Enhanced phosphorus removal from sewage in mesocosm-scale constructed wetland using zeolite as medium and artificial aeration

Abstract

Phosphorus (P) contained in sewage maybe removed by mesocosm-scale constructed wetlands (MCW), although removal efficiency is only between 20% and 60%. P removal can be enhanced by increasing wetland adsorption capacity using special media, like natural zeolite, operating under aerobic conditions (oxidation-reduction potential (ORP) above+300 mV). The objective of this study was to evaluate P removal in sewage treated by MCW with artificial aeration and natural zeolite as support medium for the plants. The study compared two parallel lines of MCW: gravel and zeolite. Each line consisted in two MCW in series, where the first MCW of each line has artificial aeration. Additionally, four aeration strategies were evaluated. During the operation, the following parameters were measured in each MCW: pH, temperature, dissolved oxygen and ORP. Phosphate () and chemical oxygen demand (COD), five-day biological oxygen demand (BOD₅), total suspended solids (TSS) and ammonium. (NH ₄⁺−N ) were evaluated in influents and effluents. Plant growth (biomass) and proximate analysis for P content into Schoenoplectus californicus were also performed. The results showed that removal efficiency was 70% in the zeolite medium, presenting significant differences (p<.05) with the results obtained by the gravel medium. Additionally, aeration was found to have a significant effect (p<.05) only in the gravel medium with an increase in up to 30% for removal. Thus, S. californicus contributed to 10–20% of P removal efficiency.

Keywords:

• artificial aeration
• constructed wetland
• phosphorus removal
• natural zeolite
• sewage treatment

Acknowledgements

I. Vera thanks CONICYT (Chile) Latin American Scholarship Programme No. D-57080066 for supporting his PhD studies at the University of Concepción (Chile).