Biocorrosion of Concrete Sewers in Greece: Current Practices and Challenges

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.

Least Cost Analysis for Biocorrosion Mitigation Strategies in Concrete Sewers

“…and then classified into different cost categories (e.g., EUR/labor hour, EUR/mechanical labor, EUR/worksheet, etc.). The inventory is enriched with data from field measurements [7], whilst specific coefficients are taken from official records (e.g., euros per hour of labor). Furthermore, valid assumptions-based on the primary data-should be made, in order to have credible results.…”

“…Concrete is still the most used material for sewer pipes in Greece, while for newly installed sewer systems, PVC pipes are favored due to their better corrosion resistance properties and lower price. In Greece there is no systematic monitoring and research on biocorrosion, and based on a recent survey, the local directors of sewerage treatment enterprises are willing to try new MIC mitigation strategies [7].…”

“…In this context, a focus on the design and management of maintenance for the existing structures is given [25], while calculating the manifold impacts for every corrosion controlling method. To further expand upon this, there is a necessity for the economic assessment of the current sewer system in Thessaloniki, Serres, Kozani, and Florina based on the survey of Fytianos et al [7]. Thessaloniki, as a capital of Northern Greece, should have higher social impacts due to maintenance in the city center, while Kozani and Florina should have difficulties with relevance to the cleaning process due to the smaller pipe sizes.…”

Novel Approaches for Biocorrosion Mitigation in Sewer Systems

“…Later, with emission into the sewer atmosphere, H2S is oxidized to sulfur and sulfur compounds, thus providing an ideal catalyst for the thiobacillus bacteria to metabolize it to sulfuric acid. A detailed explanation of the biocorrosion process in the sewers can be found in [9,10]. Concrete sewer system biocorrosion problems can be addressed with various methods such as the application of protective coatings onto the concrete surface [11,12], biocides and chemical dosing [1].…”

Properties and Performance of Novel Mg(OH)2-Based Coatings for Corrosion Mitigation in Concrete Sewer Pipes

“…The intensity and extent of MIC depends mainly on the specific configuration and characteristics of each individual sewerage network. Figure 1 presents a relevant representation from a typical concrete sewer pipe section [ 5 ]. It is a fact that the components existing in the sewerage system affect hydrogen sulfide production and microbial activity, which are indirectly responsible for the biogenic sulfuric acid production, but the main corrosive agent in MIC is considered to be the sulfuric acid.…”