The treatment of municipal, industrial and agricultural wastewater produces a semi-liquid mixture known as sludge. The costs associated with pumping, transporting, treating, storing, and disposing of sludge are significant. Therefore, sludge dewatering techniques are employed to increase the solids content of the material by separating the solid and liquid components, thus reducing the overall volume requiring further handling. Non-mechanical dewatering methods require large areas of land and favorable climatic conditions, while mechanical dewatering technologies require significant capital investment and ongoing operation and maintenance by highly trained personnel. Due to these shortcomings, the conventional methods of sludge dewatering are not applicable to scenarios where: the quantity of sludge is small, there is limited budget, there are land restrictions, or dewatering is performed seasonally. An alternative approach that has recently attracted considerable attention is the use of dewatering fabrics; specially engineered textiles supplied in the form of very large bags into which the sludge is pumped. The concept itself is simple, pressure inside the bag pushes the free water through the fabric while the solid material is retained within. Unfortunately, these products have exhibited poor dewatering performance for certain feed materials. In this work, a series of ‘next-generation’ engineered dewatering fabrics featuring elongated ‘slit’ pores were produced using laser cutting techniques. A comprehensive analysis of the effect of the filter properties on dewatering performance was performed using sludge sourced from two different operations: municipal wastewater treatment and precious metal mining. / Thesis / Master of Applied Science (MASc) / In recent years, the use of engineered dewatering fabrics has emerged as a viable alternative to conventional methods of sludge dewatering in numerous application areas including municipal wastewater, mining, and pulp and paper. Previous studies have focused on the development of empirical ratios between dewatering performance and the porous properties of the textile material. The limitation of this approach is that the latter is difficult to characterize using currently available techniques due to the complex, nonuniform pore structure of conventional woven and nonwoven dewatering fabrics. In this study, a series of dewatering fabrics were produced using advanced microfabrication techniques featuring well-defined slit-pore geometries. Full-factorial design-of-experiment frameworks were employed to evaluate the effects of slit-pore dimensions and slit-pore spacing on cake layer development and key dewatering performance metrics. Laboratory scale dewatering performance tests were performed using both anaerobic digested sludge from the Woodward Avenue Wastewater Treatment Plant in Hamilton, Ontario and metal precipitate sludge from a nickel-copper mine in Ontario, Canada. The results from this study provide new insights into the importance of the cake layer in geotextile dewatering and the impact of pore geometry, porosity, and polymer performance on cake layer development.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23753 |
| Date | January 2018 |
| Creators | Westhaver, Kurt |
| Contributors | Latulippe, David, Chemical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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