High level of nitrogen pollutants was found to be the reason of eutrophication and have harmful effects on human health. Therefore, the nitrogen removal is obligatory from the environmental protection view. Several methods have been proposed to remove nitrogen compounds from wastewater. These methods can be classified as (I) biochemical and (II) physical treatment. So, making an assessment on nitrogen removal processes to select a more efficient one seems to be necessary. Generally, Nitrogen compound enters into the environment through several ways such as landfill leachate,animal waste, agricultural activities, human waste, and etc. In this paper, the methods applied in recent papers and patents for nitrogen removal from wastewater around the world have been reviewed.

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