Biocorrosion of Concrete Sewers in Greece: Current Practices and Challenges

Georgios Fytianos,Vasilis Baltikas,Dimitrios Loukovitis,Efthimios Papastergiadis,Dimitra Banti,Athanasios Sfikas,Petros Samaras

doi:10.3390/su12072638

Abstract

This paper is intended to review the current practices and challenges regarding the corrosion of the Greek sewer systems with an emphasis on biocorrosion and to provide recommendations to avoid it. The authors followed a holistic approach, which included survey data obtained by local authorities serving more than 50% of the total country’s population and validated the survey answers with field measurements and analyses. The exact nature and extent of concrete biocorrosion problems in Greece are presented for the first time. Moreover, the overall condition of the sewer network, the maintenance frequency, and the corrosion prevention techniques used in Greece are also presented. Results from field measurements showed the existence of H2S in the gaseous phase (i.e., precursor of the H2SO4 formation in the sewer) and acidithiobacillus bacteria (i.e., biocorrosion causative agent) in the slime, which exists at the interlayer between the concrete wall and the sewage. Biocorrosion seems to mainly affect old concrete networks, and the replacement of the destroyed concrete pipes with new polyvinyl chloride (PVC) ones is currently common practice. However, in most cases, the replacement cost is high, and the authors provide some recommendations to increase the current service life of concrete pipes.

Highlights

Sulfide generation is a bacterially mediated process occurring in the submerged portion of sanitary sewage systems from Sulfur-Reducing Bacteria (SRB) [1]
Results from field measurements showed the existence of H2S in the gaseous phase and acidithiobacillus bacteria in the slime, which exists at the interlayer between the concrete wall and the sewage
The root cause of biocorrosion is the formation of H2S, which is produced from sulfates in wastewater under a reaction with sulfate-reducing bacteria located in a slime layer

Summary

Introduction

Sulfide generation is a bacterially mediated process occurring in the submerged portion of sanitary sewage systems from Sulfur-Reducing Bacteria (SRB) [1]. After H2S diffusion towards the upper part of the sewer pipe above the wastewater, due to the presence of Sulfur-Oxidizing Bacteria (SOB, e.g., Thiobacillus), H2S can be oxidized to biogenic H2SO4, which rapidly corrodes the concrete in sewer pipes [1,2]. This oxidizing process can take place wherever there is an adequate supply of H2S gas (>2 mg/L), high relative humidity, and high atmospheric oxygen content. The slime layer is typically between 0.3 and 1.0 mm thick depending on the flow vSuesltoaicnaitbyilitayn20d20s,o12li,dx sFOaRbrPaEsEiRoRnEVinIEtWhe sewage [6]

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