Nitrogen Content:

The presence of nitrogen in water may be found to occur in one or more of the following forms - free ammonia, nitrates, nitrites and organic nitrogen. Presence of nitrogen in water indicates presence of organic matter. The free ammonia indicates recent decomposition of organic matter; nitrites indicate presence of partly decomposed organic matter. Organic nitrogen represents the stage before decomposition of organic matter has started. Presence of free ammonia in water indicates the presence of undecomposed organic matter. For potable water, its value has to be restricted upto 0.15 mg/l. The presence of organic nitrogen indicates pollution and limiting value in potable water is 0.3 mg/l. Presence of nitrites is highly dangerous and, therefore, its permissible limit in potable water is nil. Nitrates represent fully oxidized organic matter and, as such, is not harmful. However, excess of nitrate may present health problems in infants and concentration has to be limited upto 45 mg/l. Excessive presence of nitrogen in any kind indicates pollution and the form in which it is present indicates period or history of the water pollution.