Location:

Outeiro da Cabeça / Vilar
Cadaval

Occupied zone:

14 hectares of deposition area.

Origin of RSU:

Undifferentiated collection

Waste accepted/treated:

​All wastes from undifferentiated collection.
Treatment process: Controlled waste disposal.

Maximum processing capacity:

3.183.000 m3 total fitting

Date of operation:

January 2002

Landfill Cells

Landfill Cells

The Western Sanitary Landfill serves as the final destination for solid urban waste produced in the municipalities that make up the Multi-municipal System for the Treatment and Valorization of Solid Waste from the West.

The landfill consists of two differentiated cells of waste deposition, the first cell consisting of three distinct alveoli (Alveoli 1, 2 and 3) and the second cell by two (Alveoli 4 and 5).

Alveoli 1 and 2 of Cell 1 were temporarily closed in August 2004 (Phases A and B of the holding). ASO Cell 2 Alveol 4 entered into operation in August 2004, and its temporary closure was started at the end of October 2006 (Phase C). The Alveolus 5 started exploration in December 2006 and was closed in October 2009 (Phase D), and gradually the Aterro work front had already advanced to Alveolus 2 (Phase E) in June 2009. The Alveolus 3 did not start exploration.

The waterproofing system at the base of the landfill consists of, from the bottom up:

  • 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.

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

Biogas Drainage and Drainage

Biogas Drainage and Drainage

The drainage of the biogas produced in the landfill is carried out by means of vertical drains and leach boxes, built or increased in a successive and dynamic process from the beginning of the exploration of the ASO, in order to follow the growth of the MSW mass. The drains consist of a steel guide tube (only three meters high and that is being uploaded) and by HDPE pipe Ø 160mm, slotted at 360º. The space between the guide tube and the HDPE pipe is completely filled with rolled pebble. When reached the coverage quota of the waste mass is placed the "capture head" of biogas.

The leachate boxes, constructed of perforated concrete rings, are run during the landfill operation to allow frank drainage of the leachate produced within the waste mass and to convey it to the existing bottom drainage system. Although this is the main objective of their execution, they also work as biogas drains, so in some situations they are equipped with pickup heads for connection to the active drainage network.

The collection heads installed either in the biogas drains or in the leachate boxes have a sampling point for the characterization of the gaseous effluent and a control valve to control the flow of each well, both of which are located in the exit to the respective suction branch.

The outputs of the pickup heads are connected to suction lines in HDPE Ø 90mm which are connected directly to two perimetric collectors or aggregates in a control and monitoring station (ERM), connected to one of these collectors.

In cell 1 of the ASO, the biogas drainage network consists of 29 biogas drains and 11 leach boxes connected to 5 ERM's (Regulating and Measuring Stations).

In cell 2 of the ASO, the biogas drainage network consists of 35 biogas drains and 14 leachate boxes, joined by groups of wells to 6 ERM's. The ERM's are linked to the perimeter collectors.

The biogas transmission and energy recovery system consists of two perimeter collectors, in PEAD Ø 200 mm, located at the level of "slope foot", at the outer boundary of each MSW cell, sending the collected biogas to the plant. biogas energy recovery. Both collectors are equipped with sampling points and regulating valves.
The two perimeter collectors converge in a single pipe in PEAD Ø 315mm (mixing point), which then forwards the biogas to the motor generator group. In the mixing tubing, there is a condensate box to remove any substances that liquefy and are drawn by the gaseous stream.

The ASO biogas energy recovery center consists of a suction / compression and biogas burning unit of 750 m³ / h and a motor generator set of 1063 kW.

Leachate drainage and treatment system

Leachate drainage and treatment system

Leachate Drainage

The drainage of the leachate produced inside the cells of the landfill is effected through drains that lead them by gravity to the Treatment Plant of Leaching Water.
The drains consist of PEAD tubing with a diameter of 225 mm, grooved and installed in the middle of the draining layer at the bottom of the cell.
The Wastewater Treatment Plant receives leachate from the landfill, domestic wastewater and effluent from hydrocarbon separators installed, respectively, in the workshop and in the vehicle washing and ecoparque platform.
 

Leachate Treatment

The ETAL of the Western Sanitary Landfill consists of a combination of a biological treatment with a physico-chemical treatment, the treatment line of the installation consisting of:
  • 2 regularization/homogenization ponds;
  • Biological treatment by an aeration lagoon;
  • Tratamento físico-químico por coagulação-floculação com adição de policloreto de alumínio, hidróxido de sódio e de polielectrólito (fase líquida);
  • Primary decanting;
  • Secondary decanting with sludge recirculation to biological treatment;
  • Discharge of the pre-treated effluent to the emissary of Águas do Oeste.
The sludge produced (primary and / or primary) is conveyed. Sludge treatment unit consisting of a silo and dehydration system with addition of polyelectrolyte (dehydration treatment runoff returns to pond of biological treatment).