Construction design project for the sludge digester expansion at the Alcala-West Wastewater Treatment Plant. The digester is a 25 meter interior diameter cylindrical post-tensioned concrete structure. The perimeter wall is 0.35 meters thick and is supported by neoprene bearings. The cover is made of reinforced concrete which is inlaid in the walls. It is a spherical dome structure with a thickness of between 0.15 and 0.30 meters.
The height of the digester is 12.50 meters at the lowest point (on the perimeter) and 15.50 meters at the centre.
The structure is calculated to hold sludge to a maximum height, taking into account the generation of thermal gradients.