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Communication Dans Un Congrès Année : 2012

Sulfur cycle in sewer networks and its consequences on cementitious materials

Résumé

Sewer networks enclose many biological and chemical transformations involving sulfur molecules oxidation leading to biogenic sulfuric acid production. Sewage effluents contain many sulfur species such as sulfates and sulfites which are reduced in anoxic zones by sulfate reducing bacteria (Desulfovibrio sp., Desulfobulbus sp.) into hydrogen sulfide (H2S). This gas is emitted in the aerial part of the pipe and degrades materials. This deterioration proceeds either directly as H2S is a corrosive gas, or indirectly through the action of microorganisms that will oxidize H2S into sulfuric acid. This acid will dissolve the cement matrix and produce expansive products (such as gypsum or ettringite). In the worst case it leads to pipes destruction. This study aims at understanding the deterioration mechanisms occuring in the aerial part of the pipe. A special attention is given to the impact of different cementitious material on microorganisms involved in the global sulfur cycle (sulfur oxidizing bacteria such as Starkeya novella, Halothiobacillus neapolitanus, Thiomonas intermedia and Acidithiobacillus thiooxidans). According to field data, cementitious materials made with Calcium Aluminate Cement (CAC) offer far better performance on site than those made of Ordinary Portland Cement (OPC). This behaviour difference is likely associated with a different microorganism diversity. This work is divided into three parts. The first one consists in an exposition of CAC and OPC mortars in real sewer networks. This on-site experiment aims to follow the evolution of biodiversity and also to characterize the degradation of cementitious materials. Capillary Electrophoresis - Single Strand Conformation Polymorphism (CE-SSCP) analyses performed on each sample reveals that biodiversity is highly related to cement composition. OPC mortars hosts more numerous and diverse microorganisms than CAC mortars. The second part is represented by various lab experiments aiming to better describe the different steps involved in the whole mechanism. According to our tests, abiotic oxidation of H2S into elemental sulfur is highly dependent on materials composition. While elemental sulfur deposition can be seen on OPC mortars, none is observed on CAC mortars. Depending on sulfur source available, bacteria will have various growth rates. We have studied the impact of three sulfur sources (S2O32-, S0, H2S) on the growth of sulfur oxidising bacteria. All results obtained are used, in a third part, to design an accelerated experiment that should be standardized to test sewer networks materials.

Domaines

Matériaux
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Dates et versions

hal-00903688 , version 1 (12-11-2013)

Identifiants

  • HAL Id : hal-00903688 , version 1

Citer

Jean Herisson, Eric D. van Hullebusch, Marielle Gueguen, Marina Moletta-Denat, Christophe Eychenne-Baron, et al.. Sulfur cycle in sewer networks and its consequences on cementitious materials. International Symposium on Microbial Ecology ISME-14, Aug 2012, Denmark. 1p. ⟨hal-00903688⟩
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