Operation of a sequencing batch reactor for cultivating autotrophic nitrifying granules

The granulation of nitrifying sludge in a sequencing batch reactor (SBR) fed with NH4 +-N-laden inorganic wastewater was investigated. After 120-day operation spherical and elliptical granules with an average diameter of 0.32 mm were observed. The hydrophobicity surface, settling velocity and specific gravity of the matured granules increased with the processing of sludge granulation. Spatial distribution of bacterial species within the autotrophic granules was analyzed with fluorescence in situ hybridization. Both ammonia- and nitrite-oxidizing bacteria were observed in the granular sludge. The Michaelis-Menten equation was used to describe their NH4 +-N utilization rate, and the kinetic coefficients were calculated to be vm = 18.0 mg/g-VSS/h and Km = 36.7 mg/l. Taking into account the NH4 +-N utilization rate and removal efficiency together, an NH4 +-N concentration range of 100-250 mg/l was found to be favourable for the operation of the SBR to cultivate nitrifying granules. © 2009 Elsevier Ltd. All rights reserved.postprin

Aerobic sludge granulation facilitated by activated carbon for partial nitrification treatment of ammonia-rich wastewater

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Effect of the food-to-microorganism (F/M) ratio on the formation and size of aerobic sludge granules

Laboratory experiments were carried out to investigate the effect of the sludge loading, or the food-to-microorganism (F/M) ratio, on the rate of aerobic granulation and the size of the granules in biological wastewater treatment. Four column batch reactors were used with a similar sludge suspended solids (SS) concentration of around 2000 mg/L. The reactors were fed with a glucose-based wastewater at different chemical oxygen demand (COD) concentrations, resulting in F/M ratios from 0.3 to 1.1 g COD/g SS-d. A higher F/M ratio appeared to promote faster formation of larger granules and a lower F/M ratio led to slower formation of smaller granules. Upon complete granulation, the granules became rather stable in size, and the mean diameter of the granules in different reactors increased from 1.2 to 4.5 mm linearly with the F/M ratio applied. Molecular analysis of the sludge did not show the domination of any particular bacterial species during the granulation process. It is apparent that applying different F/M ratios in different granulation stages, e.g., a higher F/M in the early stage and a reduced F/M in the later stage, can be an effective start-up strategy to facilitate rapid granule formation and sustain small and healthy granules in bioreactors. © 2011 Elsevier Ltd. All rights reserved.postprin

Granular activated carbon for aerobic sludge granulation in a bioreactor with a low-strength wastewater influent

Aerobic sludge granulation is rather difficult or impossible for the treatment of low-strength wastewater. In this study, a novel technique involving granular activated carbon (GAC) was developed for rapid aerobic granulation under a low organic loading condition. Laboratory experiments were conducted with two sequencing batch reactors (SBRs) running side by side. One reactor had fine GAC added to the sludge mixture, and the other had no GAC added. A low-strength organic wastewater with a chemical oxygen demand (COD) concentration of only 200 mg/L was used as the influent to the SBRs. The morphology, physical properties, and bacterial community structure of the sludge in the two reactors were characterized and compared throughout the experiments. The results showed that granules could not be formed in the SBR without added GAC. However, complete granulation was achieved in the SBR with GAC addition. Selective discharge of slow settling sludge was also essential to the granulation process. Adding GAC to the seed sludge mixture, together with the selective discharge of small and loose sludge flocs, facilitated the retention and growth of bacterial cells on GAC in attached-growth mode, leading to complete granulation. In addition, the use of GAC produced aerobic granules with strong cores to help maintain the long-term stability of mature granules. With granulation, the solid-liquid separation property of the sludge was greatly improved. Once granules were formed, the granules were quite stable and GAC addition was no longer needed. Therefore, adding GAC is a simple and effective strategy to initiate granule formation for complete sludge granulation in bioreactors treating low-strength organic wastewater. © 2011 Elsevier B.V. All rights reserved.postprin

The quorum-sensing effect of aerobic granules on bacterial adhesion, biofilm formation, and sludge granulation

Quorum sensing (QS) through signal chemical molecules is known to be essential to bacterial adhesion and biofilm formation. In this study, the QS ability of aerobic granules-a special form of biofilms used for biological wastewater treatment-was investigated and compared with that of conventional activated sludge flocs. A novel sectional membrane bioreactor was used together with a flow-cell to evaluate the possible influence of signal chemicals produced by the source sludge on the growth mode of bacterial cells. The results demonstrate the apparent production of QS chemicals from granules and its impact on initial cell attachment and granule formation. When granules were used as the signal-producing biomass, the attached-growth mode was dominant for the free cells, and the biofilm formation rate in the flow-cell was about ten times faster than in cases which used activated sludge as the signal source biomass. In addition, the intracellular extract from mature granules significantly accelerated the sludge granulation process. It is argued that the production and expression of QS signal chemicals from granules and granule precursors might have induced the gene expression of bacteria in suspension for attached growth rather than suspended growth, leading to granule formation and its stable structure. © Springer-Verlag 2010.postprin

Enabling liquid vapor analysis using synchrotron VUV single photon ionization mass spectrometry with a microfluidic interface.

Vacuum ultraviolet (VUV) single photon ionization mass spectrometry (SPI-MS) is a vacuum-based technique typically used for the analysis of gas phase and solid samples, but not for liquids due to the challenge in introducing volatile liquids in a vacuum. Here we present the first demonstration of in situ liquid analysis by integrating the System for Analysis at the Liquid Vacuum Interface (SALVI) microfluidic reactor into VUV SPI-MS. Four representative volatile organic compound (VOC) solutions were used to illustrate the feasibility of liquid analysis. Our results show the accurate mass identification of the VOC molecules and the reliable determination of appearance energy that is consistent with ionization energy for gaseous species in the literature as reported. This work validates that the vacuum-compatible SALVI microfluidic interface can be utilized at the synchrotron beamline and enable the in situ study of gas-phase molecules evaporating off the surface of a liquid, which holds importance in the study of condensed matter chemistry

A scheme for demodulation of fiber grating sensors with high resolution

2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Nanofibers Fabricated Using Triaxial Electrospinning as Zero Order Drug Delivery Systems

A new strategy for creating functional trilayer nanofibers through triaxial electrospinning is demonstrated. Ethyl cellulose (EC) was used as the filament-forming matrix in the outer, middle, and inner working solutions and was combined with varied contents of the model active ingredient ketoprofen (KET) in the three fluids. Triaxial electrospinning was successfully carried out to generate medicated nanofibers. The resultant nanofibers had diameters of 0.74 ± 0.06 μm, linear morphologies, smooth surfaces, and clear trilayer nanostructures. The KET concentration in each layer gradually increased from the outer to the inner layer. In vitro dissolution tests demonstrated that the nanofibers could provide linear release of KET over 20 h. The protocol reported in this study thus provides a facile approach to creating functional nanofibers with sophisticated structural features

Analysis of dielectric loaded surface plasmon waveguide structures : transfer matrix method for plasmonic devices

Author name used in this publication: Qi Jie WangAuthor name used in this publication: Siu Fung YuVersion of RecordPublishe

Absolute quantitation of DNA methylation of 28 candidate genes in prostate cancer using pyrosequencing

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Aberrant DNA methylation plays a pivotal role in carcinogenesis and its mapping is likely to provide biomarkers for improved diagnostic and risk assessment in prostate cancer (PCa). We quantified and compared absolute methylation levels among 28 candidate genes in 48 PCa and 29 benign prostate hyperplasia (BPH) samples using the pyrosequencing (PSQ) method to identify genes with diagnostic and prognostic potential. RARB, HIN1, BCL2, GSTP1, CCND2, EGFR5, APC, RASSF1A, MDR1, NKX2-5, CDH13, DPYS, PTGS2, EDNRB, MAL, PDLIM4, HLAa, ESR1 and TIG1 were highly methylated in PCa compared to BPH (p < 0.001), while SERPINB5, CDH1, TWIST1, DAPK1, THRB, MCAM, SLIT2, CDKN2a and SFN were not. RARB methylation above 21% completely distinguished PCa from BPH. Separation based on methylation level of SFN, SLIT2 and SERPINB5 distinguished low and high Gleason score cancers, e.g. SFN and SERPINB5 together correctly classified 81% and 77% of high and low Gleason score cancers respectively. Several genes including CDH1 previously reported as methylation markers in PCa were not confirmed in our study. Increasing age was positively associated with gene methylation (p < 0.0001). Accurate quantitative measurement of gene methylation in PCa appears promising and further validation of genes like RARB, HIN1, BCL2, APC and GSTP1 is warranted for diagnostic potential and SFN, SLIT2 and SERPINB5 for prognostic potential