Floating treatment wetlands and submerged vegetation for water quality improvement of an urban lake in megacity Jakarta, Indonesia

Abstract

Most of urban lakes in Megacity Jakarta have become shallow, polluted and in eutrophic condition due to solids and nutrient pollution which requires urgent handling and management. Aquatic vegetation especially emergent and submerged plants in the lake littoral area have been known to play an important role to reduce the contaminants in the lake water. Floating Treatment Wetlands (FTWs) are cultivated plants growing on buoyant mats in open water. FTWs are an innovative tool that has been widely used for ponds and storm water quality improvement. This study aims to examine the effect of submerged plant and the ability of two different plants grown on Floating Treatment Wetlands (FTWs) system to improve an urban lake water quality. One urban lake has been selected for this study where the lake littoral at the inlet area has been overgrown by the submerged aquatic plant of Myriophillum verticillatum. Two units of Floating Treatment Wetlands (FTWs) (size of 3 m2 each) made of rubber mat and PVC pipes (3 inches) as buoyant material and planted with Heliconia densiflora. and Vetiveria zizanioides. The performance of the FTWs applied and M. vercillatum was assessed by calculating the removal efficiency of nutrients and solids concentrations in the lake water of the coverage area. The observations of several water quality parameters including total nitrogen (TN), total phosphorus (TP) and total suspended solids (TSS) were made at the site before and after the submerged plant and FTWs. Both FTW_ H. densiflora and FTW_V. zizaniodes removed more nutrients and also suspended solids per m2 area than M. vercillatum. Although both submerged vegetation and FTWs can be used as tools to manage a long-term stability for good urban lake water quality, it will require intensive harvesting to control productivity of submerged vegetation.