TERTIARY TREATMENT

The Tertiary Treatment System aims to polish the quality of the secondary effluent, making it suitable for use in irrigation operations. It was designed to comply with Portuguese regulations - Annex XVI of Decree-Law 236/98 of 1 August and Portuguese Standard NP 4434-2005 on the Reuse of Treated Urban Wastewater for Irrigation.

CONSTITUTION OF THE SYSTEM:

SUBMERSIBLE PUMP: The submersible pump will allow the effluent to be pressurized, after the secondary treatment, to the filtration and disinfection system. It will be installed inside the aeration tank (biological reactor).

FILTRATION: Filtration aims to remove suspended matter from the water. Particles normally retained in the filters include natural organic matter (either colloidal or precipitated) and microorganisms. In order to maximise the retention of colloidal particles, a coagulant is added, ensuring a better clarification of the effluent to be filtered.

DESINFECTION: After filtration, the effluent is disinfected through the proportional dosage of sodium hypochlorite.

CONTACT RESERVE/STORAGE OF TREATED WATER: After disinfection it is necessary to ensure a minimum contact time (around 30 minutes) between the water and the disinfectant solution to guarantee its treatment. In addition to ensuring the contact time, this final tank also allows the storage of the treated water prior to its reuse.