Quantification of oxygen release by bulrush (Scirpus validus) roots in a constructed treatment wetland

Achintya N. Bezbaruah, Tian C. Zhang

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Abstract

Amount of oxygen released by bulrush (Scirpus validus) roots has been quantified based on the radial oxygen loss (ROL) exhibited by the roots, the number and the length of active lateral roots, and the field plant density. It was found that wetland bulrush contains two types of active lateral roots (showing ROL), viz., laterals of brown and white main roots. The two laterals have distinct oxygen release characteristics. Based on the dissolved oxygen (DO) microprofiles of brown and white laterals, the ROLs were found to be ≈61 ng O2 cm-2 root surface min-1 and ≈ 68 ng O2 cm-2 root surface min-1, respectively, at bulk 5-day biochemical oxygen demand (BOD5) of 76 mg L-1. The respective average active root lengths of the brown and the white laterals were ≈ 40 and ≈ 1676 μm. Based on field and laboratory measurements, the average amount of oxygen released by bulrush was found to be 2.30 mg O 2 m-2 wetland surface d-1; of this ≈ 71% is from the white roots. The results of this study indicate that plants do not release enough oxygen to meet the total oxygen demand of bulk wastewater, and therefore, constructed wetlands should be designed as an anaerobic or an aerobic-anaerobic hybrid system rather than as an aerobic system. However, the results of this study should be viewed in the background of possible errors (including a reactor design flaw), which might have made the measured oxygen release significantly lower than what plant roots actually release. Further studies are needed to quantify wetland plant oxygen release based on micro-scale measurements.

Original languageEnglish (US)
Pages (from-to)308-318
Number of pages11
JournalBiotechnology and Bioengineering
Volume89
Issue number3
DOIs
StatePublished - Feb 5 2005

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Keywords

  • Active lateral root
  • Constructed wetland
  • Microelectrode
  • Plant oxygen release
  • Radial oxygen loss

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

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