Enhanced Long-Term Nitrogen Removal and Its Quantitative Molecular Mechanism in Tidal Flow Constructed Wetlands

Tidal flow constructed wetlands (TF CWs) have recently been studied as a sustainable technology to achieve enhanced nitrogen removal; however, the underlying mechanisms responsible for removing ammonium (NH₄⁺) and nitrate (NO₃^–) have not been compared and quantified at the molecular level (genes) in controlled TF CWs. In this study, two TF CWs T1 (treating NH₄⁺ wastewater) and T2 (treating NO₃^– wastewater) achieved high removal efficiencies for chemical oxygen demand (COD, 92 ± 2.7% and 95 ± 2.4%, respectively), NH₄⁺/NO₃^– (76 ± 3.9% and 97 ± 2.2%, respectively), and total nitrogen (TN, 81 ± 3.5% and 93 ± 2.3%, respectively). Combined analyses revealed that the presence of simultaneous nitrification, anammox, and denitrification processes and the coupling of dissimilatory nitrate reduction to ammonium, ammonia oxidation, and anammox were the primary reason accounted for the robust treatment performance in T1 and T2, respectively. Results from stepwise regression analysis suggested that the NH₄⁺ removal rate in T1 was collectively controlled by <i>amo</i>A, <i>nxr</i>A, and anammox, while the NO₃^– removal rate in T2 was governed by <i>nxr</i>A and <i>nar</i>G gene

Flow cytometric analysis showing the immunophenotype of the second passage HUMSCs.

<p>The cells were positive for CD105 (97.3%) and CD44 (99%), but negative for CD34 (2.8%), CD31 (2.1%), and CD45 (1.7%).</p

HUMSCs cultured on BAMG.

<p>A SEM showed HUMSCs migrated and proliferated actively in the three-dimensional fashion of BAMG (magnification×2400) at five days. B SEM showed HUMSCs overspread the surface of BAMG at 10 days (magnification×1200).</p

Histologic analysis of reconstructed bladder at 12 weeks after implantation.

<p>(A, E and I) Hematoxylin–eosin stain (magnification×200); (B, F and J) Masson trichrome stain (magnification×200); (C, G and K) immunohistochemistry staining showed the smooth muscle cells to stain positively with α-SMA antibody (magnification×200); (D, H and L) immunohistochemistry staining showed the urothelium cell to stain positively with cytokeratin (AE1/AE3) antibody (magnification×200).</p

Lead Toxicity to the Performance, Viability, And Community Composition of Activated Sludge Microorganisms

Lead (Pb) is a prominent toxic metal in natural and engineered systems. Current knowledge on Pb toxicity to the activated sludge has been limited to short-term (≤24 h) toxicity. The effect of extended Pb exposure on process performance, bacterial viability, and community compositions remains unknown. We quantified the 24-h and 7-day Pb toxicity to chemical oxygen demand (COD) and NH₃–N removal, bacterial viability, and community compositions using lab-scale experiments. Our results showed that 7-day toxicity was significantly higher than the short-term 24-h toxicity. Ammonia-oxidizing bacteria were more susceptible than the heterotrophs to Pb toxicity. The specific oxygen uptake rate responded quickly to Pb addition and could serve as a rapid indicator for detecting Pb pollutions. Microbial viability decreased linearly with the amount of added Pb at extended exposure. The bacterial community diversity was markedly reduced with elevated Pb concentrations. Surface analysis suggested that the adsorbed form of Pb could have contributed to its toxicity along with the dissolved form. Our study provides for the first time a systematic investigation of the effect of extended exposure of Pb on the performance and microbiology of aerobic treatment processes, and it indicates that long-term Pb toxicity has been underappreciated by previous studies

Silver Nanoparticles and Growth Factors Incorporated Hydroxyapatite Coatings on Metallic Implant Surfaces for Enhancement of Osteoinductivity and Antibacterial Properties

Research on incorporation of both growth factors and silver (Ag) into hydroxyapatite (HA) coatings on metallic implant surfaces for enhancing osteoinductivity and antibacterial properties is a challenging work. Generally, Ag nanoparticles are easy to agglomerate and lead to a large increase in local Ag concentration, which could potentially affect cell activity. On the other hand, growth factors immobilization requires mild processing conditions so as to maintain their activities. In this study, bone morphology protein-2 (BMP-2) and Ag nanoparticle contained HA coatings were prepared on Ti surfaces by combining electrochemical deposition (ED) of Ag and electrostatic immobilization of BMP-2. During the ED process, chitosan (CS) was selected as the stabilizing agent to chelate Ag ions and generate Ag nanoparticles that are uniformly distributed in the coatings. CS also reduces Ag toxicity while retaining its antibacterial activity. Afterwards, a BMP/heparin solution was absorbed on the CS/Ag/HA coatings. Consequently, BMP-2 was immobilized on the coatings by the electrostatic attraction between CS, heparin, and BMP-2. Sustained release of BMP-2 and Ag ions from HA coatings was successfully demonstrated for a long period. Results of antibacterial tests indicate that the CS/Ag/HA coatings have high antibacterial properties against both Staphylococcus epidermidis and Escherichia coli. Osteoblasts (OB) culture reveals that the CS/Ag/HA coatings exhibit good biocompatibility. Bone marrow stromal cells (BMSCs) culture indicates that the BMP/CS/Ag/HA coatings have good osteoinductivity and promote the differentiation of BMSCs. Ti bars with BMP/CS/Ag/HA coatings were implanted into the femur of rabbits to evaluate the osteoinductivity of the coatings. Results indicate that BMP/CS/Ag/HA coatings favor bone formation in vivo. In summary, this study presents a convenient and effective method for the incorporation of growth factors and antibacterial agents into HA coatings. This method can be utilized to modify a variety of metallic implant surfaces

Enhanced Repairing of Critical-Sized Calvarial Bone Defects by Mussel-Inspired Calcium Phosphate Cement

The goal of this study is to investigate the biological response of mussel-inspired calcium phosphate cement (CPC) in vivo. Polydopamine (PDA), which is analogous to that of mussel adhesive proteins, was added in CPC. PDA-CPC was implanted into the femur, muscle, and critical-sized calvarial bone defects of rabbits. Histomorphometry of the sequential fluorescence sections showed that PDA-CPC was capable of forming more newborn bone than the control-CPC. More new bone, bone marrow cavity, and blood vessel were observed in PDA-CPC than in the control-CPC in decalcified and undecalcified histological sections. Necrosis bone was not observed in PDA-CPC, whereas it appeared in the control-CPC after 2 weeks. The histological sections in muscle witnessed that there was more ingrowth of collagen in PDA-CPC than that in the control-CPC. There were no significantly difference in the number of leukocyte between PDA-CPC and the control-CPC in blood. It was confirmed that the addition of PDA enhanced the bone repairing ability and biocompatibility of PDA-CPC. Push-out testing indicated that PDA increased the bonding strength between PDA-CPC and host bone in the early stage. These present results indicated that PDA-CPC might be one potential bone graft with gratifying biocompatibility and enhanced bone repairing