Full Customer Question

Can you explain how BMS use parallel (lamellae) plates for sewage settlement?


Thanks for the question.  Parallel or Lamellae Plate Settlers have been used to settle solids in potable water treatment for many years.  The main criteria to achieve settlement is the upward flow velocity.  The is flow in m3 ÷ by the surface area of the settlement tank in m2.

To achieve good settlement you need to achieve an upward flow velocity of 0.9 m/h or better.

For example, for a flow of 10 m3/h you would need at least 11.1 m2 of surface area to achieve an upward flow velocity of 0.9 m/h.

Parallel/lamellae plates radically increase the surface area in a given area.  A unique feature of the BMS Blivet is the utilisation of lamella plate settlers in both the Primary Settlement and Final Settlement Zones.

BMS worked with Dr. Michael Rodgers from the National University of Ireland Galway to adapt parallel plates for use in sewage treatment when the Blivet was being developed. The lamellas, at 60° slope and 50 mm (Primary) and 25 mm (Final) spacing, allow the average upward flow velocity of 0.9 m/hr to be achieved in approximately 25% of the volume required for conventional settlement tanks. This is the main contributor to the overall compactness of the system.

A sewage treatment balance tank at a large hotel in Ireland.

Image showing parallel plates in a BMS Blivet Package Sewage Treatment Plant

You can see how the parallel plates work in the short 3D video below.

A bit about the company

BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world.  It is a third generation family business with huge expertise in wastewater and stormwater.
BMS also manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more.  Please see our enclosed Company & Product Profile for a full summary or View our full product/services catalogue at this link

BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations.  We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location.  Let us know when suits.

We would be delighted to discuss any requirements you might have, and we are available to meet you at your convenience.  Please do not hesitate to contact us.