Nitrogen removal and transformations during simulated soil aquifer treatment (SAT)

Abstract

Nitrogen transformations were studied in 1-meter soil columns fed with primary, secondary, or nitrified-secondary effluents. The columns were packed with sand or sandy loam and operated on 7-day wet, 7-day dry cycles. Cumulative total nitrogen (TN) removals during application of secondary effluent or ozonated secondary effluent were 5% for sand and 38% for sandy loam columns. Significant TN removals were achieved using primary/nitrified-secondary effluent blends. Cumulative TN removal was 44% for three cycles of operation using a 50/50 blend of primary and nitrified-secondary effluent in sand. In a sandy loam column, cumulative TN removals were 32%, 54%, and 72% for primary/nitrified-secondary blend ratios of 25/75, 35/65 and 50/50, respectively. Assuming a mechanism of denitrification, the supply of carbon was estimated to be less than a third of what would be required to account for observed TN removals during application of primary/nitrified-secondary blends, suggesting the need to consider other possible nitrogen removal mechanisms.