Floating Treatment Wetlands For Stagnated Water Treatment
Floating Treatment Wetlands (FTWs) are an innovative alternative of the more traditional constructed wetland and pond technologies that offer great potential for the treatment of the polluted water stagnated areas. This study is aimed at designing a New Combined Treatment Wetland (NCTW) and assess the treatment efficiency by treating stagnated water in lab scale and pilot scale studies in tropical climate of Sri Lanka. Two types of floating macrophyts, Typha angustifolia and Canna irridiflora, and submerged macrophyt, Hydrilla verticillata were investigated in a lab scale study in batch experiments, using two Surface Treatment Wetlands and a Submerged Treatment Wetland (STW). Biological Oxygen Demand (BOD5 ) and total nitrogen removal efficiencies were measured at different depths of water; 0.0 m, 0.6 m, and 1.2 m from the water surface in 5 day intervals. The experimental results revealed both Typha angustifolia and Canna iridiflora can be used effectively for removing carbonaceous and nitrogenous compounds from surface water. The maximum treatment efficiencies of two Surface Treatment Wetlands were recorded at surface level. Canna iridiflora was found to perform well at maturity and Typha angustifolia perform well at the beginning. But none of them were capable of treating water at a depth greater than 60 cm. Considering the aesthetic appearance and treatment efficiency, Canna iridiflora was selected as the best vegetation for treating surface water in stagnant water bodies. On the other hand, wetland planted with Hydrilla verticillata at a depth of 60 cm in the third tank proved that it was capable of removing carbonaceous and nitrogenous compounds from polluted water even below a depth of 60 cm. Surface Treatment Wetland planted with Canna irridiflora and STW planted with Hydrilla verticillata were combined together and a NCTW was designed and its treatment efficiency was investigated in lab scale and pilot scale. The results revealed that the NCTWs show an enhanced pollutant removal efficiency as they could cover the treatment in a depth –wise basis. It could be concluded that the NCTWs ensure a more efficient removal rate of pollutants from stagnated water in comparison with individual FTWs.
Keywords- Floating Treatment Wetlands, New Combined Treatment Wetlands, Submerged Treatment Wetlands, Treatment Efficiency