Sustainable lindane waste remediation: Surfactant-driven residual DNAPL extraction and oxidation in a real landfill (LIFE SURFING)

• Published in: The Science of the total environment 2024-07, Vol.934, p.173260, Article 173260
• Main Authors: Fernández, Jesús, Lorenzo, David, Net, Jorge, Cano, Elena, Saez, Patricia, Herranz, Carlos, Domínguez, Carmen M., Cotillas, Salvador, Santos, Aurora
• Format: Article
• Language: English
• Subjects: DNAPL; Fractured landfill; LIFE SURFING; Lindane; S-ISCO; SEAR
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.173260

The LIFE SURFING Project was carried out at the Bailin Landfill in Sabiñánigo, Spain (2020-2022), applying Surfactant Enhanced Aquifer Remediation (SEAR) and In Situ Chemical Oxidation (S-ISCO) in a 60-meter test cell beneath the old landfill, to remediate a contaminated aquifer with dense non-aqueous phase liquid (DNAPL) from nearby lindane production. The project overcame traditional extraction limitations, successfully preventing groundwater pollution from reaching the river. In spring 2022, two SEAR interventions involved the injection of 9.3 m3 (SEAR-1) and 6 m3 (SEAR-2) of aqueous solutions containing 20 g/L of the non-ionic surfactant E-Mulse 3®, with bromide (around 150 mg/L) serving as a conservative tracer. 7.1 and 6.0 m3 were extracted in SEAR-1 and SEAR-2, respectively, recovered 60–70 % of the injected bromide and 30–40 % of the surfactant, confirming surfactant adsorption by the soil. Approximately 130 kg of DNAPL were removed, with over 90 % mobilized and 10 % solubilized. A surfactant-to-DNAPL recovery mass ratio of 2.6 was obtained, a successful value for a fractured aquifer. In September 2022, the S-ISCO phase entailed injecting 22 m3 of a solution containing persulfate (40 g/L), E-Mulse 3® (4 g/L), and NaOH (8.75 g/L) in pulses over 48 h, oxidizing around 20 kg of DNAPL and ensuring low toxicity levels after that. Preceding the SEAR and S-ISCO trials, 2020 and 2021 were dedicated to detailed groundwater flow characterizations, including hydrological and tracer studies. These preliminary investigations allowed the design of a barrier zone between 317 and 557 m from the test cell and the river, situated 900 m away. This zone, integrating alkali dosing, aeration, vapor extraction, and oxidant injection, effectively prevented the escape of fluids to the river. Neither surfactants nor contaminants were detected in river waters post-treatment. The absence of residual phase in test cell wells and reduction of chlorinated compound levels in groundwater were noticed till one year after S-ISCO. [Display omitted] •SEAR and S-ISCO were successfully implemented at Bailin Landfill.•About 130 kg of DNAPL were removed in SEAR and 20 kg in S-ISCO.•Low levels of toxic compounds in groundwater were maintained after S-ISCO.•Innovative barrier zone strategy was implemented avoiding the pollutant dispersion.