Effect of hydraulic loading on bioremediation of municipal wastewater using constructed wetland planted with vetiver grass, Addis Ababa, Ethiopia
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Gravel-based pilot horizontal subsurface flow constructed wetland planted with vetiver grass (Vitiveria zinaniodes) and unplanted operated at two hydraulic loading rates: 0.025 m/d and 0.05 m/d was carried out over a 3-year period. The aim of the study was to evaluate the effect of plant and hydraulic loading rate on the organic and nutrient removal performance of the constructed wetland system planted with vetiver grass (Vitiveria zinaniodes) in the removal of chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) from municipal wastewater. The removal efficiencies of COD, TN, and TP in the planted cell decreased from 95 to 90.8%, 95.2 to 86.8% and 95.2 to 88.5%, respectively, with an increase in HLR from 0.025 to 0.05 m/d. The estimated above-ground biomass of dry weights of vetiver harvested ranged from 10.1 to 10.3 kg DW/m2, the nutrients uptake increased with plant age from 2.4 to 14.6 g N/kg DW and 0.8 to 8.5 g P/kg DW and above-ground biomass nutrient standing stock ranged from 147.5 to 150.4 g N/m2 and 85.5 to 87.5 g P/m2 in 16 months. The higher removal efficiency of COD, TN, and TP was achieved in HSSFCW planted with vetiver grass as compared to unplanted at both hydraulic loading rate operations. The results concluded that both applications of HLR are capable of removing organic matter and nutrients efficiently and vetiver grass can be used for remediation of pollutants in municipal wastewater in Addis Ababa.
KeywordsBioremediation Constructed wetland Hydraulic loading rate Municipal wastewater Vetiver grass
The authors thank Ethiopian Institute of Water Resources, Addis Ababa University (AAU) who supervised the financial support provided by the United States Agency for International Development (USAID) and Research Fund for International Young Scientists (Grant Agreement No: W/5799-1). The authors are also thankful to the Addis Ababa Water and Sewerage Authority for allowing developing the pilot-scale constructed wetland system in the premises of wastewater treatment plant and the laboratory facilities. The authors also acknowledge the University of Connecticut for the facility of access to electronic library and Ann Byers for editing the manuscript at short notice.
KA conducted experiments in the field and wrote up the manuscript. SL, WM, HK, EM supervised the experimental site and structured, read, edited, and approved the final manuscript. All authors read and approved the final manuscript.
This work was supported by the United States Agency for International Development (USAID) and Research Fund for International Young Scientists (Grant Agreement No: W/5799-1).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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