Thesis (Master of Engineering in Mechanical Engineering)--Cape Peninsula University of Technology, 2018. / The present study was centred on the design of a thermal multistage solar still desalination system. The design is a multistage with new configurations such as direct vapour input into each stage using vapour make-up tubes and the integration of a multistage with a basin type solar still. The incorporation of float a valve in the secondary seawater tank to regulate the seawater in the assembly eliminated the need of pumps to the system. The circulation of seawater between the evaporator and the evacuated tube solar collector (ETC) was through the pressure difference and the flow back was controlled through the incorporation of oneway flow valve. The ETC was used as a heat source to supply the thermal energy into the multistage system. The system had no electrical connections and therefore, no forced circulation as no pumps or any electrical components were used. The system consisted of six stages in total, the evaporator supplied the vapour to five of the six stages of the system. The system was tested on the roof of Mechanical Engineering Department and this location was chosen because of less sun’s intensity obstructions. The system was tested for nine (9) days but the distillate collection was not performed for the whole each day. This was due to the controlled access to the roof and the minor repairs that had to occur before the tests were conducted. The duration on which the tests were conducted varied in each day. The data was supposed to be logged from 08h00 am to 18h00 pm but this was not so due to the controlled access to where the tests were conducted. This data logging period was chosen based on the assumptions that the sun’s intensity would be at maximum within this period. The longest period of test was approximately 7 hours and the system managed to produce about 1500 ml and the maximum temperature for the day was 28oC. The system produced a minimum of 225 ml in the space of 3 hours and the temperature of the day was 26oC. The total amount of distillate produced was about 7600 ml and this amount was produced within the period of 49 hours. The 49 hours is equivalent to two days and 1 hour. It is anticipated that the system would have produced more should there be no repairs involved during the tests. The system produced a maximum of 48 ml at night and a minimum of 8ml in some nights. The night tests were not controlled and monitored due to limited access. It was noticed that the system was empty in each morning of the first few days of the tests. This emptiness contributed to the leakage occurred to the evaporator. The leakage of the evaporator was caused by unmonitored heat supplied by the ETC. The evaporator was constructed using unsuitable material and this was another factor which contributed towards the failure of the evaporator.

A landfill is in a reserved space on land used for the disposal of refuse by utilizing the principles of engineering to confine the refuse to the smallest practical area to prevent the creation of nuisances to public health or safety (Andersen et al. 1967). However, because landfills are open to the atmosphere, rainfall can saturate them, resulting in a liquid called leachate. Leachate generated within the landfill contains suspended solids, soluble components of the waste and by-products from the degradation of the waste by various micro-organisms. Treatment of leachate is an emerging area of need. In this manuscript the main purpose is to investigate a laboratory scale batch reactor that is able to detoxify and treat leachate by using an advanced oxidation process (i.e. TiO2). Based on the results obtained from this ground breaking research, it appears that the process investigate has the potential to radically change the way landfill leachate is treated. Scale up may provide direction that can be used to improve the efficiency of the different stages of toxicity of leachate during the entire life of a landfill. / by Andrâe McBarnette. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

This doctoral research provides an advanced molecular approach for the investigation of microbial structure and function in response to operational conditions of biological nitrogen removal (BNR) processes, including those leading to direct production of a major greenhouse gas, nitrous oxide (N₂O). The wastewater treatment sector is estimated to account with 3% of total anthropogenic N₂O emissions. Nevertheless, the contribution from wastewater treatment plants (WWTPs) is considered underestimated due to several limitations on the estimation methodology approach suggested by the Intergovernmental Panel on Climate Change (IPCC). Although for the past years efforts have been made to characterize the production of N₂O from these systems, there are still several limitations on fundamental knowledge and operational applications. Those include lack of information of N₂O production pathways associated with control of aeration, supplemental organic carbon sources and adaptation of the microbial community to the repeated operational conditions, among others. The components of this thesis, lab-scale investigations and full-scale monitoring of N₂O production pathways and emissions in conjunction with meta-omics approach, have a combined role in addressing such limitations. Lab-scale experiments imposing short-term anoxic-aerobic cycling on partial- and full-nitrification based processes were conducted to investigate the microbial response to N₂O production. Interestingly, it was determined that full-nitrification systems could be a higher contributor to N₂O production and emissions than partial-nitrification. While it has been reported in the literature a higher contribution from the latter when the microbial community is not subjected to oxygen cycling conditions. Following the knowledge obtained with a single anoxic-aerobic cycle imposed to nitrifying communities, long-term adaptation of the microbial community to continued anoxic-aerobic cycling and its impact on N₂O production were investigated through a meta-omics approach. Long-term studies are particularly significant regarding engineered systems, where the microorganisms are continually subjected to cycling conditions again and again. A microbial adaptation at the RNA level was identified on both autotroph and heterotroph organisms. The transcripts of the metabolic pathways related to NO and N₂O production (nir, nor) and consumption (nor, nos) were initially induced followed by a gradual decline, leading to a parallel reduction in gaseous emissions over time. Other pathways not typically interrogated in conjunction with the nitrogen metabolism, such as electron transport chain and carbon fixation were also investigated and revealed a mechanism to overcome the imbalance in electron flow and generation of proton motive force (increased transcription of terminal oxidase genes, cco and cox) to uphold carbon fixation during continued cycling. The second part of this thesis focuses on full-scale WWTPs, where it is crucial to determine specific nuances of the systems’ dynamics and of the different types of treatment that may contribute to increased production and emissions of N₂O. For that purpose, two distinct BNR systems not usually considered and studied in terms of N₂O production and emissions were chosen. First, a separate centrate treatment (SCT) process employing glycerol as the supplemental carbon source was monitored. Significantly, this system was found to have one of the highest levels of N₂O production and emission report thus far. Glycerol revealed to foster a microbial community (i.e. Burkholderiales, Rhodobacterales and Sphingomonadales) that stores internal carbon and promote partial denitrification, leading to accumulation of nitrite and N₂O [7-11]. Second, both fixed- and moving-bed biofilm BNR systems were investigated. The overall N₂O emission fractions for the Integrated Fixed-Film Activated Sludge (IFAS)(0.09 – 1.1% infl-TKN) and denitrification filters (0.11 – 1.4% infl-TN) were similar to the reported emissions from suspended growth activated sludge systems [4-6]. For the IFAS system, aqueous and gaseous N₂O profiles paralleled the diurnal variability on influent nitrogen load. The production of N₂O was significantly correlated with ammonia concentration (p<0.05, r=0.91), suggesting the production through hydroxylamine oxidation pathway. Denitrification filters displayed a very peculiar pattern on N₂O emissions associated with intermittent operational cycles (i.e. nitrogen release cycle and backwash). These intrinsic operations of the denitrification filters contributed to transient oxygen conditions and nearly the entire N₂O emissions through gaseous stripping and production by inhibition of denitrification. Similarly to suspended growth systems, process design and operations demonstrated to also play an important role in N₂O emissions from attached growth processes. Finally, aeration strategies for energy efficient conventional nitrification based on the microbial community development and its associated performance was investigated in lab-scale. It was demonstrated that using the same air supply rate, continuous and intermittent aeration resulted in completely different microbial structure. Consequently, distinct kinetics and nitrification performance were observed. The aeration rate could be minimized (resulting in reduction in energy consumption) for high ammonia removal efficiency and lower N₂O emissions, as long as the process is designed accordingly to the microbial ecology developed in such conditions. In sum, the microbial structure, function and connection of metabolic pathways of complex engineered microbial communities as applicable to BNR systems and its operations were investigated in detail. From an engineering perspective, this dissertation provides an advancement on the molecular approach to characterize structure and function of microbial responses to engineered operations beyond the business-as-usual target genes, which can eventually result in better design and control of engineered BNR processes. This study offers more than an improved scientific understanding of the complex microbial environment and direct engineering applications. It connects sanitation with water quality and the greenhouse gas effect by prioritizing concurrent enhanced biological nitrogen removal and mitigation of N₂O production and emission. Ultimately the implications of the result presented herein can provide economical, environmental, health benefits for the society.

Inorganic arsenic exposure is a well-known toxicant of which we are still discovering harmful effects. People are exposed to inorganic arsenic in the environment through either drinking arsenic-contaminated groundwater or consuming arsenic-contaminated food. Regarding global public health, drinking water is still the most important source of inorganic arsenic exposure and is the main focus of this work. The overall goal of this dissertation is to answer some pointing epidemiological questions about exposure to inorganic arsenic: How much do we know about inorganic arsenic and non-malignant lung disease in the general population? To what extent are adolescents with lifetime arsenic exposure susceptible to the respiratory consequences seen in adults? And what actions can be taken to effectively reduce exposure from arsenic-contaminated drinking water? First, we conducted a systematic review of 29 peer-reviewed articles from various populations around the world. The review focused on the different ways in which arsenic is associated with respiratory health to help inform policy makers and public health researchers on the existing evidence. In short, associations between arsenic and respiratory health were noted throughout the lifespan: in infancy, there was growing evidence that in utero arsenic exposure was associated with increased frequency and severity of respiratory tract infections; in childhood, evidence of respiratory symptoms also began to appear; and in adulthood, there was consistent evidence that arsenic exposure was associated with deficits in lung function and increased reports of coughing and breathing problems. The review also uncovered some research gaps, including few studies with strong exposure history from early life and few studies examining respiratory effects during adolescence. Next, we used a life course epidemiological approach to create a more precise understanding of arsenic exposure and respiratory health during the teenage years. This study examined the relationship between lifetime arsenic exposure and lung function in 14-17 year olds, thus studying the period of maximal lung function before natural decline. Overall, higher arsenic exposure was associated with lower lung function levels; however, these associations were only observed in males. This study used a sensitive marker of lung function to investigate early signs of small airway disease. Incorporating this common marker of small airway disease and airflow limitation in future studies on arsenic and respiratory health may help clarify how inorganic arsenic contributes to the development of chronic respiratory disease. Lastly, we evaluated the effectiveness of arsenic removal filters at the household-level in rural Bangladesh. Identifying sustainable ways of reducing exposure to arsenic from naturally contaminated groundwater has been a major environmental health challenge. Although lab-approved arsenic removal water filters exist, there was limited evidence of their prolonged efficacy in the field. To our knowledge, this was the largest and longest deployment of filters accompanied by monitoring of urinary arsenic. Our results demonstrated that filters can temporarily reduce arsenic exposure for weeks to a few months, but should not be considered as a long-term arsenic mitigation option. This failed attempt to reduce exposure confirmed that alternative mitigation strategies need to be employed in Bangladesh, particularly among more vulnerable populations, including pregnant women and young children. This dissertation has important policy implications for future arsenic research and mitigation efforts and should be effectively communicated to policy makers, public health officials, and the general population. Given the pervasive nature of arsenic exposure and the growing evidence of health consequences at different stages throughout the life course, the continued integration of information on inorganic arsenic and research collaborations across disciplines is critical for the prevention and mitigation of arsenic-induced health consequences.

Abstract in English and German / The reported PhD research study was conceived from real water problems experienced by a rural community in South Africa (SA). Specifically, water quality in the Nandoni Dam situated in the Vhembe District, Limpopo Province, South Africa was assessed in order to determine its fitness for use, following complaints by community members using this water for drinking and domestic purposes. The dam supplies water to 55 villages with approximately 800 000 residents. At the inception of the study, there was little scientific information relating to the quality of the water in the dam. Water samples from various sites across the Nandoni Dam, a primary source of domestic water supply in the region, were collected through each season of the year over a period of 12 months to ascertain the concentrations of dissolved salts in the dam. Additionally, harmful polycyclic aromatic hydrocarbons (PAHs) and phenols were assessed. The concentrations of the ions contributing to water salinity were generally lower than the brackish water bracket (i.e. 500 – 30 000 mg/L) but too high for potable water. The concentration of the phenols was relatively higher than the threshold limit of drinking water. Therefore, the water sourced from the Nandoni Dam was found not suitable for human consumption and therefore required integrated water resource management, as well as robust and cost-effective water treatment especially since the salinity of the water was high even after treatment by a water treatment plant sourcing water from the dam. In an attempt to develop a suitable energy-efficient technology or system for complete removal of salts (desalination) from the salty water (including brackish water), electrospun polyvinylidene fluoride (PVDF) nanofibre membranes were synthesised and evaluated for removal of salts using the Direct Contact Membrane Distillation (DCMD) process. The nanofibre membranes were synthesised with combined high mechanical stability, porosity, and superhydrophobicity to prevent fouling and wetting while maintaining high salt rejection and water flux. Organically functionalised silica nanoparticles (f-SiO2NPs) were embedded on PVDF nanofibre membranes using an in-situ electrospinning technique for superhydrophobicity enhancement. These modified membranes displayed Young’s modulus of ~43 MPa and showed highly porous properties (~80% porosity, 1.24-1.41 μm pore sizes) with superhydrophobic surfaces (contact angle >150°). Membranes embedded with octadecyltrimethoxysilane (OTMS), and chlorodimethyl-octadecyl silane (Cl-DMOS), octadecyltrimethoxysilane (ODTS)-modified SiO2NPs were the most efficient; rejecting >99.9% of NaCl salt, with a water flux of approximately 30.7-34.2 LMH at 60°C, thus indicating their capacity to produce potable water. The superhydrophobic membranes were coated with a thin layer consisting of carboxylated multiwalled carbon nanotubes (f-MWCNTs) and silver nanoparticles (AgNPs) to reduce membrane fouling. The AgNPs and f-MWCNTs were uniformly distributed with size diameters of 28.24±1.15 nm and 6.7±2.1 nm respectively as evidenced by transmission electron microscopy (TEM) micrographs. The antibacterial AgNPs embedded in the PVDF nanofibre membranes inhibited the growth of Gram-positive Geobacillus stearothermophilus and Staphylococcus aureus as well as Gram-negative Pseudomonas aeruginosa and Klebsiella pneumoniae indicating their potential to prevent biofilm formation. Fouling tests were conducted using bovine serum albumin (BSA), sodium alginate, colloidal silica, and thermophilic bacteria effluent as model organic, inorganic, and bio-foulants, respectively, using DCMD. The uncoated membranes were characterised by a flux decays ranging from 30% to 90% and salt rejection decays ranging from 1.4% to 6.1%. Membrane coating reduced the flux and salt rejection decays to 10–24% and 0.07–0.75%, respectively. Although the initial flux decreased from 42 to  16 LMH when using coated membranes, the resistance of these coated membranes to water flux and salt rejection decays indicated that coating could be a suitable one-step solution for fouling mitigation in DCMD. The major challenge would be to design the MD membranes with architectures that allow a high-water flux to be maintained i.e., a highly porous layer. Furthermore, the volatile compounds bearing hydrophobic groups were pretreated to reduce their fouling capacity on PVDF nanofibre membranes. In this study, polyacrylonitrile (PAN) and polyethylene-imine (PEI) functionalised-PAN nanofibre membranes were synthesised and evaluated as a pretreatment for the removal of chlorophenol and nitrophenol from solutions. Under optimised experimental conditions, adsorption capacities ranging from 27.3 – 38.4 mg/g for PAN and PEI-modified nanofibres, respectively, were recorded. The PEI-functionalised nanofibres showed a high potential as a pretreatment step to be integrated to MD process. Ultimately an integrated water desalination system was developed. This involved a pretreatment filter (pore size ~100 μm) containing PEI-functionalised PAN nanofibre materials to reduce particulates and large molecules of dissolved organic/inorganic compounds from the water to be treated. In this research, it was observed that the pre-treatment step was not sufficient in removing all traces of compounds causing fouling of the superhydrophobic PDVF nanofibre membranes. As such, coating of the membranes with a thin hydrophilic layer and coupled with the filtration pretreatment step was found to provide fouling-resistance properties, high salt rejection, and low flux decays on brackish water collected at an estuary in Belgium and the Nandoni Dam in South Africa, demonstrating the potential of the MD separation process towards potable water recovery from brackish water. / Het onderzoek in dit proefschrift was gebaseerd op concrete waterproblemen die een landelijke gemeenschap in Zuid-Afrika (SA) ervaart. In het bijzonder werd de waterkwaliteit in het Nandoni-reservoir in het Vhembe-district in de provincie Limpopo in Zuid-Afrika onderzocht, om te bepalen of dit water geschikt is voor gebruik, na klachten van leden van de gemeenschap die dit water gebruiken als drinkwater en voor huishoudelijk gebruik. Het reservoir levert water aan 55 dorpen met ongeveer 800.000 inwoners. Bij het begin van het onderzoek was er weinig wetenschappelijke informatie over de kwaliteit van het water in het reservoir. Watermonsters van verschillende locaties in het reservoir, dat een primaire bron van drinkwater is in de regio, werden gedurende verschillende seizoenen van het jaar verzameld over een periode van 12 maanden, om de concentraties van de meest voorkomende ionen in het reservoir te bepalen. Bovendien werden de concentraties van schadelijke polycyclische aromatische koolwaterstoffen (PAK's) en fenolen gemeten. De concentraties van de ionen die bijdroegen aan het zoutgehalte van het water waren in het algemeen lager dan de drempel om het water als brak water te bestempelen (dat wil zeggen 500 – 30 000 mg/l), maar waren te hoog voor drinkwater. De concentratie van de fenolen was hoger dan de limiet voor drinkwater. Daarom bleek het water afkomstig van het Nandoni reservoir niet geschikt voor menselijke consumptie. Een beter geïntegreerd waterbeheer is dus nodig om deze bron voor drinkwater te beschermen, naast een robuuste en kosteneffectieve waterbehandeling. Deze waterbehandeling moet vooral het zoutgehalte van het water naar beneden halen, maar ook de concentraties van fenolen. In een poging om een geschikte energie-efficiënte technologie of een systeem voor de volledige verwijdering van zouten (~ontzilting) uit brak water te ontwikkelen, werden elektrisch gesponnen polyvinylideenfluoride (PVDF) nanovezelmembranen gesynthetiseerd en beoordeeld op verwijdering van zouten met behulp van Direct Contact Membraandestillatie (DCMD). De nanovezelmembranen hadden een gecombineerde hoge mechanische stabiliteit, porositeit en superhydrofobiciteit, die hielp om vervuiling (fouling) en vloeistofintrede in de poriën (wetting) te voorkomen, terwijl een hoge zoutverwijdering en hoge waterflux doorheen de membranen gehandhaafd bleven. Organische gefunctionaliseerde silica-nanodeeltjes (f-SiO2NP's) werden nadien geïncorporeerd in de PVDF nanovezelmembranen met behulp van een in-situ elektrospinning techniek om zo een nog grotere superhydrofobiciteit te bekomen. Deze gemodificeerde membranen hadden een degelijke treksterkte (Young's modulus van ~ 43 MPa) en waren zeer poreus (~ 80% porositeit, 1.24-1.41 μm poriegrootte). Het oppervlak van de membranen vertoonde inderdaad superhydrofobe eigenschappen (contacthoek met water > 150 °). De membranen ingebed met octadecyltrimethoxysilaan (ODTS) SiO2NP's waren het meest efficiënt: ze toonden een zoutretentie van> 99.9% voor NaCl, bij een waterflux van ongeveer 30.7-34.2 l/(m².h) bij 60 ° C (ten opzichte van 20°C in het permeaat), wat aangeeft dat ze in staat zijn om drinkbaar water te produceren. De superhydrofobe membranen werden nadien ook gecoat met een dunne laag bestaande uit gecarboxyleerde multiwall-carbon nanotubes (f-MWCNT's) en zilver nanodeeltjes (AgNP's), in een poging om membraanvervuiling te verminderen. De AgNP's en f-MWCNT’s hadden uniforme diameters van respectievelijk 28,24 ± 1,15 nm en 6,7 ± 2,1 nm (zoals bleek uit transmissie-elektronenmicroscopie (TEM)). De antibacteriële AgNP's ingebed in de PVDF-nanovezelmembranen remden de groei van Gram-positieve Geobacillus stearothermophilus en Staphylococcus aureus bacteriën, evenals Gram-negatieve Pseudomonas aeruginosa en Klebsiella pneumoniae bacteriën. Dit toont het potentieel van deze membranen om biofilmvorming te voorkomen. Vervuilingsproeven (in DCMD) werden uitgevoerd met behulp van runderserumalbumine (BSA), natriumalginaat, colloïdaal silica, en thermofiele bacteriën - als respectievelijk organische, anorganische en biologische vervuiling. De niet-gemodificeerde membranen werden gekenmerkt door een fluxverval, met een daling van de flux met 30% tot 90%, naast een daling van de zoutretentie met 1.4% tot 6.1%. Bij de gecoate membranen daalde de flux slechts met 10-24% en de zoutverwijdering slechts met 0.07-0.75% respectievelijk. Hoewel de initiële flux ook afnam (van 42 naar ± 16 l/(m².h)) bij het gebruik van gecoate membranen, toonde de hogere weerstand tegen vervuiling van deze gecoate membranen aan dat deze coating een geschikte oplossing zou kunnen zijn tegen vervuiling in DCMD. Bovendien kan de synthese in één stap verlopen. De grootste uitdaging zal echter zijn om MD-membranen te ontwerpen waarbij de coating de oorspronkelijke waterflux/de porositeit van de membranen niet teveel verlaagt. Daarnaast werden gemodificeerde PVDF nanovezels geproduceerd om de verwijdering van vluchtige, hydrofobe stoffen (zoals fenolen) door adsorptie aan deze vezels te verhogen. Er werden polyacrylonitril (PAN) en polyethyleen-imine (PEI) gefunctionaliseerde PAN nanovezels gesynthetiseerd, waarna deze geëvalueerd werden als adsorbens (en dus voorbehandeling voor de membraanstap) voor chloorfenol en nitrofenol. Onder geoptimaliseerde experimentele omstandigheden werden adsorptiecapaciteiten tussen respectievelijk 27.3 en 38.4 mg / g voor PAN- en PEI-gemodificeerde nanovezels gemeten. De PEI-gefunctionaliseerde nanovezels vertoonden een hoog potentieel als een voorbehandelingsstap voor de hierboven beschreven DCMD. Tenslotte werd ook een geïntegreerd waterontziltingssysteem ontwikkeld. Dit systeem bestond uit een voorbehandelingsstap met PEI-gefunctionaliseerde PAN-nanovezels (in de vorm van een membraan met poriegrootte ~100 μm), gevolgd door een gemodificeerde DCMD stap. De voorbehandeling diende om deeltjes en grote opgeloste organische verbindingen uit het te behandelen water te verwijderen voor de DCMD-stap. In dit onderzoek werd waargenomen dat de voorbehandelingsstap niet voldoende was om alle organische contaminanten te verwijderen die vervuiling veroorzaakten op de superhydrofobe PDVF nanovezelmembranen in de DCMD-stap. Toch bleek coating van de DCMD membranen met een dunne hydrofiele laag (gekoppeld aan de voorbehandelingsstap) een voldoende bescherming tegen vervuiling te bieden zodat de zoutretentie en waterflux van deze membranen hoog bleef. De combinatie van voorbehandeling – gemodificeerde DCMD werd succesvol getest op water uit de Schelde en uit het Nandoni reservoir, waarmee het potentieel van de technologie om drinkwater uit brak water te produceren werd aangetoond. / School of Science / Ph.D. (Applied Biological Science : Environmental Technology)

Dialys är en medicinteknisk teknik som används för att rena blod vid nedsatt njurfunktion. Dialysvätska är en viktig komponent i utrustningen. Syftet med examensarbetet var att utvärdera förbättrade rutiner för kvalitetskontroll av vattnet som används för tillredning av dialysvätskan. Ett program för övervakning av desinfektionseffekt i vattenrenare för dialys har utvecklats i Microsoft Visual Studio, med Windows Forms som plattform och kod skriven i C#. Mjukvaran övervakar konduktivitet, dagar sedan desinfektion, desinfektionseffekt (A₀), aktivitet hos loggningsprogram samt kontrollprogram. Larm skickas via mail vid dåliga värden eller fel, samt visas lokalt på dator i form av en textruta. Ett ytterligare program skapades för att kontrollera att huvudprogrammet är igång, och en varning skickas när aktivitet uteblir under en viss längd. Utöver övervakning skapades även en grafisk del som tillåter visning av loggade data samt beräknade A₀-värden över tid. Analys utförs kring möjligheter att bibehålla mikrobiologisk trend med stabilt låg bakterienivå i vattnet vid minskad desinfektionsfrekvens från tre till två gånger i veckan. Provtagningar tyder på att marginal till gränsvärde inte hotas, men mer data behövs för at bekräfta resultatet. Analys utförs även kring möjligheten att använda beräkning av A₀-värden för att verifiera desinfektionseffekt tidigare än resultat från mikrobiologisk provtagning, vilket resultat från den studie som utförts tyder på är möjligt, med vissa undantag där det inte finns data att förhålla sig till. Vid användning av mjukvaran rekommenderas fortsatta mikrobiologiska provtagningar. / Dialysis is a health technology used for cleaning blood in people with kidney failure. Dialysis fluid is an important component used in the dialysis process. The aim of the project is to evaluate improved quality control routines for the water used in preparation of the dialysis fluid. A program for monitoring disinfection effect in water purification systems for dialysis has been developed in Microsoft Visual Studio, using Windows Forms as platform and the code was written in C#. The software monitors conductivity, days since last disinfection, effect of disinfection (A₀), activity of logging software as well as control software. Warnings are sent by mail for bad results or errors, and a message is shown as a textbox locally on the computer running the software. An additional program was made for monitoring the main programs activity, and a warning is sent after seeing no activity within a time period. Other than monitoring, the software also has a graphical view allowing the user to view logged data and calculated A₀-values over time. An analysis is made regarding the possibility to maintain microbiological trend of low amounts of bacteria in water after reducing the disinfection frequency from three to two times a week. Test results indicate that the margin to the maximum allowed value remains on safe levels, but more data is required to confirm the results. A further analysis is made regarding the possibility to use calculations of A₀-values to verify the disinfection effect earlier than results from microbiological testing. Results from studies indicate that this is possible, but with some exceptions in cases where not enough data is available to draw conclusions. When using the software, continued microbiological testing is recommended.

Securing water in the right quantities at the right quality for the right price is a major issue around the world. Membranes are making an increasingly important contribution to meeting this need; however their performance is limited by fouling. This thesis reports on an investigation into the fouling of systems related to water treatment using the Direct Observation Through the Membrane (DOTM). The investigation focused on the measurement of critical flux and observation of particle behaviour under a variety of conditions and for a number of different particles. The range of meanings attributed to critical flux in the literature was analysed and several proposals made for the improved use of the concept. In particular, critical flux determination techniques were classified by whether they measure resistance changes or particle deposition; leading to the definition of Critical Resistance and Critical Deposition Fluxes. In this thesis the deposition definition is used exclusively. The effect of Reynolds number and spacer orientation on critical flux was correlated for spacer-filled channels. The heterogeneous deposition patterns observed with regions of heavy deposition next to areas of little or no deposition. This pattern was related to the local hydrodynamics of spacer cells (a few mm2 in size). The correlations developed for critical flux in spacer-filled channels were adjusted for submicron particle size and incorporated into a SpiralWound Module (SWM) leaf model and then used to simulate the fouling of SWM leaves under a range of operating conditions and operating policies. The Mass Balance technique of critical flux determination was also briefly assessed. The applicability of critical flux criteria to SWM arrays was discussed. Fouling, particle behaviour and critical flux were also investigated in air-sparged systems. The post-cleaning water flux was found to be enhanced when the membrane is fouled in the presence of bubbles. The rate of flux decline was reduced by bubbles. Critical flux increased with air flowrate, and decreased with increased liquid flowrate and concentration. Bubbles caused particles to periodically deposit on the membrane. Particles were observed to stream past the membrane under the influence of back-diffusive forces. Video clips of particulate fouling are provided.

The aims of this doctoral study were to: isolate naturally occurring bacteria, able to degrade microcystins (MCs), from New Zealand waterbodies; to understand the biological processes of microcystin degradation by bacteria; and to develop small scale biofilm technology for testing the effectiveness of bacteria for microcystin degradation and/or remediation. A significant amount of microcystins were required for biodegradation experiments. A modified method, using DEAE and Strata-X cartridge chromatography, was optimized for purifying microcystin variants from lyophilized bloom samples of the cyanobacterium Microcystis aeruginosa, collected en masse from Lake Horowhenua. Seven microcystin variants, MC-RR, MC-dMe-RR, MC-YR, MC-LR, [Dha7]MC-LR, MC-FR, and MC-AR were purified by chromatography and then identified by reverse-phase High Performance Liquid Chromatography (HPLC) with UV detector (UVD) and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). A mixture of [Dha7]MC-LR and MC-LR, the main microcystin variants present, was used for examining biodegradation of microcystins by degrading bacteria. Three isolates of bacteria—NV-1, NV-2 and NV-3—purified from Lake Rotoiti, New Zealand were capable of degrading [Dha7]MC-LR and MC-LR. Among these isolates, NV-3 demonstrated the strongest degradative activity and was identified as a member of the genus Sphingomonas. On the basis of 16S rRNA sequencing, and 100% nucleotide sequence homology, it aligned most closely to strain MD-1. Based on the detection of two intermediate by-products (linearized peptides and a tetrapeptide) and the identification of four genes (mlrA, mlrB, mlrC and mlrD), that encode four putative proteins (enzymes) involved in microcystin degradation, it was suggested that the degradation of [Dha7]MC-LR and MC-LR by the Sphingomonas isolate NV-3 occurred by a similar mechanism previously described for Sphingomonas strain MJ-PV (ACM-3962). The bacterium Sphingomonas isolate NV-3 was examined for its ability to inhibit the growth of the cyanobacterium Microcystis aeruginosa strain SWCYNO4. It was found that the bacterium did not have any significant affect on the growth of the cyanobacterium, either by means of secretion of bacterial extracellular products or cell-to-cell contact between bacterial and cyanobacterial cells. It was established that Sphingomonas isolate NV-3 was a moderate biofilm former, based on two types of biofilm formation assays, namely, microtiter plate assays and coupon biofilm assays. This was carried out in preparation for using the bacterium in a bioreactor for biodegradation of [Dha7]MC-LR and MC-LR. The bacterium attached most effectively to ceramic, followed by PVC, polystyrene, stainless steel, and finally glass coupons. Biodegradation of MCs by the bacterium, in an internal airlift loop ceramic honeycomb support bioreactor (IAL-CHS bioreactor), was established in batch and continuous-flow experiments. In the batch experiment, NV-3 degraded a combination of [Dha7]MC-LR and MC-LR at an initial concentration of 25 µg/ml at 30 degrees C in 30 hours, whereas in the continuous-flow experiment, NV-3 degraded the same concentration of [Dha7]MC-LR and MC-LR in 36 hours with an hydraulic retention time (HRT) of 8 hours. This study has demonstrated that microcystin-degrading bacteria are present in New Zealand waterbodies and that these bacteria could be used, potentially on a larger scale, for removing microcystins from water.

Drinking water is produced from raw water and is either from groundwater or surface water. This thesis aims to find out if the cleaning process of raw water is sufficiently effective. This is important because consumers are otherwise at risk of waterborne infection caused by pathogens. There are three groups of pathogens; bacteria, virus and parasite. These have different characteristics which mean that they require different water treatment to be separated. In addition to normal operation, a number of scenarios were examined. This is to investigate how water treatment would do if they became a reality. The thesis has examined Borg´s waterworks operated by Norrköping Vatten AB. It was defined to cover the distance from water source to the consumer. In the work, the model Quantitative Microbial Risk Assessment (QMRA) was used to perform risk analysis by simulating the normal operation and different scenarios of the water purification process. Thus, knowledge can be obtained about the effectiveness of separation by bacteria, viruses and parasites. However, the QMRA-model is considered to contain some flaws and for that reason the Norwegian model called Good Disinfection Practice (GDP) was also used. GDP is a theoretical model which is based on formulas and tables. The model takes into account the raw water quality and also provides deductions for various measures that the water plant possesses to ensure a good supply of water. The results obtained with both models were similar and showed that the water treatment is sufficient for the bacteria, but not viruses and parasites. Both models were considered to be reliable but viruses and parasites are very difficult to analyze, which has resulted in uncertain literature values and hence in the results. The result also showed that neither viruses nor parasites exceeded the limit by so much that more hygienic barriers to the reduction of them are necessary. The conclusion which may be drawn from the fact that no parasites have been detected in the raw water is that the water treatment still might be sufficient. To determine the effects that an exclusion of various barriers may give, the normal operation was simulated and a purification step at a time was excluded. The result showed that the purification steps which are most important to maintain the treatment process are chemical precipitation followed by rapid filtration, slow filtration and disinfection with chlorine. If any of these cleaning steps were to fail, this introduces a large increase in the risk of waterborne disease. The results showed that the chemical precipitation step gave the greatest separation effect on the virus but also on the parasites. However, the slow filtration gave the largest separation of the parasites. Free chlorine had the greatest effect on bacteria. The investigated scenarios were assumed to be wastewater discharges, sewage discharges in relation to flood the nearby pastures, and sewage overflows due to heavy rainfall. The results of the simulated scenarios were the same when it was only bacteria that in all cases produced a result within the limits of the daily infection probability. Both viruses and parasites exceeded both values. However, there were few studies on these and thus literature values needed to be implemented in the QMRA-model. Hence, the uncertainty of the results was great. The QMRA-model also contained deficiencies in the simulation of the discharge of effluents, where the amount of virus was about 1000-10000 times too much. If this problem as well as more specific data for the investigated area, and more Swedish studies were available, a more credible simulation of the scenarios could be implemented.

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering