Site of National Interest (SIN) – Southern Italy
Enhancend Natural Attenuation (ENA) applied to metal removal
The ENA pilot test involved the injection of an organic substrate into the aquifer in order to generate favorable environmental conditions for the metabolic activity of sulfate-reducing bacteria, strictly anaerobic bacteria that, under reducing conditions, use sulfates as terminal electron acceptors for metabolic respiration reactions resulting in the formation of sulfides. In groundwater sulfides can than react with bivalent metals, such as Cd and Zn, producing metal sulfides, insoluble salts that precipitate settling in the soil.

PROBLEM
Metal contamination in groundwater.
High levels of heavy metals, such as Cadmium and Zinc, have been found in groundwater of an Industrial area. The removal of these pollutants by conventional water treatment techniques has numerous disadvantages from both environmental and economic perspectives.
APPLIED TECHNOLOGY: Enhanced Natural Attenuation (ENA)
TYPE OF POLLUTANT: Cadmium and Zinc
CONTEXT: Metal-contaminated groundwater
SOLUTION
Use of bioremediation techniques for removal of Cd and Zn from groundwater.
In this site, after a baseline microbiological characterization, the Enhancend Natural Attenuation (ENA) technique was selected for bioremediation of metal-contaminated groundwater. The pilot test of ENA involved the injection of an organic substrate into the aquifer in order to generate favorable environmental conditions for the bacterial formation of sulfides. In groundwater sulfides can than react with bivalent metals, such as Cd and Zn, producing metal sulfides, insoluble salts that precipitate settling in the soil.
