Maintenance of public sanitation systems in Granollers, La Garriga and Congost

Granollers wastewater treatment plant:        
Total flow: 30,000 m3/day. The system collects residential water from Canovelles, part of Les Franqueses del Vallès, and Granollers, as well as local industrial facilities. The collector network in use has a total length of 22 km.
The operating scheme of the plant is as follows:
-  Water line: inlet pump, screening of fine particles, degritter-degreaser, primary decanting, bioreactor, secondary decanting (clarifiers).
-  Sludge line: primary sludge sieving, thickening (gravity) of primary sludge, thickening of biological sludge via centrifuges, anaerobic digester, sludge dewatering with centrifugal decanter.
-  Gas line: the biogas produced in the digesters is used to generate heat energy (maintenance of digesters) and electrical energy by means of co-generation units.

La Garriga wastewater treatment plant:
Total flow: 7,000 m3/day. It collects the wastewater from the city of La Garriga and part of l’Ametlla del Vallès. The purification process is biological. The water line consists of inlet pumping, screening of fine particles, degritter-degreaser, extended aeration reactor, and water outlet to the Congost River. Generated sludges are concentrated in a gravity thickener and are then dewatered with a centrifugal decanter.

El Congost wastewater treatment plant: 
Total flow: 1,150 m3/day. It collects wastes from the municipalities of Aiguafreda (Vallès Oriental) and Sant Martí de Centelles (Osona). The purification plant treats waste with a biological process. La water line consists of a pumping station, pretreatment, bioreactor, secondary decanting, and discharge into the Congost River. The sludge line begins with the secondary decanter purge and continues to the sludge silo, and uses mechanical dewatering through the use of a centrifugal decanter.