Assimilable organic carbon and biodegradable organic carbon removal by nanofiltration: full and bench-scale evaluation

2001 ◽  
Vol 1 (4) ◽  
pp. 35-42 ◽  
Author(s):  
I.C. Escobar ◽  
A.A. Randall ◽  
S.K. Hong
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Organic Carbon ◽  
Effective Means ◽  
High Hardness ◽  
Full Scale ◽  
Significant Fraction ◽  
Size Exclusion ◽  
Small Molecular Weight ◽  
Bench Scale

The main objective of this research was to evaluate the effectiveness of nanofiltration (NF) at full and bench scale for controlling AOC and BDOC, which are the main indicators of biological stability of the finished potable water. One of the major observations from full-scale operation was that nanofiltration was a very effective means to reduce BDOC, but conversely, did not reject a significant fraction of AOC. The high BDOC rejection by nanofiltration (NF) membranes at full scale can be explained by size exclusion, since a significant fraction of BDOC consists of compounds, such as humic and fulvic acids, which are larger than the pores of NF membranes (molecular-weight cutoff ≈200 daltons). The insignificant AOC rejection observed in full-scale systems was probably due to the low pH, high hardness, and high ionic strength (TDS) of the raw water. Bench scale tests using simulated waters clearly demonstrated that AOC removal by NF membranes decreases markedly with decreasing pH, and increasing hardness and ionic strength, implying that electrostatic repulsion plays a significant role in AOC removal mechanisms. These solution environments repress the electrostatic interaction between charged organic compounds and membranes, allowing passage of small molecular weight compounds and thus reducing AOC rejection.

scholarly journals A Novel Synthesis of Poly(Ester-Alt-Selenide)s by Ring-Opening Copolymerization of γ-Selenobutyrolactone and Epoxy Monomer

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1203 ◽  
Author(s):  
Ya’nan Wang ◽  
Xiaofang Lin ◽  
Zhengbiao Zhang ◽  
Jian Zhu ◽  
Xiangqiang Pan ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Effective Means ◽  
Linear Structure ◽  
Size Exclusion ◽  
Ionization Time ◽  
Flight Mass Spectrometry ◽  
Epoxy Monomer ◽  
Polymerization System ◽  
Exclusion Chromatography

Ring-opening copolymerization (ROCOP) is an effective means to prepare functionalized polyester. In this work, a type of selenide-containing polyesters with controllable structure, molecular weight, and molecular weight distribution was successfully prepared by ROCOP of γ-selenobutyrolactone and epoxy compounds. The influence of the catalyst, solvent, and reaction temperature on the reaction efficiency was examined. Then, kinetic study was investigated under an optimized condition. The structure of the copolymers was carefully characterized by nuclear magnetic resonance (NMR), 1H NMR, 13C NMR, and 77Se NMR, Matrix-assisted laser-desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and size exclusion chromatography (SEC). The resulting polymers showed a linear structure with a sequence regulated backbone repeating unit of ester-selenide. On this basis, some typical epoxides were investigated to verify the scope of the polymerization system. Due to the “living”/controlled characteristics of this ROCOP, multiblock, amphiphilic, and stereotactic copolymers could be prepared with a pre-designed structure. As expected, the selenide-containing amphiphilic copolymer could self-assemble to micelles and showed an oxidative response.

Measuring dissolved organic matter in estuarine and marine waters: size-exclusion chromatography with various detection methods

2018 ◽  
Vol 15 (7) ◽  
pp. 436 ◽  
Author(s):  
Gabriel Dulaquais ◽  
Johann Breitenstein ◽  
Matthieu Waeles ◽  
Rémi Marsac ◽  
Ricardo Riso
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Humic Substances ◽  
Size Exclusion Chromatography ◽  
Size Exclusion ◽  
Marine Waters ◽  
Wide Range ◽  
Exclusion Chromatography

Environmental contextDissolved organic matter (DOM), a key parameter in aquatic biogeochemistry, is difficult to characterise owing to its variable composition and structure. We report a chromatographic method with carbon, nitrogen and absorbance detection able to record the size distribution of DOM and changes in its composition. The method could be used to identify additional sources to river or coastal waters as well as monitoring the DOM size/reactivity continuum in open oceans. AbstractWe studied the performance and limitations of size-exclusion chromatography with organic carbon, ultraviolet and organic nitrogen detectors (SEC-OCD-UVD-OND) for characterising dissolved organic matter (DOM) in estuarine and marine waters. We identified a strong salt effect on dissolved organic carbon (DOC) determination; however, calibration gave good results at salinity levels close to those of the sample analysed (ΔS ± 2 psu (practical salinity units)), with limited matrix effects, enabling an accurate measurement of DOC, as demonstrated by an intercalibration exercise. The repeatability, reproducibility and limit of detection (3 ppb for both carbon and nitrogen) for the three detectors demonstrated the robustness of the method for a wide range of natural waters, including carbon-rich freshwaters and deep seawaters with low carbon content (6000 ppb-C to 300 ppb-C). Deeper analysis of the SEC demonstrated that proteins and polysaccharides are partly fractionated within the column, and that terrestrial humic substances, isolated on a XAD-8 resin, can also be eluted in both fractions associated with biopolymers and low-molecular-weight neutrals. Application of the method to the study of DOM along a macrotidal estuary that was influenced by agricultural activities revealed significant changes in its composition despite a conservative DOC distribution. Distinct origins and qualities of high-molecular-weight (>500 kDa) organic compounds were identified for riverine and marine end-members. A new diagram to track changes in DOM lability is proposed to complete the humic-substances diagram.

Nanofiltration for the removal of algal metabolites and the effects of fouling

2010 ◽  
Vol 61 (5) ◽  
pp. 1189-1199 ◽  
Author(s):  
M. B. Dixon ◽  
C. Falconet ◽  
L. Ho ◽  
C. W. K. Chow ◽  
B. K. O'Neill ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Drinking Water ◽  
Membrane Fouling ◽  
Size Exclusion ◽  
Low Molecular Weight ◽  
Test Unit ◽  
Organic Micropollutants ◽  
Bench Scale ◽  
Over Time

Nanofiltration (NF) has been shown to be an effective way of removing organic micropollutants from drinking water due to its size exclusion properties. A rapid bench scale membrane test unit was utilised to trial six NF membranes to remove the algal metabolites, microcystin, cylindrospermopsin, 2-methylisoborneol (MIB) and geosmin (GSM). Membrane fouling due to the algal metabolites was observed for both charged and neutral metabolites. MIB and GSM were removed effectively by low molecular weight cut-off (MWCO) membranes but less effectively by a higher MWCO membrane. Removal of MIB and GSM by the higher MWCO membrane was improved as the membrane fouled. Microcystin was initially removed to above 90% by tight NF membranes but fouling of several membranes caused decreased percent removals over time. Tight NF membranes afforded removals of 90–100% for cylindrospermopsin, while removal by the higher MWCO membrane was lower but improved with time due to fouling.

Removal of natural organic matter and trihalomethane formation potential in a full-scale drinking water treatment plant

2013 ◽  
Vol 13 (4) ◽  
pp. 1099-1108 ◽  
Author(s):  
Ekaterina Vasyukova ◽  
René Proft ◽  
Johanna Jousten ◽  
Irene Slavik ◽  
Wolfgang Uhl
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Organic Carbon ◽  
Natural Organic Matter ◽  
Treatment Plant ◽  
Drinking Water Treatment ◽  
Water Treatment Plant ◽  
Full Scale ◽  
Formation Potential ◽  
Trihalomethane Formation Potential

A multidisciplinary approach was applied in this work to characterise natural organic matter and evaluate the performance of a full-scale waterworks treating organic-rich surface water. It was shown that the combination of the treatment processes considered efficiently removed the dissolved organic matter, including its specific fractions. Most of the dissolved organic carbon and nitrogen (DOC and DON), biodegradable DOC and DON, as well as assimilable organic carbon were removed by coagulation/sedimentation. However, the coagulation process was not likely to be optimised for the removal of all molecular weight compounds. The breakdown of high molecular weight compounds into others of low molecular weight, as well as the production of biodegradable organic matter during ozonation, proved to enhance their removal efficiency by subsequent biological activated carbon filtration. The specific trihalomethane formation potential decreased during treatment, indicating a decrease in reactivity of DOC with chlorine across the treatment train. Fractionation experiments demonstrated that high and medium molecular weight organics were likely to be the main precursors for the formation of trihalomethanes. However, other disinfection by-products (such as haloacetic acids) should also be controlled, as the chlorine demand pattern did not necessarily follow that of trihalomethane formation.

Antithrombin III Binding to Surface Immobilized Heparin and Its Relation to F Xa Inhibition

1987 ◽  
Vol 58 (04) ◽  
pp. 1064-1067 ◽  
Author(s):  
K Kodama ◽  
B Pasche ◽  
P Olsson ◽  
J Swedenborg ◽  
L Adolfsson ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Surface Coating ◽  
Antithrombin Iii ◽  
Lower Class ◽  
Biologically Active ◽  
High Affinity ◽  
Heparin Coating ◽  
Continuous Surface ◽  
Approximate Molecular Weight

SummaryThe mode of F Xa inhibition was investigated on a thromboresistant surface with end-point attached partially depoly-merized heparin of an approximate molecular weight of 8000. Affinity chromatography revealed that one fourth of the heparin used in surface coating had high affinity for antithrombin III (AT). The heparin surface adsorbed AT from both human plasma and solutions of purified AT. By increasing the ionic strength in the AT solution the existence of high and low affinity sites could be shown. The uptake of AT was measured and the density of available high and low affinity sites was found to be in the range of 5 HTid 11 pic.omoles/cmf, respectively Thus the estimated density of biologically active high and low ailmity heparm respectively would be 40 and 90 ng/cm2 The heparin coating did not take up or exert F Xa inhibition by itself. With AT adsorbed on both high and low affinity heparin the surface had the capacity to inhibit several consecutive aliquots of F Xa exposed to the surface. When mainly high affinity sites were saturated with AT the inhibition capacity was considerably lower. Tt was demonstrated that the density of AT on both high and low affinity heparin determines the F Xa inhibition capacity whereas the amount of AT on high affinity sites limits the rate of the reaction. This implies that during the inhibition of F Xa there is a continuous surface-diffusion of AT from sites of a lower class to the high affinity sites where the F Xa/AT complex is formed and leaves the surface. The ability of the immobilized heparin to catalyze inhibition of F Xa is likely to be an important component for the thromboresistant properties of a heparin coating with non-compromized AT binding sequences.

Interaction of Plasminogen Activators and Plasminogen with Heparin: Effect of Ionic Strength

1993 ◽  
Vol 70 (05) ◽  
pp. 867-872 ◽  
Author(s):  
Dingeman C Rijken ◽  
Gerard A W de Munk ◽  
Annie F H Jie
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Plasminogen Activator ◽  
Plasminogen Activators ◽  
Fibrinolytic System ◽  
Tissue Type ◽  
Single Chain ◽  
Physiological Conditions ◽  
Amino Terminal ◽  
Type Plasminogen Activator

SummaryIn order to define the possible effects of heparin on the fibrinolytic system under physiological conditions, we studied the interactions of this drug with plasminogen and its activators at various ionic strengths. As reported in recent literature, heparin stimulated the activation of Lys-plasminogen by high molecular weight (HMW) and low molecular weight (LMW) two-chain urokinase-type plasminogen activator (u-PA) and two-chain tissue-type plasminogen activator (t-PA) 10- to 17-fold. Our results showed, however, that this stimulation only occurred at low ionic strength and was negligible at a physiological salt concentration. Direct binding studies were performed using heparin-agarose column chromatography. The interaction between heparin and Lys-plasminogen appeared to be salt sensitive, which explains at least in part why heparin did not stimulate plasminogen activation at 0.15 M NaCl. The binding of u-PA and t-PA to heparinagarose was less salt sensitive. Results were consistent with heparin binding sites on both LMW u-PA and the amino-terminal part of HMW u-PA. Single-chain t-PA bound more avidly than two-chain t-PA. The interactions between heparin and plasminogen activators can occur under physiological conditions and may modulate the fibrinolytic system.

Antiheparin Activity of Human Serum and Platelet Factor 4

1973 ◽  
Vol 30 (01) ◽  
pp. 093-105 ◽  
Author(s):  
C.H.J Sear ◽  
L Poller ◽  
F.R.C Path
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Blood Serum ◽  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Gel Filtration ◽  
Normal Serum ◽  
Platelet Factor ◽  
Mean Values ◽  
Antiheparin Activity

SummaryThe antiheparin activity of normal serum has been studied by comparing the antiheparin activities of sera obtained from normal whole blood, platelet-rich plasma and platelet-’free’ plasma with a purified platelet extract during differential isoelectric precipitation and by gel filtration chromatography.The mean values for the activity of PRP-serum and PFP-serum were 106% (S.D. 11) and 10% (S.D. 3) of untreated whole blood respectively. The activity of whole blood serum, PRP serum and whole blood serum plus platelet extract precipitated under identical physical conditions, i.e. pH 7.0, I =0.008, indicating that the activities of the three samples are probably associated with PF4. PF4 precipitated from human platelet extract at pH 4.0, but this is probably due to the difference in the two biochemical environments investigated, i.e. serum and platelet extract.The gel filtration experiments revealed striking similarities between the major antiheparin activities of serum and platelet extract. At physiological pH and ionic strength both activities were associated with high molecular weight material, but at physiological pH and elevated ionic strength both activities behaved as much smaller entities of molecular weight between 25,000 and 30,000 daltons and it seems very likely that both activities are associated with the same molecule, i.e. PF4.

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