Hydraulic Performance of Constructed Wetland at NUST

Abstract

Constructed Wetlands are artificially designed wetlands used for treating organic, inorganic and excess nutrient contaminant in water. It enhances the quality of water through physical, chemical and biological processes. The quality of water has deteriorated because of the discharge of untreated wastewater which has increased many environmental risks. The hydrodynamics of constructed wetland is one of the most prominent factor used to enhance the quality of water, residence time of wetland is controlled by the fluid dynamics. The present study explores the overall hydraulic performance of Constructed Wetland located at NUST H-12 Islamabad Campus. The source of wastewater is the offices, student hostels, academic blocks and residential colonies. The accumulated wastewater is directed towards Sedimentation Tank and after settling of solid waste the scum is removed manually and wastewater discharged into the Constructed Wetlands which comprises of eight ponds. The effluent from Constructed Wetland discharge through the distribution system into the Filtration and Irrigated cropping for Land Treatment and Effluent Reuse (FILTER) plot for further quality improvement. The effluent is then collected through the tile drain system for horticulture use. The present study aimed to find the hydrodynamics of Constructed Wetland by using COMSOL 5.0 software. The governing equations of flow in wetland ponds and the transport particle were solved using COMSOL Multiphysics 5.0.In this study, the simulation of model was carried out to find the dead spaces and short circuiting in wetland along with providing remedial measures to reduce the dead spaces. The comparison of two turbulent models i.e. K-ω and K-ε were also made to depict the velocity of wetland and the particle tracer study was also conducted to find the behavior of wetland. The model was simulated with experimental data and the results revealed that 15% to 20% area of wetland is experiencing short circuiting. Alternative wetland designs were suggested for the same flow condition. The K-ω model was considered to be more suitable due to limitation of K-ε model.