Monofilling water treatment residuals using geosynthetic clay liner barrier systems

Cost effective solutions for disposal of Water Treatment Plant Residual Solids (WTPRS) are currently being sought to ensure sustainable waste management practices. Monofills offer the potential for more cost effective bottom liner systems such as Geosynthetic Clay Liners (GCLs) as well as ease of source mixing and improved handling for landfill operators. Monofilling of alum residual solids requires characterization of the major components of the residual solids leachate (i.e., aluminium) as well as the compatibility analysis with the GCLs. The objective of this thesis was to examine the leachability and physical characteristics of WTPRS as well as the performance of GCLs as barrier systems for WTPRS monofills. Leachate extraction was performed on WTPRS from Lake Major Water Treatment Plant (Dartmouth, NS). It was found that aluminum and manganese were the chemicals with a concentration higher than that specified in the Canadian Drinking Water Guidelines. From the leachate extraction tests, aluminium and manganese specific residual concentrations in leachate are found to be lower than 100 mg/L. However, the chemical species, and concentrations leached will vary depending on the residual characteristics.; Two different GCLs, the NWL and CNSL, were analyzed for hydraulic conductivity, diffusion and sorption characteristics using solutions with similar concentrations to the leachate extracted from the WTPRS. Hydraulic conductivity testing provided a comparison between the NWL and CNSL with distilled water and with salt solutions at different concentrations (sodium chloride, aluminum sulfate and manganous sulfate) providing hydraulic conductivity values of k<5.0x10-11 m/s for the NWL and k<8.0x10-12 m/s for the CNSL.; Diffusion tests are compared with theoretical results obtained from modeling the tests using the software program POLLUTE. NWL consistently provides higher diffusion coefficients of at least half an order of magnitude more than the CNSL. This difference was attributed to the polypropylene coating in the carrier geotextile in the CNSL.; Generally for the described experimental conditions, both GCLs provided attenuation for aluminum and manganese with the potential to be viable options for liner systems materials in WTPRS monofills.