Assessment of Constructed Wetland Biological Integrity Using Aquatic Macroinvertebrates

R Cote,M Verma,C Galbrand,I.G Lemieux,A.E Ghaly

doi:10.3844/ojbsci.2007.52.65

Abstract

A surface flow constructed wetland consisting of seven cells was used to treat the leachates from a decommissioned landfill. Wetland monitoring was performed by evaluating the treatment efficiency of the landfill leachate and the wetland biological integrity of the wetland. The water quality samples were analyzed for iron, manganese, phosphorus (orthophosphate), pH, dissolved oxygen (DO), nitrogen (ammonia, nitrate, nitrite and TKN), chemical oxygen demand (COD), total suspended solids (TSS) and total dissolved solids (TDS). Aquatic macroinvertebrates were examined using Average Score per Taxon (ASPT) via the Biological Monitoring Working Party (BMWP) biotic index, the Ephemeroptera, Trichoptera, Sphaeriidae and Odonata (ETSD) biotic index, abundance of mayflies and trophic structure. Reductions of 49.66, 66.66, 1.91, 46.37 and 8.33% were obtained for manganese, orthophosphate, TSS, TDS and COD, respectively. The nitrite, dissolved oxygen and iron concentrations were not in accordance with the water quality guidelines for aquatic life. ASPT, ETSD, percent abundance of mayflies and trophic structure represented moderate to moderately-poor water quality in comparison to a high quality reference site. Iron had most adverse effect on the biological system of the wetland.

Highlights

Wetlands are broadly characterized as saturated land areas supporting aquatic processes as indicated by their poorly drained soils, hydrophilic vegetation and various biological activities that are adapted to a wet environment[1]
The results showed that the treatment site supported less pollution sensitive taxa than did the reference site and the outlet supported less pollution sensitive taxa than Cell 1, which would indicate that the water quality is degrading as it flows through the system
The presence of aquatic worms is often cited as indicators of biological integrity[30]. Their high abundance in the treatment wetland demonstrates that the site does support some semblance of health. It had been hoped the heterogeneity of the macroinvertebrates in the treatment wetland would be similar to that of the reference wetland and that heterogeneity would be improved with the hypothesized improving water quality, but the results revealed that the treatment wetland site lacked the biological integrity conducive to supporting appropriately distributed populations of macroinvertebrates[14,30]

Summary

Introduction

Wetlands are broadly characterized as saturated land areas supporting aquatic processes as indicated by their poorly drained soils, hydrophilic vegetation and various biological activities that are adapted to a wet environment[1]. Wetlands are nature’s purifiers which cycle and retain nutrients, pollutants and sediments through unique, naturally adapted mechanisms including, biogeochemical reactions (reduction/ oxidation transformations), phytoremediation (plant uptake of contaminants), bioremediation (microbial degradation) and sedimentation[2,3]. They have been called the kidneys of the planet because of the natural filtration processes that occur as water passes through them[4]. It is estimated that over half of the tens of millions of migratory waterfowl in North America depend on prairie pothole wetland ecosystems alone[5]

Objectives

Results

Conclusion