Multidrug-resistant plasmid RP4 inhibits the nitrogen removal capacity of ammonia-oxidizing archaea, ammonia-oxidizing bacteria, and comammox in activated sludge.

In wastewater treatment plants (WWTPs), ammonia oxidation is primarily carried out by three types of ammonia oxidation microorganisms (AOMs): ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and comammox (CMX). Antibiotic resistance genes (ARGs), which pose an important public health concern, have been identified at every stage of wastewater treatment. However, few studies have focused on the impact of ARGs on ammonia removal performance. Therefore, our study sought to investigate the effect of the representative multidrug-resistant plasmid RP4 on the functional microorganisms involved in ammonia oxidation. Using an inhibitor-based method, we first evaluated the contributions of AOA, AOB, and CMX to ammonia oxidation in activated sludge, which were determined to be 13.7%, 41.1%, and 39.1%, respectively. The inhibitory effects of C2H2, C8H14, and 3,4-dimethylpyrazole phosphate (DMPP) were then validated by qPCR. After adding donor strains to the sludge, fluorescence in situ hybridization (FISH) imaging analysis demonstrated the co-localization of RP4 plasmids and all three AOMs, thus confirming the horizontal gene transfer (HGT) of the RP4 plasmid among these microorganisms. Significant inhibitory effects of the RP4 plasmid on the ammonia nitrogen consumption of AOA, AOB, and CMX were also observed, with inhibition rates of 39.7%, 36.2%, and 49.7%, respectively. Moreover, amoA expression in AOB and CMX was variably inhibited by the RP4 plasmid, whereas AOA amoA expression was not inhibited. These results demonstrate the adverse environmental effects of the RP4 plasmid and provide indirect evidence supporting plasmid-mediated conjugation transfer from bacteria to archaea.

A novel alginate-embedded magnetic biochar-anoxygenic photosynthetic bacteria composite microspheres for multipollutant removal: Mechanisms of photo-bioelectrochemical enhancement and excellent reusability performance.

Existing wastewater treatment technologies face the key challenge of simultaneously removing emerging contaminants and nutrients from wastewater efficiently, with a simplified technological process and minimized operational costs. In this study, a novel alginate-embedded magnetic biochar-anoxygenic photosynthetic bacteria composite microspheres (CA-MBC-PSB microspheres) was prepared for efficient, cost-effective and one-step removal of antibiotics and NH4+-N from wastewater. Our results demonstrated that the CA-MBC-PSB microspheres removed 97.23% of sulfadiazine (SDZ) within 7 h and 91% of NH4+-N within 12 h, which were 21.23% and 38% higher than those achieved by pure calcium alginate-Rhodopseudomonas palustris microspheres (53% and 45.7%), respectively. The enhanced SDZ and NH4+-N removal were attributed to the enhanced photoheterotrophic metabolism and excretion of extracellular photosensitive active substances from R. Palustris through the photo-bioelectrochemical interaction between R. Palustris and magnetic biochar. The long-term pollutants removal performance of the CA-MBC-PSB microspheres was not deteriorated but continuously improved with increasing ruse cycles with a simultaneous removal efficiency of 99% for SDZ and 92% for NH4+-N after three cycles. The excellent stability and reusability were due to the fact that calcium alginate acts as an encapsulating agent preventing the loss and contamination of R. palustris biomass. The CA-MBC-PSB microspheres also exhibited excellent performance for simultaneous removal of SDZ (89% in 7 h) and NH4+-N (90.7% in 12 h) from the secondary effluent of wastewater treatment plant, indicating the stable and efficient performance of CA-MBC-PSB microspheres in practical wastewater treatment.

Derivation of human health and odor risk control values for soil ammonia nitrogen by incorporating solid-liquid partitioning, ammonium/ammonia equilibrium: A case study of a retired nitrogen fertilizer site in China.

Nitrogen fertilizer supports agricultural intensification, but its manufacturing results in substantial contaminated sites. Ammonia nitrogen is the main specific pollutant in retired nitrogen fertilizer sites with potential human health and odor risks. However, few studies focus on ammonia nitrogen risk assessment at contaminated sites, particularly considering its solid-liquid partitioning process (Kd) and ammonium/ammonia equilibrium process (R) in the soil. This study took a closed nitrogen fertilizer factory site as an example and innovatively introduced Kd and R to scientifically assess the human health and odor risk of ammonia nitrogen. The risk control values (RCVs) of ammonia nitrogen based on human health and odor risk were also derived. The maximum concentration of ammonia nitrogen was 3380 mg/kg in the unsaturated soil, which was acceptable for human health because the health RCVs were 5589 ∼ 137,471 mg/kg in various scenarios. However, odor risk was unacceptable for RCVs were 296 ∼ 1111 mg/kg under excavation scenarios and 1118 ∼ 35,979 mg/kg under non-excavation scenarios. Of particular concern, introducing Kd and R in calculation increased the human health and odor RCVs by up to 27.92 times. Despite the advancements in ammonia risk assessment due to the introduction of Kd and R, odor risk during excavation remains a vital issue. These findings inform a more scientific assessment of soil ammonia risk at contaminated sites and provide valuable insights for the management and redevelopment of abandoned nitrogen fertilizer plant sites.

Enhanced Sensitivity of Electrochemical Sensors for Ammonia-Nitrogen via In-Situ Synthesis PtNi Nanoleaves on Carbon Cloth.

Pt-based electrochemical ammonia-nitrogen sensors played a significance role in real-time monitoring the ammonia-nitrogen concentration. The alloying of Pt and transition metals was one of the effective ways to increase the detectability of the sensitive electrode. In this paper, a self-supported electrochemical electrode for the detection of ammonia nitrogen was obtained by the electrodeposition of PtNi alloy nanoleaves on a carbon cloth (PtNi-CC). Experimental results showed that the PtNi-CC electrode exhibited enhanced detection performance with a wide linear range from 0.5 to 500 µM, high sensitivity (7.83 µA µM-1 cm-2 from 0.5 to 150 µM and 0.945 µA µM-1 cm-2 from 150 to 500 µM) and lower detection limit (24 nM). The synergistic effect between Pt and Ni and the smaller lattice spacing of the PtNi alloy were the main reasons for the excellent performance of the electrode. This work showed the great potential of Pt-based alloy electrodes for the detection of ammonia-nitrogen.

Sensitive Electrochemical Detection of Ammonia Nitrogen via a Platinum-Zinc Alloy Nanoflower-Modified Carbon Cloth Electrode.

As a common water pollutant, ammonia nitrogen poses a serious risk to human health and the ecological environment. Therefore, it is important to develop a simple and efficient sensing scheme to achieve accurate detection of ammonia nitrogen. Here, we report a simple fabrication electrode for the electrochemical synthesis of platinum-zinc alloy nanoflowers (PtZn NFs) on the surface of carbon cloth. The obtained PtZn NFs/CC electrode was applied to the electrochemical detection of ammonia nitrogen by differential pulse voltammetry (DPV). The enhanced electrocatalytic activity of PtZn NFs and the larger electrochemical active area of the self-supported PtZn NFs/CC electrode are conducive to improving the ammonia nitrogen detection performance of the sensitive electrode. Under optimized conditions, the PtZn NFs/CC electrode exhibits excellent electrochemical performance with a wide linear range from 1 to 1000 µM, a sensitivity of 21.5 µA µM-1 (from 1 µM to 100 µM) and a lower detection limit of 27.81 nM, respectively. PtZn NFs/CC electrodes show excellent stability and anti-interference. In addition, the fabricated electrochemical sensor can be used to detect ammonia nitrogen in tap water and lake water samples.

Development of an electrochemical separation-Rhodopseudomonas palustris electrolysis cell-coupled system for resourceful treatment of mature leachate landfill.

Electrochemical technology is a promising technique for separating ammonia from mature landfill leachate. However, the accompanying migration and transformation of coexisting pollutants and strategies for further high-value resourceful utilization of ammonia have rarely received attention. In this study, an electrochemical separation-Rhodopseudomonas palustris electrolysis cell coupled system was initially constructed for efficient separation and conversion of nitrogen in mature landfill leachate to microbial protein with synchronously tracking the transport and conversion of coexisting heavy metals accompanying the process. The results revealed that ammonia concentration in the cathode increased from 40.3 to 49.8% with increasing the current density from 20 to 40 mA/cm2, with less than 3% of ammonia transformation to NO2--N and NO3--N. During ammonia separation, approximately 95% of HM-DOMs (Cr, Cu, Ni, Pb, and Zn) were released into the anolyte due to humus degradation and further diffused to the cathode. A significant correlation was observed between the releases of HM-DOMs. Cu-DOMs accounted for 70.2% of the total Cu content, which was the highest proportion among the heavy metals (HMs). Among the HMs in anolyte, 57.4% of Pb, 52.5% of Ni, and 50.6% of Zn diffused to the cathode, and most of the HMs were removed in the form of hydroxide precipitations due to heavy alkaline catholyte. Compared with the open-circuit condition, the utilization efficiency of NH4+-N in the R. palustris electrolysis cell increased by 445.1% with 47% and 50% increases in final NH4+-N conversion rate and R. palustris biomass, respectively, due to bio-electrochemical enhanced phototrophic metabolism and acid generation for buffering the strong alkalinity of the electrolyte to maintain suitable growth conditions for R. palustris.

Dissolved oxygen and ammonia affect ammonia production via GDH/AMPK signaling pathway and alter flesh quality in Chinese perch (Siniperca chuatsi).

The dissolved oxygen (DO) and ammonia are crucial to the growth of Chinese perch (Siniperca chuatsi). Information on the effects of DO and total ammonia nitrogen (TAN) in regulating ammonia nitrogen excretion and flesh quality in Chinese perch is scanty. This study aimed to evaluate the effects of dissolved DO at oxygen levels of 3 mg/L and 9 mg/L, as well as the TAN concentrations of 0.3 mg/L and 0.9 mg/L on ammonia excretion and flesh quality. Results showed that the ammonia contents in plasma, muscle, and liver of the 9 mg/L DO group were significantly higher than those of the 3 mg/L DO group (P < 0.05). However, the expression of AMPK-related signaling pathway genes (gdh, lkb1, and ampd) and flesh quality indicators (gumminess, chewiness, hardness) in the 9 mg/L DO group were significantly lower than those in the 3 mg/L DO group. Under long-term exposure to 0.9 mg/L TAN, the ammonia contents in plasma and gill filaments, as well as muscle flesh quality (resilience, gumminess, chewiness, cohesiveness), were significantly lower than those in the 0.3 mg/L TAN group (P < 0.05). However, the activities of GDH and AMPD enzymes in the 0.9 mg/L TAN group were significantly higher than those in the 0.3 mg/L TAN group. In summary, when fish are exposed to 3 mg/L DO and 0.9 mg/L TAN in the environment for a long time, their amino acids are used for transamination and deamination, resulting in insufficient energy supply for Chinese perch, whereas 9 mg/L DO and 0.9 mg/L TAN caused deterioration of the flesh quality.

Using predictive models unravel the potential of titanium oxide-loaded activated carbon for the removal of leachate ammoniacal nitrogen.

The TiO2 nanocomposite efficiency was determined under optimized conditions with activated carbon to remove ammoniacal nitrogen (NH3-N) from the leachate sample. In this work, the facile impregnation and pyrolysis synthesis method was employed to prepare the nanocomposite, and their formation was confirmed using the FESEM, FTIR, XRD, and Raman studies. In contrast, Raman phonon mode intensity ratio ID/IG increases from 2.094 to 2.311, indicating the increase of electronic conductivity and defects with the loading of TiO2 nanoparticles. The experimental optimal conditions for achieving maximum NH3-N removal of 75.8% were found to be a pH of 7, an adsorbent mass of 1.75 mg/L, and a temperature of 30 °C, with a corresponding time of 160 min. The experimental data were effectively fitted with several isotherms (Freundlich, Hill, Khan, Redlich-Peterson, Toth, and Koble-Corrigan). The notably elevated R2 value of 0.99 and a lower ARE % of 14.61 strongly support the assertion that the pseudo-second-order model compromises a superior depiction of the NH3-N reduction process. Furthermore, an effective central composite design (CCD) of response surface methodology (RSM) was employed, and the lower RMSE value, precisely 0.45, demonstrated minimal disparity between the experimentally determined NH3-N removal percentages and those predicted by the model. The subsequent utilization of the desirability function allowed us to attain actual variable experimental conditions.

Predicting ammonia nitrogen in surface water by a new attention-based deep learning hybrid model.

Ammonia nitrogen (NH3-N) is closely related to the occurrence of cyanobacterial blooms and destruction of surface water ecosystems, and thus it is of great significance to develop predictive models for NH3-N. However, traditional models cannot fully consider the complex nonlinear relationship between NH3-N and various relative environmental parameters. The long short-term memory (LSTM) neural network can overcome this limitation. A new hybrid model BC-MODWT-DA-LSTM was proposed based on LSTM combining with the dual-stage attention (DA) mechanism and boundary corrected maximal overlap discrete wavelet transform (BC-MODWT) data decomposition method. By introducing attention mechanism, LSTM could selectively focus on the input data. BC-MODWT could decompose the input data into sublayers to determine the main swings and trends of the input feature series. The BC-MODWT-DA-LSTM hybrid model was superior to other studied models with lower average prediction errors. It could maintain NASH Sutcliffe efficiency coefficient (NSE) values above 0.900 under the lead time up to 7 days, and the area under the receiver operating characteristic (ROC) curve could reach 0.992. The hybrid model also had higher prediction accuracies at the peak spots, indicating that it was capable of early warning when sudden high NH3-N pollution occurred. The high forecasting accuracy of the suggested hybrid method proved that further improving LSTM model without introducing more complex topologies was a promising water quality prediction method.

Removal of chemical oxygen demand and ammonia nitrogen from high salinity tungsten smelting wastewater by one-step electrochemical oxidation: From bench-scale test, pilot-scale test, to industrial test.

In recent years, electrochemical oxidation (EO) shows the characteristics of green and high efficiency in removing chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) from wastewater, which has been favored by researchers. However, at present, most of current studies on EO remain in laboratory stage, reports about pilot-scale or even industrial tests with large treatment capacity are few, which slowing down the use of the advanced technology to practical application. In this study, bench-scale tests, pilot-scale tests (treatment capacity 200-500 L/h), and industrial tests (treatment capacity 100 m3/h) were carried out by EO technology in view of the characteristics of tungsten smelting wastewater (TSW) with high salinity (NaCl), COD, and NH3-N. Results showed that the removal of COD and NH3-N was a competitive reaction in the EO process, and COD could be removed more preferentially than NH3-N. When NH3-N content was low, the influent pH had a minimal effect on its removal, and when NH3-N content was high, increasing the influent pH was beneficial to its removal. Industrial tests showed that the one-step removal of COD and NH3-N in TSW met the standard, and the power consumption per cubic meter of wastewater was only 4.2 kW h, and the treatment cost was much lower than the two-step process of "breaking point chlorination to remove NH3-N and adding oxidant to remove COD". This study has successfully realized industrial application of EO technology in TSW treatment for the first time and provided a successful case, which is helpful to accelerate the popularization and application of this technology in the field of high salinity organic ammonia nitrogen wastewater treatment.

Increasing the organic loading rate of household food waste anaerobic digestion by landfill leachate addition: Performance and mechanism.

A high amount of easily degradable organics and the absence of trace metals (TMs) in household food waste (HFW) lowered the stability and efficiency of anaerobic digestion (AD) of HFW. Leachate addition to the AD of HFW can provide ammonia nitrogen and TMs to address the accumulation of volatile fatty acids and the lack of TMs. To study the effect of leachate addition on increasing organic loading rate (OLR), both mono-digestion of HFW and AD of HFW with leachate addition were evaluated using two continuously stirred tank reactors. The OLR of the mono-digestion reactor only reached 2.5 g COD/L/d. However, with the addition of ammonia nitrogen and TMs, the OLR of the failed mono-digestion reactor increased by 2 and 3.5 g COD/L/d, respectively. The specific methanogenic activity increased by 94.4% and the hydrolysis efficiency increased by 135%. Finally, the OLR of mono-digestion of HFW reached 8 g COD/L/d, with a hydraulic retention time (HRT) of 8 days and methane production rate of 2.4 L/L/d. In the leachate addition reactor, the OLR reached 15 g COD/L/d, while the HRT and methane production were 7 days and 3.4 L/L/d, respectively. This study demonstrates that leachate addition substantially improves the AD efficiency of HFW. The two main mechanisms of increasing the OLR of an AD reactor are the buffer capacity of ammonia nitrogen and the stimulation of methanogen by TMs from leachate.

A cleaner leather chemical from feather waste for reducing ammonia-nitrogen pollution and improving biological treatment efficiency of tannery wastewater.

Feather waste is produced in millions of tons globally every year, resulting in a waste of biomass resources and even environmental pollution. A sustainable strategy for utilizing feather waste was proposed by preparing a clean deliming agent for ammonia-nitrogen (NH3-N) reduction in leather manufacture and biological treatment efficiency improvement of tannery wastewater. Briefly, chicken feather wastes were deeply hydrolyzed with sulfuric acid, and the optimized keratin hydrolysate (KHopt) that contained 53.6% crude protein and 41.2% amino acids, such as glutamic acid, serine, proline, leucine, phenylalanine, glycine, valine, and arginine, was obtained and used to delime limed cattle hides. The appropriate ratio of amino acids in KHopt gave KHopt a great pH-buffering capacity and maintained a stable float pH of approximately 9 throughout the deliming process. The isoelectric points of KHopt (3.8) and the limed hide (6.3) were both lower than the float pH, thereby bringing about an electrostatic repulsion between the KHopt and the hide surface, which is helpful for KHopt to penetrate and deswell the limed hide rapidly. Moreover, the KHopt deliming effectively removed calcium from the limed hide and achieved leather comparable to conventional leather for commercial applications. KHopt reduced the NH3-N concentrations of deliming effluent and tannery wastewater by 91.1% and 80.6%, respectively, compared with the conventional deliming agent (ammonium sulfate), and dramatically increased the biological treatment efficiency of tannery wastewater. The results showed that efficient and high-value use of feather waste was made by preparing KHopt for sustainable leather manufacturing.

Ecological risk evaluation of ammonia nitrogen pollution in China based on the ecological grey water footprint model.

The biosafety criteria of ammonia nitrogen (NH3-N) exhibit uncertainties, posing challenges to the assessment of the hazard of social NH3-N load to aquatic ecosystem. To evaluate this ecological hazard in China, an ecological grey water footprint (E-GWF) model is designed based on the uncertainty analysis theory. In the E-GWF model, the acute toxicity is quantified via short-term E-GWF (E-GWFs) and acute risk (AR), while its chronic toxicity is quantified via long-term E-GWF (E-GWFl) and chronic risk (CR). Results show the following. (i) Compared with the conventional GWF, the E-GWF performs better in the uncertainty analysis of the biosafety threshold, and it is more effective in ecological risk evaluation and environment planning. (ii) The E-GWFs and E-GWFl of NH3-N in China are 309.4 and 2382.5 billion m3, respectively. Regions with large E-GWF are concentrated in the east and south, while regions with small E-GWF are concentrated in the north and west. (iii) The ecological risks of NH3-N in Shanghai City, Tianjin City, Ningxia Province, Hebei Province, Jiangsu Province, Shanxi Province, and Shandong Province belong to the "High" grade. The ecological risks of NH3-N in Tibet and Qinghai Province belong to the "Negligible" grade. (iv) The ecological risk of NH3-N in China is mostly determined by industrial and domestic pollution. (v) To control the risk within allowable grades, the social NH3-N pollution load of China should be decreased to 988.7 kilotons.

Comparative assessment on ammonia nitrogen adsorption onto a saline soil-groundwater environment: distribution, multi-factor interaction, and optimization using response surface methodology and artificial neural network.

The adsorption of soil can reduce the leaching of NH4+-N from the external environment into groundwater. The adsorption of NH4+-N is affected by many factors. It is critical to use statistical model to quantitatively describe the effects of interaction between two or more factors on the system response. In this study, HJ-Biplot was used to analyze the correlation characteristics of soil water, salt, and nitrogen, and the response surface methodology and artificial neural network were used to statistically visualize the interaction between factors, including concentration, total dissolved solids (TDS), temperature, and pH. The results showed that the study soil was a typical saline soil, with maximum soil NH4+-N content of 85.45 mg/kg. For the adsorption experiments of NH4+-N on saline soils, the effects of factors on the adsorption capacity were assessed using the RSM model. The RSM model was coupled with an ANN to predict the adsorption of NH4+-N by saline soils. The NH4+-N concentration and water pH were both significant at a linear level (p < 0.0001). The interaction between NH4+-N concentration and pH was also more significant (p < 0.01). Under optimal conditions (concentration: 800 mg/L; temperature: 24 °C; TDS: 637 mg/L; pH: 7.83), the NH4+-N adsorption capacity was 1650.2 ug/g, which was in general agreement with the calculated values from the Box-Behnken and RSM model. In addition, a statistical error criterion for the model showed that the RSM-ANN model had greater predictive ability than RSM model.

Analysis of the characteristics of major pollutants discharged from wastewater in China's provinces.

In recent years, the discharge of major pollutants in China's wastewater has been decreasing but remains at a high level. Controlling the discharge of pollutants in sewage is of great importance for protecting water quality and maintaining ecological balance. Based on data collected from 31 provinces in China from 2011 to 2020 (except 2018), this study analyzes the spatiotemporal variation emissions of the wastewater pollutants: chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP). The entropy method was used to evaluate the effectiveness of water pollution control in different provinces. Our results revealed that the total emission per gross domestic product (GDP) for COD, NH3-N, TN and TP in China decreased by 50.7%, 81.9%, 65.4% and 70.8%, respectively. In terms of regional annual emission differences, the Northwest region was the lowest compared with other regions, accounting for 4.87%-6.59% of the national pollutant emissions, and the Central China region was the highest, accounting for 22.4%-26.05% of the national pollutant emissions. The average value of pollutant emissions per unit of GDP decreased year-to-year overall, but Guangxi and Tibet showed a trend of first decreasing and then increasing. The correlation results indicated a significant correlation (0.977) between TN and TP emissions in wastewater in China during 2011-2020. Through clustering and Multidimensional Scaling model (MDS) analysis, Beijing and Shanghai have been performing well in controlling water pollution discharge, while the provinces of Tibet and Guangxi must still increase their efforts in water pollution control. Furthermore, these results demonstrate the experience and achievements of the Chinese government in the treatment of wastewater pollution and provide a useful reference for treatment of wastewater pollution in the world.

Electrochemical removal of ammonium nitrogen in high efficiency and N2 selectivity using non-noble single-atomic iron catalyst.

Ammonia nitrogen (NH4+-N) is a ubiquitous environmental pollutant, especially in offshore aquaculture systems. Electrochemical oxidation is very promising to remove NH4+-N, but suffers from the use of precious metals anodes. In this work, a robust and cheap electrocatalyst, iron single-atoms distributed in nitrogen-doped carbon (Fe-SAs/N-C), was developed for electrochemical removal of NH4+-N from in wastewater containing chloride. The Fe-SAs/N-C catalyst exhibited superior activity than that of iron nanoparticles loaded carbon (Fe-NPs/N-C), unmodified carbon and conventional Ti/IrO2-TiO2-RuO2 electrodes. And high removal efficiency (> 99%) could be achieved as well as high N2 selectivity (99.5%) at low current density. Further experiments and density functional theory (DFT) calculations demonstrated the indispensable role of single-atom iron in the promoted generation of chloride derived species for efficient removal of NH4+-N. This study provides promising inexpensive catalysts for NH4+-N removal in aquaculture wastewater.

Comparison of metabolic kinetics during high and low solids anaerobic digestion of fecal sludge.

High solids anaerobic digestion (HS-AD) is an attractive energy-producing technology; however, high total solids (TS) content may inhibit methanogens due to high volatile fatty acid (VFA) and total ammonia nitrogen concentrations. The objective of this paper is to quantify rate-limiting metabolic kinetic parameters to determine the influence of TS content during anaerobic digestion of fecal sludge. Two TS content: 11% and 17% microcosms were analyzed. Good performance was observed in both systems, with volatile solid (VS) removal greater than 50%, CH4 yield between 0.44 and 0.56 m3 CH4 /g VS added and cumulative CH4 production between 1.78 and 2.03 m3 CH4 /m3 digester-day. At 11% TS VFA consumption and VS removal had a positive correlation to CH4 production while the 17% TS microcosm had a negative correlation with both. This is the first study to determine the kinetic parameters for hydrolysis, VFA consumption, and methanogenesis during digestion of fecal sludge. These kinetic parameters are necessary in the design and operation of anaerobic digestion systems treating fecal sludge.

Probiotic effect of Bacillus spp. isolated from African nightcrawler (Eudrilus eugeniae) on the performance of Nile Tilapia (Oreochromis niloticus L.).

This study evaluated the effects of the probiotic Bacillus spp. isolated from African nightcrawler (Eudrilus eugeniae) on the growth and survival performances of Nile tilapia (Oreochromis niloticus). A total of 400 Nile tilapia fingerlings (1.76 ± 0.07 g) were equally and randomly distributed into 20 glass aquaria and divided into five experimental groups with four replicates. Each experimental group was fed with a commercial diet (control) supplemented (at 108 CFU·g-1) with one of the four Bacillus spp. (ANSCI9, BFAR9, RM3, and RM10) at five percent of their body weight. After 30 days of feeding, the surviving fish were challenged with Aeromonas hydrophila to observe their survival. The treatment groups supplemented with BFAR9 (2.73 ± 0.26 g) and RM10 (3.15 ± 0.30 g) showed significantly higher (P < 0.05) absolute growth than the control (2.20 ± 0.16 g) group. Furthermore, those given with RM10 had better (P < 0.05) specific growth rate (SGR) (1.60 ± 0.10%·day-1) relative growth rate (RGR) (181.39 ± 18.16%) and feed conversion ratio (FCR) (1.99 ± 0.13) compared to the control group (SGR = 1.29 ± 0.07%·day-1; RGR = 129.84 ± 9.77%; FCR = 2.60 ± 0.16). The challenge test revealed that all Bacillus spp.-treated groups showed significantly higher (P < 0.05) survival rates (ANSCI9 = 82.5 ± 8.16%; BFAR9 = 80.0 ± 10.00%; RM3 = 77.5 ± 20.82%; RM10 = 85.0 ± 10.00%) than the control group (55.00 ± 19.15%), with the highest relative level of protection recorded for RM10 (66.67%). These results revealed that the probiotic Bacillus spp. isolated from E. eugeniae improved the growth, feed utilization, waste excretion, and the disease resistance of Nile tilapia.

TBC domain family 7-like enhances the tolerance of Penaeus vannamei to ammonia nitrogen by the up-regulation of autophagy.

TBC domain family 7 (TBC1D7) is one of the subunits of tuberous sclerosis complex (TSC) and an important regulator of autophagosome biogenesis. However, the function of TBC1D7 is not fully understood in crustaceans. In the present study, TBC1D7 was identified from Penaeus vannamei. The complete coding sequence of PvTBC1D7 was of 960 bp encoding a predicted polypeptide of 319 amino acids with one conserved TBC domain, which shared high similarity with TBC1D7 of that other species. The mRNA of PvTBC1D7 was highly expressed in hemocyte and hepatopancreas, and the PvTBC1D7 protein was localized specifically in the cytoplasm of hemocyte of shrimp. Besides, PvTBC1D7 was co-localized with PvTSC1 in the cytoplasm of shrimp, indicating that there might existed a binding relationship between PvTBC1D7 and PvTSC1. During the ammonia nitrogen stress, the mRNA transcripts of PvTBC1D7 were significantly upregulated in hemocyte, hepatopancreas, and gill. Functionally, overexpression of PvTBC1D7 in vitro restored the inhibition to autophagy caused by chloroquine (CLQ) and increased the autophagy level, while the silencing of PvTBC1D7 could inhibit the autophagy. More importantly, after interfering with PvTBC1D7, the autophagy level decreased significantly both in hepatopancreas and hemocyte of P. vannamei, the mRNA expression of PvmTOR was increased remarkably with the significantly decrease of autophagy-related genes (PvATG12 and PvATG14). And the reduction of PvTBC1D7 remarkably exacerbated the damage of hepatopancreas, increased the accumulation of ROS, and reduced the survival proportion of shrimp under ammonia nitrogen stress. Altogether, these results indicated that PvTBC1D7 might positively regulate the autophagy by stabilizing the negative regulation of mTOR by TSC complex, reduce the oxidative stress damage and improve shrimp ammonia nitrogen tolerance.

Ammonia-nitrogen removal from water with gC3N4-rGO-TiO2 Z-scheme system via photocatalytic nitrification-denitrification process.

Photocatalytic removal of NH3-N is expected to be an alternative to the biological method that accompanied with high energy consumption and secondary pollution. However, NH3-N is always oxidized into nitrate and nitrite during the photocatalytic processes, which also need to be removed from the water. Herein, the g-C3N4/rGO/TiO2 Z-scheme photocatalytic system was prepared and used for the NH3-N removal. The results showed the rate constant of NH3-N conversion on it was 0.705 h-1, 1.7 times as high as that on g-C3N4/TiO2, and most of the NH3-N were converted into gaseous products. And the experiment result indicated NH3-N and NO3- in water could enhance the removal of each other. According to the results, the main reaction mechanism is speculated as: ·OH radicals and ·O2- radicals were generated on TiO2 and oxidized the NH3-N into NO3-, and the latter was reduced into non-toxic N2 on the conduction band of g-C3N4. Finally, NH3-N removal performance for actual coking wastewater was investigated, and the stability of the photocatalyst was tested. This work provides some theoretical basis for the two-step degradation of pollutants by Z-scheme photocatalytic system.