Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Aral, Mustafa; Committee Member: Guan, Jiabao; Committee Member: Jang, Wonyong; Committee Member: Kim, Seong-Hee; Committee Member: Uzer, Turgay. Part of the SMARTech Electronic Thesis and Dissertation Collection.

M. Tech. Water Care. / Aims to evaluate promising technologies for local application in the removal of viruses and protozoan parasites and to provide guidelines for the selection and use of appropriate home water treatment systems that could be used in rural households.

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.

The monitoring of water distribution systems (WDSs) has been a very popular subject of study since the terrorist attacks of September 11, 2001, and the subsequent passing of laws motivating the study of WDS monitoring to provide system protection in the event of a terrorist attack. Inhibiting many WDS monitoring studies to date is the large amount of computational expense required to conduct meaningful studies, especially for larger WDSs that are of most interest. In this study, methods were developed to determine the "importance" of WDS nodes in being considered as locations for sensors used to monitor a WDS in order to make sensor placement optimization more efficient. Single-objective protection goals considered individually in optimization were maximizing detection likelihood, minimizing expected detection time, and minimizing expected contaminated demand volume. A multiobjective protection goal accounting for all three single-objective goals concurrently was also considered; the formulation of the multiobjective optimization problem was intended to minimize tradeoffs among individual protection goals. Sensor placement optimization was carried out with the Iterative Subset Search Method (ISSM) employing genetic algorithms developed in this work; ISSM used nodal importance rankings to search a small subset of nodes for the optimal solution initially then broadened the search incrementally until convergence to a best solution occurred. To demonstrate the effectiveness of the methods developed, sensor placement was performed according to each of the protection goals for three study systems--one small and two large--and a variety of attack conditions. Desirable sensor node solutions that provided for significant protection were found in all cases, and in many cases sensor placement results were comparable to or better than those of other works. Nodal importance narrowed the search for optimal sensor nodes to a relatively small proportion of WDS nodes in most cases.

Thesis (PhD.(Medical Virology)--Faculty of Health Sciences)-University of Pretoria, 2007. / Includes bibliographical references.

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.

Submitted in fulfillment of the requirements of the degree of Master of Engineering: Chemical Engineering, Durban University of Technology, Durban, South Africa, 2016. / River water is a life supporting watercourse to most communities in rural areas. It is used for both human and animal consumption, and is well becoming a collection channel for defecation and urination due to shortage or lack of access to running water and sanitation facilities. This has resulted to the contamination of water sources, which poses a great risk to human health. This has motivated researchers to study simple but yet robust systems to produce safe drinking water. Photocatalysis is one of such emerging disinfection technologies. Titanium dioxide (TiO2) which is one of the basic materials used for paint manufacturing has emerged as an excellent photocatalyst material for water purification. TiO2 was selected in this study because it is locally available with a potential to open a new market in water purification for the manufacturers. The setback in previous studies is the recovery of nano-scaled TiO2 (nTiO2) after purification when used as a suspension in treated water. Thus this study evaluates the performance of four grades of micro-scaled TiO2 (mTiO2) on the degradation of organic matters, Escherichia coli (E. coli) and total coliform in river water and to investigate the percentage recovery of the mTiO2 using a locally manufactured Polyester Woven Fabric Microfiltration (PWFMF) membrane. The PWFMF though uncharacterized has been used in a number of studies for treating domestic and industrial waste waters. The best-performing grade was used to optimize the degradation efficiency of E. coli in river water using the Design of Experiments (DOE) methodology. Grade 2 of the mTiO2, which is hydrated titanium dioxide with additions (ahTiO2) of particle size range of 0.2 – 53 µm at a concentration of 2.5 g/l displayed an advantageous photocatalytic activity. The results show that 80 % of the organics were removed in 3 hours and increased to 93% after 6 hours. Two particle size ranges of 0.2 – 53 µm and 54 – 75 µm at a concentration of 5 g/l degraded organic matters to 90 % and 77 % in 3 hours respectively. The particle size range of 0.2 – 53 µm at a concentration of 5 g/l was then filtered using a PWFMF and turbidities went below 1 NTU after 20 minutes from feed turbidity of 470 NTU for all three trials. The average percentage recovery in 2 hours was 98.91 %. The four grades of mTiO2 were analyzed for E. coli and total coliform for 4 hours at concentrations of 2, 5 and 7 g/l. Grade 2 achieved the E. coli specification of 0 count/ 100 mL at 5 g/l in 2 hours and at 7 g/l in 0.5 hours. Grade 4 E. coli specification was achieved with 7g/l in 4 hours. Grades 2 and 4 performed better since they both achieved the E. coli and total coliform specifications. Grade 2 was the best performing grade and was considered for statistical studies. Grade 2 was then used on a comparative study between the Central Composite Design (CCD) and Box-Behnken Design (BBD), which are two of the major Response Surface Methodologies (RSM). The CCD compared to BBD provides high quality predictions over the entire design space. The CCD obtained optimum results for concentration of mTiO2 (X1), temperature (X2), initial pH (X3) and aeration (X4) which were 6.94 g/l, 28.75 OC, pH = 6.04, and 13.35 L/min for the maximum degradation efficiency of 99.85 % which showed comparable optimum results to the BBD that were 6.45 g/l, 28.28 OC, pH = 6.02 and 12.21 L/min for the maximum degradation efficiency of 99.80%. These theoretical model results were validated by practical experiments that produced the maximum degradation efficiency for CCD and BBD of 99.67 and 99.26 % respectively. Grade 2 of the mTiO2 can be used as a photocatalyst for river water purification due to its strong ability for the removal of E. coli. The additions used in grades 2 and 4 during production improved the photocatalytic activity. The PWFMF membrane showed a great performance of above 98 % particle recovery of mTiO2 from treated water, although there was an indication that the smallest particles were passing through the membrane. The RSM results gave approximately the same optimum results that were well within the limits, which were experimentally validated and showed that the models were sustainable. It is recommended that the effect of additions be studied on the structures or the charge stability of the two grades. / M

Access to safe drinking water is an important health factor in many developing countries. Studies have shown that unsafe drinking water and poor sanitation practices leads to diarrheal disease, which is one of the leading causes of death of children under five in developing countries. Provision and proper use of household water filters have been shown to effectively improve health. This thesis is focused on the refinement and validation of algorithms for data collected from pressure transducer sensors that are used in household water filters (the Vestergaard Frandsen LifeStraw Family 2.0) deployed in Rwanda by the social enterprise DelAgua Health. Statistical and signal processing techniques were used to detect the use of the LifeStraw water filters and to estimate the amount of water filtered at the time of usage. An algorithm developed by Dr. Carson Wick at Georgia Institute of Technology was the baseline for the analysis of the data. The algorithm was then refined based on data collected in the SweetLab at Portland State University, which was then applied to field data. Laboratory results indicated that the mean error of the improved algorithm is 11.5% as compared with the baseline algorithm mean error of 39%. The validation of the algorithm with field data yielded a mean error of 5%. Errors may be attributed to real-world behavior of the water filter, electronic noise, ambient temperature, and variations in the approximation made to the field data. This work also presents some consideration of the algorithm applied to soft-sided water backpacks.

Submitted in fulfillment of the academic requirement for the degree Master of Engineering in Chemical Engineering, Department of Chemical Engineering, Faculty of Engineering and the Built Environment, Durban University of Technology, Durban, South Africa, 2017. / Provision of microbiologically safe drinking water for people living in the rural areas of developing countries remains a major challenge to date. One of the reasons is due to the inability to access potable water mainly because of poor existing water purification systems. Current measures have been put in place to address the challenges of rural water supply. Development of appropriate technologies such as decentralized water treatment supply in the form of point of use (POU) systems are been considered. In lieu of the above, an appropriate POU system known as the Remote Rural Water Treatment System (RRWTS) was developed at Durban University of Technology (DUT). The RRWTS is polyester based locally sourced Woven Fabric Microfiltration (WFMF) membrane system. The unit is made up of flat sheet modules that are assembled into a pack. It is a robust gravity driven system with the ability to remove suspended solids and colloids in the form of turbidity. The system has high flux of 35 ± 7 LMH and turbidity below 1 NTU, it has the ability to remove pathogens well above 95%. However, this does not comply with WHO and SANS drinking water standards of zero E. coli count/100 ml of treated water. In order to bring the water treated by RRWTS to a satisfactory level for drinking, it is then necessary to add a separate disinfection step like chlorination step to further remove the remaining microbial contaminants. Thus the main objective of the study was to evaluate the disinfection efficacy of two disinfectants namely waterguard and bromochlor tablet disinfectants and investigate their integration with the WFMF membrane. The study was categorised into three parts. The first part is the addition of disinfectants to unfiltered river water sources for the determination of residual chlorine and the most optimum dose that will yield effective disinfection and also evaluate the extent of E. coli removal by the disinfectants. The second stage was the filtration of four river water sources using the woven fibre membrane (WFM) to determine the efficiency of WFMF. Finally the effect of disinfection kinetics on disinfection was achieved by agitating the water after disinfection and allowing it to stand at different contact times. Performance of the RRWTS was determined by the amount of E. coli and turbidity removed during filtration using WFMF and by chemical disinfectants after filtration. The results on residual chlorine for different water sources showed that feed quality and disinfectant dose determines the quantity of residual chlorine on all the water sources. The effectiveness of chemical disinfectants in E. coli removal is affected by the quality of water to be disinfected. The study showed that turbidity plays a major role on disinfection by increasing chlorine demand on water sources with high turbidity levels. The WFMF demonstrated excellent filtration performance by producing permeates with turbidity less than 1 NTU for feed turbidities ranging from 10 to 200 NTU. The E. coli removal efficiency by WFMF was very high on all the water sources treated. There was 95-99.8% E. coli removal on raw feeds with influent E. coli ranging between 500 and 44500 CFU/100 ml. It was seen that major benefits are derived from integrating the WFMF (RRWTS) with chemical disinfection. The benefits includes; better disinfection that meets drinking water set guidelines of zero E. coli and improved quality of water. The need for disinfection kinetics in order to obtain superior disinfection was eliminated. The possibility of disinfection-by-product formation was reduced as smaller quantities of chemical disinfectants were required for complete disinfection on the filtered water. / M

M.Sc. / The world is focusing on increasing the number of people who have access to safe drinking water due to the ascending numbers of drinking water related illnesses reported annually in rural areas where water is not treated before consumption. To meet this goal, household water treatment has to be introduced especially in places where homes are wide apart making centralised water treatment improbable. Most readily available household water treatment systems (HWTS) such as membrane filters may not be affordable in rural areas due to power requirements and degree of ability to use and maintain them. This study was therefore aimed at designing and constructing HWTS using readily available material such as sand, gravel, zeolites and clays. Five HWTS were designed, built, evaluated and compared based on their ability to remove chemical contaminants such as iron, arsenic and fluorides from drinking water. The types of filters that were used during this study are the biosand filter (BSF), a modified biosand filter with zeolites (BSFZ), a silver impregnated porous pot (SIPP) filter, a ceramic candle filter (CCF) and a bucket filter (BF). Effectiveness of the filters in reducing physical parameters such as turbidity and visual colour was also assessed. The water treatment devices had the following flow rates; 1.74 L/h – 19.20 L/h (BSFZ), 0.81 L/h – 6.84 L/h (BSF), 0.05 L/h – 2.49 L/h (SIPP) and 1.00 L/h – 4.00 L/h (CCF). The flow rates were high at the early stages of filter use and decreased with increase in the volume of water filtered through. The flow rates of the filters were affected by the turbidity of intake water which was between 1.74 NTU – 42.93 NTU and correlated to chlorophyll a concentrations. The household water treatment technologies reduced turbidity to levels less than 1 NTU (> 90% reduction) in the following order SIPP > BSFZ > BSF > CCF > BF. The filters achieved greater than 60% retention of calcium, magnesium, iron and arsenic. These contaminants with the exception of arsenic were reduced to acceptable levels of the South African National Standard of drinking water (SANS 241, 2004). Compared to the other filters, the BSFZ performed better in removing nitrates, phosphates and fluorides although the overall retention efficiency was low. Total organic carbon was removed greatly by the CCF (39%) and the least removal was by the BF. The overall performance of the filters in reducing contaminants from drinking water was in the order BSFZ > BSF > SIPP > CCF > BF. Filter washing vi resulted in an overall increase in the flow rates of the filters but negatively affected turbidity reduction. The filters still removed contaminants after total cumulative volumes of 1200 L (BSFZ, BSF, CCF and BF) and 300 L (SIPP) were filtered through the devices. The five evaluated filters have several advantages to the readily available technologies and the advantages include ease of construction, operation and maintenance. The filters are gravity driven and work independent of temperature. These HWTS incorporate safe storages fitted with spigots to eliminate recontamination of water when it is drawn for use. The filters can produce enough drinking and cooking water for a family of six members due to their high flow rates. The BSFZ, BSF, SIPP, CCF and BF may therefore be considered for treating contaminated water at household scale in places where water is taken directly from the source without treatment.