The Oxygen Transfer Capacity of Submerged Plant Elodea densa in Wastewater Constructed Wetlands

Abstract

There are insufficient data for the development of process design criteria for constructed wetlands systems based on submerged plants as a major treatment agent. The aim of the study was to evaluate the oxygen transfer capacity (OTC) of E. densa, in relation to wet plants’ mass (w.m.), and the influence of E. densa on the oxygen concentration and contaminants’ removal efficiency from municipal wastewater. The obtained oxygen concentration and temperature data allowed to calculate the OTC values (mg O2·L−1·h−1), which had been related to wet plants’ mass unit (mg O2·L−1·h−1·g w.m.−1). The efficiency of wastewater treatment was determined in relation to initial wastewater content in the mixture of wastewater and tap water (0%, 25%, 50%, and 100%) during 3 days of the experiment duration. The simulation of day and night conditions was done by artificial lighting. Before and after finishing the second experiment, the COD, Ntotal, and P-PO4 concentration were analyzed in wastewater solutions. The OTC ranged from 3.19 to 8.34 (mgO2·L−1·h−1·g w.m.−1), and the increase of OTC value was related to the increase of wet plant’s mass. The research showed that E. densa affected positively on the wastewater treatment efficiency, and the highest efficiency was achieved in 25% wastewater solution: 43.6% for COD, 52.9% for Ntotal, 14.9% for P-PO4.

Design, Operation and Optimization of Constructed Wetland for Removal of Pollutant

“…A latest research identified the macrophyte, Typha angustifolia as a possible hyper-accumulator for the elimination of Co, Cu as well as Pb from an FWS-CW using a controlled method to phytoremediation [ 193 ]. Meanwhile, the effectiveness of several other CW plants has currently been recorded, such as Zantedeschia aethiopica, Cyperus alternifolius, Heliconia burleana, Canna indica, Acorus calamus, and Ipomoea aquatic [ 194 , 195 ], including a waterlogged plant, Elodea densa, that has already demonstrated considerable capability in pollutant purification [ 196 ].…”

Mechanistic understanding of the pollutant removal and transformation processes in the constructed wetland system

“…Within the aquatic plant species, the two pathways of O 2 transfer are: (1) internal O 2 diffusion and (2) convective‐flow. Diffusion of gases typically occurs in the root system while through‐flow a pressurized mechanism of gas transfer takes place in the rhizomes and the stems of wetland plant species (Białowiec et al, 2019, Colmer, 2003). From the atmosphere, O 2 moves from the upper part of the plants (i.e., leaves) to the lower parts (i.e., roots).…”

“…Along with the environmental conditions (i.e., temperature, humidity), diffusion of O 2 in wetland plants is affected by the physiological (e.g., root and shoot biomass), anatomical (e.g., stems, leaves and root system) and morphological (e.g., structure, shape and size) characteristics (Colmer, 2003). In SSFCW, the movement of O 2 to the rhizosphere enhances pollutant degradation (aerobically) and the nitrification process (Brix, 2003; Białowiec et al, 2019; Yang et al, 2020). Table 3 shows the degree of importance of various functions of wetland plants based on the types of constructed wetlands.…”

Effects of Ornamental Plant Density and Mineral/Plastic Media on the Removal of Domestic Wastewater Pollutants by Home Wetlands Technology

“…The presence of DO indicates the type of conditions found in the systems: aerobic, anaerobic/anoxic for biological processes [23]. Therefore, the presence of oxygen in systems with greater vegetation than in non-planted systems could be due to its release in the radical zone [24,25]. In relation to the total dissolved solids (TDS), these mainly include organic salts and residues, therefore, in terms of their decrease in treatment systems it becomes an indicator of their effectiveness [26].…”