UASB or EGSB digesters use gas/liquid/solids (GLS) separators and overflow weirs in the digester top section to (a) separate biogas and biomass and (b) settle and return biomass to the digester sludge bed. Longterm operational experience has shown the following deficiencies:

• Clogging of gas hoods with fat/oil/grease
• Clogging of weir notches
• Poor leveling of overflow weirs and consequently uneven flow distribution
• Corrosion near the air/liquid interface
• Odour generation beneath the digester covers

To avoid these problems IB-MR developed a novel type of GLS separator with special emphasis on simple design with good hydraulic characteristic in order to achieve optimal retention of granular and floccullant sludge particles

The GLS separators are manufactured in a workshop as modular units - Figure 1 shows a module during the manufacturing process.

Special emphasis is given to the choice of materials for manufacturing of the GLS separator module to minimize maintenance problems and to ensure stable longterm operation.

IB-MR GLS separtors can be used in round aswell as rectangular tanks. They are suitable for new UASB plants and tanks adapted for use as UASB digesters.

As a result of longterm experience with UASB- and EGSB-digester AAT prefers design and implementation of UASB plants mainly because of their superior operational stability.