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M. Tech. (Biotechnology, Department of Biosciences, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Reverse osmosis (RO) membranes are widely used in water purification. The presence of biofilms in water and industrial water purification systems is prevalent. As a result, biofouling which is a biofilm problem causes adverse effects on reverse osmosis process, which include flux decline, shorter membrane lifetime and an increase in energy consumption The effect of biofouling on RO membranes was investigated at a water treatment facility at Sasol, Sasolburg by investigating the quality of water purified by the RO system and the extent of fouling that is attributed to biofouling. Chemical and microbiological data was averaged based on the results obtained from water analysis and samples from a fouled membrane. Bacteriological plate counts ranged between log 1.5 to 4 cfu/ml in water samples and log 3.9 to 4.5 cfu/cm2 on biofilm from the membrane surface. Water analysis indicated a high conductivity of 121 µS/cm in the feed and 81 ppm of the TDS, whereas in the permeate conductivity was found to be around 6 µS/cm and 3.8 ppm of the TDS. This indicated that components present in the feed were retained by the membrane. This was supported by membrane autopsy which showed that the bacteria and elements found in the feedwater were also present on the membrane surface, hence contributing to fouling. An average of 33% of cellular ATP was measured on the biofilm from membrane sample, showing that the fouling bacteria are metabolically active in situ. The results clearly indicated that an important biological activity occurred at the membrane surface.

This licentiate study was initiated by copper, zinc and galvanized steel producers in Europe, who felt a need to assess runoff rates of copper and zinc from the pure metals and commercial products at marine exposure conditions. Their motive was the increasing concern in various European countries and the on-going risk assessments of copper and zinc within the European commission. Also the circumstance that available runoff rates so far, had been reported for mainly urban exposure conditions, rather than marine. A collaboration was therefore established with the French Corrosion Institute, which runs a marine test site in Brest, and a set of vital questions were formulated. Their answers are the essence of this licentiate study. Based on the ISO corrosivity classification and one-year exposures, the marine atmosphere of Brest is fairly corrosive for zinc (class C3) and highly corrosive for copper (C4). Despite higher corrosivity classifications for both metals in Brest compared to the urban site of Stockholm, used as a reference site, nearly all runoff rates assessed for copper, zinc and their commercial products were lower in Brest compared to Stockholm. This was attributed to a higher surface wetting in Brest and concomitant higher removal rate of deposited chloride and sulphate species from the marine-exposed surfaces. The comparison shows that measured corrosion rates cannot be used to predict runoff rates, since different physicochemical processes govern corrosion and runoff respectively. For copper, the runoff rate in Brest was approximately 1.1 g m-2 yr-1 with cuprite (Cu2O) as main patina constituent. During periods of very high chloride and sulphate deposition, paratacamite (Cu2Cl(OH)3) formed which increased the runoff rate to 1.5 g m-2 yr-1. For zinc, with hydrozincite (Zn5(CO3)2(OH)6) as the main patina constituent, the runoff rate was relatively stable at 2.6 g m-2 yr-1 throughout the year, despite episodes of heavy chloride and sulphate deposition. The application of organic coatings of varying thickness on artificially patinated copper or on different zinc-based products resulted in improved barrier properties and reduced runoff rates that seem highly dependent on thickness. The thickest organic coating (150 µm thick), applied on hot dipped galvanized steel, reduced the runoff rate by a factor of 100. No deterioration of organic coatings was observed during the one-year exposures. Alloying zinc-based products with aluminium resulted in surface areas enriched in aluminium and concomitant reduced zinc runoff rates. The release rate and bioavailability of copper from different anti-fouling paints into artificial seawater was also investigated. It turned out that the release rate not only depends on the copper concentration in the paint, but also on paint matrix properties and other released metal constituents detected. Far from all copper was bioavailabe at the immediate release situation. In all, the results suggest the importance of assessing the ecotoxic response of anti-fouling paints not only by regarding the copper release, but rather through an integrated effect of all matrix constituents. / QC 20101126

This dissertation reports on research related to ultrafiltration (UF) membranes in drinking water applications. A pilot-scale investigation identified seasonal surface water quality impacts on UF performance and resulted in the development of a dynamic chemically enhanced backwash protocol for fouling management. Subsequent analysis of UF process data revealed limitations with the use of specific flux, transmembrane pressure (TMP), and other normalization techniques for assessing UF process fouling. A new TMP balance approach is presented that identifies the pressure contribution of membrane fouling and structural changes, enables direct process performance comparisons at different operating fluxes, and distinguishes between physically and chemically unresolved fouling. In addition to the TMP balance, a five component optimization approach is presented for the systematic improvement of UF processes on the basis of TMP variations. Terms are defined for assessing process event performance, a new process utilization term is presented to benchmark UF productivity, and new measures for evaluating maintenance procedures are discussed. Using these tools, a correlation between process utilization and operating pressures was established and a sustainable process utilization of 93.5% was achieved. UF process capabilities may be further enhanced by pre-coating media onto the membrane surface. Silicon dioxide (SiO2) and powdered activated carbon (PAC) are evaluated as precoating materials, and the applicability of the TMP balance for assessing pre-coated membrane performance is demonstrated. The first use of SiO2 as a support layer for PAC in a membrane pre-coating application is presented at the laboratory-scale. SiO2-PAC pre-coatings successfully reduced physically unresolved fouling and enhanced UF membrane organics removal capabilities.

<p dir="ltr">Pea protein is one of the most used plant proteins in food products, acting as an alternative to conventional animal protein sources due to its abundant, nutritious, and ease in supply chain characteristics. The objective of this study was to investigate the impact of homogenization and UHT processing parameters on the properties of protein emulsion. Protein emulsions (8% w/w pea protein isolate and 1% w/w sunflower oil) were freshly prepared prior to processing, and the untreated sample was considered as the control (NT). The pilot-scale aseptic processing system (APS) used in this study consisted of two coil-in-shell heaters and two coolers. Samples flowed through each section of the APS system following this order: balance tank, pre-heater, final heater, hold tube, pre-cooler, and final cooler. The homogenizer was located either after the pre-cooler (AC) or the pre-heater (AH) with a controlled temperature of 165F. A third setup was utilized by bypassing the homogenizer in the UHT system. An additional 8-hour continuous run was conducted to mimic a commercial manufacturing operation by recirculating the protein emulsion in the UHT system, and fouling detections were made using a non-intrusive sensor (NICS). 5% w/w soy protein, 1% w/w sunflower oil oil-in-water emulsion was also used for fouling tests. Protein concentration, pH and zeta potential, Cryo-SEM microscopic image, particle size distribution, flocculation index (FI), coalescence index (CI), viscosity and color data were collected and analyzed. The protein concentration had a 23.20 ± 4.00 %, 28.35 ± 5.02 %, 27.98 ± 5.05% and 21.38 ± 5.75% reduction for AC, AH, UHT and NT samples, respectively, when compared with the initial concentration in the formula. AC, AH, UHT and NT samples had pH values of 7.24 ± 0.01, 7.27 ± 0.01, 7.28 ± 0.02, 7.41 ± 0.01, and zeta potential values of -42.91 ± 0.89, -47.30 ± 0.91, -46.91 ± 1.40 and -50.11 ± 1.47 mV. AC sample had a smaller and NT sample had a bigger, respectively, mean weighted size D 4,3 value than AH and UHT samples, which could also be seen in Cryo-SEM images where only AC images contained more visually observable smaller particles. FI and CI for AC, AH and UHT indicated the formation of flocs but no irreversible aggregations were found. Shear-thinning AC, AH, UHT and NT samples had viscosity decreases from 4.00 to 3.56, 3.88 to 3.75, 4.02 to 3.79 and 10.42 to 9.56 mPa*s in 1 1/s to 100 1/s shear rate range. NT sample had a very noticeable color difference from the other three treated samples. Overall, AC samples had similar or better emulsion stability in all aspects than AH and UHT samples, suggesting that AC processing could potentially be used in the protein beverage industry for manufacturing products with improved shelf stability. Severe foulants buildups were neither observed nor detected by a non-intrusive continuous sensor (NICS) in the UHT system within 8 hours of process for both pea protein and soy protein emulsion, indicating that this UHT-homogenization processing can potentially be adapted to current industrial practices for higher-quality protein beverages.</p>

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The EU waste hierarchy includes energy recovery facilities where waste is used as fuel in combined heat- and powerplants. When waste is incinerated can the thermal energy be used in for example, district heating networks and or electricity generation. The purpose of the degree project is to make a pre-study of Heat Management's system solution HISS, optimization of steam soot blowing at Mälarenergi's waste boiler. Waste is a heterogeneous fuel that typically contains a variety of substances such as alkali, chlorine and heavy metals that often contribute to fouling on heat transfer surfaces. These coatings reduce the efficiency of heat transferring surfaces such as superheaters. Cleaning by soot blowing using steam is done at regular intervals to maintain efficiency. Superheater cleaning on the Block 6 is done by retractable rotating soot blowers equipped with a nozzle from where steam is sprayed out at pressure of 25 bar. The blowers are inserted one at a time in a sequence, which means that they wait for the previous blower before the next one can enter. Steam is taken from the main process, which leads to reduction in load on the turbine and causes wear during the sweeping process due to the high impact force. This can lead to erosive damage and thinning of the material on the tubes, thus shortening the lifespan of the superheaters. The optimisation adjusts the soot sequence so that full steam pressure is used only in one direction of travel of the lance, this allows an overlapping soot sequence to be used and thus halves the time required for sooting. Analysis of shorter sooting time and reduced steam consumption based on production data and case studies has led to the following results. The energy consumption of the auxiliary power is reduced by 14.25 MWh per sweeping sequence and 7 115.5 MWh annually. The turbine can produce 2.51 MWh more electricity per sweeping as the time it runs at reduced load is reduced, totalling 1 254.39 MWh in one year. 24.03 tonnes of steam are saved per sweeping and 12 003 tonnes in one year. Payback time for the optimisation is 1.01 years based on an average spot price from Mälarenergi's budgeting from last year. Considering current electricity prices could the payback time be further reduced. The conclusion from the pre-study is that the optimisation as the investment is economically viable and has other positive benefits such as: steadier steam flow and reduced pressure surges. Wear and tear on superheaters are reduced as they are only sprayed with high pressure once instead of twice per sweeping sequence. / I EU:s avfallshierarki ingår energiåtervinningsanläggningar där avfall används som bränsle i förbränningsanläggningar. Vid förbränning utav avfall så kan den utvunna termiska energin användas exempelvis i fjärrvärmenät och- eller generering utav el. Examensarbetets syfte är att göra en förstudie på Heat managements systemlösning HISS, optimering utav ångsotning på Block 6 som är Mälarenergis avfallspanna. Avfall är ett heterogent bränsle som typiskt innehåller en mängd olika ämnen som alkali, klor och tungmetaller som ofta bidrar till att beläggningar bildas på värmeöverförningsytor. Dessa beläggningar försämrar ytors värmeöverförningsverkningsgrad på till exempel överhettare. Rengöring i form av ångsotning görs i jämna intervall för att hålla verkningsgraden uppe. Sotning av överhettare på Block 6 skes av en utdragbar, roterande sotlans utrustad med en dysa där ånga sprutas ut med 25 bars tryck. Lansarna körs in en åt gången i en sekvens vilket innebär att dem väntar på föregående lans innan nästa kan köras. Ångan som används tas från huvudprocessen vilket medför reducerad last på turbinen och dessutom uppstår slitage vid sotningen ty den höga anslagskraften. Detta kan leda till erosiva skador och förtunning utav godset på tuberna och således förkortas livslängden på överhettarna. Optimeringen justerar sot sekvensen så att fullt ångtryck används bara i ena färdriktningen av lansen, detta möjliggör att en överlappande sotsekvens kan användas och på så vis halveras tidsåtgången för sotningen. Analysen utav kortare sottidsåtgång samt minskad ångförbrukning baserat på produktionsdata hämtad från styrsystemet 800xA samt fallstudier har mynnat ut i följande resultat. Hjälpkraftens energianvändning minskas med 14,25 MWh per sotningssekvens och årligen 7 115,5 MWh. Turbinen kan producera 2,51 MWh mer el vid varje sotning då tiden som den körs med reducerad last blir kortare, totalt på ett år blir det 1 254,39 MWh. Vid varje sotning sparas 24,03 ton ånga och på ett år 12 003 ton. Återbetalningstiden för optimeringen blir 1,01 år baserat på ett medelspotpris från Mälarenergis budgetering från förra året. Med hänsyn till dagens elpriser förkortas återbetalningstiden ytterligare.   Förstudien rekommenderar optimeringen då dels är investeringen lönsam rent ekonomiskt, dels medför den andra positiva fördelar. Optimeringen med överlappande sotning skapar ett jämnare ångflöde, det reducerar tryckstötar som är skadliga. Slitage på överhettartuber minskas då dem bara besprutas med högt tryck en gång i stället för två gånger per sotningssekvens. Behovsstyrd sotning skulle kunna implementeras upp till 3 gånger per dygn utan att det skulle kosta mer mot dagsläget där man stora 1,5 gånger per dygn.

Combustion of coal is one of the primary sources of electricity generation worldwide today. Coal contains different chemicals that cause particulate matter(PM) and sulfur dioxide (SO2) emissions. These are health hazards and are responsible for deteriorating the ambient air quality. Particulate matter also forms ash deposits inside the coal combustor, which in turn decreases the energy efficiency of the power plants. Using biomass as a fuel in these utility boilers can potentially reduce the problems of particulate matter emissions and ash deposition, and can significantly reduce the SO2 emissions. However, biomass needs to be pretreated to make its properties similar to coal in terms of energy density, grindability, and durability before it can be fired in utility boilers. Steam explosion is one of the leading biomass pretreatment methods that enhances the physicochemical properties of biomass. A comprehensive review of the steam explosion process, its product properties, its comparison with other treatment processes, as well as its economic analysis and lifecycle assessment, have been explored in this work. Steam-exploded biomass has been co-combusted with bituminous coal in a 1500 kWth combustor to analyze the ash aerosol particle size distribution, composition, and deposition behavior. The primary results of these tests showed that both particulate matter emissions and ash deposition amount reduced significantly as more biomass was co-fired with coal. The submicron-sized particulate matter concentration showed a high correlation with the final mass of ash deposits (R2 > 0.96). Predicting ash deposition rates is important during the combustion of solid fuels. A Machine Learning tool was applied and trained with a fuel composition database of 92 fuels obtained from a thermodynamic equilibrium software (FactSage). When fully operational, this model should be integrated with an existing ash deposition model, which should make it self-sufficient in terms of generating equilibrium composition data. SO2 emissions were analyzed during the co-combustion of biomass and coal, and a synergistic decrease in SO2 emissions was observed with higher biomass blends. Experiments were conducted in a full-scale 471 MWe furnace to analyze the SO2 emissions, and an 85%-15% blend of coal and biomass was responsible for a 28.1% reduction in emissions and 22.1% reduction in the lime slurry utilization in the flue gas desulfurization (FGD) towers compared to pure coal combustion. Ash deposit characterizations by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) combined with thermodynamic equilibrium simulations revealed that calcium and potassium were responsible for this synergistic reduction as these metals captured the SO2 from the flue gases and retained them in the ash phase. The SO2 research was important since the current literature is deficient in research conducted at suspension-fired full-scale utility boilers to reduce SO2 emissions by co-firing coal and biomass blends. The research in this dissertation should provide valuable insights to the energy industries that are considering a transformation of fuel portfolio from coal to biomass and explore how the mineral matter present in pretreated biomass would behave inside a utility boiler. The primary conclusions are that during the co-combustion of coal and biomass, ash deposition mass and particulate matter ash load decreased, and SO2 emission saw a synergistic reduction in emissions due to higher calcium and potassium content in biomass compared to pure coal combustion.

Various potential methods and techniques for modifying surfaces to make themless sensitive to contamination have been researched for various applicationsbefore, to varying degrees of success. These are discussed in detail to potentiallyapply them in the automotive sector, to face the increasing technical cleanlinessrequirements, that are linked to more complexity in design and electrification. TheTheoretical background in dust adhesion and contact mechanics is discussed, withdevelopments in analytical and numerical methods highlighted. Then, someexamples of the surfaces in question are presented, and their topographiesmeasured. Potential techniques are identified from previous experimental research in otherfields, and their applicability and feasibility are discussed within the limits ofavailable data, then an attempt at a structured approach for choosing candidatesfor further experimental testing on a case by case basis is laid out, and suggestionsfor more comprehensive research into effective parameters and analytical methodsare made.