Removal of sulfadiazine and tetracycline in membrane bioreactors: linking pathway to microbial community shift

<p>In this study, the removal pathway of sulfadiazine (SDZ) and tetracycline (TC) and their roles in shaping microbial community were separately explored in two lab-scale membrane bioreactors (MBRs) operating in parallel with one control MBR. Results show that the MBR system eliminated more than 90% of TC in the feed, whereas removal efficiency of SDZ decreased from 100% to 40% with increasing SDZ concentrations (1-1000 μg/L). Based on batch tests, biodegradation and adsorption was the main removal route for SDZ and TC, following pseudo-first-order kinetic and pseudo-second-order kinetic model with a rate constant of 1.21 L/(g MLSS·d) and 1.91 h^-1, respectively, in the acclimated sludge. As expected, the acclimated sludge possessed a higher removal potential for the antibiotics compared with unacclimated sludge. Notably, high-throughput sequencing revealed that the most abundant phylum <i>Proteobacteria</i> was resistant to TC (1-1000 μg/L), but was suppressed by SDZ (100-1000 μg/L). Members of the phylum TM7 were likely responsible for SDZ degradation. Overall, TC exhibited a stronger inhibitory effect on bacterial species and significantly reduced the biodiversity compared with SDZ, which could be strongly related to the persistent toxicity of TC to microbes resulting from its high adsorption potential on activated sludge.</p

A new alkaloid glycoside from the rhizomes of <i>Aristolochia fordiana</i>

<div><p>A new alkaloid glycoside named fordianoside (<b>1</b>), together with three known compounds arabinothalictoside (<b>2</b>), 6-<i>O</i>-<i>p</i>-coumaroyl-β-fructofuranosyl-(2 → 1)-α-d-glucopyranoside (<b>3</b>) and 4-[formyl-5-(hydroxymethyl)-1<i>H</i>-pyrrol-1-yl] butanoic acid (<b>4</b>), was isolated from the rhizomes of <i>Aristolochia fordiana</i>. The structure of <b>1</b> was established as (1<i>S</i>)-1,2,3,4-tetrahydro-7-hydroxy-1-[(4-hydroxybenzyl) methyl]-2,2-dimethyl-8-<i>O</i>-isoquinolinyl β-d-glucopyranoside by using chemical and spectroscopic methods including HR-ESI-MS, 1D and 2D NMR.</p></div

Characterization and Significance of Sub-Visible Particles and Colloids in a Submerged Anaerobic Membrane Bioreactor (SAnMBR)

The distribution, composition and morphological structure of subvisible particles and colloids (0.01–10 μm) in the supernatant of a lab-scale submerged anaerobic membrane bioreactor (SAnMBR), and their role in membrane fouling, was investigated. Photometric analysis showed that the supernatant and membrane foulants were dominated by particles and colloids (0.45–10 μm), which accounted for over 90% of the total organics (proteins and polysaccharides). Excitation–emission matrix (EEM) fluorescence spectra and monosaccharide analysis showed that these particles and colloids were rich in fluorescent proteins, rhamnose, ribose and arabinose, all of which could be related to cellular and extracellular substances. Fluorescence and scanning electron microscopy confirmed the presence of bacterial cells in/on the subvisible particles and colloids. The microparticles (5–10 μm) were primarily composed of Streptobacilli and/or filamentous bacteria in the form of microcolonies, while the submicrometer particles and colloids (1–5 μm and 100 kDa-1 μm) had more free/single cocci and bacilli. The ratio of live/dead cells varied in different size-fractions, and the particles (1–10 μm) contained more live cells compared with the colloids (100 kDa-1 μm). Our findings suggest that bacterial cells in/on the particles and colloids could have an important effect on fouling in SAnMBRs as they represent pioneering species attaching to membranes to form fouling layers/biofilm. Such insights reveal that previous foulant-characterization studies in MBRs tended to overestimate organic fouling, while the biofouling induced by these bacteria in/on the particles and colloids was overlooked

Unveiling the Susceptibility of Functional Groups of Poly(ether sulfone)/Polyvinylpyrrolidone Membranes to NaOCl: A Two-Dimensional Correlation Spectroscopic Study

A clear understanding of membrane aging process is essential for the optimization of chemical cleaning in membrane-based facilities. In this study, two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (CoS) analysis was first used to decipher the sequential order of functional group changes of NaOCl-aged poly­(ether sulfone)/polyvinylpyrrolidone (PES/PVP) membranes. The synchronous maps showed 12 major autopeaks in total. Based on the asynchronous maps, a similar aging sequence of membrane groups was clearly identified at three pHs (i.e., 6, 8, and 10): 1463, 1440, and 1410 (cyclic C–H structures) > 1662 (amide groups) > 1700 (succinimide groups) > 1320, 1292 (SO asymmetric) > 1486, 1580 (aromatic structures) > 1241 (aromatic ether bands) > 1105, 1150 cm^–1 (OSO symmetric). Among them, membrane chlorination occurred at 1241, 1410, and 1440 cm^–1. Moreover, the initial degradation of PVP and the subsequent transformation of PES could be highly responsible for the increased water permeability and the enlargement of membrane pores, respectively, both leading to serious fouling with humic acid filtration. In summary, the 2D-FTIR-CoS analysis is a powerful approach to reveal the interaction mechanisms of NaOCl-membrane and could be also useful to probe the process of membrane fouling and chemical cleaning

Microbial Transformation of Biomacromolecules in a Membrane Bioreactor: Implications for Membrane Fouling Investigation

<div><h3>Background</h3><p>The complex characteristics and unclear biological fate of biomacromolecules (BMM), including colloidal and soluble microbial products (SMP), extracellular polymeric substances (EPS) and membrane surface foulants (MSF), are crucial factors that limit our understanding of membrane fouling in membrane bioreactors (MBRs).</p> <h3>Findings</h3><p>In this study, the microbial transformation of BMM was investigated in a lab-scale MBR by well-controlled bioassay tests. The results of experimental measurements and mathematical modeling show that SMP, EPS, and MSF had different biodegradation behaviors and kinetic models. Based on the multi-exponential G models, SMP were mainly composed of slowly biodegradable polysaccharides (PS), proteins (PN), and non-biodegradable humic substances (HS). In contrast, EPS contained a large number of readily biodegradable PN, slowly biodegradable PS and HS. MSF were dominated by slowly biodegradable PS, which had a degradation rate constant similar to that of SMP-PS, while degradation behaviors of MSF-PN and MSF-HS were much more similar to those of EPS-PN and EPS-HS, respectively. In addition, the large-molecular weight (MW) compounds (>100 kDa) in BMM were found to have a faster microbial transformation rate compared to the small-MW compounds (<5 kDa). The parallel factor (PARAFAC) modeling of three-dimensional fluorescence excitation-emission matrix (EEM) spectra showed that the tryptophan-like PN were one of the major fractions in the BMM and they were more readily biodegradable than the HS. Besides microbial mineralization, humification and hydrolysis could be viewed as two important biotransformation mechanisms of large-MW compounds during the biodegradation process.</p> <h3>Significance</h3><p>The results of this work can aid in tracking the origin of membrane foulants from the perspective of the biotransformation behaviors of SMP, EPS, and MSF.</p> </div

Origin, concentration, and composition of initial solutions before the tests.

<p>Variations in the replicates (n = 3) are described as the average ±SD.</p

Contour plots of the seven components identified from the SMP-EEMs, EPS-EEMs and MSF-EEMs dataset.

<p>Contour plots of the seven components identified from the SMP-EEMs, EPS-EEMs and MSF-EEMs dataset.</p

Measured data and modeling of BMM biodegradation in the 21-day bioassay tests.

<p>Measured data and modeling of BMM biodegradation in the 21-day bioassay tests.</p

Parameters describing the fit of degradation data by the multi componential G model.

<p>- Not possible to estimate; BMM-<i>rd</i>, BMM-<i>sd</i> and BMM-<i>nd</i> are the readily biodegradable, slowly biodegradable and non-biodegradable fraction in the BMM.</p