An ecology-based analysis of irreversible biofouling in membrane bioreactors

2007 ◽  
Vol 55 (8-9) ◽  
pp. 395-402 ◽  
Author(s):  
K. Zhang ◽  
H. Choi ◽  
M. Wu ◽  
G.A. Sorial ◽  
D. Dionysiou ◽  
...  
Keyword(s):  
Restriction Analysis ◽  
Membrane Surface ◽  
Acinetobacter Calcoaceticus ◽  
Paper Mill ◽  
Membrane Bioreactors ◽  
Bacterial Populations ◽  
Membrane Biofouling ◽  
Significant Difference ◽  
Microfiltration Membranes ◽  
Highly Correlated

To provide the first step towards a microbial ecology-based understanding of irreversible membrane biofouling, four laboratory-scale membrane bioreactors (MBRs) were operated to investigate the identity of bacterial populations highly correlated with irreversible membrane biofouling. The conventional MBR was divided into two separate experimental units. Unit one consisted of four suspended-growth, activated sludge, sequencing batch bioreactors treating a synthetic paper mill wastewater. Unit two consisted of a microfiltration membrane cell. Amplified ribosomal deoxyribonucleic acid restriction analysis (ARDRA) was used to compare the predominant bacterial populations in samples of mixed liquor and irreversibly bound to the membrane surface. The results of ARDRA showed a significant difference between the planktonic and sessile bacterial communities suggesting that irreversible biofouling of microfiltration membranes may be more highly correlated to specific bacterial populations rather than the total, bulk concentration of biomass. A custom-built mini-flow cell and light microscopy were used to visualise the early formation of biofilms by two pure cultures (Escherichia coli and Acinetobacter calcoaceticus) on membrane surfaces. The results confirmed that A. calcoaceticus was able to enhance the initiation of biofilm formation on microfiltration membranes.

scholarly journals Membrane bioreactors for wastewater treatment: A review of microbial quorum sensing and quenching to control membrane biofouling based on engineering quorum quenching bacteria

2020 ◽  
Vol 194 ◽  
pp. 04026
Author(s):  
Xinmeng Jiao ◽  
Kang Xie ◽  
Liping Qiu
Keyword(s):  
Wastewater Treatment ◽  
Quorum Sensing ◽  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Membrane Surface ◽  
Quorum Quenching ◽  
Membrane Bioreactors ◽  
Practical Application ◽  
Membrane Biofouling ◽  
New Strategy

Membrane bioreactor (MBR) is a kind of reputable and prospective technology for wastewater treatment and reformation applications. However, membrane fouling caused by the formation of biofilm on the membrane surface, especially biofouling, is a major obstacle that limits the energy-saving operation and maintenance of the membrane bioreactor (MBR). Microbial communication (known as Quorum Sensing (QS)) is the cause of this fouling phenomenon. A new strategy called Quorum Quenching (QQ) seems to have been successfully used for biological pollution control in wastewater treatment MBR. This review summarizes the latest findings regarding membrane fouling, QS mechanisms and QQ applications. We discussed the opportunities for further practical application of self-cleaning engineering QQ bacteria in MBR.

Detection of Circulating Tissue Factor and Factor VII in a Normal Population

1996 ◽  
Vol 75 (05) ◽  
pp. 772-777 ◽  
Author(s):  
Sybille Albrecht ◽  
Matthias Kotzsch ◽  
Gabriele Siegert ◽  
Thomas Luther ◽  
Heinz Großmann ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Normal Population ◽  
Mean Value ◽  
Factor Vii ◽  
Significant Difference ◽  
Age Dependent ◽  
The Mean ◽  
Highly Correlated ◽  
And Gender

SummaryThe plasma tissue factor (TF) concentration was correlated to factor VII concentration (FVIIag) and factor VII activity (FVIIc) in 498 healthy volunteers ranging in age from 17 to 64 years. Immunoassays using monoclonal antibodies (mAbs) were developed for the determination of TF and FVIIag in plasma. The mAbs and the test systems were characterized. The mean value of the TF concentration was 172 ± 135 pg/ml. TF showed no age- and gender-related differences. For the total population, FVIIc, determined by a clotting test, was 110 ± 15% and the factor VIlag was 0.77 ± 0.19 μg/ml. FVII activity was significantly increased with age, whereas the concentration demonstrated no correlation to age in this population. FVII concentration is highly correlated with the activity as measured by clotting assay using rabbit thromboplastin. The ratio between FVIIc and FVIIag was not age-dependent, but demonstrated a significant difference between men and women. Between TF and FVII we could not detect a correlation.

scholarly journals O29 Aberrant expression of BMP8A and the BMPRs involves in the progression of breast cancer

2021 ◽  
Vol 108 (Supplement_5) ◽  
Author(s):  
L J Sui ◽  
A Sanders ◽  
W G Jiang ◽  
L Ye
Keyword(s):  
Breast Cancer ◽  
Poor Prognosis ◽  
Gene Array ◽  
Breast Cancers ◽  
Sequencing Data ◽  
Aberrant Expression ◽  
Bmp Receptors ◽  
Significant Difference ◽  
Highly Correlated ◽  
Spearman Test

Abstract Introduction Role of Bone morphogenetic protein 8A (BMP8A) and BMP receptors (BMPRs) in the tumourigenesis and progression of breast cancer remains elusive. Present study aims to investigate the expression of BMP8A and related BMPRs in breast cancer and their clinical implication. Method Expression of BMP8A and BMPRs was analysed using the RNA sequencing data of the TCGA breast cancer cohort. Findings were further validated in a meta gene array dataset (E-MDTA6703, n = 2302). STRING dataset was applied to explore the predicted receptors of BMP8A. Clinical relevance of deregulated BMP8A and BMPRs in breast cancer was assessed using both ANOVA and Kaplan-Meier tests. Correlation with markers of proliferation and invasion was evaluated using Spearman test. Result Analysis of datasets revealed that BMP8A and BMPR1B were highly expressed in breast cancer while ACVRL1, ACVR1, BMPR1A, ACVR1C, TGFBR2, TGFBR3, BMPR2 and ACVR2A were lower-expressed compared with normal controls. Expressions of BMPR1B, BMPR1A, BMPR2, ACVR2A and ACVR2B were highly correlated with BMP8A in the breast cancers. Overall survival in the group with higher BMP8A expression was shorter(median= 122.3 months), P = 0.012 compared with lower-expressed group(median = 215.2 months). No significant difference was observed in BMP8A and BMPRs in tumours according to their staging and lymph node involvement. Positive correlations were found between BMP8A and tumour proliferation, EMT, angiogenic markers. Conclusion BMP8A is increased in breast cancer and correlates with poor prognosis. The highly correlated BMPRs might be involved in the signal transduction of BMP8A to co-regulate BMP responsive genes and cellular functions which is yet to be investigated. Take-home Message BMP8A is increased in breast cancer and correlates with poor prognosis.

scholarly journals Effectiveness of calcium hydroxide in reducing bacterial load comparing with chemo-mechanical preparation- A systematic review

2019 ◽  
Author(s):  
SaiSiva Naga GayathriNaidu ◽  
B Vikram Simha ◽  
Koka Krishna Mohan ◽  
Rammohan Modem ◽  
Kommineni Harish Chowdary
Keyword(s):  
Clinical Trials ◽  
Calcium Hydroxide ◽  
Bacterial Load ◽  
Bacterial Reduction ◽  
Bacterial Populations ◽  
Hand Search ◽  
Root Canals ◽  
Mechanical Preparation ◽  
Infected Root ◽  
Significant Difference

Aim: To determine and compare to what extent the intra-canal medicament like calcium hydroxide along with chemo-mechanical preparation reduces the bacterial load in infected root canals. Methodology: PubMed Cental, Medline, Google Scholar and hand search was carried out using the keywords calcium hydroxide (Ca(OH)2) , intra-canal medicament(ICM) and chemo-mechanical preparation. Selection Criteria: Clinical trials in which bacterial samples were evaluated at 3 intervals (Baseline, after chemo-mechanical preparation, after dressing with intra canal medicament ICM and trials which use Ca(OH)2 with any vehicle as ICM, but not compared with any other ICM were selected for this review. The data collection form was customized. The primary outcome measures were reduction of bacterial populations in infected root canals. Results: Seven clinical trials that met all inclusion criteria involving 117 participants were reviewed. Included studies showed significant difference in bacterial reduction after chemo-mechanical preparation and placement of Ca(OH)2 dressing for a week. In all included trials, Ca(OH)2 reduced bacterial load further compared with chemo-mechanical preparation. Conclusion: Ca(OH)2 as an inter-appointment medication promoted further decrease in the bacterial bioburden to levels significantly below those achieved by the chemo-mechanical procedures alone. Intra-canal medicament such as Ca(OH)2 should be considered for bacterial reduction along with chemo-mechanical preparation for long term success. Key Words: Intra-canal medicament, calcium hydroxide, Root canal treatment, bacterial load, Pulpitis

scholarly journals Influence of Membrane Vibration on Particles Rejection Using a Slotted Pore Membrane Microfiltration

Membranes ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 709
Author(s):  
Asmat Ullah ◽  
Kamran Alam ◽  
Saad Ullah Khan ◽  
Victor M. Starov
Keyword(s):  
Membrane Fouling ◽  
Produced Water ◽  
Separation Efficiency ◽  
Membrane Surface ◽  
Water Separation ◽  
Oil Droplet ◽  
Pore Blockage ◽  
Oil Water Separation ◽  
Microfiltration Membranes ◽  
Membrane Vibration

A new method is proposed to increase the rejection in microfiltration by applying membrane oscillation, using a new type of microfiltration membrane with slotted pores. The oscillations applied to the membrane surface result in reduced membrane fouling and increased separation efficiency. An exact mathematical solution of the flow in the surrounding solution outside the oscillating membrane is developed. The oscillation results in the appearance of a lift velocity, which moves oil particles away from the membrane. The latter results in both reduced membrane fouling and increased oil droplet rejection. This developed model was supported by the experimental results for oil water separation in the produced water treatment. It was proven that the oil droplet concentration was reduced notably in the permeate, due to the membrane oscillation, and that the applied shear rate caused by the membrane oscillation also reduced pore blockage. A four-times lower oil concentration was recorded in the permeate when the membrane vibration frequency was 25 Hz, compared to without membrane vibration. Newly generated microfiltration membranes with slotted pores were used in the experiments.

Comparison of four types of membrane bioreactor systems in terms of shear stress over the membrane surface using computational fluid dynamics

2013 ◽  
Vol 68 (12) ◽  
pp. 2534-2544 ◽  
Author(s):  
N. Ratkovich ◽  
T. R. Bentzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Membrane Fouling ◽  
Two Phase Flow ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Bioreactors ◽  
Phase Flow ◽  
Two Phase ◽  
Computational Fluid Dynamics Cfd

Membrane bioreactors (MBRs) have been used successfully in biological wastewater treatment to solve the perennial problem of effective solids–liquid separation. A common problem with MBR systems is clogging of the modules and fouling of the membrane, resulting in frequent cleaning and replacement, which makes the system less appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be greatly improved with a two-phase flow (sludge–air) or higher liquid cross-flow velocities. However, the optimization process of these systems is complex and requires knowledge of the membrane fouling, hydrodynamics and biokinetics. Modern tools such as computational fluid dynamics (CFD) can be used to diagnose and understand the two-phase flow in an MBR. Four cases of different MBR configurations are presented in this work, using CFD as a tool to develop and optimize these systems.

scholarly journals Design of a Novel Membrane Draft Tube Jet Loop Reactor (MDJLR) and Treatment of Slaughterhouse Wastewater

Membranes ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 155
Author(s):  
Burhanettin Farizoğlu ◽  
Süleyman Uzuner
Keyword(s):  
Membrane Fouling ◽  
High Efficiency ◽  
Draft Tube ◽  
Membrane Surface ◽  
Membrane Bioreactors ◽  
Operating Conditions ◽  
Membrane Module ◽  
Circulation Rate ◽  
Slaughterhouse Wastewater ◽  
Loop Reactor

The most important obstacle to the widespread use of membrane bioreactors (MBRs) is membrane fouling. In this study, a high-efficiency compact MBR was developed. Therefore, the draft tube of the jet loop reactor (JLB) was planned for use as a membrane module. The high-velocity jet streams, which are present according to the nature of the JLBs, provide high crossflow (cut-off force) on the membrane surface. Thus, the produced membrane module is operated in submerged membrane mode. This enhanced JLB modification is named the membrane draft tube jet loop reactor (MDJLR). This new system has a KLa value of 139 h−1 (at E/V of 2.24 kW m−3). In the next stage, treatment of slaughterhouse wastewater with the MDJLR was carried out. Under the 5.5 kg COD m−3 d−1 loading rate, efficiencies over 97% were achieved. The system operated continuously for 50 days without membrane backwashing or cleaning. During this period, fluxes of 3 L m−2·h−1 were approximately obtained at operating conditions of 850 mg L−1 MLSS (mixed liquor suspended solids) concentration, 1 bar suction pressure (∆P), and 3000 L h−1 circulation rate. This developed MDJLR will make jet loop membrane bioreactors (JLMBRs) and MBRs more compact and improve their performance.

Feasibility of submerged anaerobic membrane bioreactor (SAMBR) for treatment of low-strength wastewater

2008 ◽  
Vol 58 (10) ◽  
pp. 1925-1931 ◽  
Author(s):  
Z. Huang ◽  
S. L. Ong ◽  
H. Y. Ng
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactors ◽  
Organic Loading Rate ◽  
Effluent Quality ◽  
Significant Difference ◽  
Anaerobic Membrane Bioreactors ◽  
High Purification ◽  
Low Strength ◽  
Set Up ◽  
Internal Pore

Two 6-L submerged anaerobic membrane bioreactors (SAMBR) with SRT of 30 and 60 d (denoted as R30 and R60, respectively) were set up and operated for five months, with a mixture of glucose as substrate. Feasibility of SAMBR was studied for treatment of low-strength wastewater. First two months were identified as acclimation stage. A COD removal efficiency was achieved stably at around 99% and biogas productions were maintained at 0.023 and 0.028 L CH4/gMLVSS∙d for R30 and R60, respectively. Even though R60 contained higher MLVSS concentration, no significant difference of treatment performances between both reactors was found due to the low organic loading rate and high purification function of membrane. In the investigation of membrane fouling, less irreversible fouling was observed for R30 compared to R60. High non-flocculent concentration of R60 would be responsible for membrane internal pore blocking and deteriorated effluent quality.

scholarly journals Numerical simulation of filtration performance in submerged membrane bioreactors: effect of particle packed structure

2017 ◽  
Vol 76 (9) ◽  
pp. 2503-2514 ◽  
Author(s):  
Zhidong Wang ◽  
Kuizu Su ◽  
Tong Shu ◽  
Weihong Wang
Keyword(s):  
Membrane Surface ◽  
Membrane Bioreactors ◽  
Navier Stokes ◽  
Permeate Flux ◽  
The Finite Element Method ◽  
Brinkman Equations ◽  
Filtration Performance ◽  
Cake Layer ◽  
Packed Structure ◽  
Cake Porosity

Abstract It is widely known that the accumulation of solid matter forming a cake layer on the membrane surface is one of the major limitations of the filtration performance in submerged membrane bioreactors (SMBR). This study is focused on the influence of the cake porosity of different particle microscopic packed structures on the filtration performance of hollow fiber systems. An integrated model based on the finite element method to simulate numerically the flow in an SMBR is presented. The model coupled the Navier–Stokes and Darcy Brinkman equations to simulate a complete filtration run. The cake growth took into consideration not only the deposition with local filtration velocity but also the effect of aeration scouring. A novel solution of mesh deformation was adopted to investigate transient cake growth along the fiber. Comparisons between simulations and experiments are in good agreement. The results show that a higher porosity particle packed structure causes non-uniform filtration and cake thickness but also higher permeate flux. Meanwhile, the proportion of cake resistance to total resistance increases with the decrease of porosity.

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