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.
Highlights
Aquatic plants due to their properties are a key element of the constructed wetlands (CW)
Obtained preliminary results indicate that E. densa may be suitable for use in CW as a tool for treating wastewater in the final phase of multistage systems
The conducted research showed that the E. densa influences on the O2 concentration in the water leading to oversaturation
Summary
Aquatic plants due to their properties are a key element of the constructed wetlands (CW). Proper design of these systems is largely dependent on plants choice. This aspect should be the subject of continuous research, especially since only a few species are widely used [1]. Plants in CW are used to remove nitrogen, phosphorus, other nutrients, heavy metals, and antibiotics [2]. Their contribution in removing nitrogen and phosphorus varies from 14.29% to even. The efficiency of removing contaminants depends on the species, plant growth rate as well as the physical and chemical properties of the environment [7]. The vegetation of water areas shows adaptations to environmental features, such as access to sunlight, pH, redox potential, hydraulic retention time, the presence of dissolved oxygen, organic carbon, salinity, and water depth [8,9]
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