Projects

Canoas Wastewater Treatment Plant Secondary Treatment Design

Bogotá
COLOMBIA
Canoas Wastewater Treatment Plant

Greeley and Hansen, A TYLin Company, provided the design of the secondary treatment and disinfection for the 370 MGD Canoas Wastewater Treatment Plant for the City of Bogotá, Colombia.

With a population of about nine million, Bogotá is among the largest cities in the Americas. The Canoas Wastewater Treatment Plant (WWTP) will have an average flow capacity of 370 MGD and serve approximately two-thirds of the wastewater generated in the City. The remaining wastewater is treated at the existing El Salitre WWTP, currently being expanded and upgraded to secondary treatment. 

The Water and Wastewater Utility of Bogota (Empresa de Acueducto y Alcantarillado de Bogota, EAAB), along with other governmental entities in Bogotá, are responsible for the implementation of the Bogotá River Cleaning Program. This program is the result of a government mandate to accelerate the cleaning of the Bogotá River, which runs through the city from north to south and has been heavily contaminated over the years due to direct wastewater discharges. The major components of the program include upgrading and expanding the existing El Salitre WWTP on the north of the city, a series of interceptors including a major interceptor tunnel along the bank of the river which will convey the wastewater to the south end of the city, an 830 MGD pump station to be located at the end of the interceptor tunnel, and the 370 MGD Canoas WWTP that will treat the pumped wastewater. 

The Canoas WWTP Secondary Treatment Design project brought an existing design developed for primary treatment to the design of full secondary treatment and disinfection facilities. The secondary treatment facilities designed include an activated sludge system, secondary clarification, and chlorine disinfection. The aeration tanks will be a three-pass configuration with step feed feature for wet weather management. Although there are currently no nutrient removal requirements, the aeration tanks will be implemented with selector zones for improving settleability. Full floor coverage of membrane disc diffusers with tapered placement will be implemented, and submerged large blade mixers on selector zones to operate when used as anoxic zones. The aeration facilities for the secondary treatment are expected to include two Blower Buildings to be able to supply a total air flow of approximately 285,000 scfm. Dual core high efficiency gearless turbo blowers were specified for these facilities. 

In harmony with the secondary treatment design, the existing solids train design had to be upgraded and expanded to process the waste activated sludge (WAS) in addition to the primary sludge that had been considered before. The existing primary treatment design had contemplated a solids train headlined by circular gravity thickeners for primary sludge, followed by pre-dewatering centrifuges before carrying over to a Thermal Hydrolysis Process, anaerobic digestion and biosolids dewatering by means of belt-filter presses. Finally, the existing design planned for biogas utilization through a Combined Heat and Power facility. The secondary treatment design developed by Greeley and Hansen included the update and review of the primary sludge load, following a full-plant process modeling and mass balance, and the new design loads for waste activated sludge coming from secondary treatment. A new WAS Thickening building was designed to include Gravity Belt Thickeners for secondary sludge exclusively and the review of the existing primary treatment designs to include additional units for WAS on all the remaining processes. 

Another important component of the project developed by Greeley and Hansen was a product marketing plan for the beneficial utilization of biosolids. To this end, an analysis of potential markets for the biosolids produced by the WWTP has been conducted as the main input for an integral Biosolids Master Plan for the City of Bogotá, which is currently under development by the utility. 

Project Highlights: 

  • Detailed design of aeration tanks with aerobic and anoxic zones, aeration blowers, aeration diffusers and anoxic zone mixers, and chlorine contact tanks. 

  • Design of solids treatment, thickening and dewatering. 

  • Evaluated technologies and equipment based on process needs, energy efficiency, operators’ safety, operation and maintenance needs and difficulty. 

  • Biosolids product beneficial utilization and marketing plans.