Contracting authority: Empresa Municipal de Aguas de Sevilla (EMASESA) and Aguas del Huesna S.L.

This operation, maintenance and conservation service for the Mairena and El Viso del Alcor WWTP includes the operation, maintenance and conservation of a WWTP with a capacity for an average flow of 15,672 m³/day. It has a pre-treatment system with a coarse screen and clamshell bucket; roughing through coarse screens and sieves, subsequent desanding and degreasing before passing on to biological treatment with prolonged aeration, and finally clarification by decanting. The sludge is pumped for thickening by gravity. It passes to the dewatering zone by centrifugal action with a polymer as a coagulant. It has two water lines.