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Thesis submitted in fulfillment of the academic requirement for the degree of (M.Tech.: Chemical Engineering), Durban University of Technology, South Africa, Durban, 2015. / Woven Fibre Microfiltration (WFMF) membranes have several advantages over its competitors with respect to durability, making it a favourable alternative for the developing world and operation during rough conditions. Wide application of membrane technology has been limited by membrane fouling. The durability of the WFMF membrane allows more options for flux enhancement and cleaning methods that can be used with the membranes even if they are vigorous. Therefore, the purpose of this work was to develop and evaluate flux enhancement and cleaning strategies for WFMF membranes. Feed samples with high contents of organics and turbidity were required for the study. Based on this, two rivers which are Umkomaasi and Duzi River were identified to satisfy these criteria. A synthetic feed with similar fouling characteristics as the two river water was prepared and used for this study. The synthetic feed solution was made up of 2 g/ℓ of river clay in tap water and 0.5% domestic sewerage was added into the solution accounting for 2% of the total volume. A membrane filtration unit was used for this study. The unit consisted of a pack of five membrane modules which were fully immersed into a 100 litres filtration tank. The system was operated under gravity and the level in the filtration tank was kept constant by a level float. The study focused on evaluating the performance of the woven fibre membrane filtration unit with respect to its fouling propensity to different feed samples. It also evaluated and developed flux enhancement and cleaning strategies and flux restoration after fouling. The results were compared to a base case for flux enhancement and pure water fluxes for cleaning. The WFMF membrane was found to be prone to both internal and external fouling when used in the treatment of raw water (synthetic feed). Internal fouling was found to occur quickly in the first few minutes of filtration and it was the major contributor for the loss of flux from the WFMF membrane. The fouling mechanism responsible for internal fouling was found to be largely pore blocking and pore narrowing due to particle adsorption on/in the membrane pores. The structure (pore size, material and surface layout) of the WFMF membrane was found to be the main cause that made it prone to internal fouling. The IV major fouling of the WFMF membrane was due to internal fouling, a high aeration rate of 30 ℓ/min had minimal effect on the fouling reduction. An aeration rate of 30 ℓ/min improved the average flux by only 36%, where a combination of intermittent backwashing with brushing and intermittent backwashing with aeration (aeration during backwashing only) improved average flux by 187% and 135% respectively. Pre-coating the WFMF membrane with lime reduced the effects of pore plugging and particle adsorption on the membrane and improved the average flux by 66%. The cleaning strategies that were most successful in pure water flux (PWF) recovery were high pressure cleaning and a combination of soaking and brushing the membrane in a 0.1% NaOCl (desired) solution. PWF recovery by these two methods was 97% and 95% respectively. Based on these findings, it was concluded that the WFMF membrane is susceptible to pore plugging by colloidal material and adsorption/attachment by microbiological contaminants which took effect in the first hour of filtration. This led to a 50% loss in flux. Also, a single flux enhancement strategy proved insufficient to maintain a high flux successfully. Therefore, combined flux enhancement strategies yielded the best results.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: At the Mondi Kraft paper mill in Piet Retief, paper machine effluent is pre-treated by means of dissolved air flotation (DAF) and a mierostrainer prior to ultrafiltration (UF). Despite the rigorous pre-treatment of the effluent, severe fouling of the UF membranes still persisted, resulting in a sharp decrease in operational flux. In an attempt to improve the flux performance of the UF membranes an investigation was launched into the possible causes of membrane fouling. The study yielded the following results: Ultraviolet-visible (UV-Vis) spectrophotometric analyses of varIOUS effluent samples collected from different locations at the mill indicated the presence of aromatic compounds. Lignosulphonate appeared to be the main constituent in all the samples analysed. UV-Vis spectrophotometry was also performed on fouling extracted from membranes In order to evaluate the different approaches attempted to reduce membrane fouling. Most of the UV-Vis spectra obtained did not show the absorbance maxima below 210 nm that were seen for the paper machine effluent, DAF product, lignosulphonate and mierostrainer product. This indicated that the compounds with absorbance at lower wavelengths did not foul the membranes to the same extent as the aromatic substances with absorbance maxima between 230 and 400 nm. The influence of pH on the absorption of the various effluent samples was also investigated. An increase in pH resulted in (1) a "shift" in the wavelength scans from a lower to a higher wavelength, suggesting ionisation (deprotonation) with a subsequent delocalization of electrons and (2) an increase in the turbidity. The increase in turbidity which accompanied the Increase in pH could be explained by complex formation between the carboxylate ions, phenolic groups and divalent metal ions present in the effluent. Inductively coupled plasma analyses of several effluent samples with pH values 7 and 13 indicated the presence of significant amounts of Ca2+ ions in the effluent. There was a significant decrease in the Ca2+ levels with an increase in pH, which supported the hypothesis that Ca2+ might contribute to complex formation. This resulted in a decrease in solubility and an increase in turbidity. The addition of a chelating agent (ethylenediaminetetra-acetic acid disodium salt) to an effluent solution at pH 13 redissolved the precipitate and considerably reduced the turbidity. The subsequent addition of CaCh again induced precipitation and increased turbidity, confirming the role of Ca2+ in complex formation. Gel permeation chromatographic analyses of mierostrainer product at pH 13 showed the formation of high molecular mass organo-calcium complexes. The exact molecular mass of the complexes present in the mierostrainer product could not be determined by electro spray mass spectrometry because of their poor ionisation ability. Atomic force microscopy and scanning electron microscopy (SEM) showed distinct differences in the membrane surface texture before and after fouling. Furthermore, SEM images of the UF membranes exposed the limited ability of the 30 urn microstrainer, installed downstream from the DAF unit, to remove residual fibres from the DAF product. Static fouling experiments performed on all the flocculants and coagulants used In the paper-making process at the mill showed that none of these substances fouled the UF membranes. Cleaning of the UF membranes with Triton XIOO®, a nOn-IOnIC surfactant, caused a temporary increase in the operating flux to values higher than that of the initial flux. Mechanical cleaning of the UF membrane surface with spongebalIs proved to be one of the most effective and successful methods to prevent flux loss caused by fouling. Pre-coating of the UF membranes with Plutonic" FI08, another non-ionic surfactant, did not promote membrane productivity. Evaluation of various types of membranes indicated that hydrophilic or negatively charged membranes withstood membrane fouling more effectively than hydrophobic UF membranes under the same operating conditions. / AFRIKAANSE OPSOMMING: By Mondi Kraft se papier meule in Piet Retief word afloopwater vanaf die papiermasjiene vir hergebruik met behulp van ultrafiltrasie (UF) behandel. Opgeloste lugflotasie (OLF) en mikrosiwwing word as voorbehandeling vir die UF membraanproses ingespan. Ondanks die intensiewe voorafbehandeling wat toegepas word, vind daar geweldige aanvuiling van die UF membrane plaas wat tot die vinnige verlaging in bedryfsfluks aanleiding gee. 'n Ondersoek na die moontlike oorsake van membraan-aanvuiling het die volgende bevindinge opgelewer: Ultraviolet-sigbare (UV-Vis) spektroskopie van water monsters wat by die meule versamel is, het die teenwoordigheid van aromatiese komponente aangetoon, met lignosulfonaat die hoofkomponent in al die monsters wat ontleed is. Ekstrakte afkomstig van aangevuilde membrane is ook met behulp van UV-Vis-spektroskopie geanaliseer om verskeie benaderings te evalueer om 'n afname in membraan-aanvuiling te bewerkstellig. Die oorgrootte meerderheid spektra het nie die absorpsie maksima onder 210 nm aangetoon wat teenwoordig was in monsters van die papier masjien afloopwater, OLF uitvloeisel, lignosulfonaat en mikrosif produkwater nie. Dit het aangedui dat die komponente wat by laer golflengte absorbeer nie die UF membrane in dieselfde mate aanvuil as daardie komponente wat by hoër golflengtes (tussen 230 en 400 nm) absorbeer nie. Die invloed wat pH op die absorpsie van komponente teenwoordig in die onderskeie afloopwatermonsters het, is ook ondersoek. 'n Toename in pH het bygedra tot (1) 'n verskuiwing in die spektra vanaf 'n lae na 'n hoër golflengte vanweë ionisasie (deprotonering) met gevolglike delokalisasie van elektrone en (2) 'n toename in turbiditeit. Die toename in turbiditeit wat verband hou met die toename in pH was verduidelik aan die hand van kompleksvorming tussen die karboksilaat ione, fenoliese groepe en divalente metaal ione in die afloopwater. Induktief gekoppelde plasma analise van verskeie water monsters by pH 7 en 13 het die teenwoordigheid van 'n groot hoeveelheid Ca2+ aangetoon. 'n Verlaging in die vlakke van opgeloste Ca2+ het met die toename in pH verband gehou. Dit het die moontlike verbintenis tussen Ca2+ en kompleksvorming ondersteun wat bygedra het tot die afname in oplosbaarheid en toename in turbiditeit. Die byvoeging van etileendiamientetra-asynsuur-dinatriumsout, 'n kelerings reagens by afloopwater (pH 13) het die presipitaat weer in oplossing gebring en die turbiditeit merkwaardig verlaag. Die byvoeging van CaCh het weer presipitasie geïnduseer, met 'n gevolglike toename in turbiditeit. Hiermee is Ca2+ se rol in kompleksvorming bevestig. Gelpermeasie-chromatografiese analise van die mikrosif produk (pH 13) het die vorming van hoë molekulêre massa organo-kalsium komplekse bevestig. Dit was egter nie moontlik om met behulp van massaspektrometrie die korrekte molekulêre massa van die komplekse te bepaal nie vanweë hul onvermoë om te ioniseer. Atomiese krag mikroskopie en skandeer elektron mikroskopie (SEM) het duidelik die voor en na verskil getoon wat aanvuiling op die membraantekstuur gehad het. 'n SEM foto van die aangevuilde UF membraan het die onvermoë van die mikrosif blootgelê om oorblywende vesels vanuit die OLF produkwater te verwyder. Resultate bekom gedurende passiewe aanvuilingseksperimente het aangetoon dat al die in-proses flokkulante en koagulante wat gebruik word by die papier meule geen bydrae tot die aanvuiling van die UF membrane maak nie. Skoonmaak van die UF membrane met Triton XIOO® bring 'n verhoging in bedryfsvloed teweeg, maar die verhoging, wat hoër as die oorspronklike vloed is, is kortstondig. Meganiese skoonmaak van die buismembrane met behulp van sponsballe blyk die mees effektiewe skoonmaakmetode te wees. Voorafbehandeling van die UF membrane met Plutonic" F 108 het nie die membraanproduktiwiteit verhoog nie. Daar is ook bevind dat hidrofiliese of negatief gelaaide membrane groter weerstand bied teen aanvuiling in vergelyking met hidrofobiese UF membrane onder dieselfde bedryfstoestande.

<p>In the pilot plant at Hammarby Sjöstad, Sjöstadsverket, several new methods are tested in order to achieve a good use of resources. When a new technique is considered it is often the performance of the technique itself, under given conditions, that is evaluated. However, in order to evaluate the overall function the whole picture is needed. With a system analysis it becomes possible to make a comparison where all the positive aspects are put up against the negative ones, for the technique itself as well as its requirements. In this way the influence that minor components have on an entire system can be considered.</p><p>This report presents a system analysis of an anaerobic membrane reactor (MBR) with a VSEP-membrane (Vibratory Shear Enhanced Process). The MBR is tested at the research treatment plant at Hammarby Sjöstad. In the analysis presented two different treatment techniques treating two different types of wastewaters are compared. The considered techniques are conventional (represented by an active sludge process) and the MBRtechnique. The waters treated are a mixed wastewater and wastewater from a separating system where closet water is separated from greywater and mixed with food waste from waste disposers.</p><p>The system analysis has been carried out with the URWARE (URban WAter REsearch) system analysis tool. A new URWARE-model that describes the anaerobic reactor and the VSEP membrane was created in order to generate the system structures needed for the analysis. The model consists of two submodels, which as the other URWARE-models are mass-flow, steady-state models based on yearly average-values. The model was tested and calibrated from the test-results at the Hammarby Sjöstad pilot plant. In the study the systems are compared considering energy, exergy and recirculation of nutrients.</p><p>The VSEP-technique has some advantages compared to the conventional system as it ensures that a large part of the nutritional content in the wastewater can be retained. The advantage is more obvious with the separated system, where food waste is mixed with closet water. Also the global warming potential of the new technique is lower. However, conventional treatment is better from an exergy-perspective. This is mostly due to the high energy consumption as a result of the reversed osmosis (RO) required for post treatment.</p> / <p>I försöksanläggningen vid Hammarby Sjöstad, Sjöstadsverket undersöks flera olika metoder för att uppnå största möjliga resursutnyttjande. När en ny teknik utprovas är det i allmänhet funktionen hos den givna metoden under givna förutsättningar som undersöks. För att få ett helhetsperspektiv krävs emellertid att den sätts in i sitt sammanhang. En systemanalys gör det möjligt att få en bild av alla för- och nackdelar, såväl av tekniken i sig som av de förutsättningar den kräver. Även effekter som små delar har på ett helt system kan då belysas och dess betydelse för helheten fastställas.</p><p>Föreliggande studie möjliggör en systemanalytisk utvärdering av en anaerob membranbioreaktor (MBR) kopplad till ett VSEP-membran (Vibratory Shear Enhanced Process) som är under utprovning vid Sjöstadsverket. Studien jämför två vattenreningstekniker för behandling av två olika typer av avloppsvatten. Dels rör det sig om konventionell teknik (aktiv slam-rening liknande den behandlingsmetod som används idag), dels den nya MBRtekniken. De vatten som behandlas är blandat avloppsvatten respektive sorterat klosettvatten blandat med matavfall från avfallskvarnar.</p><p>Systemanalysen har utförts med hjälp av systemanalysverktyget URWARE (URban WAter REsearch). För att kunna bygga upp önskade systemstrukturer har en ny modell för att beskriva den anaeroba reaktorn och VSEP-membranet skapats inom ramen för detta examensarbete. Modellen består av två delmodeller, som liksom övriga modeller i URWARE är substansflödesmodeller där beräkningar är baserade på årsmedelvärden. Modellen har utprovats och kalibrerats mot mätresultat från pilotförsöken vid Sjöstadsverket. I studien jämförs systemen med avseende på energi, exergi och återföring av närsalter.</p><p>Utifrån systemanalysen konstateras att MBR-tekniken ger vissa fördelar gentemot konventionell teknik då en stor del av näringsinnehållet från avloppsvattnet kan fångas upp. Detta gäller speciellt då tekniken används i kombination med ett separerat avloppssystem där matavfall blandas med klosettvatten. Även växthuspotential för den nya tekniken är lägre totalt sett. Ur exergisynpunkt är konventionell teknik emellertid mer fördelaktig. Till stor del beror detta på hög energiförbrukning pga. den efterbehandling med omvänd osmos (RO) som systemet i dess nuvarande utformning kräver.</p>

The possibility to extract bio-SNG from the product gas obtained from gasification of biofuel with a pressurized, oxygen-blown CFB gasifier connected to a heat and power station using only membrane separation was theoretically investigated. Selling the methane, instead of feeding it to the plant’s turbine(s), might mean that overall profitability is increased. The considered product gas mainly consists of H2, CO, CO2, H2O and CH4. By doing a literature review different membrane types were studied and it was concluded that for now only polymers may be of interest, due to high production costs for other membranes or for the fact they are still at laboratory stage. It was further determined though that neither membranes made of glassy polymers (fixed polymer chains) nor rubbery polymers (mobile polymer chains) are probably capable of separating the methane from the other gas components on their own. Glassy membranes will most likely have trouble separating CO from CH4 due to similarity in size of the two molecules, while a separation using rubbery membranes will result in at least H2 accompanying the methane. The rubbery polymers’ incapability of separating H2 from CH4 despite greatly differing condensation temperatures between the two components can be explained by the fact that rubbery membranes, apart from condensation temperature, also separate according to molecular diffusivity. If a multistep process with recirculation that combines both glassy and rubbery polymers is applied, satisfying results may be obtained. This, however, builds on a higher separation of CH4 and CO with rubbery membranes than condensation data indicates and needs to be further investigated with help of real life experiments and more advanced computation programs than used in this study.

The two most common commercial copper baths are the acid sulfate copper bath and the alkaline cyanide copper bath. Alkaline copper baths are mostly used to coat parts with complex geometry and to avoid galvanic deposition when depositing a metal on a less noble substrate. Because of the toxicity of cyanide compounds, alternative baths have been developed using different complexing agents. The starting point of the present study is a cyanide-free strike bath developed for copper plating on Zamak substrates developed by the Institute for Technological Research of the State of São Paulo/ Brazil. The replacement of a raw material such as cyanide must be economically advantageous and technically feasible. Therefore, this study intended to propose an alternative to the treatment of liquid wastes from the mentioned bath, aiming at simultaneous water reclamation and chemicals recovery in a closed system. The electrodialysis membrane separation process was studied, using a laboratoryscale system operating with a synthetic solution simulating the rinsing waters from the HEDP-based bath. The feasibility of the technique was evaluated by analyzing operational parameters such as ion extraction, demineralization rate, concentration rate, current efficiency for each anionic specie and average energy consumption. Because HEDP is a chelating agent, the transport of Cu(II)-HEDP chelates through anion-exchange membranes was also evaluated by means of electrochemical methods. Chronopotentiometric and current-voltage curves were constructed for different model solutions containing the same compounds as the original bath. A relation between the presence of chelates in the solutions and the fixed ion exchange group could be established. Lastly, deposition tests were performed using electrolytes containing the recycled inputs and the characteristics of the coatings were analyzed. The results showed that an electrodialysis stack using strongly basic anion-exchange membranes was suitable to produce treated solutions and a concentrate containing the ions from the bath. The concentrate could be added to the copper bath to compensate eventual drag-out losses without affecting the quality of the coatings. Thus, the application of electrodialysis was shown to be a feasible alternative for recovering water and inputs from the evaluated solution, reducing the wastewater generation and saving natural resources. / Os dois banhos de cobre comerciais mais comuns são o banho ácido à base de sulfato e o banho alcalino à base de cianeto. Os banhos alcalinos são usados principalmente para recobrir peças com geometria complexa e para evitar a deposição por deslocamento galvânico quando se deposita um metal em um substrato menos nobre. Por causa da toxicidade dos compostos cianídricos, banhos alternativos vêm sendo desenvolvidos usando diferentes agentes complexantes. O ponto de partida do presente estudo é um banho toque isento de cianeto para deposição de cobre em substratos de Zamak, desenvolvido pelo Instituto de Pesquisas Tecnológicas / Brasil. A substituição de matérias-primas como o cianeto deve ser economicamente vantajosa e tecnicamente viável. Desta forma, este estudo pretendeu propor uma alternativa para o tratamento de resíduos líquidos do banho mencionado, visando à recuperação simultânea da água e das matérias-primas em um sistema fechado. Foi estudado o processo de separação por membranas de eletrodiálise, usando um sistema em escala laboratorial operando com uma solução sintética que simulava as águas de lavagem do banho à base de HEDP. A viabilidade da técnica foi avaliada por meio da análise de parâmetros operacionais, como a extração dos íons, a taxa de dessalinização, o percentual de concentração, a eficiência de corrente calculada para cada espécie iônica e o consumo médio de energia. Devido ao HEDP ser um agente quelante, o transporte de quelatos Cu(II)-HEDP através de membranas aniônicas foi avaliado por meio de métodos eletroquímicos. Curvas cronopotenciométricas e curvas corrente-potencial foram construídas para diferentes soluções sintéticas que continham os mesmos compostos que o banho original. A relação entre a presença de quelatos nas soluções e os grupos fixos de troca iônica pôde ser estabelecida. Por fim, testes de deposição foram realizados usando eletrólitos contendo os compostos reciclados e as características dos depósitos foram analisadas. Os resultados mostraram que o sistema de eletrodiálise usando membranas aniônicas contendo grupos de troca fortemente básicos pôde produzir soluções tratadas e um concentrado contendo os íons do banho. O concentrado pôde ser adicionado ao banho original para compensar eventuais perdas por arraste sem afetar a qualidade dos depósitos. Assim, a aplicação da eletrodiálise se mostrou uma alternativa viável para a recuperação de água e de insumos da solução avaliada, reduzindo a geração de efluentes e economizando recursos naturais.

La production industrielle des silicones génère des effluents aqueux contenant des siloxanes et polysiloxanes, chargés en sels à divers stades de la filière. Dans une perspective de développement durable et pour tenir compte des préoccupations grandissantes autour de l'impact environnemental des rejets industriels, des procédés d'épuration sont recherchés. L'objectif de cette étude est d'évaluer les performances de deux procédés, nanofiltration et oxydation biologique, pour le traitement des effluents aqueux polysiloxaniques. Des expériences de nanofiltration frontale ont été réalisées. Les essais préliminaires avec des solutions synthétiques, mélange d'eau et des siloxanes, ont montré une rétention quasi-totale des siloxanes dans tous les cas testés. Des expériences ont ensuite été menées avec des effluents représentatifs des effluents usines de différentes compositions pour évaluer la robustesse du procédé. Nous avons montré que la nanofiltration réduit efficacement la charge organique globale de l'effluent et réduit significativement la concentration en siloxane. La dilution provoque une diminution de l'abattement du COT et de la rétention des siloxanes mais la qualité du perméat est améliorée. L'augmentation de la salinité réduit la qualité du filtrat. Des essais de micro et ultrafiltration des mêmes effluents ont montré que seule la NF permet d'atteindre un niveau de rétention important des siloxanes. Des essais de nanofiltration tangentielle ont ensuite été réalisés afin de préparer une étude plus complète nécessaire en vue d'une éventuelle l'industrialisation du procédé. La biodégradabilité des siloxanes a été explorée par la méthode Oxitop. Aucune activité biologique provoquée par les siloxanes n'a été enregistrée lors de tests Oxitop réalisés avec des boues activées de stations d'épuration, mais aucun effets toxique ou inhibiteur n'ont été observés non plus. Un bioréacteur à membrane pilote a été alimenté pendant 5 mois au laboratoire avec une solution contenant des siloxanes pour tenter d'acclimater les boues activées aux siloxanes. Les tests Oxitop effectués avec des boues issues du pilote n'ont pas mis en évidence d'acclimatation des micro-organismes aux siloxanes. / Industrial production of silicones generates liquid streams containing siloxanes with high salinity. In a perspective of sustainable development and to consider the growing concern about the environmental impact of industrial residues, we are looking for treatment processes to remove siloxanes in wastewater. This study aims to evaluate the performance of two processes for the treatment of effluents containing siloxanes: nanofiltration and biological oxidation, Frontal nanofiltration experiments were carried out. Firstly, experiments with synthetic solutions (mix of water and siloxanes) have shown almost total siloxane retention in all conditions investigated. Then, experiments were performed with effluents of different compositions representative of industrial ones in order to evaluate the process robustness. It was concluded that nanofiltration is efficient to reduce the total organic content of the effluent and significantly reduces siloxanes concentration. Dilution of the effluent causes a decrease in TOC reduction and siloxanes retention, but the permeate quality is improved. Increasing salinity reduces the filtrate quality. Micro and ultrafiltration of identical effluents confirmed that only NF can reach a high level of siloxane retention. Tangential nanofiltration experiences were performed in order to prepare a more complete study which is necessary to anticipate industrialization of the process. Siloxanes biodegradability was explored by Oxitop method. No biological activity induced by siloxanes was recorded in Oxitop tests with activated sludge from wastewater treatment plant, but no toxic or inhibitory effects were observed. A pilot membrane bioreactor was fed in the laboratory for 6 months with a solution containing siloxanes to try to acclimate activated sludge to siloxane. Oxitop tests performed with sludge taken from the pilot did not show acclimation of microorganisms to siloxanes.