The Effect of Effluent Recirculation in a Full-Scale Constructed Wetland System

• Published in: Sustainability Vol. 15; no. 5; p. 4310
• Main Authors: Herrera-Melian, Jose Alberto, Guedes-Alonso, Rayco, Tite-Lezcano, Jean Carlos, Santiago, Dunia E, Ranieri, Ezio, Alonso-Bilbao, Ignacio
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2023
• Subjects: Algae; Ammonium; Aquatic plants; Artificial wetlands; Biochemical oxygen demand; Chemical oxygen demand; Coliforms; College campuses; Composition; Control; E coli; Effluents; Environmental aspects; Measurement; Nitrogen; Phosphorus; Pollutant removal; Pollutants; Ponds; Purification; Solid suspensions; Spain; Sulfates; Sustainability; Testing; Total suspended solids; Turbidity; Wastewater treatment; Water; Water pollution; Water quality; Water treatment; Wetlands; Spain
• ISSN: 2071-1050; 2071-1050
• DOI: 10.3390/su15054310

This study deals with the effect of effluent recirculation (ER) on the pollutant removal efficacy of a full-scale, hybrid treatment system composed of a macrophyte pond and a horizontal flow constructed wetland. The average removals of 5-day biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), turbidity, total N (TN), ammonium nitrogen (NH4-N), total phosphorus (TP), sulfates, E. coli and Total coliforms (TC) for the years 2017–2018 (no recirculation), 2019 (50% recirculation) and 2021 (100% recirculation) were compared. Results show a general improvement of the effluent with ER. Removals for 0%, 50% and 100% ER, respectively, were: 59%, 61% and 66% for COD; 90%, 96% and 96% for BOD; 94%, 94% and 99% for TSS; 33%, 40% and 67% for TN; 22%, 30% and 55% for NH4-N; 92%, 98% and 96% for sulfates; 99.6%, 99.7% and 99.9% for E. coli; and 99.5%, 99.7% and 9.9% for TC. No clear effect was observed on the removal of TP and dissolved PO4-P, which were very low. 50% ER improved turbidity removal from 88% to 91%, but 100% ER provided worse results. The removal of NH4-N and TN significantly improved with 100% ER. This indicates that ER can be a simple, economic, and feasible way to upgrade the performance of full-scale natural wastewater treatment systems.