Choosing an appropriate sewage treatment system
The existing treatment infrastructures in Brownsea were old, costly and risky: the pollution risk to soils and potential aquifers by sewage was high. These structures were also impractical, needing to be emptied and cleaned regularly. Therefore, The National Trust decided to upgrade the treatment system.
- To centralise and export the waste to the mainland
- To centralise and use upgraded on-island sewage treatment works
- Implementing a flow splitting chamber, rotating biological contractor, second final settlement tank, new pipes, and composting bays
- Preventing the sewage treatment system from impacting the visitors
- Exporting composted waste and dried sludge off of the island
- By centralising and exporting to the mainland
- Pumping waste from outlying buildings to the central sewage treatment works.
- Adding composting bays, new pipes, a second final settlement tank, rotating biological contractor, and a splitting chamber to the existing structure.
- Transporting elements of the new system and the engines into the island
- The combined treatment system was completed in 2019.
- The sewage treatment system no longer impacts visitors, is more easily managed by staff and contractors, and is more automated with electronic alarm systems for on and off-island staff and contractors.
- The project has been working correctly since then, with discharge maintained below legal limits.
- End products of composted waste and dried sludge are currently exported off the island.
For more information, please refer to pgs. 23-26: