at each stage, respectively, and aimed to improve decentralized wastewater treatment efficiency. In start-up phases, AA-TFCW accelerated NH4+-N decline, reaching transformation rates of 6.68 mg NH4+-N/(L·h). In stable phases, SC-AA-TFCW resisted low-temperatures (<13 °C), achieving stable NH4+-N and TN removal with effluents ranging 6.36-8.13 mg/L and 9.43-14.7 mg/L, respectively. The dominant genus, Ferribacterium, was the core of HN-AD bacteria, simultaneously removing NH4+-N and NO3--N by nitrate assimilation and complete denitrification (NO3--N â†’ N2), respectively. The quantitative associations highlighted importance of nitrification, nitrate assimilation, and denitrification in nitrogen removal. HN-AD bacteria (e.g., Lactococcus, Thauera, and Aeromonas) carried high-weight genes in quantitative associations, including napAB, nasA and gltBD, implying that HN-AD bacteria have multiple roles in SC-AA-TFCW operation.

The synergy of porous substrates and functional genera for efficient nutrients removal at low temperature in a pilot-scale two-stage tidal flow constructed wetland.

A pilot-scale two-stage tidal flow constructed wetland (TFCW) with working volume of 0.46 m3/d packing with shale ceramsite (SC) and activated alumina (AA) was constructed (named as SC-AA-TFCW) for nutrients removal at low temperature (<15 °C). SC-AA-TFCW achieved stable removals of 78.1% nitrogen and 98.3% phosphorous. SC-TFCW contributed to 55.2% of organics and 85.6% of particulate phosphorous removal. Among 17 denitrifiers, the absolute abundance of aerobic denitrification bacteria (ADNB) was highest, followed by facultative anaerobic denitrification bacteria (FADNB) and autotrophic denitrification bacteria (AUDNB). Nitrogen assimilating into organic nitrogen, dissimilatory and assimilatory nitrate reduction and complete denitrification may be main nitrogen metabolic pathways. Some ADNB (e. g. Zoogloea, Pseudomonas and Acidovorax) showed positive interactions with various key functional genes related to nutrients removal. Dissolved oxygen and reducing elements were main environmental factors in changing ADNB compositions. This study highlights the importance of ADNB and their synergy to porous substrates in SC-AA-TFCW.

Response of bacterial regrowth, abundant and rare bacteria and potential pathogens to secondary chlorination in secondary water supply system.

This study investigated the effects of secondary chlorination on bacterial regrowth, microbial communities (abundant and rare taxa) and bacterial functions of pipe wall biofilm and bulk water in simulated secondary water supply system (SWSS). Continuous secondary chlorination was more effective than short-term secondary chlorination to control the bacterial regrowth in both biofilm and water samples. Bacterial diversity slightly reduced after continuous secondary chlorination, and 19.27% of the total operational taxonomic units (OTUs) were shared by biofilm and water samples, with Bacillus as the dominant genus. Abundant and rare taxa exhibited different community structures. Proteobacteria and candidate division WPS-1 predominated in abundant and rare phyla were sensitive to chlorine, while Firmicutes, Acidobacteria and Bacteroidetes, exhibited relative strong chlorine resistance. The abundant genera in control sample (e.g., Bosea, Sphingobium and Gemmata) exhibited poor tolerance to chlorine, while Bacillus in biofilm and Defluviimonas in water were the main chlorine-resistant genera. Moreover, the composition of rare genera in each sample was obviously different. Furthermore, a total of 18 potential pathogens were detected with Pseudomonas as the dominant genus, most of which were significantly reduced after disinfection. There were mainly positive interactions among potential pathogenic bacteria, with Enterococcus, Legionella and Vibrio as the hub genera as revealed by network analysis. Similar bacterial functions in both biofilm and water were observed with metabolism as the predominant bacterial function, while, human disease function only accounted for 1.07% of bacterial functions. These results highlighted the importance of continuous secondary chlorination for controlling biosafety of SWSS and identified the dissimilar responses of abundant and rare bacteria to the disinfection, as well as the co-occurrence patterns among potential pathogens, improving our understanding of bacterial communities in SWSS.

Intensified nitrogen removal by heterotrophic nitrification aerobic denitrification bacteria in two pilot-scale tidal flow constructed wetlands: Influence of influent C/N ratios and tidal strategies.

This study investigated the influence of C/N ratios and tidal strategies on nitrogen removal and bacterial communities in two pilot-scale tidal flow constructed wetlands (TFCWs) with simultaneous nitrification-denitrification process. Heterotrophic nitrification aerobic denitrification (HNAD) was the main nitrogen transformation pathway in both TFCWs. High C/N ratios and effluent circulation at low temperature promoted HNAD in TFCWs with high nitrogen removal efficiencies (72.6%-95.5% for NH4+-N and 70.9%~91.8% for TN). Effluent circulation had more influence on bacterial community structure and diversity than C/N ratios. Among 16 detected genera related to nitrogen removal, HNAD bacteria (HNADB) were abundant. Especially, some dominant HNADB (e.g. Aeromonas, Hydrogenophage and Gemmobacter) were core genera, showing positive interactions with other genera related to nitrogen removal. Tidal strategies had more contribution to the shifts in these genera than C/N ratios. This study highlights the importance of HNADB in pilot-scale TFCWs and their responses to C/N ratios and tidal strategies.

Effect of two selenium sources on hepatocarcinogenesis and several angiogenic cytokines in diethylnitrosamine-induced hepatocarcinoma rats.

This experiment was designed to compare the effect of two selenium sources at the dosage of therapeutic level on hepatocarcinogenesis and angiogenic cytokines in DEN-induced hepatocarcinoma rats to further approach their possible anticancer's mechanism. One hundred and seventy-eight Sprague-Dawley (SD) rats (average weight being 100-120g) were randomly divided into 5 groups (I-V). Animals in group I, group II and group III served as the negative control, sodium selenite control (SS) and positive controls respectively, and received 0.1, 3.0, and 0.1mg/kg selenium from sodium selenite supplemented diets during the whole experimental time. Rats in group IV and group V were fed with selenium from selenium-enriched malt (SEM) and sodium selenite (SS) supplemented diets (3mg/kg respectively). To balance the nutritional content among each group, normal malt which was not treated with selenium was added into the diets of the challenge groups. The nutrition contents, except the selenium of the diet in each group, were similar and in accordance with NRC standards. Rats in groups III-V were treated by aqueous diethylnitrosamine solution (100mg/L) at the dosage of 10mg/kg body weight every day for 16 weeks to induce hepatocarcinoma, and drank sterilized water for an additional two weeks. Rats in group I and group II drank sterilized water throughout the experiment. At 4th, 8th, 12th, 16th week, five rats in each group were then sacrificed by cervical decapitation. At the termination of the study, at 18th week, the surplus rats were sacrificed by cervical decapitation. Feed was withheld from the rats for 12h before sampling. The number of hepatoma nodules in liver and mortality of rats were calculated. The values of the following items, including α-fetoprotein (AFP), gamma-glutamyltranspeptidase (GGT), tumor necrosis factor-α (TNF-α), insulin-like growth factors-II (IGF-II), nitric oxide (NO) and total nitric oxide synthase (T-NOS) in plasma were determined. At the same time, the positive numbers of vascular endothelial growth factor (VEGF) and protein kinase C-α (PKCα) staining cells in tumor tissue were analyzed by immunohistochemistry using the Envision two step methods with a kit. The results indicated that SEM could significantly decrease the mortality of rats and the number of hepatoma nodules, values of GGT and AFP, and the levels of IGF-II, NO and NOS and lessen the positive numbers of VEGF and PKCα staining cells in tumor tissue. Moreover, SEM could increase the levels of TNF-α in the initiated time of hepatocarcinogenesis, whereas, decrease the levels of TNF-α in the progressive time of hepatocarcinogenesis. SS could only significantly inhibit the positive numbers of PKCα staining cells in tumor tissue, decrease the levels of GGT, AFP and TNF-α at minority sampling times, and increase the levels of NO. In conclusion, SEM could reduce the mortality. It might be related to deaden significantly the lesion of liver, delay the cause of hepatocarcinogenesis, and inhibit the progress of angiogenesis to increase the livability of DEN-induced hepatocarcinoma rats. SS at the same therapeutic dosage had less effect on the hepatocarcinogenesis by inhibiting angiogenesis and relative cytokines to some extent.

The intravenous glucose tolerance test in water buffalo.

OBJECTIVE: The response to intravenous glucose loading in the buffalo using the intravenous glucose tolerance test (IGTT) was investigated to provide a reference for intravenous glucose injection in buffaloes. METHOD: Twelve healthy, fasted, male swamp buffaloes were divided into three groups. Group I: six buffaloes were given 50% glucose at a dosage of 1 g/kg body weight via the jugular vein. Group II: three buffaloes received normal saline. Group III: three buffaloes were not injected. Blood samples were taken from the opposite vein at 60 and 10 min pre-injection (pre60 and pre10), and at 1, 5, 10, 30, 60, 120, 180, 240, 300, 360 and 420 min post-glucose injection (PGI). Plasma glucose was analyzed by the oxidase method. Insulin and glucagon were soon determined with a human radioimmunoassay kit. The insulin (pmol/l)/glucose (mmol/l) ratios (IGR) were also calculated for each sampling time. RESULTS: Mean plasma glucose, insulin and glucagon concentrations of buffaloes in groups II and III were similar at all the sampling times (p > 0.05) and the curves of the IGR for group II and group III were flat throughout. Group I Buffaloes showed an immediate 20 times increase in the mean plasma glucose concentration PGI, over the pre60 and pre10. The peak plasma insulin concentration occurred at 30 min PGI. The mean plasma glucose and insulin concentrations remained above pre-administration levels until 420 min PGI (p < 0.05). However, the mean plasma glucagon concentrations were different only at 1 and 5 min PGI sampling times. The curve of the IGR for group I showed an initial decrease at 1 min PGI, and fluctuated from 10.18 to 25.55 for the remainder of the sampling period. The correlation analysis showed that the mean plasma glucose concentration was positively correlated with insulin level (r = 0.73, p < 0.005), and significantly negatively correlated with mean plasma glucagon (r = -0.58, p < 0.05). The mean plasma insulin level did not show significant correlation with the glucagon (r = 0.06, p > 0.05). CONCLUSION: The hyperglycemia, high insulin, and protracted glucose and insulin curves, the initial decrease in the insulin/glucose ratio indicates that there was an unexpected glucose tolerance to acute intravenous glucose loading in water buffalo compared with other ruminants. The possibly suggested intravenous glucose load in buffaloes is about 5.09-8.28 mmol/l.