Environmental Assessments On Radioactive Material Discharged Into City Sewers

1. Environmental Assessments On Radioactive Material Discharged Into City Sewers 城市污水中放射性物质的污染评价 陈庆迁

2. Households Businesses Runoff Where does the radioactivity in sewer coming from naturally occurring radionuclides Radium-226 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 hospitals Iodine-131 university laboratories Carbon-14 pharmaceutical industry Tritium research facilities Americium-241

3. Most common radionuclides found in the sewage treatment work (STW)

4. Hospitals Research laboratories bypass STW Households Sewer System Sewage Treatment Works River Businesses Runoff Sludge Preliminary Treatment Landfill Sludge Landfill Primary Treatment Sequential batch reactor Incinerator Effluent Sludge Secondary Treatment Agr.land sea Tertiary Treatment River/sea Sewage Treatment Model - Conceptual model

5. Sewage Treatment Model - Conceptual model Surface run-off bypass STW overflow river Tertiary micro-straining etc Preliminary screening Primary sedimentation Secondary percolating/activated Public sewer system effluent sea clean waste Radionuclides partition ontosludge Landfill Effluent treatment Imported sludge Sludge treatment Sludge mixing Initial processing thickening non-radioactive Stabilisation digestion, composting radioactive De-watering drying De-watering drying Incineration multiple hearth or fluidized bed slurry air sludge cake/pellet ash landfill agricultural land

6. STW worker Waste generation irrigation landfill worker ingest general public external radiation Inhalation ingest STW worker Incineration effluent sludge / ash Radionuclide transport in the environment and human exposure pathways

7. 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. Sewer model interface

9. Some illustrative calculation Worker’s dose at recovery stage

10. Some illustrative calculation Public dose raised from effluent and sludge disposa

11. 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.