Combining tracer studies and biomimetic design principles to investigate clogging in constructed wetlands

  • Ricky Bonner 1. Industrial and Mining Water Research Unit, School of Chemical & Metallurgical Engineering University of the Witwatersrand, Johannesburg, 1 Jan Smuts Avenue, Braamfontein, 2000, Johannesburg, South Africa; 2. Centre in Water Research and Development, University of the Witwatersrand, Johannesburg, 1 Jan Smuts Avenue, Braamfontein, 2000, Johannesburg, South Africa
  • Lara Aylward 1. Industrial and Mining Water Research Unit, School of Chemical & Metallurgical Engineering University of the Witwatersrand, Johannesburg, 1 Jan Smuts Avenue, Braamfontein, 2000, Johannesburg, South Africa; 2. Centre in Water Research and Development, University of the Witwatersrand, Johannesburg, 1 Jan Smuts Avenue, Braamfontein, 2000, Johannesburg, South Africa
  • Uwe Kappelmeyer Helmholtz Zentrum für Umweltforschung UFZ, Leipzig-Halle, Dept. of Environmental Biotechnology, Permoserstraße 15, D-04318 Leipzig, Germany
  • Craig Sheridan 1. Industrial and Mining Water Research Unit, School of Chemical & Metallurgical Engineering University of the Witwatersrand, Johannesburg, 1 Jan Smuts Avenue, Braamfontein, 2000, Johannesburg, South Africa; 2. Centre in Water Research and Development, University of the Witwatersrand, Johannesburg, 1 Jan Smuts Avenue, Braamfontein, 2000, Johannesburg, South Africa
Keywords: wastewater treatment, step-change tracer study, velocity profiles, constructed wetland, clogging, biomimicry

Abstract

In this study, we suggest a clogging maintenance strategy and design alteration for constructed wetlands. Such a system could benefit rural communities who rely solely on constructed wetland systems for provision of household and agricultural water and for whom regular system shut-down for maintenance is essentially not viable. A newly established, pilot-scale horizontal subsurface flow constructed wetland was investigated by means of step-change tracer experiments. Sampling was carried out at multiple points down the length of the wetland and at three depths for each location. The mean residence time data
were used to generate velocity profiles. This methodology enabled the development of a three-dimensional hydraulic model to identify dead zones and regions of short-circuiting within the system. Biomimetic principles were then incorporated to propose improvements to conventional constructed wetland design, which would potentially allow for better clogging management and continuous operation. In particular, modularizing the regions of the wetland most prone to clogging (those containing dead space) would accommodate isolation, removal and replacement of such sections, while still allowing treatment of wastewater in adjacent sections.

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Published
2018-10-31
Section
Research paper