The solar corona

Abstract

The effects of temperature on pollutant removal of two plant species (Oenanthe javanica D.C. and Nasturtium officinale) were evaluated using simulated microcosms of the floating eco-island system (FEIS). Both the planted FEIS (P-FEIS) and the non-planted FEIS (NP-FEIS) dramatically decreased NH4–N concentration in the hypereutrophic water at low (10 °C), medium (22 °C), and high (35 °C) temperatures, and to a greater extent for the P-FEIS and at medium temperature. The NO2–N concentration was effectively decreased from 0.23 to 0.01 mg/L after 4 d treatment with the P-FEIS at all the three temperatures, but was slightly increased in the NP-FEIS at low temperature. The P-FEIS could decrease NO3–N concentration in the eutrophic water over 1–3 times depending on temperature, with greater decrease at high temperature. The remove of total P (TP) reached 78%, on average, with the FEIS treatment for 4 d at all temperatures, which was over three times greater than those with the NP-FEIS at low temperature. The removal rates of Chla, CODMn, and BOD5 by the P-FEIS from the hypereutrophic water were, on average, 70%, 85%, 83% at 22 °C and 35 °C, respectively, while over 1–2 times smaller at 10 °C. More effective removals of Chla, CODMn, and BOD5 (over 1–2 times) were noted with the P-FEIS than those with the NP-FEIS. N. officinale showed more efficiency in removing ammonium and TN at low temperature, and BOD5 at medium and high temperatures, as compared to O. javanica. Whereas O. javanica could more effectively decrease Chla at 22 °C and 35 °C and CODMn at 10 °C than N. officinale after 4 d treatment. Higher dissolved oxygen concentration and pH was found in the FEIS with N. officinale than that with O. javanica D.C. The results imply that plant eco-island system had remarkable purification ability to remove pollutants from hypereutrophic water, and mixed planting of O. javanica D.C. with N. officinale on the FEIS may enhance nutrient removal and water quality improvement of eutrophic water bodies, especially at low temperature season.