Enhanced pollution removal from canal water by coupling aeration to floating treatment wetlands.

Abstract

Floating treatment wetlands (FTWs) are natural solutions for purifying polluted water, providing a green surface area and improving city landscape. This study investigated if the efficiency of FTWs can be improved by aeration for treating contaminated canal water. The three used plant species were Canna generalis, Phragmites australis, and Cyperus alternifolius. The experiment was carried out in three FTWs with aeration and three without aeration to compare the removal for COD, NH₄⁺-N, E. coli, PO₄^3--P, and Fe. In the aerated FTWs, air blowers were installed to run at two different air flow rates of 2.5 L min^-1 (Batch 1) and 1.0 L min^-1 (Batch 2). Aeration increased the dissolved oxygen concentrations in each tank, which came over 6.5 mg L^-1 in both batches. This study sheds light on the positive impact of aeration has on COD and NH₄⁺-N removal: these are nearly three-fold higher compared to non-aeration conditions and reached approximately 99% (1.7-log reduction) for E. coli removal. Additionally, the plant growth rate in the aerated FTWs was higher than in the non-aerated ones. The average shoot growth rate of Phragmites australis was 0.76 cm d^-1 for the aerated FTW which was two-fold higher compared to the non-aerated one.