Thesis (MTech (Engineering))--Cape Peninsula University of Technology, 2007 / The removal of the colour-eausing natural organic matter (NOM) from natural brown water (NSW) to be used for drinking purposes is of paramount importance. One of the methods available to remove NOM from NSW is the use of pressure-driven membrane separation systems. One of the limitations in efficiently applying membrane filtration in the treatment of NOM-eontaining water is membrane fouling that is caused by foulants, such as NOM, that accumulate on the membrane surface and in the membrane pores. Microfiltration (MF), as a membrane separation system, is susceptible to severe membrane fouling during membrane filtration of NSW. Fouling is characterized by a rapid decline in permeate flux and loss of productivity. Progress in developing more effective control and prevention of fouling is impeded by the absence of suitable fouling measurement and characterization techniques. An in situ method for measuring membrane fouling is necessary for detection of membrane fouling during MF of NSW at the eartiest stages so that the corrective actions can be taken before fouling is permanently adsorbed onto the membrane surface. In this study, an ultrasonic-based method was effectively used to detect and measure the growth of membrane fouling dUring MF of NSW, in situ. Fouling exp~riments results showed the formation of a new peak on the ultrasonic response echo signal due to the presence of a fouling layer on the surface of the membrane. The ultrasonic signals acquired during the in-situ detection of membrane fouling were analysed using wavelet transforms (WTs). Wavelet analysis was applied to differential signals to obtain additional information about fouling. Differential signals were calculated by subtracting the baseline measurement signals from the test signals. The presence of the fouling layer on membranes was verified by atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses of the fouled membranes.

This thesis investigates the susceptibility of various bacterial species to standard purification process.

The fate of antimicrobials entering the aquatic environment is an increasing concern for researchers and regulators, and recent research has focused on antimicrobial contamination from point sources, such as wastewater treatment facility outfalls. The terraccumulation of antimicrobials and mobility in diffuse pollution pathways should not be overlooked as a contributor to the spread of bacterial resistance and the resulting threat to human drug therapy. This review critically examines recent global trends of bacterial resistance, antimicrobial contaminant pathways from agriculture and water treatment processes, and the need to incorporate diffuse pathways into risk assessment and treatment system design. Slow sand filters are used in rural regions where source water may be subjected to antimicrobial contaminant loads from waste discharges and diffuse pollution. A simple model was derived to describe removal efficiencies of antimicrobials in slow sand filtration and calculate antimicrobial concentrations sorbed to the schmutzdecke at the end of a filtration cycle. Input parameters include water quality variables easily quantified by water system personnel and published adsorption, partitioning, and photolysis coefficients. Simulation results for three classes of antimicrobials suggested greater than 4-log removal from 1 ��g/L influent concentrations in the top 30 cm of the sand column, with schmutzdecke concentrations comparable to land-applied biosolids. Sorbed concentrations of the antimicrobial tylosin fed to a pilot filter were within one order of magnitude of the predicted concentration. To investigate the behavior of antimicrobial contaminants during multi-stage filtration, five compounds from four classes of antimicrobials were applied to a mature slow sand filter and roughing filter fed raw water from the Santiam River in Oregon during a 14-day challenge study. Antimicrobial removal efficiency of the filters was calculated from 0.2 mg/L influent concentrations using HPLC MS/MS. and sorption coefficients (K[subscript d], K[subscript oc], K[subscript om]) were calculated for schmutzdecke collected from a mature filter column. Sulfonamides had low sorption coefficients and were largely unaffected by multi-stage filtration. Lincomycin, trimethoprim, and tylosin exhibited higher sorption coefficients and limited mobility within the slow sand filter column. The lack of a significant increase in overall antimicrobial removal efficiency indicated biodegradation is less significant than sorption in multi-stage filtration. / Graduation date: 2004

Submitted in fulfilment of the requirements of the Degree of Master of Technology: Chemical Engineering, Durban University of Technology, 2013. / Lack of access to clean and safe potable water, especially for people living in rural areas of developing economies, is a matter of great concern in different parts of the world. Measures taken to address the challenges arising from this problem include the improvement of existing water purification methods and development of new appropriate technologies such as point of use (POU) water treatment technologies. One such appropriate POU technology is the Remote Rural Water Treatment System (RRWTS) developed at Durban University of Technology (DUT) in South Africa. The RRWTS is based on polyester woven fabric microfiltration (WFMF) membranes and other locally sourced materials. The filtration unit consists of flat sheet modules assembled into a pack and permeate outlets connected to a manifold and then to a tap. The system is gravity driven and therefore eliminates the use of pumps and electricity. This system has shown potential for use in water treatment as it produces permeate with turbidity below 1 NTU, has a high permeate flow rate, and is easy to use and maintain. However, the major challenge facing its use is that permeate does not meet the set microbiological standards for drinking water (zero E. coli in 100 mL treated water). The RRWTS can ideally remove 95 to 99 per cent of the influent E. coli. This necessitates the use of a separate disinfection step, often using chlorine for complete removal of microbial contaminants. The objectives of this study were: to investigate the incorporation of silver nanoparticles (AgNPs) into the WFMF membrane; to evaluate the disinfection efficacy of the AgNPs impregnated filter (coated filter); and to determine the long term performance of the coated filter in terms of disinfection and silver elution (90 days). The study was conducted in four stages. Firstly, AgNPs were incorporated on the membrane using in situ chemical reduction of silver nitrate using sodium borohydride. Secondly, the filters were characterized using scanning electron microscopy (SEM) to determine the morphology, and the Sessile drop method for contact angle measurement was employed to determine the membrane hydrophilicity. In addition, X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy and UV- Visible Spectroscopy iii were used to investigate the presence of AgNPs on the coated filter. Thereafter, the antibacterial efficacy of the filters was evaluated using a laboratory scale experimental rig and different microbial assays. Raw river water and deionized water spiked with E.coli (synthetic feed) were used as feed. Lastly, the effects of concentration of E.coli in the feed and silver elution on the disinfection performance of the coated filter over time were investigated. The performance criteria were based on permeate quality and they included: turbidity, concentration of E.coli, and silver concentration. The characterization results depicted that AgNPs were successfully immobilized on the WFMF membranes by in situ chemical reduction. The incorporation of AgNPs was ascertained using UV-Vis Spectrophotometry, FT-IR and XRD. The Sessile drop test indicated that the membrane became more hydrophilic (77 per cent decrease in water contact angle) and the permeability increased significantly as a result of the coating (p <0.05). The coated filters demonstrated excellent filtration performance producing permeate with turbidity less than 1 NTU for feed turbidities between 40 and 700 NTU. The disinfection efficacy was found to be excellent, producing permeate with zero E.coli concentration for feed concentrations between 10,000 CFU/ 100 mL and 85,000 CFU/100 mL. The E.coli removal efficiency was 100 per cent for a period of 63 days of continuous filtration. The ICP Atomic Emission Spectrometer (ICP-AES) results showed that the leaching of silver from the coated filters over time (90 days) was always below 0.1 mg/L which is the widely accepted guideline for potable water. From the literature surveyed, this is the first study which investigated the use of AgNPs in WFMF membranes for potable water disinfection. The coated filters treated water to the set international standards for potable water in terms of physical and microbiological quality. However, the study did not comprise investigation into the effect of different silver loadings on the filter performance. The study also employed E.coli as the indicator organism for faecal contamination. The results obtained can be used as a model for future work using other microorganisms and different silver loadings in order to compare the performance.

Submitted in fulfillment for the requirements of the degree of Master of Technology: Chemical Engineering,Durban University of Technology. Durban. South Africa, 2015. / Access to safe drinking water supply is still a major problem especially in remote rural areas of developing countries. These communities rely solely on untreated surface and ground waters for survival due to the lack of financial resources to provide access to piped water. The consumption of this water in turn makes them easily susceptible to water related diseases. Hence, there is a need for an interim solution while the government is still sourcing funds for the distribution of water to these communities. Membrane filtration is a promising technology for the treatment of surface water as it does not alter the taste or smell of the end product. The main limitation for the implementation of membrane technology in rural areas is still energy demand, fouling and the skills required for membrane cleaning. Biological ultrafiltration is an emerging technology that produces water of high quality in terms of turbidity, organics and bacteria removal. The technology has been evaluated using a gravity driven dead-end mode on European waters and it offered acceptable stabilisation of fluxes for extended periods without any chemical cleaning or backwashing. This is a promising technology which can be implemented to act as an interim solution for the treatment of surface water in remote rural areas prior to consumption. This study concerns the evaluation of a biological ultrafiltration membrane system on local three South African rivers, namely, Tugela River, Umbilo River and Umgeni River. A laboratory systems comprising of a feed tank and six membrane modules connected in parallel was set up to assess the performance of a bio-UF membrane on a range of surface waters. The performance was assessed on the system’s ability to produce stable fluxes from the three rivers, the system ability to produce water with acceptable quality in terms of SANS 241:2011 for turbidity, TOC, total coliforms and E-coli. The membranes were initial cleaned and the flux rates for ultra-pure water were determined for each membrane prior to being exposed to raw water. Raw water samples were collected from three rivers with varying turbidity, total coliforms and organics. The concentrations of these contaminants were tested prior to running the raw water through the system. Thereafter, permeate was collected with time and its quality was evaluated in terms of turbidity, TOC and coliforms. The impacts of algae on flux stabilisation were evaluated by allowing the bio-UF system to run for a minimum of 3 months with and without algae growth. The system was found to be able to produce water that is compliant with the SANS 241:2011 standard in terms of turbidity, total coliforms, E-coli and TOC concentration. The system was also found to be unable to produce stable fluxes for all three rivers. The observed responses were noted to be similar to normal dead-end response, however, a slow declining flux rates was observed for Umgeni River. The presence of algae during the operation was a bio-UF membrane system was noted to further decrease the rate of flux decline. There appears to be a correlation between the raw water quality and the rate of flux decline. A further investigation was carried out aimed at assessing the relationship between the concentration of bacterial counts, TOC and turbidity. From the obtained results, it was noted that feed water with low turbidity (≤ 5 NTU), high bacterial count (≥30 000) and high total organic carbon (≥70 mg/L) is able to reduce the rate of flux decline. Hence, it can be concluded that a dead-end gravity driven Bio-UF membrane system can be used for the treatment of surface water in remote where the most main contaminants are from natural organic matter, micro-organisms and turbidity. Furthermore, it is able to produce slower declining flux rates which will increase the filter run time. It is recommended that the impacts of algae, type of bacteria and organics that enable slow decline in flux rates during the operation of Bio-UF should be investigated in order to identify means of enhancing the flux rates. Microfiltration membranes are available on the local markets hence it is also recommended that the performance of Bio-UF should be evaluated in comparison to Bio-MF.

In potable water preparation, chlorination is the last step before the potable water enters the distribution network. Umgeni Water Wiggins Waterworks feeds the Southern areas of Durban. A reservoir at this facility holds treated water before it enters the distribution network. To ensure an adequate disinfection potential within the network, the free chlorine concentration in the water leaving the reservoir at the Umgeni Water Wiggins Waterworks should be between 0.8 and 1.2 mg/L. The aim of this study was to develop an effective strategy to predict and control the chlorine concentration at the exit of the reservoir. This control problem is made difficult by the wide variations in flow and level in the reservoirs, together with reactive decay of the chlorine concentration. A Computational Fluid Dynamic study was undertaken to gain understanding of the physical processes operating in the reservoir (FLUENT software). As this kind of modelling is not yet applicable for real-time control, compartment models have been created to simulate the behaviour of the reservoir as closely as possible, using the results of the fluid dynamic simulation. These compartment models were initially used in an extended Kalman filter (MATLAB software). In a first step, they were used to estimate the kinetic factor for chlorine consumption and in a second step, they predicted the chlorine concentration at the outlet of the reservoir. The comparison between predictions and data, allowed the validation of the compartment models. A predictive control strategy was developed using a Dynamic Matrix Controller, and tested offline on the compartment models. The controller manipulated the chlorine concentration in the inlet of the reservoir in order to control the chlorine concentration in the outlet of the reservoir. Finally, the simplest compartment model was implemented on-line, using the Adroit SCADA system of the plant, in the form of a Kalman filter to estimate the chlorine decay constant, as well as a predictive model, using this continuously-updated decay parameter. The adaptive Dynamic Matrix Controller using this model was able to control the outlet chlorine concentration quite acceptably, and further improvements of the control performance are expected from ongoing tuning. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

D.Phil. / Clean water (i.e. water that is free of toxic chemicals and pathogens) is essential to human health and in South Africa the demand is fast exceeding the supply. The prevalence of toxic contaminants in water remains a huge challenge for water supplying companies and municipalities. However, the presently used water treatment technologies either fail to remove these contaminants to acceptable levels or they transform them into more toxic substances (e.g., DBPs). Nanocatalysts, especially TiO2 (titania) have a proven potential to treat ‘difficult-to-remove’ contaminants and hence are expected to play an important role in solving many serious environmental and pollution challenges. In this study TiO2 nanocatalysts were used for the degradation of Rhodamine B dye both under UV and visible light irradiation. Two phases of titania, i.e. anatase and rutile phases, were compared for the degradation of Rhodamine B under UV light irradiation. The anatase titania was found to be more photocatalytically active for the degradation of Rhodamine B than the rutile phase. It completely degraded 100 mg ℓ–1 (100 mℓ) of Rhodamine B within 270 min and was two times more photocatalytically active than the rutile phase (Kapp of 0.017 min–1 compared to 0.0089 min–1). To extend the band edge of the titania nanocatalysts towards visible-light, TiO2 was doped with metal ions (Ag, Co, Ni and Pd). These metal-ion-doped titania nanocatalysts were photocatalytically active under visible-light illumination. The Pd-doped titania had the highest photodegradation efficiencies, followed by Ag-doped and Co-doped, while Ni-doped had the lowest. The optimum metal-ion loading percentage was found to be at 0.4%, with the exception of Co-doped titania as it had the highest efficiencies at 1% loadings. The free and metal-ion-doped titania nanocatalysts were embedded on carbon-covered alumina (CCA) supports. The CCA-supported TiO2 nanocatalysts were more photocatalytically active under visible light illumination than they were under UV-light irradiation. The CCA-supported metal-ion-doped titania nanocatalysts were more photocatalytically active under visible light than their unsupported counterparts. The CCA-supported Pd-TiO2 nanocatalysts were the most active while CCA-supported Ni-TiO2 catalysts were the least active. The improved photocatalytic activities observed were as a result of increased surface areas of the CCA-supported nanocatalysts. Also, supporting the nanocatalysts did not destroy the anatase phase of the titania while doping with metal ions and supporting on CCAs resulted in decreased band gap energies, hence the visible-light photocatalytic activities. Finally, the metal-ion-doped titania nanocatalysts were supported on glass slides using the layer-by-layer thin film self-assembly technique. This was to overcome the aggregation and post treatment problems associated with the use of TiO2 in suspension form. PAH and PSS were the polyelectrolytes used. These metal-ion-doped titania thin films were highly porous and strongly adhered by the polyelectrolytes onto the glass slides. The thin films were photocatalytically active for the degradation of Rhodamine B under visible light irradiation. The photocatalytic degradation efficiencies observed were similar for all four metal-ions (i.e. Ag, Co, Ni and Pd) with average degradation of 30%, 50%, 70% and 90% for 5 catalysts (5 glass slides) of 1, 3, 5 and 10 bi-layers, respectively, after 330 min. Although, these were less active than the suspended titania nanocatalysts, this study proved as a stepping stone towards large scale use of titania nanocatalysts using solar energy as the irradiation source. Also, catalyst reusability studies were performed and the PAH/PSS m-TiO2 thin films were found to be highly stable over the five cycles it was tested for.

In this research, a heat localizing solar thermal membrane distillation system has been developed for producing potable water from untreated surface water, wastewater, and seawater, using solely solar thermal energy. Unlike most other membrane technologies, this system requires no electrical power or equipment for its operation. The high production rate was achieved through the effective evaporation of water molecules within the pores of the membrane without dissipating much heat to the bulk feed water. It can remove suspending particles, microorganisms, inorganic salts, as well as organic contaminants from the feed water. The system can produce potable water for 32, 18, and 10 days on average under simulated sunlight when distilling seawater, canal water, and municipal wastewater, respectively, without cleaning the membrane. Low cost, high energy efficiency (i.e., 55%), and good water quality make the new system feasible for undeveloped areas where basic water treatment is lacking. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Beginning at least as early as 1977, the international community formally recognized that drinking water and sanitation were not a reality for large percentage of the world and that it was necessary to take action to change this. Over the following three decades more actions and agreements were made, each with a progressively acute awareness of the requirements to achieve this goal and the failures of previous attempts. Poor information sharing and underestimation of cost were identified as two of the greatest recurring impediments. The Millennium Declaration made in 2000 is the newest campaign to move towards this goal, among others, and provides a metric against which progress and success can be measured. At this point, great success has been made overall towards the Millennium Development Goals. Millions of people have gained access to improved sources of drinking water and several regions have surpassed their goals. Unfortunately this progress is not homogenous and the definitions of success are misleading. Sub-Saharan Africa is lagging significantly behind due to water scarcity, large population growth, urban versus rural disparities, and slow growth of piped infrastructure. Limitations to the sector as a whole have been identified as logistics, funding limitations, inadequate cost recovery, and inadequate operations and maintenance. Additionally, the metric of access to an "improved" source does not equate to safe drinking water and is not attached to sanitation improvements or overall health improvements. In further examining the financial aspects of achieving the goals, it is clear that there is a great deal of inconsistency. Many donors, whether public or private, international or local, are giving money to the development goals. But the money given is often not equivalent to the original commitment, not given to the countries with the greatest need, not given to the water and sanitation sector specifically, given in the form of loans which must be repaid, given to new large scale systems which are not always appropriate, or not sufficient to achieve the desired target. This makes it very difficult to achieve and sustain progress in the areas which have been difficult to reach thus far, including Sub-Saharan Africa. The need for progress toward safe water is clear from the perspective of health. Water is needed for hygienic practices, as well as consumption, and it is counterproductive to use water that is not clean. One of the leading causes of both death and disability worldwide is diarrheal disease which can largely be attributed to unsafe water. Studies have shown that there is a positive correlation between drinking water interventions and improved health outcomes, especially with increased proximity of the source, and for this reason there is an even greater need to tie the definition of success in improved water to overall health outcomes. It is also important that public health practitioners, engineers, and professionals from other related sectors work together to improve knowledge sharing and ultimately efficiency in achieving the goal of safe water for all. Point-of-use interventions are among the best approaches to delivering means of water treatment to unreached communities because they can be deployed much more quickly and easily than a traditional piped system, require less expertise, and reduce recontamination that may occur during transport and storage. Such technologies utilize a variety of mechanisms to address a range of contaminants and concerns. In order for any technology to be successful though, it must be accompanied by a method of safe storage as well as education, training, and continued external support. This information is synthesized in a technology selection guide, which attempts provide assistance in technology selection by addressing the immediate issue of water quality for the sake of health benefits, while also considering the context of the installation, the user preferences, the level of expertise of the implementers, the cost, operations and maintenance requirements, and common areas of failure. Simultaneously it allows for technologies to be compared so that the most appropriate technology may be chosen. The guide is marketed towards a non-technical audience with the intention of promoting knowledge sharing and serving as a translation between the developers of the treatment technology and those who implement it in developing countries.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy