Affiliations: Environmental Simulation and Pollution Control State
Key Joint Laboratory, Department of Environmental Sciences and Engineering,
Tsinghua University, Beijing 100084, China | Department of Environmental Engineering, Qingdao
Institute of Architecture and Engineering, Qingdao 266033, China
Abstract: Influence of packing media on nitrogen removal in a subsurface
infiltration system was studied. System A was filled with loamy soil and system
B was filled with mixed soil of 75% red clay with 25% cinder. Both systems were
fed with sewage at the same hydraulic loading of 2 cm/d at continuous operation
mode. The same excellent removal performances of COD and T-P could be achieved
in both infiltration systems with removal rates about 85% and 98%,
respectively. In system A, NH^+_4-N removal rate was as high
as 96.5% and TN removal rate was relatively much lower as 55.7%. And in system
B, NH^+_4-N removal rate was as Iow as 75.4% and T-N removal
rate was relatively much higher as 75.5%. The difference was attributed to
different soil oxidation- reduction condition that was greatly influenced by
soil texture in subsurface infiltration system. Loamy soil led to oxidative
condition that was favorable to nitrification and disadvantageous to
denitrification. The results were just adverse to the system filled with clay.
Intermittent operation was adopted to improve nitrogen removal in system B.
N-H^+_4-N removal rate could be increased to about 95% and
T-N removal rate could be increased to about 90% at intermittent operation mode
in system B. Analysis of nitrogen removal mechanisms indicated that
nitrification-denitrification was the primary nitrogen removal path in
subsurface infiltration system and crop uptake was another important nitrogen
removal way. It was the key to improve the total N removal performance that a
suitable packing soil was available to present favorable oxidation-reduction
condition for simultaneous nitrification and denitrification.
