Hydraulic tracer studies in a pilot scale subsurface flow constructed wetland

• Published in: Water Science & Technology Vol. 35; no. 5; pp. 189 - 196
• Main Authors: King, Andrew C., Mitchell, Cynthia A., Howes, Tony
• Format: Journal Article Conference Proceeding
• Language: English
• Published: London Elsevier Ltd 1997; IWA Publishing
• Subjects: Approximation; Artificial wetlands; Biological effects; Coastal inlets; Commissioning; Computational fluid dynamics; constructed wetlands; Design; Fluid flow; Gravel; Gravel beds; Hydraulics; Modelling; pilot scale; Plug flow; Plug flow chemical reactors; Pollutant removal; Pollutants; Procedures; Removal; Sewage; Storm seepage; submerged flow wetlands; subsurface flow wetlands; tracer studies; Tracers; Wetlands; Australia, Queensland, Brisbane; subsurface flow wetlands; hydraulics; submerged flow wetlands; tracer studies; constructed wetlands; gravel beds; pilot scale; Artificial wetlands
• ISBN: 9780080431031; 0080431038
• ISSN: 0273-1223; 1996-9732
• DOI: 10.1016/S0273-1223(97)00068-1

Current design procedures for Subsurface Flow (SSF) Wetlands arc based on the simplifying assumptions of plug flow and first order decay of pollutants. These design procedures do yield functional wetlands but result in over-design and inadequate descriptions of the pollutant removal mechanisms which occur within them. Even though these deficiencies are often noted, few authors have attempted to improve modelling of either flow or pollutant removal in such systems. Consequently the Oxley Creek Wetland, a pilot scale SSF wetland designed to enable rigorous monitoring. has recently been constructed in Brisbane, Australia. Tracer studies have been carried out in order to determine the hydraulics of this wetland prior to commissioning it with settled sewage. The tracer studies will continue during the wetland's commissioning and operational phases. These studies will improve our understanding of the hydraulics of newly built SSF wetlands and the changes brought on by operational factors such as biological films and wetland plant root structures. Results to date indicate that the flow through the gravel beds is not uniform and cannot be adequately modelled by a single parameter, plug flow with dispersion, model. We have developed a multiparameter model, incorporating four plug flow reactors, which provides a better approximation of our experimental data. With further development this model will allow improvements to current SSF wetland design procedures and operational strategies, and will underpin investigations into the pollutant removal mechanisms at the Oxley Creek Wetland.