Assessing the Costs of Constructed Floating Wetlands for the Treatment of Surface Waters and Wastewater

Abstract

The development of constructed floating wetlands (CFWs) as a nature-based solution for water treatment has progressed over the last 25 years. However, full-scale CFW adoption remains relatively limited due in part to the uncertainty regarding the costs of CFWs in terms of capital and operational expenditure (CAPEX and OPEX) and treatment capacity. This study reports on the costs of 11 international CFW schemes including the factors affecting CAPEX and OPEX and levelized costs of nitrogen and phosphorus removal. The estimated levelized CAPEX and OPEX ranged from US$15/m2to $2537/m2and from $0.5/m2y–1to $181/m2y–1, respectively, for CFW schemes of 55–3926 m2. Data from six full-scale CFWs showed that the costs per kg of nitrogen removed ($10 to $120/kg) by plant uptake were consistently lower than those of phosphorus ($15 to $3250/kg). CFW scheme scale was found to be a key influencing factor on cost, with cost per kg of nitrogen and phosphorus removed declining as CFW size increased. Use of this cost information can be generalized when considering nutrient removal and adoption of CFW technology compared to other engineered treatment options worldwide.