During April and May 2017, REGROUND applied first full-scale installment of permeable reactive barrier using Iron-oxide nanoparticles. The injections took place in same contaminated aquifers as pilot injections (June 2016); one in Barreiro, Portugal, and one in La Felguera, Spain. Prior to application, a remediation and monitoring plan was prepared. At each site, 9 injection wells were designed to inject REGROUND nanoparticles into aquifer. Four multichannel wells and 11 normal pizeometers were also placed in order to monitor the transport of NPs and efficiency of installed barriers. A 3D numerical model was developed and used in order to simulate the hydrogeological effects of NP injection into each aquifer. The model was calibrated based on the data acquired during and after test pilot injections (June 2016).
For each site ca. 15000 KG of concentrated nanoparticles was produced and modified according to heavy metal contamination in groundwater. This is the first large-scale production of nanomaterials for a field application. The produced nanoparticles were designed in a way to remain stable during transport to site and during injection into aquifer, where then they are destabilized and precipitate on sediments. These immobilized nanoparticles then adsorbed heavy metal contamination dissolved in groundwater.
The nanoparticles were diluted on site using local municipally water and then were injected. In Barreiro and Nitrastur, after observing NPs in downgradient wells, Calcium was injected downstream the barrier in order to ensure faster immobilization of all nanopartilces inside planned barrier.
Before, during, and after injection of REGROUND nanoparticles, groundwater and soil samples were taken according to the monitoring plan. These samples were analyzed (and continuously will be taken and analyzed) using high accuracy analytical tools in order to monitor the effects of nanoparticle injection in immobilization of toxic heavy metals. Hydrological tests such as slug test were also performed, and showed limited effects on normal groundwater flow.
In coming months, additional groundwater and soil samples will be taken and analyzed to continuously monitor the efficiency of installed barrier. These analytical results then will be combined by Life Cycle Assessment and Market analysis into a business plan.