Partially saturated vertical flow constructed wetland for urban wastewater treatment

Abstract

Partially saturated vertical flow constructed wetland (SVF) emerge as an alternative to classical vertical flow due to improved carbonaceous organic matter removal and nitrogen transformations without of the need for external energy source. In this context, the main objective of this study was to show the long-term evaluation of a SVF wetland with 7.5 m2 of surface area (filter media depth of 0.75 m where 53% of total depth was saturated) and planted with Typha domingensis macrophyte, operated as secondary/advanced treatment unit of urban wastewater under subtropical climate conditions. Sampling and analysis of conventional wastewater quality parameters, oxygen consumption rate estimation, and assessment of bacterial dynamics were conducted over 6 years, which allowed inferring that operating the SVF wetland with a specific hydraulic load around 4 L∙m-2∙min-1 and hydraulic regime with feeding and resting cycles of 3.5 d, all wastewater quality parameters met local legislation release standards in river water bodies. Saturated zone of the wetland favors the presence of denitrifying bacteria representing a potential of 44% of TN removal due to simultaneous nitrification-denitrification.