Introduction

Nitrogen occurs in natural waters in organic and inorganic forms. There are several environmentally important forms of nitrogen that differ in the extent of oxidation of the nitrogen atom. Nitrate ion is the most oxidized form, while ammonia (NH3) and the ammonium ion are the most reduced forms. The common oxidation states of nitrogen occurring in nature are illustrated in Table 29-1.

Nitrate and nitrite ions in drinking water are a potential health hazard because they can result in methemoglobinemia. The nitrite combines with and oxidizes the hemoglobin in blood, thereby leading to respiratory failure. Nitrate ion is also implicated in stomach cancer.

Occurrence

The main source of nitrate ion is the runoff from agricultural land. Fertilizers are the major source of nitrates. Nitrate-bearing wastes result from production of fertilizers, explosives, nitro-organic compounds, and pharmaceuticals (Pinar et al., 1997). Other industries such as nuclear fuel processing use significant amounts of nitric acid. While these industries do not produce nitrogen-containing products, they can generate significant volumes of nitrate-bearing waste streams. In response to this problem, nitrate-containing compounds were added to the U.S. Environmental Protection Agency (U.S.