Nitrogen Removal by Ecological Purification and Restoration Engineering in a Polluted River: Water

Protecting clean water supplies and improving water quality of degraded rivers has become a key environmental issue worldwide because rivers are important water resources. There is an urgent need for appropriate techniques to improve river water quality. Here we test effects of a series of restoration techniques on reducing and eliminating nitrogen (N) in a polluted river. These techniques include (I) constructed wetlands (CWs) restoration, (II) parallel coupling multiple-stage CW wastewater purification, (III) shallow aquifer infiltration, and (IV) river restoration and ecological water quality improvements. During the restoration period, we monitored loads of total nitrogen (TN), ammonia (NH4+-N), and nitrate (NO3-N) along a polluted river that was implemented with the above mentioned restoration techniques. Overall, NH4+-N, NO3-N, and TN were reduced by 63.76 ± 31.63, 42.10 ± 5.88, and 78.17 ± 14.68% in the studied river, respectively. The results show that techniques I and IV effectively removed N. Technique II was most effective in NH4+-N removal but may be site-specific.