In China, nitrogen concentration of 2mg /l TN refers to V type of water based on
environmental quality standards for surface water (AQSIQ, 2002a),
10 mg /l NO3eN refers to standards for drinking water quality (SAC, 2006),
and 20 mg /l TN refers to primary B based on the discharge standard of pollutants for municipal wastewater treatment plants (AQSIQ, 2002b).