2018

Detailed diagnosis of the civil engineering aspects and definition of technical specifications for the rehabilitation works of the SPRET

Diagnosis of the civil engineering

Effluent pre-treatment plant with a capacity of 2,500m³/h
H2S gases

Context

SEURECA, the consulting and engineering branch of Veolia, requested the service of Altereo to address a civil-engineering related issue at the SPRET (Effluent pre-treatment plant with a capacity of 2,500m³/h). The plant is located in Tangier, which has a population of one million.

The mission comprises a detailed diagnosis of the civil engineering together with the definition of technical specifications for the rehabilitation works leading to call for proposals for the performance of the plant.

Given the complexity of the subject matter, SEURECA asked Altereo to begin by carrying out a preliminary reconnaissance visit.

Project Description

This first short-term mission comprised taking into account the issue of visition the facility to meet the partners, namely AMENDIS (a subsidiary of VEOLIA), operator of all facilities within Tangier, and LPEE (Moroccan structure and material laboratory).

The degradation of the facilities is linked to very high concentrations of H2S gases (up to 300 ppm during midsummer). This gas is present in confined structures such as those of the SPRET, and is oxidized to sulfuric acid H2SO4 by chemical means but mainly by biochemical means.

On the Tangier facility, the concrete is leached and completely disintegrates under acid attack, sometimes passking through a thicknesses of more than 30 mm. Most of the epoxy resin or hydraulic binder coatings on the vertical walls of some structures have been completely destroyed and the lower reinforcement beds of the roof slabs are visible.