Project for the Expansion of the Sewer Network and Construction of the Wastewater Treatment Plant in Arnas

Municipality of Sernancelhe

Introduction

This technical project consisted of the design and implementation of an integrated solution for the wastewater drainage network and the construction of a Wastewater Treatment Plant (WWTP) in the town of Arnas. The intervention focused on providing this town with modern sanitation infrastructure, ensuring the efficient treatment of domestic wastewater and compliance with current environmental standards.

Context and Need

The project’s necessity was based on providing Arnas with a sanitation system capable of serving an equivalent population of 350 inhabitants. The technical design prioritized compliance with Decree-Law No. 152/97, ensuring the rigorous reduction of pollutants such as TSS, BOD5, and COD. The central objective was to implement a stable and easy-to-maintain technology that would guarantee the protection of the receiving environment, even in the face of variations in influent organic load.

Summary of the Project Completed

The implemented solution is based on a biological process of Extended Aeration, a technique selected for its optimal performance in terms of purification and low sludge production. The main components of the project include:

• Biological Treatment System: Uses a cylindrical unit made of steel sheet with an approximate volume of 80 m³. The process operates through a sequential biological reactor where the aeration (via fine bubble diffusion with a blower) and sedimentation phases occur cyclically (4 cycles daily).
• Purification Stages: The system comprises a manual screening phase to remove coarse solids, followed by aerobic biological treatment that converts organic matter into stable, odorless products.
• Construction and Equipment: The tank was manufactured from steel sheet with anti-corrosion protection and equipped with submersible electric pump groups and high-quality air blowers.
• Complementary Infrastructure: Installation of an automatic electrical panel with alarm signaling and phase failure protection, in addition to the construction of a ventilated support building and access paving in a gravel base layer.
• Waste Management: The system allows for the aerobic stabilization of sludge, reducing the need for periodic extraction, estimated every 2 years, and allowing this sludge to be subsequently used in agriculture.

The assembly involved complex logistical operations, including truck transport and mobilization via rotating crane for meticulous positioning and leveling of the units.

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