A field-scale remediation of residual light non-aqueous phase liquid (LNAPL): chemical enhancers for pump and treat

Paolo Ciampi,Paolo Rizzetto,Gian Piero Deidda,Carlo Esposito,Marco Petrangeli Papini,Giorgio Cassiani

doi:10.1007/s11356-021-14558-2

Abstract

The remediation of petroleum-contaminated soil and groundwater is a challenging task. The petroleum hydrocarbons have a long persistence in both the vadose zone and in the aquifer and potentially represent secondary and residual sources of contamination. This is particularly evident in the presence of residual free-phase. Pump-and-treat is the most common hydrocarbon decontamination strategy. Besides, it acts primarily on the water dissolved phase and reduces concentrations of contaminants to an asymptotic trend. This study presents a case of enhanced light non-aqueous phase liquid (LNAPL) remediation monitored using noninvasive techniques. A pilot-scale field experiment was conducted through the injection of reagents into the subsoil to stimulate the desorption and the oxidation of residual hydrocarbons. Geophysical and groundwater monitoring during pilot testing controlled the effectiveness of the intervention, both in terms of product diffusion capacity and in terms of effective reduction of pollutant concentrations. In particular, non-invasive monitoring of the reagent migration and its capability to reach the target areas is a major add-on to the remediation technique. Most of the organic contaminants were decomposed, mobilized, and subsequently removed using physical recovery techniques. A considerable mass of contaminant was recovered resulting in the reduction of concentrations in the intervention areas.

Highlights

The remediation of the areas contaminated by petroleum hydrocarbons and the selection of the best decontamination methods represent a growing global concern (Kuppusamy et al 2020; Ossai et al 2020; Verardo et al 2021)
The most recent deposits are related to a PlioQuaternary depositional sequence of alluvial sediments (Bini 2013), organized in two macro-levels: an upper level is characterized by gravels and sands with the presence of fine fraction, extending to maximum depth between 4 and 6 m, and a lower level featured by gravel and sand in a silty-clay matrix, reaching a depth between 8 and 10 m
Geophysical surveys and groundwater sampling during pilot testing evaluated the effectiveness of the intervention, both in terms of product diffusion capacity and effective reduction of pollutant concentrations

Summary

Introduction

The remediation of the areas contaminated by petroleum hydrocarbons and the selection of the best decontamination methods represent a growing global concern (Kuppusamy et al 2020; Ossai et al 2020; Verardo et al 2021). The progressive aging of the contaminants corresponds to a reduction of the more mobile and degradable fractions and the increase of compounds with a higher molecular weight (Tran et al 2018) Such immobile, less volatile, less soluble, more viscous, and high molecular weight materials constitute the residual hydrocarbons, which are difficult to be mobilized by traditional extraction (i.e., pumping) technologies (Lari et al 2019b; Ossai et al 2020; Teramoto et al 2020; Trulli et al 2016). Verification of amendment distribution in soils should be part of the performance monitoring (Fan et al 2017)

Methods

Results

Discussion

Conclusion