M.Tech. / This project aimed to develop the Potpaz ceramic water filter into an improved filter design optimally suited to South African rural conditions, to provide potable water rather than contaminated water to households. Communities that do not have access to in-house treated water often end up with a contaminated water supply, as the water to be consumed is usually sourced from communal water collection points and stored in containers. There is evidence that the water consumed at point-of-use in rural areas is not always of a potable quality due to possible contamination between collection and consumption. The existing Potpaz home water treatment device has been scientifically proven to return contaminated water to a potable state. A limited number have been imported to South Africa for use in a project that studied the effect of household point-of-use treatment on the health of the consumer. It was not at all certain whether the households would use these devices effectively because this filter was not part of their everyday water system. Part of investigating whether or not they would effectively use this filter was the inclusion of industrial design within the filter assessment section of a larger research project conducted in the Vhembe region to understand the requirements of the user. Industrial design concerns itself with the requirements of the user, as well as knowledge regarding product design, development and manufacturing. Households that took part in the point-of-use project used the Potpaz home water treatment device for more than two months and were approached to provide feedback regarding its use. From the feedback, it became evident that there were aspects of the Potpaz design that needed modification towards an improved water filter more suited for its intended use in rural households. An Action Researchinfluenced methodology and User Centred Design approach informed the collection of original data and feedback on areas of improvement. This, together with visits to local shops and community potters, provided sufficient background to understand the needs and preferences of the intended rural users regarding the use of the device. This informed the design process and increased the chances of developing a readily accepted, more suitable product to the intended users and the domestic environment in which they live. To achieve this, this project focused on the following aspects regarding Potpaz filters: placement, use and design aspects of usability and ergonomics. Development of the improved filter design culminated in rapid prototyping of a scale model and the fabrication of a full-size working model allowing for physical interface to evaluate the success of the design solution.

This research strived to examine the potential for carbon fibre to improve the strength characteristics of ceramic water filters (CWFs) to improve their length of use in the field while maintaining, or improving, existing flow and bacteria attenuation capabilities. Model-scale CWF discs were made exploring several configurations of carbon fibre reinforcement and were tested for flow through rates, E coli attenuation, and equi-biaxial flexural strength. It was determined that, while the particular carbon fibre configurations explored in this study did not increase the strength of the CWF discs, they did provide some benefit such as improving flow-through rates while minimally detracting from bacteria removal. This indicates that the reinforcement of CWFs has potential and further research should be conducted to determine an appropriate reinforcement configuration to improve both their strength characteristics. Given that CWFs are gaining more widespread use in many countries worldwide, extending their lifespan of use would have significant value.

Silver nanoparticles (Ag NPs) are frequently added as a disinfectant to ceramic filters used for household drinking water treatment. To provide suspension phase particle stability, Ag NPs can be synthesized using a number of different molecules to cap the metal core. The goal of this doctoral work was to advance the fundamental understanding of how stabilizing agents influence the attachment and detachment of Ag NPs from ceramic water filters. To achieve this goal, deposition experiments onto Al₂O₃ membranes and clay-based ceramic filters were performed using Ag NPs stabilized by three different agents: citrate, polyvinylpyrrolidone (PVP), and branched polyethylenimine (BPEI). Laboratory and field- scale filtration experiments were also conducted to evaluate the removal of Ag NPs from ceramics under different water conditions -- the presence of hardness and natural organic matter (NOM). Citrate-stabilized Ag NPs were found to have the highest attachment densities, regardless of filter material. Differing attachment densities for the three types of Ag NPs were extensively explained using a combination of classic Derjaguin, Landau, Verwey and Overbeek (DLVO) theory, steric forces, and particle-particle interaction energy calculations. A multilevel statistical model was built to describe the removal of Ag NPs from ceramic water filters under different water conditions. The type of Ag NP was found to affect the initial release of Ag from the filters, while the interaction of the type of Ag NP and water were found to affect the rate of removal. Hardness and NOM prolonged the release of Ag from ceramic water filters.

Diarrhoeal diseases are a global public health burden, killing 1.8 million people annually. Diarrhoea disproportionately affects children and those in poverty. Most diarrhoeal cases can be prevented through safe drinking water and basic hygiene and sanitation measures, with drinking water interventions having the most impact on reducing diarrhoeal disease. A metaevaluation of studies assessing a specific household water treatment method, the biosand water filter, was completed. Results from the meta-evaluation illustrated that biosand water filters improve drinking water quality and reduce diarrhoeal disease. However, short follow-up times and inconsistent measures are a concern. Furthermore, there is no generally accepted field method for determining biosand water filter effectiveness that is useable in low-resource communities. This study adds to understanding of biosand water filters.

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.