Application of a Constructed Floating Wetland for Treatment of Wastewater: A Case Study in Horana Export Processing Zone in Sri Lanka

Abstract

Constructed floating wetland (CFW) has been a popular phytoremediation based water treatment method for water purification purposes since the turn of the century. Natural macrophytes form floating hydroponic mats on the water’s surface and a root system that acts as a natural filter. This study was conducted at Horana Export Processing Zone to evaluate the potential use of floating wetland plants of Cyperus iria, Heliconia psittacorum and Canna indica for removing pollutants from wastewater. The CFW unit (size of 0.75 m Ö 0.46 m Ö 0.15 m (LÖWÖH)) was made with coconut husk chips, rice hulls, and soil media. Triplicate CFW with varying plant densities and three units without plants as control treatment were established in 90 L tanks. Water samples were collected over an 8 week period for analysis. Water quality parameters (BOD, COD, TSS, TDS, Nitrates, Phosphates and Heavy metals (Pb, Cr, Ni)) were measured once a week. One Way ANOVA Repeated measure analysis (95% confidence interval) with Tukey’s Post Hoc Test was carried out. Canna indica showed high removal efficiency in TSS, COD, Cr, Ni and nitrates as 58.1%, 73.0%, 72.0%, 86.6%, and 59.5%, respectively. Cyperus iria showed high reduction efficiency in BOD (56.7%) and phosphates (87.2%). Heliconia psittacorum showed high reduction efficiency in TDS (71.6%), Pb (58.0%). The results of the study suggested the selected Cyperus iria, Heliconia psittacorum, Canna indica could be potential plant species used in the CFW system to improve treated wastewater quality.