Abstract
The anionic surfactant Sodium Lauryl Ether Sulfate (SLES) is the principal component of several commercial foaming products for soil conditioning in the tunneling industry. Huge amounts of spoil material are produced during the excavation process and the presence of SLES can affect its re-use as a by-product. Anionic surfactants can be a risk for ecosystems if occurring in the environment at toxic concentrations. SLES biodegradability is a key issue if the excavated soil is to be reused. The aim of this study was to identify bacteria able to degrade SLES, so that it could potentially be used in bioaugmentation techniques. Enrichment cultures were performed using bacterial populations from spoil material collected in a tunnel construction site as the inoculum. A bacterial consortium able to grow in a few hours with SLES concentrations from 125 mg/L to 2 g/L was selected and then identified by Next Generation Sequencing analysis. Most of bacteria identified belonged to Gamma-Proteobacteria (99%) and Pseudomonas (ca 90%) was the predominant genus. The bacterial consortium was able to degrade 94% of an initial SLES concentration of 250 mg/L in 9 h. A predictive functional analysis using the PICRUSt2 software showed the presence of esterase enzymes, responsible for SLES degradation. The bacterial consortium selected could be useful for its possible seeding (bioaugmentation) on spoil material from tunneling excavation.
Highlights
Due to the many and ever larger tunneling projects planned in Europe and worldwide, several hundreds of millions of tons of soil debris will be produced in the coming years, bringing the associated issue of how to manage and dispose of them (Milligan, 2000; Tokgöz, 2013, 2020; Oggeri et al, 2014)
Bacterial Isolation and Fluorescent in situ Hybridization (FISH) Analysis The growth of bacterial colonies on Petri plates was only found with 500 mg/L of Sodium Lauryl Ether Sulfate (SLES)
The Fluorescent in situ Hybridization analysis of the isolates showed that most bacteria identified belonged to Gamma-Proteobacteria (88%)
Summary
Due to the many and ever larger tunneling projects planned in Europe and worldwide, several hundreds of millions of tons of soil debris (spoil material) will be produced in the coming years, bringing the associated issue of how to manage and dispose of them (Milligan, 2000; Tokgöz, 2013, 2020; Oggeri et al, 2014). The spoil material can be a safe by-product if it is temporarily stored at the construction site for the time needed for its biodegradation (Barra Caracciolo et al, 2019) This practice is currently used in several tunneling sites in Italy where SLES is generally found to degrade in about 7 days with an initial concentration of about 200 mg/kg (Mariani et al, 2020). The degradation of SLES can sometimes require several weeks (Finizio et al, 2020), with a significant increase in the duration of the temporary storage at the construction site In some cases, such as tunneling for a metro in a city, an area for temporary storage of the spoil material is not available. A possible nature-based solution (Keesstra et al, 2018) for preventing loss of soil and useless waste production can be spoil material bioaugmentation with a bacterial consortium able to promote a quick degradation of SLES
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
