BIOLOGICAL DENITRIFICATION OF GROUNDWATER: BIO-PRB COLUMN TEST PERFORMANCES EVALUATION

The occurrence of nitrates in groundwater is steadily raising concern due to possible health consequences of nitrate ingestion. Biological denitrification in BIO-PRB is the enhancement of a natural process that occurs naturally when bacteria live in an environment void of oxygen with carbon availability. Bio-PRB represent a perspective of development for PRB technique but, despite the fact that this technology has already been widely used for chlorinated solvents, data on denitrification PRBs are still scarce. This paper reports on the results of an experimental study carried out for 214 days on a bench-scale pilot column (10 cm in internal diameter and 100 cm in length with sampling ports at different heights). The column was filled with a mixture of sand, agricultural soil and sawdust (30%, 20% and 50% v/v respectively) and was fed in continuous with a solution maintained at constant concentration of 25 mg/dm3 NO3-N for early 110 days and then gradually increased to 50 mg/dm3 NO3-N. Good nitrate removal performance (up to 99%) were observed with a direct correlation between nitrates removal rate and carbon availability in column.