Cold-climate constructed wetland applications in Canada and Northern China and modeling applications in the Canadian Arctic using SubWet 2.0

Abstract

This comparative study explores the mechanisms of pollutant removal efficiency in cold-climate constructed wetlands (CWs) and investigates the benefits, standing and practicability of using these systems to treat wastewater in Canada and Northern China. Treatment efficiencies defined by the Canadian and Northern China experience vary considerably. Experience in both countries shows that the majority of effluent values are generally better than that required by discharge standards in Canada and China. A review of the available case studies on cold weather treatment in both countries indicates that this technology is feasible in Canada and Northern China, although further monitoring data are needed to optimize CW design and ensure that the effluent quality standards are consistently met. In both of these countries and around the globe, increasingly strict water quality standards and the growing application of treatment wetlands for wastewater treatment is an important motive for the development of better numerical models as predictive process design tools. An investigation of the SubWet 2.0 model, a horizontal subsurface flow modeling program used to predict the level of treatment that can be expected was conducted. It has been shown that SubWet can consider the influence of several factors at one time, where empirical equations are generally not able to consider more than two factors at one time and usually in isolation of the other influential parameters. Three different data sets, two from natural wetlands from the Canadian Arctic and one from a CW in Africa were used to illustrate how SubWet can be calibrated to specific wetlands. Compared to other models, it is suggested that SubWet provides one of the best modeling options available for natural tundra wetlands. Further calibration of SubWet with twelve municipal treatment wetlands in the Canadian Arctic clearly demonstrated its ability to model treatment performance within natural tundra wetlands and thus provide an additional predictive tool to aid northern stakeholders in the treatment of municipal effluents. It is anticipated that increased monitoring and the generation of additional measured data will help to better identify the level of year to year variability and improve the overall predictive capability of the model.