Bogotá River Environmental Restoration Project: Upgrade/Expansion of Salitre WWTP

Client: Empresa de Aqueducto y Alcantarillado de Bogotá
Location: Bogotá, Colombia

As part of an international consortium, Hazen and Sawyer is providing preliminary design, specifications, and construction bid documents for the upgrade and expansion of the Salitre Wastewater Treatment Plant in Bogotá, Colombia.

Project Outcomes and Benefits

  • Part of the Bogotá River Environmental Restoration Project, this work will reduce wastewater pollution and improve water quality in the middle basin of the Bogotá River.
  • Project will transform existing 4 m3/s primary plant into a much larger 7 m3/s secondary treatment plant, overcoming hydraulic profile constraints with innovative use of second headworks.
  • Methane gas produced in the digesters will be used as fuel to generate in-plant electricity in the new cogeneration works.

One of the first processes of the existing Salitre Wastewater Treatment plant is the aerated grit chambers. Each of these units is more than 120 feet long and 15 feet wide. The proposed expansion will include the addition of new aerated grit chambers prior to the secondary treatment works.

The Salitre Wastewater treatment plant currently has 8 primary clarifiers more than 150 feet in diameter. The proposed expansion includes the installation of 8 new primary clarifiers and 12 secondary clarifiers.

The digester gasholders at the Salitre plant serve as a pressurized storage volume for biogas produced in the digesters. Hazen and Sawyer’s design allows methane gas produced in the digesters to be used to generate in-plant electricity through the proposed cogeneration works.

Wastewater is discharged from the Salitre interceptor to this open channel which transports wastewater from the Salitre River, Torca, and Jaboque water sheds. This channel will be eliminated as part of the proposed design in an effort to reduce odors.

Hazen and Sawyer performed inspections of each of the existing structures and equipment on site. This facility is the electrical generation building for which Hazen and Sawyer recommended a series of upgrades which will improve the integrity of the facility without disrupting operations.

The Salitre Wastewater Treatment Plant, located in the north of Bogotá, has an average design flow of 4 m3/s and provides chemically-assisted primary treatment. The Bogotá Wastewater Master Plan calls for the upgrading and expansion of the Salitre Plant to a 7 m3/s secondary plant. The Salitre Wastewater Treatment Plant is currently the only plant in Bogota.

Commissioned in 2000, the Salitre plant is operated by the Empresa de Aqueducto y Alcantarillado de Bogotá (EAAB), which is wholly owned by the Bogotá District Government. In 2010, the World Bank and the Colombian government approved a loan to the Corporación Autónoma Regional de Cundinamarca (CAR) – the regional environmental authority – to help finance the Salitre project.

In 2009 the CAR contracted an international consulting firm, a consortium consisting of Hazen and Sawyer and Nippon Koei, to prepare a preliminary design for the upgrading and expansion of the Salitre plant. The consultants, working in close collaboration with both the CAR and the EAAB completed the preliminary design in early 2011. The preliminary design (approximately 30% of overall design effort) defines the basic treatment process, specifies design criteria and key equipment, and provides a general plant layout. The preliminary design serves as the technical basis for the contract bidding documents.

The average design flow is 7 m3/s with peak dry hourly flow of 14 m3/s, and a wet weather maximum flow of 26 m3/s. A key design consideration was how to incorporate the existing 4 m3/s primary plant into a much larger 7 m3/s secondary treatment plant, particularly taking into account hydraulic profile constraints. A unique design feature of the plant is the use of two head-works; the new head works will accommodate dry weather flows, while the existing head works will employed during wet weather conditions. All other aspects of the preliminary design utilize standard technologies and engineering approaches.

The activated sludge process will be utilized for biological treatment. The aeration basins will have an anoxic selector zone and aerobic zones with a total detention time of about 5 hours. A fine bubble diffuser system will provide high-efficiency oxygen transfer in the aerobic zones. Dissolved oxygen levels will be monitored in the aerobic zones to optimize performance and minimize electrical power consumption of the aeration blower system.

Thickened primary sludge and waste activated solids will be stabilized in mesophilic anaerobic digesters. The dewatered solids will be discharged into trucks and hauled by the Owner to disposal sites in accordance with approved environmental practices.

Methane gas produced in the digesters will be used as fuel to generate in-plant electricity in the new cogeneration works. New on-site gas storage spheres will be sized for 3 days operation in the event of an extended electrical power outage. Electrical generation capacity with high efficiency generators is 6,000 KW plus a standby unit.

Liquid hypochlorite receiving, dilution, storage and pumping works will be provided to feed chlorine solution to the new disinfection contact tanks. An effluent pump station will be installed at the discharge structure to lift final effluent when the Rio Bogota water levels are high.

Additional buildings will be provided to house the new control center, administrative, operational and maintenance functions and personnel facilities. The process control and information management system will be upgraded to include existing and new facilities.

For more information on this project, or to discuss a similar project in your area, contact

Fernando Chiriboga, Latin America Operations Manager, at fchiriboga@hazenandsawyer.com