Modeling nitrogen removal in a constructed wetland treatment system.

A constructed wetland treatment system (CWTS) has been adopted for removal of nitrogen from wastewater. The design methodologies developed for CWTS in previous studies were based on thumb rules, and first order/Monod type kinetics models. The use of kinetic models is system/environment specific. There is scope to assess the potential of other reaction kinetic models for their usefulness and applicability. In the present study, lumped and distributed parameter models incorporated with various reactions kinetic were developed. The various processes were incorporated in distributed parameter model for nitrogen transformations. Laboratory/pilot-scale field experiments were carried out and used for verification and application of models developed. The reaction rate parameters were estimated using non-linear least square analysis. The results showed that the conditions within CWTS can be simulated by plug flow. The plant uptake rate was found to be higher than denitrification for nitrate removal. Nitrification and plant uptake are equally dominant for the removal of ammonia nitrogen. The relative contributions by various processes for nitrogen removal can be established using the distributed parameter model. The developed simulation model can be used as a CWTS planning and design tool for the effective control and treatment of nitrogen induced pollution.