A non-traditional approach for Soil remediation

Erick Monge 13 June, 2019

Through our compromise with environmental care and development of sustainable projects, we are exploring and improving state-of-the-art technologies for remediation of affected sites. Challenging scenarios including a vulnerable environment, different contaminants and social and operative restrictions, demand that our expert team design and assembly the best environmental and cost-effective solutions. This case study summarizes non-traditional in situ remediation technology aimed to reduce TPH concentrations in subsoil and groundwater, generated by a diesel spill, inside a very sensitive area in the jungle in Ecuador.

In 2014, a diesel spill occurred in a pipeline system inside a sensitive area due to a geologic fault. Terrain movement provoked pipe break, generating as consequence the spill to went inside the subsoil affecting groundwater too. As a common practice in these scenarios, the client first approach to handle the problem was to excavate, transport and treat the resulting soil out of the affected area. Considering that no in situ or alternative technologies were available at the time, the ex situ method was approved by local authorities.

Reevaluating risks and environmental impacts derived from excavation tasks stopped this first initiative. In 2016, our team took note of the problem and came up with a new alternative.  Analysing restrictive conditions mentioned, we designed and adapted an in situ non-invasive electro kinetic + enhanced bioremediation technology to reduce TPH concentration in all affected matrixes: soil and groundwater.

An environmental assessment phase 2 (ESA-P2) was conducted as the first step. Using results from ESA-P2, secondary and preliminary analyses of the affected area, our team built the Conceptual Site Model (CSM). CSM showed that the contamination in soil was above 13.000 mg/kg of TPH and 1.300mg/L of the same contaminant in groundwater. Non-aqueous phase liquid (NAPL) was identified too. The contaminant was distributed inside a 2.800m2 area and reached >5m of depth.

To understand the hydrogeological and microbiological behavior of subsoil, infiltration and treatability test were conducted. An expertise team formed by geologists, biotechnologists, environmental engineers, chemical engineers and microbiologists prepared the essays to determine the operative conditions in which in situ electrokinetic enhanced bioremediation process should be performed.

The combined technology consists in the performance of EKO GRID® electrokinetic system, which applies an electric pulse through a special electric grid (cathodes and anodes) installed directly inside the affected area, plus a well-studied bio-augmentation procedure based on the treatability study. The perfect combination of both technologies generated the natural and massive mineralization of the present contaminant (diesel), into water and CO2 as resulting products.

At the end of 10 months of operation, our in situ methodology was able to reduce TPH content in soil under 200 mg/kg and to 15 mg/L in groundwater. Remediation target parameters, 1.000 mg/kg in soil and 20 mg/L in the water of TPH, were fully accomplished. No excavation processes or environmental impacts were produced as well as no contaminant sub-products were registered.

Lamor’s innovative method is the product of several years of experimentation and on-field testing. The obtained results show that a new and different perspective could be the best way to face the most complicated scenarios in remediation. Analysing all the variables of the process, while focused on environmental care, will provide the expected results for all the stakeholders.