Comparison between two anammox fiber fillers under load impact and the effect of HCO3− concentration

Based on the establishment of a stable anaerobic ammonia oxidation treatment system in 100 days, the impact resistances of two different anammox fiber fillers (the curtain filler: R1 and the bundle filler: BR) were compared.

Understanding Catalytic Activity Trends of Electrochemical Ammonia Oxidation Reaction using Density Functional Theory Calculations and Microkinetic Modeling

Electrochemical ammonia oxidation reaction (AOR) is promising as an alternative anodic reaction to oxygen evolution in water electrolysis system. Herein, we develop a microkinetic model based on density functional theory (DFT) calculations for all possible reaction pathways considering both thermochemical and electrochemical N-N bond formation processes. From the microkinetic analysis, we discover that Faradaic bond formation contributes to AOR more significantly than non-Faradaic counterpart and we observe good agreements with the experimental results. We then construct a kinetic volcano plot using binding energies of two reaction intermediates as descriptors, which suggests a catalyst design strategy. Following this strategy, we enumerate numerous alloy combinations and identify a few promising candidates with higher catalytic activity than the most active monometallic Pt catalyst.

Integration of anammox into the MBR process for main stream sewage treatment

The integration of Anaerobic ammonia oxidation (anammox) into the membrane bioreactor (MBR) process (AX-MBR) is proposed in this study to reduce operating costs. The temperature was not controlled during the study. Anammox, denitrification, and nitrification were studied in the AX-MBR for 210 days. The reactor was fed with mainstream sewage from Guilin City, China. The results showed that AX-MBR could run with reduced dissolved oxygen (DO) concentration, and COD, NH4+-N, and total nitrogen removal were maintained or improved. The microbial analysis results demonstrated that the added anammox sludge could survive in the AX-MBR, but the sludge microbial diversity decreased. Nitrospira, Candidatus Kuenenia, and Nitrosomonas dominated the anammox sludge. In a word, the AX-MBR developed in this study could treat mainstream sewage with the appropriate management, and the operation costs are expected to reduce by decreasing the amount of aeration.

Dual Use of Copper-Modified TiO2 Nanotube Arrays as Material for Photocatalytic NH3 Degradation and Relative Humidity Sensing

In this paper, we emphasized the dual application of Cu-modified vertically aligned TiO2 nanotube arrays as photocatalyst and a relative humidity sensor. The TiO2 nanotube arrays were obtained by anodization of the titanium layer prepared using radio frequency magnetron sputtering (RFMS) and modified with different copper concentrations (0.5, 1, 1.5, and 2 M) by a wet-impregnation method. The sample modified with 2 M Cu(NO3)2 solution showed the highest efficiency for the NH3 photocatalytic degradation and the most pronounced humidity response in comparison to the other studied samples. In order to investigate the structure and impact of Cu modification, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used. The photocatalytic activity and the kinetic study of ammonia oxidation were studied in a mini-photocatalytic wind tunnel reactor (MWPT), while relative humidity sensing was examined by impedance spectroscopy (IS). Higher NH3 oxidation was a direct consequence of the increased generation of •OH radicals obtained by a more efficient photogenerated charge separation, which is correlated with the increase in the DC conductivity.

Rapid Start-Up of Anammox by Immobilization and Its Response to Low Temperature Stress

In view of the problems of slow start, easy loss and sensitive to low temperature environment in the suspension culture of anaerobic ammonia oxidation bacteria (AnAOB) suspension culture, polyvinyl alcohol (PVA) was used to prepare the anaerobic ammonia oxidation (anammox) immobilized filler, so as to realize the rapid start-up and activity improvement of anammox. Meanwhile, the response of nitrogen removal performance of encapsulated biomass to temperature reduction was determine by batch experiment. In addition, changes in the internal structure, flora composition and diversity of the filler were analyzed by scanning electron microscopy (SEM) and high-throughput sequencing. The results showed that the nitrogen removal capacity of the immobilized filler (E1) was significantly higher than that of the suspended sludge contrast system (S1) after 100d enrichment culture. The final nitrogen removal rate reached 1.168kg·(m3·d-1) -1, and the total nitrogen removal efficiency was 92%. The immobilization improved the resistance of AnAOB to low temperature. At 15°C, the effluent ammonia and nitrite of S1 were seriously accumulated, and E1 could maintain a stable nitrogen removal effect under the regulation of HRT. The population diversity was maintained in the immobilized filler, and the functional bacteria of anammox Candidatus Kuenenia was effectively enriched, accounting for 32.55% in E1. The results of this study provide valuable information for the application and popularization of anammox immobilized filler.

Enhanced biodegradation of ciprofloxacin by enrich nitrifying sludge: assessment of removal pathways and microbial responses

Antibiotics are mostly collected by sewage systems, but not completely removed within wastewater treatment plants. Their release to aquatic environment poses great threat to public health. This study evaluated the removal of a widely used fluoroquinolone antibiotic ciprofloxacin in enriched nitrifying culture through a series of experiments by controlling ammonium concentrations and inhibiting functional microorganisms. The removal efficiency of ciprofloxacin at an initial concentration of 50 μg L−1 reached 81.86 ± 3.21% in the presence of ammonium, while only 22.83 ± 8.22% of ciprofloxacin was removed in its absence. The positive linear correlation was found between the ammonia oxidation rate (AOR) and ciprofloxacin biodegradation rate. These jointly confirmed the importance of the AOB-induced cometabolism in ciprofloxacin biodegradation with adsorption and metabolic degradation pathways playing minor roles. The continuous exposure of AOB to ciprofloxacin led to decreases of ammonia monooxygenase (AMO) activities and AOR. The antibacterial effects of ciprofloxacin and its biodegradation products were further evaluated and the results revealed that biodegradation products of ciprofloxacin exhibited less toxicity compared to the parent compound, implying the potential application of cometabolism in alleviation of antimicrobial activity. The findings provided new insights into the AOB-induced cometabolic biodegradation of fluoroquinolone antibiotics.