Utebo WWTP (Zaragoza)

Water line

Inlet structure

The raw water is sent to the WWTP from the Casetas-Aliviadero and Utebo pumping stations through two pipelines with diameters of 600 and 800 mm respectively.

The inlet structure is equipped with a safety spillway to relieve excess flow or to send the water to the general plant bypass line if so required in the event of an emergency.


Subsequent to arriving at the plant, the water is sent to the three filtering channels, two of which are fitted with automatic fine screens. The third filtering channel functions as a bypass line and is equipped with a manual bar screen with a space between bars of 20 mm.

The filtering channels are fitted with motorised sluice gates enabling a certain number of channels to operate depending on the raw water flow.

A screw conveyor/compactor and a container with a capacity of 4 m3 are installed for waste collection and storage.

The filtering equipment, along with the grit washer and grease concentrator, is located in the pretreatment building, which is equipped with an odour control system.


At the outlet of the filtering channels, the water flows into the distribution channel to the degritters. The distribution channel is designed to provide a slow water flow to facilitate uniform distribution to the degritters.

A motorised weir gate is installed at one end of the distribution channel to prevent the accumulation of floating solids. When the gate is opened, the top layer of the water is extracted, along with the floating solids, which are sent to the grease concentrators.

The WWTP is fitted with 2 rectangular, spiral-flow degritters/ degreasers of 4.5 m in width (including a degreasing zone of 1.50 m), 22 m in length and a water surface height of 3.07 m at maximum flow.

The grit is extracted from the degritters by means of 2 (1 per degritter) vertical positive displacement pumps, each with a flow rate of 30 m3/h at 2.5 wcm, representing an extraction capacity of 30 l/m3 of sand at peak flow.

The screw-type grit washer has a capacity of 60 m3/h and is installed alongside one of the filtering channels near the degritters. A container with a capacity of 4 m3 is installed for storage purposes.

The water with grease and oils extracted from the degritters is sent by gravity to a grease concentrator. The concentrated grease is sent to a container with a capacity of 1 m3.

Air is supplied by means of 3 (2 + 1 standby) rotary lobe blowers with a unitary capacity of 695 m3/h at 4.2 wcm. These blowers are housed in soundproof cabinets and feature variable speed drives. The air is distributed within the degreasers by means of a grid of coarse bubble membrane diffusers arranged in a single line with 50 diffusers per degritter.

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Published in: FuturENVIRO #45 November 2017