QUANTIFICATION OF OXYGEN RELEASE BY BULRUSH (SCIRPUS VALIDUS) ROOTS

The amount of oxygen contributed by wetland plant (bulrush, Scirpus validus) roots toward wastewater treatment has been estimated in the backdrop of conflicting reports about the role wetland plants play in wastewater treatment. Dissolved oxygen (DO), pH, and oxidation-reduction potential (ORP) microenvironments in the Scirpus validus rhizosphere were studied using microelectrodes (3-10 μm tip size). A methodology for in-situ measurement of oxygen near wetland plant roots was established during this research. A layer of oxygen was detected around the lateral roots, and its thickness (760-1160 μm) also increased with bulk BOD5. Bulrush plants have two different types of main roots, that is, brown and while roots. The active root lengths (i.e., the length of the root that exhibits ROL) in brown and white laterals were ∼ 40 μm and ∼ 1675 μm, respectively. The ROL value was ∼ 97 and ∼ 313 ng O2 cm−2 min−1, respectively, for white and brown lateral roots in primary settled municipal wastewater. The amount of oxygen released by bulrush (Scirpus validus) was estimated to be ∼ 5.0 to 7.65 mg O2 m−2 (of wetland surface) d−1. Of this amount ∼ 63% was contributed by the brown roots which made up ∼ 95% of total roots. An oxygen release of ∼ 5.0 to 7.65 mg O2 m−2 d−1 by wetland plants may not have any practical implication in wastewater degradation.