Projects

A New Wastewater Collection and Treatment System in Senegal

Hazen and Sawyer is working with a team of local subconsultants to perform a study and provide conceptual design for a new wastewater treatment plant in Dakar, Senegal. Using the results from the detailed evaluation, Hazen and Sawyer will the select the most feasible and desirable treatment, collection, and discharge alternatives for the project.

Project Outcomes and Benefits

• Characterization of wastewater influent and determination of average, minimum, and peak flows.
• Treatment plant site selection on the basis of physical, environmental, political, and social factors.
• Determination of treatment, collection, and discharge alternatives for the project based on expected performance and effectiveness, capital and operating costs, and future expandability.

Using existing information and data, along with information gathered from the site visit, Hazen and Sawyer evaluated the different possible sources of wastewater within the service area, determining wastewater quality and quantity.

The wastewater source analysis determined average, minimum, and peak wastewater flows, including impacts from wet weather and seasonal variations. In addition, Hazen and Sawyer determined projected wastewater flows based upon expected population growth and commercial/industrial development in the Corniche West region. Results from the analysis were summarized in a Technical Memorandum that detailed the findings of the study and identified the wastewater flow values that will be used for completing the feasibility study.

Hazen and Sawyer next developed a field sampling plan to ascertain the quality and quantity of different wastewater sources that are to be treated at the Corniche West Wastewater Treatment Plant. Following this work, the firm utilized maps, blueprints, and engineering schematics of the existing wastewater collection system, coupled with information compiled during the site visit, to develop a preliminary layout and design of an expanded collection system that will deliver raw wastewater to the new treatment plant.

Paramount to the project was the site evaluation and selection process. The site screening process involved investigating each site on the basis of physical, environmental, political, and social factors. The decision factors listed in the site selection criteria were independently evaluated and rated in terms of suitability. A site that best met these criteria was ultimately selected for constructing the treatment plant.

Hazen and Sawyer is currently evaluating treatment technologies that could be used to meet the target effluent wastewater quality. Upon completion, Hazen and Sawyer will conduct a detailed economic evaluation on the most appropriate and feasible technologies.

Using the results from the detailed evaluation, Hazen and Sawyer will select the most feasible and desirable treatment, collection, and discharge alternatives for the project. These alternatives will include specific details on selected technologies and equipment. The evaluation and selection process will utilize an economic model that will take into account the following:

• Expected performance and effectiveness.
• Reliability and expected lifecycle.
• Implementability and constructability, including phased construction and implementation issues.
• Expandability.
• Lifecycle costs.
• Public health and environmental concerns.
• Operation and maintenance.