Open procedure, pursuant to art. 60 and 114 of Legislative Decree 50/2016 as well as derogated from the provisions of Decree-Law No. 77 of 2021, converted, with amendments, by Law No. 108 of 2021, and by Decree-Law No. 13 of 24 February 2023, for the assignment of the works of "Adaptation of the sewage treatment scheme No. 11-12 Castelsardo-Lu Bagnu" ID 2006-1058 – with the criterion of the most economically advantageous offer on the basis of the best quality/price ratio.

Intervention financed with:

• Three-year Operational Programme 2004-2006, year 2006 (€ 12,200,00.00);

• Decree no. 262 of 08/08/2023 of the Ministry of the Environment and Energy Security (PNRR) - Code: PNRR-M2C4-I4.4_DEP440000291 (€ 12,300,00.00).

CIG A01FD858D5. CUP E32G10000300006. ID 2006-1058. PNRR code PNRR-M2C4-I4.4_DEP440000291.

The project involves the construction of a new centralized plant and related wastewater collection systems serving the agglomerations of Castelsardo and Lu Bagnu. The intervention is aimed at adapting both the agglomerations of Castelsardo and Lu Bagnu to Directive 91/271/EEC and Legislative Decree 152/2006.

The purification plant envisaged in the project, designed to treat wastewater from the town of Castelsardo and the hamlet of Lu Bagnu and minor hamlets, is a membrane plant (MBR) with a sewage line consisting of:

• Rotating drum grilling;

• Sand and oil removal on 2 circular mechanized sand removal units of the Pista type;

• Accumulation tank for the surplus of rain;

• Lifting and distribution to the biological line

• Denitrification compartment consisting of 4 basins;

• Oxidation compartment consisting of 4 basins;

• MBR compartment consisting of 4 basins;

• Filtered water storage basin;

• Final disinfection with peracetic acid;

• Lifting for unloading at the Riu Frigianu.

The sludge treatment will be carried out through the following phases:

• Aerobic stabilization basin for sludge extracted from membrane sections;

• Mechanical dewatering with centrifuge.

With regard to the collection system serving Castelsardo and Lu Bagnu, the installation of about 6 km of sewage collectors (partly gravity and partly pressurized, with diameters between DN 355 mm and DN 630 mm) and the construction of 3 lifting stations, as well as the laying of a 1.6 km long discharge pipe for the disposal of purified wastewater in the body surface water called Rio Frigianu.

The planned interventions include the following preliminary works:

• Reclamation of war ordnance (service), preparatory to the execution of the works;

• Removal of existing flooring;

• Excavation, clinging, movement of materials, backfilling and restoration;

• Laying of sewer pipes and connection to the existing network upstream and to the treatment plant downstream and with the lifting stations;

• Construction of the purifier and lifting stations, construction part: reinforced concrete works, masonry, floors, plasters and paintings, roofing, waterproofing, fixtures;

• Construction of the products of the purifier and lifting stations, plant engineering part: electrical systems and electromechanical equipment, monitoring and remote control;

• Construction of manholes along the line and drainage and venting (where provided), installation of operating devices and special pieces;

• Construction of sub-riverbed crossings of riverbeds and ditches;

• Transport and disposal of all waste materials from processing;

Green works.

Main Category: OS22 (Drinking water and purification plants) classification VII - Separable Category: OG6 (Aqueducts, gas pipelines, oil pipelines, irrigation and evacuation works) classification V - Reclamation of war ordnance (Registration in the Register of Ministerial Decree 82/2015, category B-TER classification I).