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In Santiago de Chile, our wastewater treatment plants generate power using biogas

Aguas Andinas, the largest sewerage and drinking water operator in Chile, mandated SUEZ to construct the largest wastewater plant in Latin America to treat the urban water supply to 50% of the population of Santiago (i.e. 3.7 million people), with a capacity of 8.8 m³/s. On this basis, the wastewater produced by greater Santiago was treated at two main plants towards the end of the year 2000: El Trebal and La Farfana. In 2011, SUEZ contributed to the renovation of the existing El Trebal plant and the construction of the new Mapocho plant.
The mission

Remove sediment and biofilm without causing damage to the pipe network

In addition to constructing La Farfana in record time, renovating El Trebal and completing Mapocho, under its contract to treat and manage water supplies in the Santiago region (Region Metropolitana), SUEZ is in charge of Operating and Maintaining these three Wastewater treatment plants (PTARs) thanks to its past experience with water treatment facilities.

 

SUEZ completes a series of improvements, such as using 100% of the biogas generated by extending the Mapocho-Trebal treatment plant, and optimising current processes to double the El Mapocho-Trebal plant's capacity to treat urban effluents from 380,000 m³/day (equivalent to 2 million inhabitants) to a peak future capacity of 760,000 m³/day (equivalent to 4 million inhabitants).

 

This assignment also includes designing and constructing a treatment plant in order to eliminate nitrogen from the digested sludge drying residues from La Farfana and Mapocho-Trebal, and modernising equipment to take full advantage of the energy generated by the facility from sludge digestion, heat recovery and power generation, as per the targets set by Aguas Andinas. We also aim to use 100% of the biogas produced for either power or heat.

Our solution

We operate, maintain and improve the wastewater treatment plants in Greater Santiago

We are responsible for continuously operating and maintaining the Mapocho-Trebal and La Farfana plants for the operator, Aguas Andinas, and optimising existing processes at all times over the 10-year period of the contract.

In addition, we manage selected nitrogen treatment processes for digested sludge residues from the La Farfana and Mapocho-Trebal wastewater treatment plants. This involves a deammonification process using the Anammox method of anaerobic oxidation of ammonium with nitrites. This process offers an alternative, low-cost and environmentally-friendly solution compared with traditional nitrogen removal techniques using nitrification and denitrification.

 

This biological process is broken down into two phases:

  • Initial aerobic phase: partial nitritation of ammonium (NH4+) present in the backflow from the digested sludge dehydration process, with Ammonium Oxidizing Bacteria (AOB)
  • Second anaerobic phase: The nitrites (NO2-) produced react with the remaining ammonium and produce nitrogen gas (N2). Bacteria responsible for this transformation are referred to by their generic name “anammox” (abbreviation of anaerobic ammonium oxidation).

 

Unlike conventional deammonification methods, this process does not require the addition of biodegradable carbon. Available carbon increases biogas production capacity.

Mapocho-Trebal

In addition, the extension to the Mapocho-Trebal cogeneration plant includes two cogeneration units and facilities, and/or the services required to run the equipment to be fitted at the plant. The new facilities will include the following units:

  • A generator installed in the current generator room
  • A generator installed in a container, outside of the current generator room
  • A NOx reduction system (selective catalytic reduction system)
  • A heat recovery system (steam and hot water)
  • Two power transformers (23/0.4 kV) installed in the current generator room.
The results

SUEZ uses the principles of the circular economy by providing the Santiago region with a treatment system able to function as a biofactory, or independent energy plants, establishing benchmark technological performance levels at an international level, guaranteeing quality of service and providing a sustainable water supply to Santiago.

The main benefits:

  • Optimised plant O&M costs
  • Compliance with the applicable standards
  • No excess nitrogen
  • Excellent nitrogen elimination performance, at the usual temperatures for residues (about 30°C)
  • Low chemical usage for nitrogen elimination
  • Current biological treatments unaffected by the nitrogen treatment process + low energy consumption
  • Renewable energy source providing high added value at a reduced cost.
  • Energy independence and guarantees ensuring a stable supply when faced with future variations in energy prices
100
%
biogas use
80
%
ammoniacal nitrogen elimination
0
non-renewable power use
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#SUEZ4CLIMATE / Part 1/ La Farfana

Credit: SUEZ group

[Video] La Farfana biofactory

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