What is an Aerotor and how is it different from a normal RBC (Rotating Biological Contactor) and who came up with the idea?

Thank you for the question.  The BMS Aerotor is actually a next generation RBC, with all the advantages of traditional RBCs such as low maintenance costs and power requirements with none of the disadvantages such as one sided growth placing eccentric loads on the shaft, flow bypass in shock loading conditions and lack of aeration...

Seamus Butler, BMS Managing Director, is the inventor and original patent holder of the Aerotor, which is manufactured at BMS factory in Longford, Ireland and is in more than 38 countries worldwide.  The Aerotor is also the biological heart of the world’s most compact sewage treatment plant, the BMS Blivet.

Unlike old activated sludge and RBC systems the Aerotor is a hybrid of active aeration and fixed film reaction with an intense spiral GRP (Fibreglass) media mounted on a rotating horizontal shaft meaning that 97% of the Aerotor’s surface area is actually inside the rotor drum rather than only on the outside as is the case with traditional RBC systems. The rotational media is enclosed in an outer drum to provide active aeration, intense surface area and net hydraulic lift. The BMS Aerotor is self-cleansing and no extraneous pumping or sludge returns are required. 

When settled sewage liquor flows into an Aerotor unit, it is piped to the first chamber of the BMS Aerotor which contains a lift rotor. The liquor enters the rotor through 50 mm inlet ports on the peripheral face of the rotor. The rotor is rotating at 6 rpm and the internal spiral formation lifts the liquor and cascades it through the 100 mm sandwich sections, making contact with the surface biomass (fixed film reaction) while actively aerating the liquor. The liquor emerges from the lift rotor below the centre of the rotor on the opposite face to the peripheral 50 mm inlet ports and spills into a captive tray to be conveyed into the next rotor compartment. Here it enters a float rotor below the centre and the same process occurs as in the lift rotor. This continues until the final splitter box in the BMS Aerotor which divides the elevated flow between a 110 mm recirculation pipe and a pipe into the separated final settlement zone.  The BMS Aerotor is in essence a plug flow system, which ensures full treatment up to 3 x DWF and up to 6 x DWF for up to 2 hours. The rate of recirculation, which is under gravity due to the 450 mm lift occurring in the lift rotor, can be adjusted by hand stops in the splitter box.

This unique ability to recirculate under gravity means that the flow can be adjusted depending on process requirements and without the need for extra pumping.  In low flows recirculation can be set to high to maintain growth and/or maximise treatment.  Equally recirculation can be adjusted downwards during high flows.  This is especially useful on sites that experience seasonal flows such schools, hotels and caravan parks.  The recirculation can also be readjusted upwards to achieve intensive nitrification (the reduction of ammonia) and in the case of the Blivet denitrification (the reduction of Nitrate and Total Nitrogen) in the primary settlement area, which acts as an anoxic zone.

Overall the BMS Aerotor is a world leading package low power & low maintenance solution for package sewage treatment that can achieve multiple high quality effluent parameters such as BOD & Suspended Solids (SS) of less than 10 mg/l, Ammonia of less 5 mg/l, Phosphorus of less than 1 mg/l and Total Nitrogen of less than 10 mg/l.

Thank you for your question, if you any queries about the above answer or have questions on any areas of package waste water or surface water treatment please do not hesitate to contact BMS.