Urban Water Interfaces

Corrosion in sewers caused by biochemical processes – microbiological investigations and inhibition effects

Romy Birnstengel

Background

Regarding our modern civilization, sewer systems play a crucial role in sustainability and health issues. As most sewer pipes are made of concrete, ensuring durability and longevity is of great concern to authorities and engineers. Microbial induced concrete corrosion (MICC) is recognized as the main degradation process in sewer environments and is considered to have enormous damage potential and significantly reduce the service life of concrete-based sewer systems, e.g. from expected 100 years down to 30-50 years (Grengg et al. 2018a; Wang et al. 2020; Wu et al. 2020).

MICC can be considered as a process of biological sulfate reduction and re-oxidation events. In the water phase of a gravity sewer, sludge and sediment are deposited and the initial formation of sulfide takes place. Different microbial processes (fermentation, sulfate respiration and methanogenesis) occur in this sludge and sediment layer with decreasing redox potential. Sulfate and sulfur-containing organic compounds, which are present in the wastewater, are converted to H2S(aq) through biological activities of anaerobic sulfate-reducing bacteria (SRB), e.g., Desulfovibrio spp. and Desulfomaculum spp., residing in biofilms within the sediment layer. Gaseous H2S, together with CO2, is formed and partly released into the atmosphere of the sewer pipe, where it accumulates in the moist pore phase of the concrete. Due to abiotic acid-base reactions, the initially strongly alkaline pH (around pH13) of the concrete is lowered, which results in the colonization of sulfur-oxidizing bacteria (SOB), e.g., Thiobacillus spp., on the concrete surface. These SOB are able to produce sulfuric acid due to the oxidation of reduced sulfur species. The produced sulfuric acid attacks the concrete matrix, leading to the deterioration of the material (Grengg et al. 2018b; Grengg et al. 2018a; Hvitved-Jacobsen et al. 2013; Wang et al. 2020; Wu et al. 2020). The main processes of MICC are illustrated in Fig. 1.

Aim

The main objective of the project S3 is to study the influence of different building materials, exposed to real sewer conditions in a sewer pilot plant, on the biofilm formation. Further to investigate the differences in biofilm diversity on cementitious materials of various characteristics as well as their corrosion rates and -depths.
For this purpose, a range of cementitious mortars with very different chemical compositions as well as doped samples will be exposed to the sewer pilot plant of the Berlin waterworks (BWB) in Berlin-Neukölln, which is operated with real waste water out of the pump station. The different mortars differ due to their binder composition and therefore show different behavior when exposed to acids and may also lead to the formation of biofilms with different bacterial diversity.

 

Methods

The sewer pilot plant used in this project is located at the BWB pumping station Neukölln II in Berlin, Germany. The wastewater entering the pumping station is a mixture of wastewater from the discharges of combined and separate sewer systems. The pilot plant is designed to mimic the operation of a real sewer system through the direct inflow of raw wastewater from the pump station and consists of a pressure pipe and a gravity pipe. Figure 3 shows a schematic representation of the sewer pilot plant, modified from Despot et al. 2021.

The different concrete specimens (OPC, OPC with slag, OPC with fly ash, white OPC, SR-OPC, HAC, GP, OPC with MnO2-NP, OPC with CuO-NP) will be prepared with a size of 160x40x40 mm3 at the TU Berlin and afterwards exposed in the headspace of the sewer pilot plant, as shown in Figure 3, to investigate the influence on the biofilm diversity.

In order to characterize the environmental conditions, the H2S-concentrations, pH-values, temperature, CO2-concentrations and humidity in the pipe will be monitored regularly.

After exposure of the mortar specimens, ground joints and thin sections are produced and the samples will be characterized by μ-X-ray fluorescence, light and low-vacuum scanning electron microscopy and inductively coupled plasma optical emission spectrometry (ICP-OES) to study the binder degradation as well as the soluble components.

The bacterial composition of biofilms grown on exposed mortar samples will be analyzed by Next Generation Sequencing (Oxford Nanopore Technologies). Therefore, the DNA will be extracted from the collected biofilm samples. Further different DNA-extraction and DNA-cleaning Kits will be tested and compared to achieve the highest purity and amounts of DNA for the following sequencing procedure. The results will be compared and statistically evaluated using the epi2me platform as well as the software “R” for statistics.

References

  • Despot, Daneish; Pacheco Fernández, Micaela; Barjenbruch, Matthias (2021): Comparison of Online Sensors for Liquid Phase Hydrogen Sulphide Monitoring in Sewer Systems. In: Water 13 (13), S. 1876. DOI: 10.3390/w13131876.
  • Grengg, Cyrill; Mittermayr, Florian; Ukrainczyk, Neven; Koenders, Eddie; Koraimann, Günther; Kienesberger, Sabine; Dietzel, Martin (2018a): Microbial induced acid corrosion from a field perspective - Advances in process understanding and construction material development. In: MATEC Web Conf. 199, S. 2002. DOI: 10.1051/matecconf/201819902002.
  • Grengg, Cyrill; Mittermayr, Florian; Ukrainczyk, Neven; Koraimann, Günther; Kienesberger, Sabine; Dietzel, Martin (2018b): Advances in concrete materials for sewer systems affected by microbial induced concrete corrosion: A review. In: Water research 134, S. 341–352. DOI: 10.1016/j.watres.2018.01.043.
  • Hvitved-Jacobsen, Thorkild; Vollertsen, Jes; Nielsen, Asbjrn Haaning (2013): Sewer Processes. Microbial and Chemical Process Engineering of Sewer Networks. In: Taylor & Francis Group.
  • Wang, Tian; Wu, Kai; Kan, Lili; Wu, Min (2020): Current understanding on microbiologically induced corrosion of concrete in sewer structures: a review of the evaluation methods and mitigation measures. In: Construction and building materials 247, S. 118539. DOI: 10.1016/j.conbuildmat.2020.118539.
  • Wu, Min; Wang, Tian; Wu, Kai; Kan, Lili (2020): Microbiologically induced corrosion of concrete in sewer structures: A review of the mechanisms and phenomena. In: Construction and building materials 239, S. 117813. DOI: 10.1016/j.conbuildmat.2019.117813

 

BearbeitungRomy Birnstengel  
BetreuungProf. Dr. rer. nat. Dietmar StephanProf. Dr.-Ing. Matthias BarjenbruchDr. rer. nat. Burga Braun
KollaborationenS4, F5Dr. Adrian Augustyniak (Kollegiat)Berliner Wasserbetriebe (BWB)