LEACHATE MANAGEMENT OF PORT HOPE LONG-TERM WASTE MANAGEMENT FACILITY (LTWMF)

摘要

This paper explains the implementation and commissioning results for the leachate treatment system at the Port Hope Long Term Waste Management Facility (LTWMF). It will also summarize system performance to date. Approximately 1.2 million cubic meters of historic low-level radioactive waste (LLRW) resulting from historic uranium and radium processing operations located in various locations throughout urban Port Hope will be stored in this facility. Transfer of impacted waste to the facility began in 2018. A combination of precipitation, clarification, reverse osmosis (RO), and evaporation were selected for removal of radionuclides from LTWMF leachate as the most effective treatment method to achieve optimal contaminant removal. A schematic of the process is shown in Figure 1. Project commissioning was conducted in two separate phases. The first phase covered the commissioning and optimization of primary treatment and the RO system. The second phase included the commissioning and optimization of the residuals management system which included evaporative and slurry drying technologies. In the first phase, a polymer assisted clarification unit was implemented prior to the media filtration / RO treatment for removal of the suspended solids. In the residuals management phase, an evaporative system was used to further concentrate the RO concentrate stream into a highly concentrated brine. A slurry drying system was then used to dry the resulting brine to a solid suitable for disposal at the waste management facility. The paper will delve into the challenges faced during both phases of the commissioning process and explain how the leachate treatment system was adapted to meet these challenges. Challenges addressed will include the concentrating effects of concentrate recirculation on the primary collection lagoon and management of residuals water content. Phase 1 commissioning results showed that the Chemical of Concerns (COCs) concentrations met the design objectives. For instance, an average removal efficiency of 99.3 and 94.96 percent for total Uranium and Radium-226 were obtained, respectively. By considering the current discharge limits for uranium and radium-226 which are 0.15 mg/l and 0.37 Bq/l, respectively, it is predicted that this treatment system could handle the leachate with concentration of uranium dilution factor of 2.6 was estimated using a dispersion model for large lake coastal situations, and by assuming a 14 meters down shore distance mixing zone, the effluent concentration of these two radionuclides will fall below CCME short-term discharge limit for protection of freshwater aquatic life.