An analysis of performance criteria of porous ceramic water filter production methods
Scannell, Luke Weber
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The World Health Organization estimated in 2013 that 768 million people lack access to improved drinking water sources. Ceramic water filters have grown in popularity over the past several decades as a point-of-use treatment option to improve water quality. Water treatment reduces the health risks from disease from microbial pollution and potentially other causes. To improve filter design, a more thorough analysis is needed of the effects of the clay and organic materials used to make ceramic water filters. The research presented in this dissertation investigates the effect of four variables on ceramic water filter performance: type of organic matter, total percent volatile matter, air drying compared to oven drying at 105°C, and organic matter particle size. Ceramic water filters were made using the two most common material compositions, clay and sawdust, and clay and rice husks. The moisture content, volatile matter content, and ash content of each material was measured. Ceramic discs 7.6 cm in diameter were made and fired to test for flow rate, porosity, and microbial removal efficiency. Ceramic bars were tested for flexural and impact strength. Flow rate increased with increasing volatile matter, and therefore with porosity. The Carman-Kozeny equation was fitted to sawdust and rice husk flow rate data with an R 2 value of 0.414 and 0.970 respectively. Oven drying filters resulted in a 0.80 to 1.8 log decrease in bacterial removal. Filters produced with a mixture of 75% large (0.297–0.841 mm) and 25% small (<0.297 mm) organic particles demonstrated a 68% increase in flow rate without reduction in microbial removal compared to filters made with 100% large particles. Microbial removal efficiency decreased with increasing volatile matter content, porosity, and organic matter particle diameter. The flexural and impact strength of sawdust specimens decreased with increasing volatile matter content. Flexural strength of rice husk specimens decreased with increasing volatile matter. However, impact strength of rice husk specimens increased with increasing volatile matter. The model by Li and Aubertin (2003) was fitted to sawdust and rice husk flexural strength data with an R 2 value of 0.925 and 0.935, respectively. The results presented in this dissertation provide a range of flow rate and porosity values for sawdust and rice husk filters that can be used to predict the expected microbial removal efficiency. They compose a system of standard methods to test ceramic water filters that will allow for accurate comparison of filters made with different materials and methods.