1. Centre for Radiation, Chemical and Environmental Hazards Radiation Protection Division formerly the National Radiological Protection Board Environmental Assessments On Radioactive Material Discharged Into City Sewers 陈庆迁 城市污水中放射性物质的污染评价

2. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Where does the radioactivity in sewer coming from Households Businesses Runoff hospitals university laboratories pharmaceutical industry Carbon-14 Tritium Iodine-131 research facilities naturally occurring radionuclides Radium-226 Americium-241 liquid radioactive wastes from these non-nuclear establishments to the public sewer systems are permitted in the UK under authorisations issued by the Environment Agency (England and Wales) or the Scottish Environmental Protection Agency under the provisions of Radioactive Substances Act 1993

3. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Most common radionuclides found in the sewage treatment work (STW)

4. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Sewage Treatment Model - Conceptual model Households Hospitals Research laboratories Businesses Runoff Preliminary Treatment Primary Treatment Secondary Treatment Sludge Landfill Tertiary Treatment Sequential batch reactor Incinerator Landfill Agr.land River/sea Effluent sea bypass STW Sewer System Sewage Treatment Works River

5. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Sewage Treatment Model - Conceptual model Preliminary screening De-watering drying Initial processing thickening Sludge mixing Primary sedimentation Secondary percolating/activ ated Tertiary micro- straining etc Incineration multiple hearth or fluidized bed Stabilisation digestion, composting air Public sewer system bypass STW landfill agricultural land Surface run-off De-watering drying Imported sludge Radionuclides partition onto sludge cake/pellet sea Landfill slurry ash clean waste effluent river Effluent treatment Sludge treatment sludge overflow non-radioactive radioactive

6. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Radionuclide transport in the environment and human exposure pathways

7. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Sewer model and other model involved Sewer treatment work (STW) model River model Farmland model Plume transport model (incineration) Marine model Landfill model (including geosphere transport model) Sludge spread model (arable land and pasture)

8. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Sewer model interface

9. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Some illustrative calculation Worker’s dose at recovery stage

10. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Some illustrative calculation Public dose raised from effluent and sludge disposa

11. © HPA Centre for Radiation, Chemical and Environmental Hazards - Radiation Protection Division. Formerly the National Radiological Protection Board Summary A model has been developed to assess doses arising from authorised disposals of radionuclides to sewers. Dose to workers and member of the public can be calculated, it can be used for normal assessment and assessment at emergency situation. Work shows that the dose are well below the maximum public dose constraint of 300 mSv y -1 for a single practice.