Topic Area: 8a. Advances in Tools and Techniques for Assessing MNA

Formatted Title:

Application of Biomolecular and Isotopic Methodologies for Monitoring Natural Attenuation (MNA) Processes in a Chlorinated Solvents-Contaminated Site: A Successful Case in Italy

Background/Objectives:

The project focuses on the full-scale bioremediation of an industrial site near Milano city used for waste management and paraffin production since 1996. In 2005, groundwater contamination was confirmed primarily due to the presence of chlorinated ethenes, and, to a lesser extent, to benzene and metals (Fe and Mn). A pump and stock (P&S) system was promptly installed and operated for over a decade. However, due to the high energy costs of the P&S system, the feasibility of applying a bioremediation strategy was assessed as a more sustainable alternative for groundwater management.

In 2017-2018, comprehensive chemical and microbiological site characterization revealed a significant natural biodegradation potential, particularly for the reductive dechlorination of chlorinated ethenes. Based on these findings, a full-scale bioremediation project was designed and approved by regulatory agencies in 2020. The project consisted of monitored natural attenuation (MNA) processes using a multi-evidence approach, combining hydrochemical, biomolecular, and isotopic analyses. The goal was to implement a cost-effective and operationally sustainable strategy, minimizing both installation and maintenance expenses for the site.

Approach/Activities:

The full-scale bioremediation project included hydrochemical, biomolecular, and isotopic analyses for a three-year MNA process. Specifically, the following methodologies were applied:

Hydrochemical analyses: chlorinated ethenes (PCE, TCE, DCE, VCM), BTEX compounds, Fe and Mn, dissolved oxygen, Redox potential, etc.
Biomolecular analyses: Next generation sequencing (NGS) to identify the structure of the autochthonous bacterial community, and quantitative PCR (qPCR) to quantify specific gene markers (Dehalococcoides pceA, tceA, vcrA, bvcA) involved in the reductive dechlorination process.
Isotopic analyses: Compound specific isotope analysis (C-CSIA) of ¹³C/¹²C ratios of target contaminants.

These analyses were performed every six months, with a total of seven monitoring campaigns conducted from 2021 to 2024.

Anna Espinoza

Affiliation

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(Group 2, Poster Board #32) Application of Biomolecular and Isotopic Methodologies for Monitoring Natural Attenuation (MNA) Processes in a Chlorinated Solvents-Contaminated Site: A Successful Case in Italy