Upgrading a horizontal surface flow constructed wetland with forest waste and aeration

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Ecological Engineering

Background:

• Constructed wetlands (CWs) are sustainable wastewater treatment systems, but open systems like horizontal surface flow CWs (SF-CWs) can harbor mosquitoes, posing health risks.
• Conventional CW media (gravel, sand) have environmental impacts from mining, and CWs often require large land areas, limiting their application.
• There is a need for sustainable CW substrates and methods to mitigate mosquito breeding and reduce land footprint.

Purpose of the Study:

• To investigate the efficacy of using forest residue (palm tree branches) as a sustainable filling material in a full-scale SF-CW.
• To evaluate the impact of aeration in combination with the palm tree branch substrate on wastewater treatment performance.
• To assess the potential of this approach to address limitations of conventional CWs, including environmental impact and land use.

Main Methods:

• A full-scale horizontal surface flow constructed wetland was modified by filling it with palm tree branches.
• The system was operated with and without aeration to assess treatment efficiency.
• Key parameters monitored included E. coli, Total Coliforms, BOD5, turbidity, and ammonium removal rates and surface loads.

Main Results:

• Filling the CW with palm tree branches increased the percentage removal of E. coli and Total Coliforms.
• The combination of filling and aeration significantly improved the removal of BOD5, turbidity, and ammonium.
• Surface load analysis showed increases in E. coli and Total Coliforms with filling alone, and for BOD5, turbidity, E. coli, Total Coliforms, and ammonium with filling plus aeration.

Conclusions:

• Palm tree branches are a viable, sustainable alternative substrate for constructed wetlands, enhancing pathogen removal.
• Aeration significantly boosts the treatment efficiency of CWs filled with forest residues, particularly for organic matter and nutrient removal.
• This study provides valuable insights for designing more sustainable and effective constructed wetlands, addressing environmental concerns and operational limitations.