Denitrification field study at a wastewater land application site

A few risks restrict the sustainable development of wastewater land application including potential nitrogen contamination to groundwater. One important component is nitrogen loss caused by denitrification in a nitrogen mass balance to control nitrogen leaching. Few field studies have been specifically conducted to investigate denitrification in wastewater land application systems. The objective of this study was to quantify denitrification at a wastewater land application site located in a semiarid area. The denitrification rate was measured within three soils at the City of Lubbock Land Application Site in three different months. One-way ANOVA and a t-test were used to compare the differences of averages of many groups of data and of two groups of data at the p < 0.05 level, respectively. If ANOVA or the t-test is not applicable, the Kruskal-Wallis one-way analysis of variance on ranks and the Mann-Whitney rank sum test were employed to compare the differences of medians of many groups of data and of two groups of data at the p < 0.05 level, respectively. The denitrification rate in January was as high as 210 g N₂O-N/ha/day, while soil moisture was 19.4%. The denitrification rate ranged from 0.5 to 2,229.2 g N₂O-N/ha/day, which were the results of combined effects of environmental variables. Further and more detailed field investigation and quantification of denitrification are required in order for advanced nitrogen mass balance and sustainable nitrogen management at a wastewater land application site.