Project for the Expansion of the Sewage Network and Construction of the Wastewater Treatment Plant in Povoação da Cunha

Cunha and Chosendo, Municipality of Sernancelhe

Introduction

This technical project consisted of the design and implementation of an integrated solution for expanding the sewage network and constructing a Wastewater Treatment Plant (WWTP) in the village of Cunha. The intervention focused on providing this locality with modern sanitation infrastructure, ensuring environmental preservation and public health.

Context and Need

The intervention arose from the need to serve a population of 350 equivalent inhabitants, responding to specific topographical and environmental constraints. The absence or insufficiency of an adequate treatment system required the implementation of a unit capable of rigorously meeting the discharge limits and minimum percentages of pollutant reduction established in current legislation (Decree-Law No. 152/97). The project thus aimed to replace or complement the precarious systems with a suitable technical solution for the flow rates and organic loads of the settlement.

Summary of the Project Completed

The implemented solution was based on a biological treatment system using extended aeration, a technique selected for its high degree of purification, simplicity of operation, and reduced sludge production.

The treatment system was organized into the following main stages:

• Screening: Manual removal of coarse solids using a cleaning screen to protect downstream equipment.
• Sequential Biological Reactor: Cylindrical unit made of steel sheet where aeration (diffusion by fine bubbles) and sedimentation operations occur cyclically (4 daily cycles of 6 hours each).
• Electromechanical Systems: Installation of air blowers for aerobic degradation and submersible pump sets for the discharge of treated effluent.
• Sludge Management: Self-oxidation process that minimizes waste production, resulting in stabilized sludge that can be sent for agricultural recovery or landfill.

The infrastructure also includes a support building for the electrical control panel and the compressor, as well as civil works involving mechanized excavations, preparation of sand beds, and gravel paving on the access roads. The system was equipped with automation and alarm signaling to ensure efficient and safe operation.