Pollutant removal modeling in a hybrid wetland system for industrial wastewater treatment

Modeling of treatment wetlands allows the prediction of system behavior and facilitates large-scale design by evaluating the effects of modifying the operating parameters. The aim of this study was to calibrate and verify applicable models in vertical flow (VF) and horizontal subsurface flow (HSSF) wetlands -first and second stage of the hybrid wetland (HW) system- operating in site-specific environmental conditions. Stepwise multiple linear regression analysis, oxygen demand model, and k-C* model, were applied to each stage of the HW system as appropriate. All models were calibrated and verified based on the data observed by monitoring the HW system. Afterwards, simulations were performed at each stage of the HW system. The simulations show the dependence of nitrification on the availability of NH4+-N and also that both, the increase in Org-N and COD loading, affect the efficiency of nitrification in the VF stage. In the HSSF stage, simulations show that the increase in hydraulic or pollutants loading rate has a positive impact on the performance of the system. The fit achieved in the models was satisfactory and the results obtained by simulation provide a useful tool to evaluate the performance of the HW system in different possible operating scenarios.

Automated summary

Modeling of treatment wetlands allows the prediction of system behavior and facilitates large-scale design. In this study, applicable models for vertical flow (VF) and horizontal subsurface flow (HSSF) wetlands in a hybrid wetland (HW) system were calibrated and verified. Simulations showed the dependence of nitrification on NH4+-N availability and the impact of organic nitrogen and COD loading on nitrification efficiency in the VF stage. In the HSSF stage, simulations demonstrated the positive impact of hydraulic or pollutants loading rate on system performance. The satisfactory fit of the models and the useful tool provided by simulations for evaluating the performance of the HW system in different operating scenarios.