Location:
Mato da Cruz
2615-623 Calhandriz - Vila Franca de Xira

Occupied zone:
Valorsul UK cells 1 and 2 (on hold): area - 13.8 ha
Future Cell 3 of RU Valorsul: area - 1.45 h
VFXira RU cell (sealed): area - 8.0 ha
Cells 1 and 2 of Inertial Ash (on farm): area - 4.5 ha
Platform for treatment and recovery of slag - 2,8 ha
Total land - 42 ha

Origin of inert ash and slag:
Urban Solid Waste Treatment Plant
Waste oils / treaties:
All wastes from undifferentiated collection.

Treatment process:
Controlled Waste Disposal.

Maximum processing capacity:
Valorsul UK cells 1 and 2: capacity - 3,213,000 m3
Future Cell 3 of RU Valorsul: capacity - 249,300 m3

Date of entry into operation:
July 1998

Landfill Cells

Solid Waste Disposal Cell

Waterproofing system: The bottom waterproofing of the MSW deposition zone has the objective of avoiding the possibility of any contamination, either of the surrounding soils or of aquifers existing in its vicinity.

So, from the bottom up, there is:

  • layer of compacted soils at a thickness of 0.5 m;
  • bentonite geocomposite
  • PEAD geomembrane with a thickness of 2 mm;
  • geotextile with geomembrane protection function;
  • drainage layer (rolled pebbles) with a thickness of 0.5 m;
  • geotextile with filter function.


Inertia ash deposition cell

Waterproofing system: Inert ash, although free of danger, is deposited in a double sealing cell, which is characteristic of landfills for hazardous waste, in order to prevent any possibility of contamination of the surrounding soils or of aquifers existing in their vicinity.

So, from the bottom up, there is:

  • layer of compacted soils at a thickness of 0.5 m;
  • bentonite microplate (composed of 300 g / m2 PP geotextile and 350 g / m2 PEAD support, including a bentonite layer of 4700 g / m2), with a thickness of 7 mm
  • PEAD geomembrane with a thickness of 2 mm;
  • sand layer 0.1 m thick, with sensors to detect leaks in the first depositions;
  • PEAD geomembrane with a thickness of 2 mm;
  • geotextile with geomembrane protection function;
  • drainage layer (rolled pebbles) with a thickness of 0.5 m;
  • geotextile with filter function.

In the slopes of both cells, the geotextile and the draining layer are replaced by a "Secudrain" type geomembrane.

Biogas drainage and flaring system

Biogas drainage and flaring system

The drainage of the gases produced in the landfill is carried out through PEAD drilled vertical pipes with a diameter of 160 mm, inserted in the waste mass from the base of the cell, which are executed gradually during the operation, using mobile steel heads . The surrounding spaces of these tubes are filled with geogrid protected, coarse grained granite, up to the sealing layers. With the sealing of the respective zone, the movable head of the well will be replaced by a definitive head.

The biogas collection, drainage and energy recovery system consists of three independent networks, one in each RSU cell, and two motor generators, to which the networks are connected.
In the already sealed MSW cell (cell corresponding to the old landfill operated by the Vila Franca de Xira Municipality), the biogas drainage network is composed of 36 wells, attached to a central collector, which in turn is connected to the energy recovery unit. The network is in PEAD, the central manifold having a diameter of 125 mm and the connecting pipes between the wells and the central manifold having a diameter of 90 mm. All pipelines have a sampling point for characterization of the gaseous effluent and a control valve for flow control of each well.

In cell 1 Valorsul (already closed), the biogas drainage network consists of 35 wells, joined by groups of wells to 5 ERMs (Regulating and Measuring Stations). These MREs are connected to a central collector, which, in turn, is connected to the energy recovery unit. Also this network is in HDPE and is also endowed with sampling points and regulating valves.

In cell 2 Valorsul (in operation), the biogas drainage network is composed of 14 wells, joined by groups of wells to 3 ERMs. These MREs are connected to a central collector, which, in turn, is connected to the energy recovery unit. Also this network is in PEAD and is also endowed with sampling points and regulating valves.
The energy recovery system, where the three drainage and drainage networks are connected, consists of 2 suction units of 500 m³ / h each and 2 groups of motor generators of 834 kW each.

Leachate drainage and treatment system

Leachate drainage and treatment system

Drainage of the leachate produced within the cells of the landfill is carried out through spiked netting of drains that lead them by gravity to a visiting box outside the cell and from there to a pumping well, from which they are sent to the Treatment of leachate.

Each drain consists of a 225-gauge PEAD pipe, grooved and installed in the middle of the draining layer at the bottom of the cell.
The treatment system of the Mato da Cruz Landfill (ASMC) Landfill Treatment Station is a combination of a biological treatment with a physico-chemical treatment, and the treatment plant line consists of:

  • measurement of incoming flows to the entry site;
  • addition of phosphoric and antifoam acids to the entry site, upstream of biological treatment;
  • biological treatment by two aeration ponds;
  • physico-chemical treatment by coagulation-flocculation with addition of polyvinyl chloride and polyelectrolyte (liquid phase);
  • neutralization of the effluent with sodium hydroxide;
  • decantation with sludge recirculation to the biological treatment;
  • discharge of the pre-treated effluent to the emissary.
The leachates from the RSU cells (Vila Franca de Xira cell and Valorsul cells 1 and 2), the Inertial Grain cells and the Treatment and Valorisation of Slag Installation are pumped to the ETL. In the final section of the respective lifting lines, electromagnetic flow meters are installed.

The leachates flow into the entry site, where phosphoric acid is added to ensure the phosphorus concentrations necessary for the proper functioning of the biological and antifoam treatment to avoid the formation of foams during treatment. Then, the flow rates are evenly distributed to feed the two aeration ponds.

In ponds, microorganisms degrade the organic matter present in the leachates, with the help of oxygen supplied by floating turbines (two in each lagoon).

After this phase, the effluent from the biological treatment is sent to the physical-chemical treatment. In this, coagulation-flocculation is carried out, in which aluminum polychloride (coagulant) and a polyelectrolyte (flocculant) are added. These reagents will allow them to form flakes of sufficient size and weight to be able to decant in the decanter. Also during this step sodium hydroxide is added to neutralize the effluent.

After this treatment, the effluent follows to a decanter, in which the flakes are separated by gravity, forming the sludge in the bottom.

The pretreated effluent exiting the decanter is discharged to the municipal collector.

The sludge from the decanter is recirculated to the two aeration ponds in order to promote biomass growth within the lagoons.