Correction: Białowiec, A., et al. The Oxygen Transfer Capacity of Submerged Plant Elodea densa in Wastewater Constructed Wetlands. Water, 2019, 11, 575

In the published article [...]

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

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.

ACCUMULATION OF LEAD AND OTHER TOXIC METALS BY AQUATIC PLANTS

Three toxic metals-lead, copper and zinc - were measured in the biomass of the aquatic higher plants of Elodea densa. The method of atomic absorption spectrophotometry was used. Plants were incubated at elevated concentrations of three metals in the aqueous medium. This has led to a significant increase in lead content in plant biomass. Namely, the concentration of lead in biomass increased to 1567% compared to the background concentration of this element in the biomass in the control (the background concentration was taken as 100%). After incubation, the concentration of copper in the biomass was 594% of the background concentration. After similar incubation, zinc concentration was 133% of the background concentration. The results can be useful in the analysis of biological monitoring and water purification.

A Short-Term Model Experiment of Organic Pollutants Treatment with Aquatic Macrophytes in Industrial and Municipal Waste Waters

Ability of plants to degrade waste water pollutants was studied in model experiment. The following aquatic macrophytes were used: Eichhornia crassipes, Cyperus alternifolius, Elodea densa and a mix of plants. Industrial and municipal waste water diluted by tap water to content 10% and 20% were used as a growth media for plants. Concentration of TOC, TN, chlorides and sulfates was measured in water during 7 days of incubation. The best results were obtained for Eichhornia crassipes which was able to decrease TOC and TN in water in 3 days of incubation: for TOC (in mg/l) from 47 to 24 (20% industrial waste water) and from 25 to 10 (20% municipal waste water); for TN (in mg/l) from 5,6 to 1,2 (20% industrial waste water) and from 2,5 to 0,35 (20% municipal waste water). Other plants also demonstrated improvement of water quality but were less effective. Concentration of chlorides remained close to initial level. Concentration of sulfates in several cases increased due to oxidation of sulfides.