Nanofiltration retentate treatment in drinking water production

status: accepte

Development of Hybrid Processes for Retentate Treatment in Nanofiltration (Ontwikkeling van hybride processen voor retentaatbehandeling bij nanofiltratie)

Nanofiltration is an attractive technology to treat surface water for the production of drinking water. However, fouling of the membrane limits the water recovery for this application to about 80%. As problems with water scarcity are expected to grow worse in the coming decades, it cannot be tolerated that 20% of the feed water is wasted. Therefore, it is necessary to develop technologies that make the discharge of retentate superfluous. The general concept of this study is to remove specific pollutants so that the concentrate can be returned to the feed side of the membrane without increased membrane fouling. In this way, a closed cycle with a recovery of almost 100% may be obtained. The main membrane foulants are the natural organic matter (NOM) and sparingly soluble salts present in the retentate. The NOM in the retentate is decomposed by ozone oxidation and the salts by electrodialysis.Dankwoord I Samenvatting VI Abstract VIII List of abbreviations X List of symbols XI Chapter 1 Introduction 1 1.1 Membrane filtration 1 1.1.1 Process description 1 1.1.2 Types of membranes 3 1.2 Problem sketch 6 1.3 General approach 7 1.4 Ozone oxidation and advanced oxidation 8 1.4.1 The use of ozone in drinking water treatment 8 1.4.2 Advanced oxidation processes 11 1.5 Electrodialysis 14 1.5.1 Process description 14 1.5.2 Ion exchange membranes 15 1.5.3 Donnan exclusion 17 1.5.4 Limiting current density 20 1.6 Research goals 22 1.7 Scientific relevance and innovative value 23 1.8 The project within the scope of the involved research groups 24 Chapter 2 Ozone oxidation for the alleviation of membrane fouling by natural organic matter: a review 25 2.1 The chemical composition of different NOM fractions 26 2.2 The decomposition of NOM by ozone and hydroxyl radicals 28 2.2.1 O3 reacts selectively with certain functional groups 28 2.2.2 Which functional groups in NOM can act as a promotor or inhibitor of O3 decomposition? 34 2.2.3 Reaction mechanisms of NOM with •OH radicals 38 2.2.4 The effect of H2O2 addition throughout O3 oxidation 39 2.2.5 Guidelines for finding the optimal dose of H2O2 41 2.3 Determination of the fouling mechanism of NOM 43 2.3.1 Molecular mass 43 2.3.2 Hydrophobicity/hydrophilicity 47 2.3.3 Electrostatic interactions 50 2.4 The structural changes of NOM by ozone oxidation relevant to membrane fouling 53 2.4.1 Hydrophobic interactions 53 2.4.2 Molecular mass 53 2.4.3 Electrostatic interactions and hydrogen bonds 55 2.5 Conclusion 63 Chapter 3 Materials and methods 65 3.1 Preparation of the feed solutions 65 3.1.1 Commercial humic acid solutions 65 3.1.2 Natural humic acid solutions 66 3.1.3 Nanofiltration retentate solutions 67 3.2 Ozone experiments 68 3.3 Membrane fouling experiments 70 3.4 Characterisation of the organic constituents 74 3.5 Molecular mass distribution 76 3.5.1 Humic acid solutions 76 3.5.2 Nanofiltration retentate solutions 77 3.6 Experimental error and variance 77 3.7 Determination of the •OH concentration 79 3.8 Electrodialysis 81 3.8.1 Equipment and membranes 81 3.8.2 Analytical methods 81 Chapter 4 Ozone oxidation of humic acids in aqueous solutions 85 4.1 Introduction 85 4.2 Results for Fluka humic acids and discussion 87 4.3 Results for natural humic acids and discussion 92 4.3.1 Effect on the COD and the UV absorbance 92 4.3.2 Effect on the hydrophobic COD and the molecular mass distribution 94 4.3.3 Effect on the quality of the NF permeate 98 4.3.4 Effect on membrane fouling 100 4.3.5 The addition of H2O2 during O3 oxidation 106 4.4 Conclusion 110 Chapter 5 Ozone oxidation of nanofiltration retentate streams 111 5.1 Effect on membrane fouling 111 5.2 FTIR spectra of the membrane foulants 116 5.3 Explanations of fouling alleviation by ozone 120 5.3.1 Hydrophobic interactions 120 5.3.2 Molecular mass 124 5.3.3 Electrostatic interactions 126 5.4 Effect on the quality of the NF permeate 127 5.5 The addition of H2O2 during O3 oxidation 129 5.6 Conclusion 131 Chapter 6 Kinetic regime and scale-up of the oxidation of nanofiltration retentate streams by ozone 133 6.1 Introduction 133 6.2 Model equations 134 6.2.1 The two-film theory of gas-liquid reactions 134 6.2.2 The solubility of O3 in pure water 140 6.2.3 The decomposition of NOM and its kinetics 144 6.2.4 Estimation of kapp from literature data 146 6.3 Determination of the kinetic regime 147 6.3.1 Calculation of the diffusion coefficients 147 6.3.2 The solubility of O3 in pure water 151 6.3.3 The Hatta number for the decomposition of O3 in pure water 154 6.3.4 The apparent rate constant between O3 and NOM 155 6.3.5 The Hatta number and enhancement factor for the reaction between O3 and NOM 157 6.4 Calculation of the reactor volume at industrial scale 159 6.5 Conclusion 165 Chapter 7 The concentration of •OH radicals and bromate during ozone oxidation 167 7.1 Introduction 167 7.2 Model equations 171 7.3 Results and discussion 181 7.3.1 Experimental determination of •OH concentration 181 7.3.2 Simulation of •OH concentration 183 7.3.3 Simulation of bromate concentration 187 7.4 Conclusion 190 Chapter 8 Electrodialysis for scaling prevention at high water recoveries 193 8.1 Introduction 193 8.2 Desalination of nanofiltration retentates 195 8.3 Separation efficiency 200 8.4 Current density 205 8.5 Conclusion 206 Chapter 9 Economic assessment 207 9.1 Introduction 207 9.2 Model equations 207 9.2.1 Nanofiltration unit 208 9.2.2 O3 oxidation 209 9.2.3 Electrodialysis 209 9.3 Results and discussion 214 9.3.1 O3 oxidation 214 9.3.2 Electrodialysis 217 9.4 Conclusion 223 Chapter 10 Conclusions 225 Reference list 235 Publication list 265 Curriculum vitae 267nrpages: 288status: publishe

Ozonbehandeling vermindert membraanvervuiling in de drinkwatersector

Nanofiltratie is een aantrekkelijke technologie voor de productie van drinkwater uit oppervlaktewater. De vervuiling van het membraan, door het natuurlijk organisch materiaal in het oppervlaktewater, beperkt de wateropbrengst tot 80%. Dit betekent dat 20% als retentaatstroom achterblijft, wat een vrij hoog volume is. De retentaatstroom wordt meestal terug in het oppervlaktewater geloosd. Om waterschaarste te vermijden, is het noodzakelijk om de wateropbrengst te verhogen. Daarom werd onderzocht of het mogelijk is om via ozonoxidatie van de retentaatstroom de membraanvervuiling te verminderen. Vervolgens werd onderzocht of de investering van een ozonisatie-eenheid economisch verantwoord is. Hieruit blijkt dat ozonbehandeling de membraanflux met minstens 30% kan verhogen, en dit resulteert in een duidelijke kostenreductie.status: publishe

Persisting complaints after carpal tunnel release : nerve compression by the palmaris profundus muscle

We present the case of a 66-year-old man who had persisting complaints after initial classical open carpal tunnel release. During revision a reversed palmaris profundus muscle was identified as being the cause of residual compression of the median nerve. Neurolysis with release of the palmaris profundus muscle was performed without resection of this anatomical variant and resulted in full resolution of the complaints

Een 21-jarige Somaliër met spier- en gewrichtspijn en aanhoudende koorts

status: publishe

The removal of natural organic matter and inorganic salts in nanofiltration concentrates

Membrane fouling limits the water recovery of nanofiltration to 80-85% in drinking water production. In order to increase the water recovery, a closed cycle is under investigation where the concentrate stream is treated by specific technologies, so it can return to the feed side of the membrane without increased membrane fouling. In this way, a closed cycle with a recovery of almost 100% may be obtained. The natural organic matter in the concentrate stream is decomposed by O3 oxidation. The membrane flux of three of the four investigated nanofiltration membranes (NF270, NF90, NF-PES 10, N30F) is higher during the filtration of the ozonated concentrate stream than during the filtration of the (prefiltered) surface water. The chemical oxygen demand and the UV absorption is reduced by 44% and 75%, respectively, for a specific O3 dose of 2.56 g O3 per g COD. The salts in the concentrate stream are removed by electrodialysis. Electrodialysis membranes with a high permselectivity for divalent ions are desired. The FTAM anion exchange membranes of Fumatech show a high selectivity for sulphate ions relative to chloride ions. The FTCM cation exchange membranes (same manufacturer) were non-selective for calcium and magnesium ions with respect to sodium ions.status: publishe

Doorlichting en optimalisatie van een ziekenhuisapoteek i.h.b. wat betreft voorraadbeheer en administratie /

Diss. burgerlijk elektrotechnisch ingenieu