Assessing the performance indices and design parameters of treatment wetlands for H +, Fe, and Mn retention

Abstract

Using correlations analysis on water quality and wetland design parameters from a set of 35 natural wetlands receiving mine water, treatment efficiency was found to be a better index of Fe and Mn treatment than area-adjusted mass removal. However, area-adjusted mass removal was found to be a better index of performance for pH treatment. Weaknesses of using an area-adjusted measure to evaluate wetland performance for Fe retention included a significant load dependency aspect, strong positive correlations to inlet and outlet Fe concentrations, null correlations with vegetation parameters, and a tendency to rate highly small wetlands receiving high flow rates. H + retention was a better indication of pH treatment than treatment efficiency because of its relationships with inlet H + concentration, Fe treatment efficiency, and H + load. Design parameters enhancing Fe treatment efficiency included broad shapes, non-channelized flow patterns, high plant diversity, a southern exposure, and low Fe loads. Design parameters enhancing Mn treatment efficiency included large areas, non-channelized flow patterns, high vascular plant and bryophyte cover, high plant diversity, and low inlet Fe concentrations. Design parameters favoring pH mitigation included broad shapes, low flow rates, low surface water depths, non-channelized flow patterns, high plant diversity and cover, and low inlet Fe concentrations.